I'm using Ivlarks vero layout here http://tagboardeffects.blogspot.ca/2011/01/tonebender-mki.html
From what I have read so far, biasing can be difficult with this circuit. Since his layout is using trimmers I assume it will be much easier.
I have searched the forum and read a little about using slightly leaky transistors in certain spots, and various opinions on gain ranges for Q1, Q2 and Q3.
Can anyone offer some advice on bias, leaky germaniums and gain for this circuit?
If you have a lot of germanium to choose from skip the trimmers and build it with stock values. It is all about the germanium/leakage and the interaction of the stages. The trimmers are not going to dictate that interaction properly and they are just going to complicate the build. If you have them OC75s and/or AC125s work well in this circuit. I have built a few of these and it became alot easier after I scrapped the trimmers.
Build it on breadboard and swap your transistors until you get close. Make lots of notes on the combinations you like and keep swapping transistors with the same or very close HFE and leakage. You can get a beautiful sounding MKI and then copy the transistor selection with new transistors having the exact same HFE and leakage and it will sound completely different.
Dropping the trimmers and auditioning alot transistors is the best advice I can offer.
Thanks. What about voltages? What should I be aiming for?
The FSB thread on the MKI is a good place to find information.
Read about the zonk machine at GEOFEX.
YOu have to experiment with different transistors at Q2 and Q3 until you get a set that sounds good.
mac
It's funny. There are long threads on various forums with no conclusive ways to build this one well. You usually get the standard "try a bunch of combos until it sounds right" comments.
Though, after building a bunch that sounded excellent, I was going to post a "guide" with some explanations...but the response for vintage stuff here is so underwhelming, I didn't...
I can still remember much, so I'll try to help from memory.
I think the first misconception is that it should sound like an FZ-1 or 1A. It doesn't. Secondly, many shoot for certain gains in the different slots (a common set would be 60 / 100 / 60), but I have found that leakage is far more important as long as the gains are 50+...and as usual, the model # transistor means almost nothing. I almost always use transistors with leakage of at least 200uA for the 3 positions.
The first thing I do is simply breadboard stage one and play thru it. You should get a decent clean boost that doesn't sound misbiased. You want the notes to fade out nicely. I've seen a large range of voltages for Q1E. The last one I built I marked down as .6V.
Secondly, a load of discussion goes into biasing Q2 and whether to use a 180K or 470K on Q2 base. It's no big deal whichever you use. When you're at lowest fuzz setting, Q2 collector is close to 9V and when you increase that fuzz pot, the voltage drops. The max fuzz is usually in the 3-5V range. If you use 180K, you'll probably hit 3-5v at only 5 - 15K instead of at 50K, so all you have to do is replace the 50K pot with a 10K one...very simple. Look at the Zonk. They only have around 3K there!
http://fuzzcentral.ssguitar.com/schematics/zonkIschem.gif
With a 470K, you will be able to use most or all of the 50K pot range to get to 3-5v. So, just measure the K where it's max fuzz (around 3-5v) and put the exact value pot there (use a resistor across the lugs to get the exact value you want...remember, it's only a variable resistor). If you drop the C voltage much lower (1-2V and lower), you'll get a thin, synthy, gated fuzz...and it will also get noisy sometimes <5V, so set the max fuzz where it's cool for you. If you pick a Q with the wrong leakage, C will be too high when fuzz is at minimum, so you must choose one that sounds good at min (C voltage not too high). With 180K, the last one I set max at 4V with a 7K pot. At min fuzz setting, it was in the high 8V range (I think ~ 8.75 - 8.9V).
Q3 works similarly to Q2, but the C voltage is much higher. I have found it's best in the 7.5 - 8V range. So, I just choose a transistor that gets me in that range using the stock 15K. The leakage is usually 300uA+. I usually use a trimmer instead of the 15K to fine tune it, but you want to be close to 15K. If the transistor doesn't have enough leakage C will be closer to 8.5 or 9V and just like Q2, won't fuzz well and you'll get more gating. The last one I set to 7.75V with the trimmer at 13K. Set the voltage too low and the volume will drop and the tone thinner.
After I've chosen Q2 and Q3, I always throw a few different Q1's in with similar leakages, just to see if it sounds any better that my initial choice.
I still have these handy:
2N1144 (72 / 210uA)
2SB376 (69 / 250uA)
2N1038 (54 / 380uA)
Quote from: mac on February 07, 2013, 10:23:11 PM
YOu have to experiment with different transistors at Q2 and Q3 until you get a set that sounds good.
All three transistors - not just Q1 and Q2 - need to tailored to the circuit.
I agree on leakage being the paramount factor. I think the reason that there is no clear cut maner to do this is because each transistor works and sound differently in the circuit. Even transistors with almost idetical HFE/leakage cannot always be swapped out. Lucifer, I am surpised that the unit you built with those numbers wasn't a crackling mess on the fade out based on my eperiences. I like Q1 to have the most leakage and Q3 the least for the circuit to minimize or completely remove the crackle and sizzle. It just goes further to my point that the individual transistors are the key and set gains/leakages are not necessarily going to get you close.
Quote from: Arcane Analog on February 08, 2013, 07:05:57 AM
Quote from: mac on February 07, 2013, 10:23:11 PM
YOu have to experiment with different transistors at Q2 and Q3 until you get a set that sounds good.
Lucifer, I am surpised that the unit you built with those numbers wasn't a crackling mess on the fade out based on my eperiences.
nope...long smooth sustain and nice decay. you will get noise if you set max fuzz at too low voltage for q2, set q3 voltage too low or if you don't have a nice decay for the q1 stage by itself (which is why I test that first before adding q2 & q3).
remember, closer to 9v for q2/3 is less fuzz and gatey, so if I really wanted less noise, I'd just set max fuzz to 6v and I'd set q3 C voltage 8.5V+
This is good. Although there are tons of thread talking about the various important points behind the circuit, it's nice to get them all in one.
Quote from: LucifersTrip on February 08, 2013, 08:22:14 AM
nope...long smooth sustain and nice decay. you will get noise if you set max fuzz at too low voltage for q2, set q3 voltage too low or if you don't have a nice decay for the q1 stage by itself (which is why I test that first before adding q2 & q3).
remember, closer to 9v for q2/3 is less fuzz and gatey, so if I really wanted less noise, I'd just set max fuzz to 6v and I'd set q3 C voltage 8.5V+
Long and smooth sustain is not really a characteristic of a vintage MKI. What type of gating do you have?
Read the history at DAM
http://www.stompboxes.co.uk/History.html
"The MKI was a three transistor circuit that was based upon the Gibson built Maestro Fuzz-tone that was modified by Hurst to produce more sustain than its American counter part."
As I wrote above, I can easily dial in gating by combinations of increasing the voltage on Q3 and turning down the fuzz
Quote from: LucifersTrip on February 08, 2013, 07:01:21 PM
Read the history at DAM
http://www.stompboxes.co.uk/History.html
"The MKI was a three transistor circuit that was based upon the Gibson built Maestro Fuzz-tone that was modified by Hurst to produce more sustain than its American counter part."
As I wrote above, I can easily dial in gating by combinations of increasing the voltage on Q3 and turning down the fuzz
More sustain than the FZ-1 doesn't really have any bearing on what I said and that comparison is of zero relevance. :icon_rolleyes:
You can tune your MKI to sound more like a MKII but you are entirely missing the point.
Quote from: LucifersTrip on February 08, 2013, 07:01:21 PM
As I wrote above, I can easily dial in gating by combinations of increasing the voltage on Q3 and turning down the fuzz
And for the record, the voltage on Q3 does not fluctuate at all - just a tiny bit. The voltage of Q2 is the one that changes alot with the fuzz pot.
EDIT:
MKI: Primal, gritty, spitty, jagged and a little tasty gate. Not a long and smooth sustain - it last for a few seconds and then fades with just a little bit of crackle.
Long and smooth sustain is a MKII. You can certainly try to tune more sustain into a MKI but that defeats the entire point of making a MKI.
Quote from: Arcane Analog on February 08, 2013, 08:22:10 PM
Quote from: LucifersTrip on February 08, 2013, 07:01:21 PM
As I wrote above, I can easily dial in gating by combinations of increasing the voltage on Q3 and turning down the fuzz
And for the record, the voltage on Q3 does not fluctuate at all - just a tiny bit. The voltage of Q2 is the one that changes alot with the fuzz pot. Perhaps you need to revisit the circuit.
What are you talking about? I only said that I can adjust the voltage of Q3 to get any type of gating I want. I've seen Q3 C voltage reported anywhere from ~ 7.5V to 8.5V+ ...and guess where you can dial in more gating? 8.5V
The question you should be asking yourself is:
How much gating, if any did the original designer intend...and can you prove it?
QuoteYou can tune your MKI to sound more like a MKII but you are entirely missing the point.
Mine sounds nothing like a MKII. Missing the point? To make a MKI that sounds exactly like everyone else's or to copy some ideological tone you've heard somewhere...maybe at DAM. I've heard demos of original MkI's and Zonk machines with tones and gating amounts all over the place.
Haha. Wow.
Quote from: Arcane Analog on February 08, 2013, 08:22:10 PM
EDIT:
MKI: Primal, gritty, spitty, jagged and a little tasty gate. Not a long and smooth sustain - it last for a few seconds and then fades with just a little bit of crackle.
Right...I can easily tune mine that way....just did. set Q3 to 8.75V w/ 9.6 supply. But again, what makes you think all vintage MKI's sound that way when the circuit is so finicky with transistors?
Well the first batch I tried out were all around 100, as recommended in the Zonk Machine article on Geofx (thanks for that tip btw). I've got it tweaked with the trimpots (by ear) and it's sounding pretty good. It sustains and then the notes kinda trail off in what sounds like intermodulation or something.
I'll experiment with different gains a little later.
Thanks for the offer Lucifer but I think I have better things to do that roll around the mud with you.
These are not originals, of course...but Brad usually knows what he's doing.
Are these poor MKI's because they have longer, smoother sustain? Before I set Q3C to 8.7V, these are very close to what I have.
http://www.stompboxes.co.uk/History.html
"The two pictured MKI's on this page when side by side do sound different."
"The output level is well over double that of the other MKI and when correctly dialled in has fierce amounts sustain with truly astounding clarity for such an old device."
Edit: Not worth it.
I've watched a couple demos of the D*A*M 1965 and they seem to gate on the decay. I'm finding with transistor swapping with hFe92 Q2 and hFe 123 in Q3 as D*A*M suggests it's either noisy hissy decay or gated.
Not sure what gain I should be aiming for in Q1 though. I'll keep swapping.
I agree with you. The DAM 1965, while certainly more refined, has that hint of gate which is a staple of the MKI sound - even in the full chords you can dial it in there. That gate mixed with the way the note decays and the ragged/earthy fuzz you get is what the MKI is all about. Primal and beastly. Even the Creepy Fingers demo that was posted has some gate on the decay. From my listening of the demo the only time there is alot of long sustain is when chords are hit hard on the Zonk. When only one is active you get that ragged fuzz with the sizzle on the decay which is obvious at the end of the demo. I do not hear alot of smooth fuzz going on there at all but I guess eveyone has their own definitions of sound. You can certainly get rid of all of the sizzle and gate if you want but that is some of the charm of the MKI.
Loads of long sustain is not really what the MKI is about. You can certainly have "ferocious" amounts of sustain without that sustain carrying on for a long time. that's what i think of when I think MKI. If you want loads of singing sustain you build a MKII. If you want that primal fuzz of the 60s like the Yardbirds or the Spiders you throw down the MKI. If you want 'Ziggy' Ronson you get the MKI and hit it with a Wah which pushes the fuzz and removes that gate and gets you more sustain. Lots of fun!
I have spent quite a bit of time on this circuit and built several pedals for different customers. I have developed a preference that mimics some of the preferences posted by several builders I very much respect (SonicVI, Creepy Fingers, DAM, etc). Mind you don't take that as me saying that I can build a MKI that rivals these builders at all. I simply like the vibe they have and try to get there myself. I have built a MKI that had more of a splatty gate on full chords yet still retained the agressive signature ragged fuzz tone. More extreme but kind of fun albiet a one trick pony.
You can use trimmers until you drive yourself crazy but if you pick the right leakage and HFE numbers for each transistor you can build one stock values wthout a lot of difficulty. You have to remember that even with HFE/uA values that are perfect for one set of transistors you can sound like garbage with another. I have found that when you approach the pedal from a transistor selection stand point over the "lets play with the bias" idea it becomes alot easier. The caveat here is that you need s decent amount of transistors to choose from.
For me it really boils down to transistor type and that individual transistor's properties. I really like 3 x OC75s (which were used in very early units) or a combination of OC75s and AC125s. I always seem to go back to an OC75s - I really like they way the circuit sounds with them. I have also had alot of success with AC128s. I seem to stick to lower gain transistors and usually find 60-100 is plenty. I do not recall ever reading Mr Main (DAM) suggesting specific HFE or leakage though. ia m curious - where did you read that?
Some folks like low leakage for Q1 while others dig a little leakage. Start at 60-80 HFE and 100uA and work up to see what you like. I usually like Q1 to have the lowest HFE but I also like 200+uA here.
Q2 determines the fuzz quality. Try around 80 HFE and 100-300 uA of leakage. I like Q2 to have the highest HFE. I find this one is most reposnsible for the texture and fuzz content.
Q3 seems to prefer lowish leakage for a quiet build - somewhere around 100uA is a good place to start. The gain of Q3 determines the treble content. Start in the 80s and work your way into the 120s and see what you like. Too much gain and/or too much leakage will get the sizzle going on the decay.
Bust out the breadboard, make a stock circuit and start experimenting. Leave yourself enough of room to swap transistors about.
Sorry for the typo/edits. I am on a difficult medium.
I'm thinking shielded wire would help a bit with the noise. Hopefully. I have the board all wired up and everything, but the noise is unbearable. I'm going to box it up and do the transistor swapping with it boxed up, just to eliminate the RF.
Thanks for the info about your transistor preference. I have a couple OC81's I yanked out of an old radio and a bunch of 2N404's and 2SBXXX's so I'll probably get something workable. This pedal is for a customer who wants that early Yardbirds "Roger the Engineer" sound. It's been quite fun though, I have been learning some of Becks weird licks to compare tones.
Edit: Damn typos.
I always build them with sheilded wire on the in/out to the board and the in/out to the jacks - absolutely makes a big difference.
My last one - just finished it a while ago for a Ronson fan.
(http://img.photobucket.com/albums/v89/Troublestarter/MKI-1_zps2ba3acb1.jpg)
(http://img.photobucket.com/albums/v89/Troublestarter/MKI11_zps13433659.jpg)
Nice enclosure! Make it yourself?
That is a Peadalenclosures Jorgan. Extremely durable box and powdercoat.
I think I found the right combo. Minimal noise and crackliness, somewhat smooth decay.
(http://i1030.photobucket.com/albums/y370/rouejeremy/9BA51B53-4630-4CFC-9E3F-423BDF80CD2C-3236-000002693F644A4F_zps684d3138.jpg)
Nice. For what it is worth, I usually end up auditioning about 5-10 transistors for each position.
That's probably what I had to do. I was hoping there was a trick like the Fuzz Face trimpot to get bias on this pedal. Looks like you just gotta go for it. No wonder reproductions are so expensive.
I think if I have to do this again I'll get that enclosure you have and have some decals made up to make a true tribute pedal. Oh, and PTP construction of course. Looks classy.
I like tagboard. Not true PTP but it is very durable - much more so than a PCB in my books. Damn near bullet proof. I have built them with the plain drilled phenlonic board as well but I am much more of a tagboard fan.
I 100% agree on going for it. In the end the trimmers really are just extra work you do not need to do.
Jeremy, can you post transistors data and voltages please?
mac
Q1-2N404 hFE 57 E-0.05 B- 0.10 C- 9.03
Q2-2SB186 hFE 123 E- 0.00 B- 0.16 C- 3.66
Q3-Unmarked hFE 93 E-0.00 B- 0.03 C- 8.44
All these voltages are with the attack pot dimed. I don't know the exact leakage of these transistors but they are all under 300.
I have found that the higher you go with the HFE the more apt you are to get that 'snap, crackle and pop' staccato sound and the subsequent gate/sizzle on the fade. Then again, the random nature of germanium can toss you for a loop. I would wager that this one has higher gain transistors than the 'normal' ranges (60-100) most people use. Understandably, Mr Main keeps his specific preferences under his hat.
My guess is that this one has lower gain transistors. Less chop, splat and sizzle than the previous example but I would bet you could definitely dial in more if you wanted - the demo did not really cover that end of things. Note the decay is alot smoother too.
Of course it also depends on what type of rig and how you are running it in combination with your playing technique. Pickup slection is a big factor. There are definitely big differences in the variants and even in pedals by the same builders due to transistor selection but getting some amount of that gate/sizzle/splat in with the ragged fuzz/sustain is pretty key to getting a MKI sound in my books. I do not think the sustain lasting along time is nearly important as getting those signature MKI aspects. If not you just get something that sounds like another type of Bender.
I checked out both of those vids before building and they just confused me. The GMD demo sounded great, but those were humbuckers and he didn't really let the notes decay naturally.
The other demo, man that pedal does not sound good IMO.
I think they both sound great! Haha.
The GMD video really does not help with learning about the decay - only in a few spots. It is a pretty generic sounding - still great though. Devin's box sounds amazing to me. Nothing else sounds like that - just the MKI. There are folks who will pay a truck load of cash to get that sound. I like it somewhere in between. This one by SonicVI is great middle ground.
Here it is. I think I need to make more adjustments to get a little more sustain out of the thing.
Trim pots and such adjustments really will not get you where you want to be. Subbing transistors until you get three you like is the only way to go.
I have three transistors that got me in the ballpark. The trimpots are actually helping a bit, that or I'm just reaching the acceptance stage of grief.
It all boils down to whether you are happy with "in the ballpark" or if you want to achieve a certain sound. I go through dozens of transistors. Trim pots only prolong the inevitable fact that you need to audition lots of transistors. I find OC75s are the easiest to dial in for this circuit. No trimmers required.
I have to disagree about the trimmers. If you understand what's happening, they are your friends.
Here's a perfect example (start 1:22):
http://www.youtube.com/watch?v=jkn29p1aLdI&list=UUqQDtCG7rijf_O408zPaqpA&index=42
The first thing you need to know about Q2 & Q3 is that they are biased very standardly. Nothing unusual....and just like many other fuzzes, the hot spot will be at around 1/2 the supply voltage (~4.5 - 5v). But, with the MKI, you don't want that. You want it almost misbiased, much nearer 9V (8V+) so you get that dirty gating effect (the most common cause of gating in circuits like this is misbiasing).
The next thing you need to know is that the higher leakage the transistor in (Q2/3), the lower Q2/3C voltage....and the lower the collector voltage, the hotter, the sound...and the hotter the sound, the more noisy it will be. That is precisely why it is recommended not to use a high leakage Q3...unless you trim it, of course. For example, in my last one that I wrote about earlier in this thread, I used Q3 = 2N1038 (54 / 380uA). The voltage was ~ 7V on Q3C, so I adjusted it up to ~8V (Note: just realized that was with a weak battery...with strong battery, closer to 8.5V).
In the video, blondegraemey has a trimmer on Q3. You have 2 choices. If you sub it for the 15K, you can alter the bias much quicker, but I have found you can't get it to gate as well. I found a trim for the 8.2K is better to tune in the gating. What blondegraemey did was adjust one of those 2 resistors to raise Q3C voltage closer to 9V till the noise disappeared.
===============
A trimmer for Q2 is not commonly used since you're setting the bias with the attack pot, but you still can use a trimmer for the 1.8K limiter to set the lowest attack. Note that the max attack Q2C voltage is different when using a 470K or 180K. With the 470K, you wind up closer to 5V and with the 180K, you could get closer to 2V and even lower. When you go past the "hottest" spot (~ 1/2 supply), the sound will get thinner and more compressed. It's your choice. Again, you can set the max attack anywhere you want by changing the size of the attack pot. Just like with Q3C, the larger resistance from base to ground will lower the Q2C voltage...and a Q2 with too high leakage will also lower the Q2C voltage and will set the the low attack setting too hot. You probably want it to be 8V+ at low attack.
===============
A trimmer on Q1 can be used to set how hot (gain) the overall circuit is. I rarely use that since it's the easiest of the 3 transistors to choose, but hfe seems to matter as much or more than leakage. The higher the hfe, the hotter and noisier the circuit can be. You can choose one in the classic 50-70 range but you can always trim it to produce less gain and the circuit will be less noisy....especially if you chose a Q1 with too high hfe.
Here's a great post from 2009 that Arcane quoted some info from.
http://stompboxes.co.uk/forum/viewtopic.php?f=10&t=37
Dragonfly
"A trim pot on the Q1 emitter definitely influences gain, and would allow you to use a wider range of germaniums. You should be able to "get away with" using a little bit higher gain device. I agree that Q1 likes that 50-70 range (if you're not using a trimmer)."
===============
The bottom line here is not to depend on trimmers too much, but to use them to tweak to exactly where you want the sound. In other words, you shouldn't have to tweak a trimmer too far from the stock values.
If you look at many the professional builds there are no/few bias values tweaked. You do not need to do that. They simply dropped in transistors that worked. David Main, PigDog, Castledine, SonicVI, Germs - none of those gents use trimmers and they do not drastically tweak - if they even do any tweaking at all - any of the resistors you have trimmers on.
What Lucifer seems to skip over is that some transistors simply will not work well in the MKI no matter what you do or how you try to tweak it. Period. He can try to throw out as much half-understood theory as he can muster but the bottom line is that you need to audition transistors. You are experiencing it yourself in that you have tried tweaking that transistor selection with trimmers and you still are unhappy with it. You can hit the volatges exactly as Lucifer is preaching and still not have it sound properly biased. That the way the MKI is. Breadboard the circuit and swap transistors until you have it where you want it and go from there. You could be playing transistors that will never get the sound you want.
All of these quotes are found in the FSB thread and none are by me:
- Don't bother with the trimpots, you'll drive yourself nuts. Just plug and play until you get a good transistor trio. I've built mine all stock. (Phibes)
- In case of MKI you cannot depend on numbers. It's bitch to bias it properly... and usually with trannies in correct gain/leakage bucket it sounds like sh*t... only swaping transistors till it sounds good could help here IMO. (Beedotman - Turretboard.org)
- I'd just breadboard, no need for a test bed. Tone Benders are pretty low are the part count so it should only take 5 minutes to put the circuit together. With Germaniums, it's a MUST to test run them before soldering them to a board. Having say 15 good transistors to try is better than just going with the 3 and crossing your fingers. (Phibes)
- Stock Mk-I circuit. Tone controll is a 100K lin pot that blends in a 22uf in parallel with the 10nf output cap.
Biassing consists of about 10 hours of transistor swapping and a box of OC75's. (Radiotron - Mr Morphine)
You mention OC75's a lot. Unfortunately the only Mullards I have are a couple OC140. I appreciate everyones input here. Once this pedal is finished and out the door I'm deleting every MKI schematic and layout I have.
I never said you need Mullard OC75s. I also mentioned AC125s work just as well. They are cheap and plentiful. You can buy bags of 150 pieces for $60.
If you follow my advice the circuit is not nearly as difficult to build as you are finding.
I know you are getting voltages, trimmer, etc suggestions. Ignore them. This circuit is not that difficult to build.
You can build MKIs on breadboard with stock values and plug in transistors that you have sorted for gain/leakage until you get a trio you like. You are not going to have success sticking to a few transistors and trying to make them work. Plain and simple.
Also, plugging in transistors that you have measured will teach you alot more than simply twisting a trim pot to hit voltages that may or may not work.
The glaring fault in Lucifer's advice is that this is not your typical circuit where relying on voltages will ensure that you get a decent sounding pedal. That is just a crutch for the MKI that you need to toss. It is good as a reference but that is about it. I build them with zero attention to voltages and I know several other people who do the same. I do record them when I am finished.
You can get the exact voltages of the best sounding MKI on the planet dialed into your circuit and it might still sound bad. The interaction between leakage is paramount in each stage and each germanium device will react different - even when they have the same HFE/leakage properties and even if they are the exact same brand/type of transistor.
No amount of futzing with trimmers and voltages can make up for that. Some transistors will simply not work in this circuit.
I guess you didn't read what I wrote:
"The bottom line here is not to depend on trimmers too much, but to use them to tweak to exactly where you want the sound. In other words, you shouldn't have to tweak a trimmer too far from the stock values." You still need to find transistors that are close to what you're shooting for.
All the info I gave is not half understood theory. Those are simple facts about how transistor voltages & leakages relate to gain in this circuit that would definitely help anyone that hasn't built this circuit loads of times.
There are just as many good builders that use trimmers/non-stock values as ones that don't. This can be said about almost any circuit. If the builder is fortunate enough to have enough supply to choose from, yes, of course, you won't need trimmers. The builders that don't use trimmers are mostly sellers/dealers/boutique guys who need to sell their product as exact clones.
Remember, you showed numerous videos above with varied amounts of gating. That is the perfect reason to use a trimmer or an external bias pot.
I think ultimately lucifer's trip and arcane analog are both right. I've built several of these and trimmers can definitely be useful in dialing in a good sound, especially if you have a limited selection of transistors to choose from. I also feel that you can go with the stock values and if you have a good selection of transistors you can play around with it a bit and find a combination that will sound good as well. This is a notoriously finicky circuit and will probably require some fine tuning no matter how you build it.
the funny thing is that many times I've trimmed the circuit within the error of the resistor values.
for instance, an 8.2K with 5% tolerance can be 7.79K to 8.61K and with 10%, it can be 7.38K to 9.02K
it is very common that my Q3 trimmer is set around 7.5V. it just needed that little bit to tweak out the unwanted noise and bring the voltage closer to 9V
Quote from: LucifersTrip on March 08, 2013, 05:05:53 PM
There are just as many good builders that use trimmers/non-stock values as ones that don't. This can be said about almost any circuit. If the builder is fortunate enough to have enough supply to choose from, yes, of course, you won't need trimmers. The builders that don't use trimmers are mostly sellers/dealers/boutique guys who need to sell their product as exact clones.
Remember, you showed numerous videos above with varied amounts of gating. That is the perfect reason to use a trimmer or an external bias pot.
Gating is simple transistor selection.
Who are all of these quality builders you speak of that make MKIs? I made a list of builders that have videos available as reference. None of those builders except DAM make production runs. They are all built to order and most do not make replicas.
Damn phone cut off half of my response.
Thunderbird, Radiotron, etc. All excellent. All no trimmers. Jimmy Behan does one sometimes with an external pot. I am interested in your quality builder list.
Quote from: Arcane Analog on March 08, 2013, 07:15:13 PMThunderbird, Radiotron, etc. All excellent. All no trimmers.
so if instead of using a trimmer set to 7.5K to put Q3C exactly where I want it, I went thru a bucket of 8.2K's until I found one that measured 7.5K, I can claim I didn't use a trimmer? genius
Quote
Gating is simple transistor selection.
gating = biasing the transistor. do you think the MKI will gate more or less if you choose a transistor that puts C voltage closer to 9V?
QuoteI am interested in your quality builder list.
why would I spend time looking thru 5+ years of dam, fsb & youtube to find vids for a single person thinks he can judge which is better?
My list was from the top of my head. I expected the answer you provided.
too many builds...too many years
;)
AKA I cant name any.
Quote from: reverberation66 on March 08, 2013, 06:06:29 PM
I think ultimately lucifer's trip and arcane analog are both right. I've built several of these and trimmers can definitely be useful in dialing in a good sound, especially if you have a limited selection of transistors to choose from. I also feel that you can go with the stock values and if you have a good selection of transistors you can play around with it a bit and find a combination that will sound good as well. This is a notoriously finicky circuit and will probably require some fine tuning no matter how you build it.
What happens if you have a device that falls well within the established HFE and leakage parameters and biases up where Luciferbsays it should land yet still sounds shitty? This happens alot. This is why trimmers will just prolong your aggony and drive you nuts. Some transistors will not work no matter what you do. Voltages be damned. You can set the voltages this way and that for an eternity and get nowhere simply becausenthe device you are working with sounds like trash in the circuit. Trim the bastard to death - it wont help you.
Preselect a pile of transistors and swap until you are happy.
QuoteSome transistors will not work no matter what you do. Voltages be damned.
Of course...that's true with many fuzzes. Did I ever say that you could use any transistors? you have to get close! then, tweak the gating, noise, sizzle, decay, etc...
"The bottom line here is not to depend on trimmers too much, but to use them to tweak to exactly where you want the sound. In other words, you shouldn't have to tweak a trimmer too far from the stock values."
Quote
Preselect a pile of transistors and swap until you are happy.
if you repeat that enough times, it will be true
http://www.youtube.com/watch?v=jkn29p1aLdI&list=UUqQDtCG7rijf_O408zPaqpA&index=42
[1:22]
Still no list Lucy? Lets here a video of those excellent sound builds you have. After all there are so many.
the discussion is whether a trim is helpful. you have (1) a clear video above showing a perfect use to kill noise and as you mentioned earlier (2) Jimmy Behan uses an external bias...
there's also (3) ghosteffects:
http://www.youtube.com/watch?v=p9mT-61E4uY
and of course, there's (4) fuzzfaceless, who uses 2 bias controls:
http://www.worthpoint.com/worthopedia/tonebender-mk1-fuzz-pedal-166580510
and how many builders use trimmers on the breadboard, then sub a fixed resistor?
whether you choose to put those controls on the inside as a trim or outside is up to you. I do both or neither...
I have already awknowledged people use them for fetaures including jimmy b :icon_mad:y name. Those are not necessary uses though. They are features.
Funny. Graham is using bags of AC125s and OC75s. I bet he didnt even need the trimmer.
Strange that the original poster has trimmers and cannot get his dialed in.
Anyway. Everyone knows you are the self proclaimed fuzz king. All hail Lucy.
when you get owned, start insulting...very mature.
Quote from: LucifersTrip on March 09, 2013, 05:28:52 PM
when you get owned, start insulting...very mature.
Please. Owned? All you do is quote other peoples work from various forums and repost voltages and purport yourself to be an expert.
Who starts out giving advice by saying things like "after building many great sounding pedals I have this to say."
Quote from: LucifersTrip on February 08, 2013, 03:37:21 AMThough, after building a bunch that sounded excellent, I was going to post a "guide" with some explanations...
Will you pair just give it up ::)
Quote from: Pyr0 on March 09, 2013, 05:42:58 PM
Will you pair just give it up ::)
Agreed. You are right Pyro. Just a stupid thread now.
It would be a great thread if all you seasoned MKI builders would just tell us some ideal transistor Hfe and leakages values to use. ;D
Quote
It would be a great thread if all you seasoned MKI builders would just tell us some ideal transistor Hfe and leakages values to use. ;D
There are some guidelines for Q2 and Q3, but not a precise answer for your question. This is because of the very nature of germs.
Tiny changes of hfe, leakage or even Vbe from device to device, and temperature of course, have big impact on the collector voltages. What you heard yesterday while breadboarding can, and will, sound differently next day, if you live like me by the sea, or in desert areas :)
Some weeks ago, I put a set of leaky 2sd352 matsushita germs, +600ua, hfe:65, and it sounded great with stock values. But it was hot the first day. Next days temperature went down by 15C and both Q2 and Q3 went up and sounded more bizarre, not bad but different.
I said nothing new, I know, but I hope this example can clarify things a bit for the one time builder.
The stock circuit calls for leaky germs, 500ua<leakage<1000ua, 50<hfe<150.
Those eBay ACXXX many members complain about can be OK for this.
So if you plan to build this for your own use, and you have just a few germs that are non-leaky, or for any reason do not bias ok, you'll have to tweak/add some resistors.
Which ones?
Q1
If emiter voltage is below a volt because your germ is low leakage, some mega ohms resistance from Vcc to B will increase emiter voltage.
My advice is to set Q2 emiter above 2v.
Q2
The problem here is to make the fuzz pot work all the way up and down. If leakage is low, the fuzz pot will set collector voltage near 9v until it reaches say 10k or more. If this is the case, increasing the 1k8 resistor to 4k7 or more can help.
Q2 collector should vary from Vcc to 5v - 6v or so.
Q3
The 8k2 sucks a lot of leakage from the base, that's why you need a leaky germ here.
Non-leaky germs will hardly bias here. In this case you can send collector voltage down by adding a resistor +470k or so, from Vcc to B, to feed the base.
Some like Q3 collector ringing near Vcc, some like it at 7v, others at 4.5v. Salt and pepper to taste.
Would this changes have a great impact on the sound by changing impedances?
Q2 and Q3 input impedances are very low for this changes to have great effect.
For this reasons I designed a Silicon TB MKI ::)
I think it would be a nice idea if we all work on better biased GE TB MKI, designed for a specific range of germs to get consistent results.
Now, how companies build this pedal without using trimmers that are a waste of time and money?
By wasting time and money making deals with suppliers to get devices on a specific range.
I'd really like to compare many pedals from the same company and check if they all sound the same.
mac
Good God.
It's no wonder that I haven't tried the Tonebender Conundrum yet, after building for over 5 years. And I LOVE the sound of this circuit. Or at least some of the sounds, it seems.
Thanks for the good advice nonetheless. Mac, I for one hope you can get that Silicon Mk I to sizzle just right. The desert is not kind to Ge pedals.
Thanks mac, some good info there. I'm also following progress in your silicon MKI thread. It's starting to sound good.
Hey guys!
Check out this video (http://www.youtube.com/watch?v=p_cof6xknbY) and listen to the noise it makes at around from about 3:10 to 3:23 (it's especially bad at about 3:20).
This is exactly the noise I get with the circuit on the breadboard as the notes decay. Is this normal for this circuit and is there any way of getting rid of it?
I am assuming that biasing the transistors to gate will help. Also, I can get rid of the noise by using a low gain transistor for Q1 (about 30-40 hfe), but then the fuzz is too light.
I have had a pretty easy time getting good voltages with the stock circuit, but that noise is awful!
Otherwise, the circuit sounds great!
I never had that noise, even when transistors, Si or Ge, were very close to Vcc.
mac
Thanks, Mac! Any idea on what could be causing it? I thought it was just me until I found the example I posted.
I had that kind of noise. Swapped the 180k between Q2's base and -9V for a 470k and all was good. I used OC75s btw..
Thanks, EW! I'll give that a try! I am also using OC75's, which so far are my favorite in this circuit and the MKII.
Quote from: jrod on March 12, 2013, 11:00:21 AM
This is exactly the noise I get with the circuit on the breadboard as the notes decay. Is this normal for this circuit and is there any way of getting rid of it?
I am assuming that biasing the transistors to gate will help. Also, I can get rid of the noise by using a low gain transistor for Q1 (about 30-40 hfe), but then the fuzz is too light.
I have had a pretty easy time getting good voltages with the stock circuit, but that noise is awful!
Otherwise, the circuit sounds great!
This is pretty much case in point as to what I have been saying all along in this thread.
The crackling fizzles on the deacy are very common - if not the norm. The circuit is either misbiased or, if you are seeing close to the voltages you should, you need a new transistor(s). I have said it a bunch in this thread - even with proper voltages some transistors just sound like that. No amount of trimmers/voltage corrections will get rid of it. Anyone who has built several of these should know this to be a fact and a hard reality. You can minimize the number of transistors that will not inherently work by using OC75s and AC125s - they seem to work well in this circuit. Other folks like AC128s but I have never tried any as the OC75/AC125 combo works like a charm for me.
In my experience, a minimum HFE ~70 is required for Q1. Anything less and you will probably not have enough fuzz.
Again, I have said it many times in this thread, getting the voltages where you want them is pretty damn easy. Trimmers can certainly get you there. What the argument between myself and Lucy has been about is that I contend that trimmers cannot always make the transistor sound good or remove the crappy artifacts. You can play with trimmers until you are blue in the face and utterly insane and never get a good sounding pedal. Or, once you have determined that your tranistor is biased properly but still sounds like crap only swapping different transistors can help you out. Simply starting with a pile of transistors is always going to be your best bet. Some OC75/AC125 combos are plug and play with stock values. Indeed, I have never built this circuit with anything but stock values (except the 180/470K swaps or 'Hurst' values) and there are a great number of others that have had success doing the same.
Thanks, AA! I appreciate what you are saying. Unfortunately, I don't have a large stock of OC75's to work with (I have 9 or 10) and the 6 AC125's are all a bit high beta for this circuit (low 200's). However, I do have a lot 2N13XX and have swapped transistors for hours and always had the noise.
Like I say, the only thing that got rid of the noise was low gains for Q1 and you are right, the fuzz is lacking.
I did just listen to the blondegraemey video that LT posted and his use of the trim pot seems to kill the noise, which leads to me to believe that the noise issue stems from Q3 bias. Maybe Q3 is the one to focus on swapping out?
I'm getting married this weekend, so after the dust settles, I am going to get back to this circuit and try these suggestions.
Sorry - I thought you had stated you had good voltages on the circuit including Q3. If the voltages are off it will probably sound off.
Swapping out Q3 for me is a preference for highend content. Higher HFE = more treble. Lower leakage makes for lower noise.
This circuit is all over the place though. I have had combos work that shouldn't.
Quote from: Arcane Analog on March 12, 2013, 12:10:58 PM
Sorry - I thought you had stated you had good voltages on the circuit including Q3. If the voltages are off it will probably sound off.
No, you are correct. I don't seem to have a problem getting the "right" voltages. It's just that that dreadful noise I get on the note decays. The circuit sounds great until the notes start to trail off. My experience so far has been, no matter what combo I have tried, the noise is always there. I was just wondering if adjusting the bias on Q3 would help get rid of the noise. I swapped out a bunch of transistor combos, but adjusting resistor values is something I haven't done because I want to use the stock circuit.
Thanks for your input, AA!
You can check videos of some 'commercial' builders who send them out with the rough decay.
The thing with this circuit is that no one builds a great number of these for good reason. They arebpretty much only a commissioned pedal.
Yeah, I've wondered if the key to using this circuit to just not let the notes ring out too long! ;D
QuoteThanks, Mac! Any idea on what could be causing it? I thought it was just me until I found the example I posted.
Mhhh, hard to say. When do you get that noise, near Vcc? Maybe one transistor is too off. In that case try to turn it on a little more.
QuoteI had that kind of noise. Swapped the 180k between Q2's base and -9V for a 470k and all was good. I used OC75s btw..
Or the 470K for a 180k?
mac
Quote from: mac on March 12, 2013, 03:16:40 PM
QuoteThanks, Mac! Any idea on what could be causing it? I thought it was just me until I found the example I posted.
Mhhh, hard to say. When do you get that noise, near Vcc? Maybe one transistor is too off. In that case try to turn it on a little more.
Hey Mac! I'll try to set it up tonight on the breadboard and get some measurements. But, IIRC, I had Q3C at about 8.5V, Q2C varied from about 2V-8V, and Q1E about 1.5V & collector at Vcc. So, all 3 transistors were close to Vcc with Fuzz pot maxed.
When you say to "turn it on a little more" are you saying to feed more voltage to the collector?
Thanks!
Im a bit late on this discussion, but I'm glad I found this thread as I'm about to breadboard a sola sound tone bender MK1. I've read about this particular tone bender being difficult to get the sound right as it is very picky with tranistors. I've was informed that Small Bear sells a transistor set and specifically matched for the tone bender mk1, http://www.smallbearelec.com/servlet/Detail?no=1311 I figure ordering one set of these transistors for the tone bender MK1 would be a great idea, so wouldn't have to do the leg work in buying a whole bunch of trannys and sorting them out. Has anyone sucessfully built a tone bender MK1 using the small bear tranistor set?
I ordered the generic and OC75 mki sets a little while back when I was first playing with this on breadboard. Tax refund has let me grow my ge collection a lot since then. Mainly some OC75 and a bag of ac125z vi from the ebay. A lot of the difference between a small bear set and one I pick out after some swapping is really a matter of personal taste, I think. The OC75 set I got just popped in and sounded very good. Seems to be kinda representative of what I can get using that type or similar transistors, I guess. The generic set was a 3ax31c for q1, 2n508 for q2 and q3. The 2n508 I got seem to have *just* enough leakage to work. I had to go with 180k off q2 base, and I think I doubled the 1.8k or something just to line up one of the cooler sounds with 0 attack. So a little more fuss, the end result was a much weirder sound, attack knob sweep was a little more askew... but still awesome in the end. Maybe not for everyone though. I live in an apartment, and one of the neighbors from the complex asked with a bit of concern about "those weird sounds" the day after I was fiddling around with the generic set. :)
I say go for it! Unless you have scary neighbors...
I am pretty sure the OC75 sets from SB are simply gain audited for the "general consensus" as to HFE preferences although I know many would not agree. The two sets sent to me were not leakage audited. They will work fine in a MKII but I don't think they will always drop in and play in a MKI and you will almost definitely have artifacting. It is also worthy to note that the SB MKII sets are audited to get 4.5V and not 7+V so buying one of these sets will not guarantee success without some understanding of the circuit(s).
QuoteHey Mac! I'll try to set it up tonight on the breadboard and get some measurements. But, IIRC, I had Q3C at about 8.5V, Q2C varied from about 2V-8V, and Q1E about 1.5V & collector at Vcc. So, all 3 transistors were close to Vcc with Fuzz pot maxed.
When you say to "turn it on a little more" are you saying to feed more voltage to the collector?
Exactly. Q2 depends on the fuzz pot, so tweak Q3 to decrease its voltage a bit, 7.5v-8v.
Q1E seems ok, but have you tried a resistor from Vcc to B, say 1M, to increase the emiter voltage. I'm wondering if Q1 below 1.5v is too low...
For those having decay noises, maybe, and I say maybe, the lack of Vcc to B (or C to B) resistors at Q1 and Q3 can cause this.
That and/or the 22uf cap.
If I were to build it, I would add a pot at Q3 to adjust the collector at will.
QuoteI say go for it! Unless you have scary neighbors...
The basement of my building has displaced 10 feet since I moved in ;D
mac
Quote from: Merman on March 19, 2013, 06:01:43 AM
I ordered the generic and OC75 mki sets a little while back when I was first playing with this on breadboard. Tax refund has let me grow my ge collection a lot since then. Mainly some OC75 and a bag of ac125z vi from the ebay. A lot of the difference between a small bear set and one I pick out after some swapping is really a matter of personal taste, I think. The OC75 set I got just popped in and sounded very good. Seems to be kinda representative of what I can get using that type or similar transistors, I guess. The generic set was a 3ax31c for q1, 2n508 for q2 and q3. The 2n508 I got seem to have *just* enough leakage to work. I had to go with 180k off q2 base, and I think I doubled the 1.8k or something just to line up one of the cooler sounds with 0 attack. So a little more fuss, the end result was a much weirder sound, attack knob sweep was a little more askew... but still awesome in the end. Maybe not for everyone though. I live in an apartment, and one of the neighbors from the complex asked with a bit of concern about "those weird sounds" the day after I was fiddling around with the generic set. :)
I say go for it! Unless you have scary neighbors...
Great to hear that. I placed an order for those transistor MK1 set. So a bag full of OC75 can still be had for a reasonalbe price, or should I just go with a bag full of Russian Ge trannies?
I don't live in an apt, I have an extra room near behind the house that I use as a "Man Cave" with all my musical stuff work area and my neighbors can't hear me and I can't hear them :icon_biggrin:
Quote from: Arcane Analog on March 19, 2013, 06:39:39 AM
I am pretty sure the OC75 sets from SB are simply gain audited for the "general consensus" as to HFE preferences although I know many would not agree. The two sets sent to me were not leakage audited. They will work fine in a MKII but I don't think they will always drop in and play in a MKI and you will almost definitely have artifacting. It is also worthy to note that the SB MKII sets are audited to get 4.5V and not 7+V so buying one of these sets will not guarantee success without some understanding of the circuit(s).
I can verify the SB MK2 set audited for Q3C at 4.5v. I used the included resistor that came with the set and indeed set the Q2C voltage to 4.5v, but if I didn't use the included resistor and use 47K or 33K, it brought the voltage closer to the 7.5-8.5v range.
The leakage is arguably more important than the gain in the MKI so it will be more effort to get the circuit where it is supposed to be.
I'm thinking of building another one of these. Someone slap me.
I have enough Ge stuff now to probably make an attempt.. but reading this whole thread I'm not sure it's worth it ;) I built a Mk IV and still can't get it to sound right