hi guys,
was surfing around evilbay earlier, and spotted this:
http://www.ebay.com/itm/150894762099?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2648
(http://i605.photobucket.com/albums/tt137/pinkjimiphoton/HEATHKITOVERDRIVE.jpg)
they were kind enough to provide this:
(http://i605.photobucket.com/albums/tt137/pinkjimiphoton/Heathkit_Ta28_fuzzbooster.jpg)
and a gutshot!
(http://i605.photobucket.com/albums/tt137/pinkjimiphoton/HEATHKIT5.jpg)
and even a schematic, too:
(http://i605.photobucket.com/albums/tt137/pinkjimiphoton/HeathkitT28Fuzz.jpg)
so i looked up the transistors, to see what would sub, and it came up mpsa18 for q1, and our old friend 2n3906 for q2. i decided to suggest germanium there, but pretty much anything should do i would imagine.
that said, i was bored, so i worked up a vero...
(http://i605.photobucket.com/albums/tt137/pinkjimiphoton/HEATHKITTA28FUZZBOOSTER.png)
gonna build it at some point just for sh*ts and grins...
just thought i'd share...was mighty nice of them to provide enough info to not need to build the pedal. ;)
if anyone whacks it together, please let me know!
happy fumes!
I have one of these, along with a copy of the manual. There are some schematics floating around the net, but that one is the schematic from the manual.
I wonder how they decided on those substitutions for the original transistors. When researching the X29A829 I came across some info on a ham radio forum that suggested these subs for it: 2n2907, 2n4403, or an NTE159. One caveat is that the application they were discussing was as a "relay driver" in a Heathkit HW-8.
I think Smallbear may have the 2n3391.
It would be interesting to do a side by side comparison of the specs of those transistors. Either way, you could also just take whatever garden variety transistors you have and see how they sound.
As for how the example I have sounds, it's a sort of fuzzy overdrive, but there is a volume cut with it engaged. It needs another amplifier stage at the end. Something to try is to see if it sounds better with a buffer on the front. Come to think of it, I wonder why it was designed to operate at 1.5vdc, and how it would sound at a higher supply voltage.
yah, you know i'm gonna try it with a 9volt. :icon_twisted: :icon_twisted: :icon_twisted: :icon_twisted: :icon_twisted:
i did a search on appropriate subs for the q1 transistor, and almost all said mpsa18, alot said 2n3904...so i'm figuring it's not too crucial.
i have some matched pairs of ac127/128's i may try in it. thinking maybe try a diode clipper on the output to get it a little louder. i bet 9v will make a difference, tho it may need biasing to run that hot.
thanks for the info bro! ;)
ii actually have a couple of most of the trannys you named, so i'll try some of them, too.
Quote from: pinkjimiphoton on September 08, 2012, 01:46:23 AM
thinking maybe try a diode clipper on the output to get it a little louder.
If you mean adding some clipping diodes between signal and ground (like a Dist +), that will just cut the signal more, and you'll really need the extra booster stage on the end.
This pedal has been discussed elsewhere on here, so it might be helpful to check out those discussions.
Quote from: pinkjimiphoton on September 07, 2012, 09:06:23 PM
hi guys,
was surfing around evilbay earlier, and spotted this...
hey jimi!
cool to see you're still looking out for the odd fuzzes.
I built that one a while ago from the same schematic:
http://www.muzique.com/schem/heathkit.gif
To my ears, it is most similar in sound to the Sam Ash Fuzzz Boxx/ Astrotone...but better. It's one of the few 1.5V fuzzes that are silicon. Still my favorite is the Sun Buzz...
Quote
so i looked up the transistors, to see what would sub, and it came up mpsa18 for q1, and our old friend 2n3906 for q2. i decided to suggest germanium there, but pretty much anything should do i would imagine.
I actually had some vintage 2N3391's laying around, which had hfe's ~ 350 -400. The MPSA18 is way higher, 800+.
You know how it is with cross references...they're many times ridiculous. Coincidentally, I did use a 2N3906 for Q2 with a gain of around 200 - 250. Note that my vintage ones are in the 100 - 150 hfe range. I have no idea why you're thinking about a germanium there. I doubt it'll bias well.
according to the analogguru schematic, Q2 would be cool with BC309B, which has min hfe 250.
http://analogguru.an.ohost.de/193/schematics/Heathkit_TA-28.gif
I did try many different Q2's before deciding on the 2N3906.
Quote
gonna build it at some point just for sh*ts and grins...
just thought i'd share...was mighty nice of them to provide enough info to not need to build the pedal. ;)
if anyone whacks it together, please let me know!
yah, you know i'm gonna try it with a 9volt.
There are a couple things that are unusual about that pedal...It uses an NPN / PNP combo and it's a 1.5V silicon...so it'd be sacrilege to change to 9V...the 1.5V is part of the fun! just kidding...you should always try everything.
Quote
Electron Tornado:
As for how the example I have sounds, it's a sort of fuzzy overdrive, but there is a volume cut with it engaged. It needs another amplifier stage at the end.
When tweaking, I noticed it was not loud enough and there was a simple fix. Just lower or remove the 10K before the tone control. I actually wound up putting a 10K pot there.
I also used a switch between the original input cap and a .033uF which smoothens out some of the raspiness when the drive (50K) is higher up.
Anyway, here's my final version with voltages & notes. If Electron Tornado could post voltages from the original, that'd be killer.
(http://www.luciferstrip.com/fuzz/heathkit-fuzz-final.jpg)
Quote from: Electron Tornado on September 08, 2012, 02:31:25 AM
Quote from: pinkjimiphoton on September 08, 2012, 01:46:23 AM
thinking maybe try a diode clipper on the output to get it a little louder.
If you mean adding some clipping diodes between signal and ground (like a Dist +), that will just cut the signal more, and you'll really need the extra booster stage on the end.
This pedal has been discussed elsewhere on here, so it might be helpful to check out those discussions.
it has been discussed? cool; i did a search but only got one or two hits.
i was thinking maybe an led clipper at the end of the circuit would boost it up some...thanks for the insite.
i love weird old fuzzes, is the volume drop that severe that it will need another stage ET?
thanks!
Quote from: LucifersTrip on September 08, 2012, 03:40:11 AM
Quote from: pinkjimiphoton on September 07, 2012, 09:06:23 PM
hi guys,
was surfing around evilbay earlier, and spotted this...
hey jimi!
cool to see you're still looking out for the odd fuzzes.
I built that one a while ago from the same schematic:
http://www.muzique.com/schem/heathkit.gif
To my ears, it is most similar in sound to the Sam Ash Fuzzz Boxx/ Astrotone...but better. It's one of the few 1.5V fuzzes that are silicon. Still my favorite is the Sun Buzz...
hi lu! cool, i had seen the schem in passing, but looking at it made me want it.... you know how THAT trip is!! ;)
Quote
so i looked up the transistors, to see what would sub, and it came up mpsa18 for q1, and our old friend 2n3906 for q2. i decided to suggest germanium there, but pretty much anything should do i would imagine.
Quote
I actually had some vintage 2N3391's laying around, which had hfe's ~ 350 -400. The MPSA18 is way higher, 800+.
You know how it is with cross references...they're many times ridiculous. Coincidentally, I did use a 2N3906 for Q2 with a gain of around 200 - 250. Note that my vintage ones are in the 100 - 150 hfe range. I have no idea why you're thinking about a germanium there. I doubt it'll bias well.
350 - 400 i can do...tons of silicon trannys in that range. i thought it seemed a little odd to reccomend the A18....IME they are way too hot for a lot of things.
i was thinking ge for q2 to try it,i often will try and put a germ in where i can cuz i just love the sound of them, so far, it seems to be more stable messing with q2 in a lot of circuits than q1.
thanks for the advice! i love hybrids lately...building a LOT of fuzzfaces like that. this thing was screaming harmonic percolator at me for some reason...tho i realize it's not related. i guess it was the way the input was wired. anyways... ;)
Quote
according to the analogguru schematic, Q2 would be cool with BC309B, which has min hfe 250.
http://analogguru.an.ohost.de/193/schematics/Heathkit_TA-28.gif
I did try many different Q2's before deciding on the 2N3906.
that's why i was thinking GE...i have a bunch of lo hfe mp16b's still, and they often sound great instead of an 06...but good to know the 06 worked out for you.
that'll simplify things some when the time comes to build it! ;)
Quote
gonna build it at some point just for sh*ts and grins...
just thought i'd share...was mighty nice of them to provide enough info to not need to build the pedal. ;)
if anyone whacks it together, please let me know!
yah, you know i'm gonna try it with a 9volt.
Quote
There are a couple things that are unusual about that pedal...It uses an NPN / PNP combo and it's a 1.5V silicon...so it'd be sacrilege to change to 9V...the 1.5V is part of the fun! just kidding...you should always try everything.
i liked the npn/pnp combo...these kind of fuzzes always have a "unique" sound to them... i WILL try it at 9 v, but i don't expect it to sound very good!!! figure i'd have to really mess with the biasing most likely. i'll report back if i do mess with it! ;)
btw, remember one time i had said something about having to flip trannys 180 degrees? this was one of the kind of circuits i was talking about...if ya notice, q2 is opposite of q1's pinout. i guess i didn't know how to explain it that well back then!! ;)
Quote
Electron Tornado:
As for how the example I have sounds, it's a sort of fuzzy overdrive, but there is a volume cut with it engaged. It needs another amplifier stage at the end.
When tweaking, I noticed it was not loud enough and there was a simple fix. Just lower or remove the 10K before the tone control. I actually wound up putting a 10K pot there.
I also used a switch between the original input cap and a .033uF which smoothens out some of the raspiness when the drive (50K) is higher up.
Anyway, here's my final version with voltages & notes. If Electron Tornado could post voltages from the original, that'd be killer.
(http://www.luciferstrip.com/fuzz/heathkit-fuzz-final.jpg)
[/quote]
that's awesome lu!! do you mind if i add that info on to the vero i did?
may try and hit this thing tonite...appreciate the info...
electron tornado, voltages would indeed be sweet!!
thanks guys!
EDIT
thats excellent Jimi , good work bro .
i am just gonna throw this out there , i am guessing they designed it for a AA cell , was cost .
9 volt batts were more expensive , i am sure there are quite a few here that remember the radio shack battery club . did anyone ever get anyting BUT the free 9 volt ? who would , lol .
i think i still have one of those floating round here , a green radio shack 9 volt battery ...
remember when realistic tagged the moog synth and they had one you could mess with in the showroom ?
or how about the trs-80 w/ speech synth module , you could type in " radio shack sucks " and make it loop with dos .
good times .
i know this is really off topic , but i just cant stop now , morning coffee is kicking in so i apologize in advance . here is a great one to do in best buy , if you have the balls .
go to the karoake machine isle , ( this works well with 2 or more offenders ) test all the machines to make sure the mics work , and turn the echo up all the way , shut them off . they should have at least a half dozen models from small to pretty large , make sure you utilize every single ione for it to work properly . now prop the mics up to the speaker grilles and crank all the volumes to max . synchronize your watches , and throw all the power switches simultaneously then walk away as gracefully as possible .
trust me , its freakin awesome , you WILL get asked to leave , but man is it worth it . extra bonus points are possible if you have enough people to activate ALL of the casio demos , at full volume of course , at the same time , or as an encore , if you get away with it the first time and really want to get caught .
Quotei am just gonna throw this out there , i am guessing they designed it for a AA cell , was cost .
9 volt batts were more expensive , i am sure there are quite a few here that remember the radio shack battery club . did anyone ever get anyting BUT the free 9 volt ? who would , lol .
I built a 9v version without the tone control. Just for fun :)
mac
Quote from: LucifersTrip on September 08, 2012, 03:40:11 AM
When tweaking, I noticed it was not loud enough and there was a simple fix. Just lower or remove the 10K before the tone control. I actually wound up putting a 10K pot there.
I also used a switch between the original input cap and a .033uF which smoothens out some of the raspiness when the drive (50K) is higher up.
Anyway, here's my final version with voltages & notes. If Electron Tornado could post voltages from the original, that'd be killer.
I can check the voltages on the actual pedal later this evening. There are voltages labelled on the Heathkit schematic in Jimi's first post above, if that helps. Q1 collector and Q2 base should be at the same voltage (1v), and Q2 emitter is 1.5 volts, in case it's not obvious.
I had this on the breadboard a while back and found it sounded better with a single transistor stage at the input. Off-hand, I don't recall whether I used a buffer or amplifier. It seemed to do a better job of playing well with others.
Here's something else I wanted to try with this. Take the notch filter circuit from the Univox Superfuzz and a DPDT switch to switch between the normal tone control and the notch. If I recall, my idea was to use a dual gang pot for the tone control, so you could also tweak the notch. I'm not sure just how tweakable the notch filter would be, however.
Come to think of it, I recently heard a pedal by Jetter that kind of reminded me of the TA-28. I don't recall which one, though.
Quote from: Gus on September 08, 2012, 11:24:42 AM
EDIT
hi gus, thank god i got the email with this post in it...
i like your idea, i'll try running it at 3v...maybe with a lithium coin cell!!
and sub out the 82k for a 100k trimmer, and see what happens.
probably not today, but soon..so stay tuned my friend! ;)
Quote from: pinkjimiphoton on September 08, 2012, 09:10:33 AM
350 - 400 i can do...tons of silicon trannys in that range. i thought it seemed a little odd to reccomend the A18....IME they are way too hot for a lot of things.
i was thinking ge for q2 to try it,i often will try and put a germ in where i can cuz i just love the sound of them, so far, it seems to be more stable messing with q2 in a lot of circuits than q1.
thanks for the advice! i love hybrids lately...building a LOT of fuzzfaces like that.
preaching to the germ choir! I still build primarily ge stuff, but the odd silicon one catches my eye. I usually do try germs in si fuzzes that are harsh or very trebly and ones that look like the biasing scheme wouldn't have to be altered too much.
I thought this sounded pretty cool stock so I didn't screw around (except for the volume jack), but if I do build this again, I'll try 100% germanium.
Quote
that's awesome lu!! do you mind if i add that info on to the vero i did?
you can always do anything with any of the info I post anywhere...
Quote
may try and hit this thing tonite...appreciate the info...
like I always say...the more fuzzes, the better...
I have an excel-based bias calculator for this if you want to experiment with vcc.
mac
Quote from: Electron Tornado on September 08, 2012, 12:33:01 PM
I can check the voltages on the actual pedal later this evening. There are voltages labelled on the Heathkit schematic in Jimi's first post above, if that helps. Q1 collector and Q2 base should be at the same voltage (1v), and Q2 emitter is 1.5 volts, in case it's not obvious.
thanx & damn, I actually breezed over that since I already had the schematic...and damn again...It's looks like my fuzz ear is pretty good. I'm really close to the posted voltages.
() = on orig
Q1
.35 (.36)
.86 (.87)
.97 (1)
Q2
.97 (1)
1.20 (1.30)
your orig voltages would still be cool if you have the time...
Quote from: petey twofinger on September 08, 2012, 12:01:42 PM
i am just gonna throw this out there , i am guessing they designed it for a AA cell , was cost .
that could very well be...and whether the reason they give in the add is bull or not, who knows:
http://i605.photobucket.com/albums/tt137/pinkjimiphoton/Heathkit_Ta28_fuzzbooster.jpg
but one of the coolest things I've always loved about 1.5V fuzzes is not having to worry about the battery. I just checked the voltages for mine, which has had a battery in there for ~ 2 years and it measures 1.53V
edit:
speaking of 1.5V, I use these leds (they are not super bright, but work good enough) for my 1.5V fuzzes
http://www.futurlec.com/LED/LED2PINRpr.shtml
since they're the only ones (and the only color of those type) that I have found that can light at 1.5V without any "pump"
QuoteI have no idea why you're thinking about a germanium there. I doubt it'll bias well.
Add a silicon diode after both emiters to simulate a silicon tranny voltage drop, and bypass them with a large cap. That and a little tweak of the original network will do it... if leakage is very low :)
mac
curious about that ad so i googled - $18 1970 dollars in todays money would be around $100 - does that make the heathkit a relative boutique? :P
http://www.measuringworth.com/m/calculators/uscompare/ (http://www.measuringworth.com/m/calculators/uscompare/)
Quote from: mac on September 08, 2012, 03:50:55 PM
I have an excel-based bias calculator for this if you want to experiment with vcc.
mac
i sooooo don't have a clue how to use excel. ;)
Quote from: pinkjimiphoton on September 08, 2012, 05:54:15 PM
i sooooo don't have a clue how to use excel. ;)
get that printed on a t-shirt and where it with pride.
:icon_mrgreen:
lol... i likes it...
Quote from: mac on September 08, 2012, 03:50:55 PM
I have an excel-based bias calculator for this if you want to experiment with vcc.
I'm interested in taking a look at that.
Quote from: LucifersTrip on September 08, 2012, 03:53:23 PM
your orig voltages would still be cool if you have the time...
OK, here are the voltages from the pedal itself:
Supply voltage was a fresh battery and read 1.5 V. All voltages are measured with respect to ground.
Q1 C = 1.0v
B = 0.60v
E = 0.31v
Q2 C = 1.15v
B = 1.0v
E = 1.5v
On the schematic, the Q1 base voltage is listed as 0.87v.
More from the Heathkit manual: from the input, "...the signal is coupled through capacitor C1 to the base of amplifier transistor Q1. The amplified signal from the collector of Q1 is direct-coupled to the base of overdriven amplifier Q2. This amplifier is so named because it operates in such a manner that a small signal will either saturate it or cut it off. In either state, harmonic distortion is added to the signal that is passing through the stage."
From that, it sounds like much of the tone is determined by the signal level of the output from Q1 and the clipping characteristics of Q2.
Now someone just needs to post a table comparing the specs on the suggested subs for Q2.
ET...excellent. thanx alot for posting em!
QuoteI'm interested in taking a look at that.
In my gallery, follow this link,
http://www.aronnelson.com/gallery/main.php/v/mac/apps/9v+Heathkit+TA-28.xls.html (http://www.aronnelson.com/gallery/main.php/v/mac/apps/9v+Heathkit+TA-28.xls.html)
Depending on your system, you have to use period or comma as decimal separator.
mac
thanks mac. ;)
gonna give this thing a go....soon as i finish typing this. found the 3391's at tayda, so i ordered 30 of 'em...will swap 'em in when they arrive.
will letcha know how i make out, guys
wellp, i built it, the vero is good...
the mpsa18 works great in q1...i tried a couple germaniums in q2, but the best sounding transistor i have there is a 3906.
tried it at 9v...ummm...needs the bias played with.
i didn't find it to be quiet at all, but the tone control works almost more like a volume control...kinda like the "attack" control on a tonebender.
so the 10k resistor before the tone stack is good.
at 1.5 volts, it actually sounds really good!! very fuzzy, a lot of sag, useful into a clean or dirty amp. nice sustain, tho at times if ya really lean on it, it begins to sound like many really classic
cheap-ass fuzzes like the kay. i mean that in a cool way!!
right now i got the AA soldered to the power supply...heh heh...i'll get a AA holder tomorrow. gonna try it with a 3v lithium coin cell, too...it was almost useable at 9v, so 3 v it may be ok with....and a cr2032 oughta last about ...oh....the rest of my life span. ;)
very nice sounding little fuzz...the fuzz control doesn't go all the way to 0, and the tone control is pretty weird.. but not bad!!
(http://i605.photobucket.com/albums/tt137/pinkjimiphoton/314118_4197182260739_1460897670_n.jpg)
Quote from: pinkjimiphoton on September 10, 2012, 12:42:05 AM
i didn't find it to be quiet at all, but the tone control works almost more like a volume control...kinda like the "attack" control on a tonebender.
...then something's gotta be a bit off. the tone has a nice sweep from bass to treble with little volume change..
Quote
so the 10k resistor before the tone stack is good.
yes, it just gets you to around unity...try with lower and see if you like. it didn't change the tone or character for me.
Quote
very nice sounding little fuzz...the fuzz control doesn't go all the way to 0
note the 3.3K
...it does get more broken up as you increase that control, as I wrote earlier, if you want to smooth out that break up when the level is maxxed, decrease the input cap.
Quote
and the tone control is pretty weird.. but not bad!!
double-check that...and see if your voltages are close. it's not weird.
edit:
If you're looking for more output from the circuit don't forget about the two 1K resistors to ground on either of the tone control. Increase them a bit and you'll get more output.
you beat me to it!...as you posted, I was just looking thru my notes and I found the thread. It seems people believed the two 1K's in the tone control could actually have been an error...and should have been 10K. That was the first thing I changed when I heard that vol drop.
I'll fix my final schematic...
edit:
funny, totally forgot about that old thread from a year and a half ago...hey, Electron Tornado was in on it, too
http://www.diystompboxes.com/smfforum/index.php?topic=90489.msg769429#msg769429
Final Configuration:
Q1: 2N3391, hfe = 305
Q2: 2N3906 hfe = 265
Replace 2 x 1K's with 10K's
Replace 10K with 10K pot
Switch to choose between .1uFd and .033uFd input cap
Quote from: LucifersTrip on September 10, 2012, 02:16:12 AM
you beat me to it!...as you posted, I was just looking thru my notes and I found the thread. It seems people believed the two 1K's in the tone control could actually have been an error...and should have been 10K. That was the first thing I changed when I heard that vol drop.
Those resistors have been a point of discussion before, but the 1k value in the Heathkit schematic agrees with both the parts list and the assembly instructions in the manual. So they might not be a mistake as such, but using 10k might just be a great mod.
Here are some other specs according to Heathkit. These are all with the fuzz control at max.
Input impedance - 28k Ohms
Sensitivity - 30mV rms for a balanced output
Voltage output - 45mV into 10k load at 100Hz output
the clip sounds pretty much just like the one i built...thanks bro.
i will check the tone part out, and get some voltage readings while i'm at it...
gimme a little bit! ;)
i MAY have confused the tone and volume pots...was late :icon_mrgreen:
let me see what i got...everyone is up now, so i can make a little noise! ;)
AHA!!! found a mistake... i made the 1k resistor off the 22n cap 10k...that may explain why the tone stack is acting weird.
i'll probably just go with the pair of 10k's...as one side of the tone control seems much louder than the other.
thanks guys..will update the vero when i can...
There's been some speculation that this may be related to the onboard fuzz built into the Messenger guitar used on the early Grand Funk albums.
hi guys,
swapped out that one resistor,
now the tone control seems to work perfectly, nice sweep from treble to bass.
here's the voltages with a 1.5v alkaline
mpsa18
q1
e .98
b .83
c .30
2n3906
q2
c 1.55
b .98
e 1.10
this thing sounds really good... pretty high gain!! may have to add a snubber, cuz it's picking up some RFI, but it's not boxed yet.
will try and record a clip shortly
Quote from: Electron Tornado on September 10, 2012, 09:20:30 AM
Quote from: LucifersTrip on September 10, 2012, 02:16:12 AM
you beat me to it!...as you posted, I was just looking thru my notes and I found the thread. It seems people believed the two 1K's in the tone control could actually have been an error...and should have been 10K. That was the first thing I changed when I heard that vol drop.
Those resistors have been a point of discussion before, but the 1k value in the Heathkit schematic agrees with both the parts list and the assembly instructions in the manual. So they might not be a mistake as such, but using 10k might just be a great mod.
Here are some other specs according to Heathkit. These are all with the fuzz control at max.
Input impedance - 28k Ohms
Sensitivity - 30mV rms for a balanced output
Voltage output - 45mV into 10k load at 100Hz output
The .022uf cap and 1k resistor form a highpass filter with an 8khz corner frequency, where using a 10k resistor gets you an 800hz corner frequency. Which would you prefer when you turn the tone pot all the way to the treble side?
Those wishing to "muff it up" might consider placing a cap in parallel with the 10k resiastor on the non-treble side of the tone control. For example, a .01uf cap gets you a rolloff starting around 2.3khz, which will yield a rounder tone. Given that shaving off treble tends to reduce apparent loudness, you might want to up the value of the 10k to ground to 12k or even 15k for less attenuation.
By the way, I'm curious. What does the contemporary pedalboard user power this with? Do you rely on an AA, or use an external supply and drop it, via suitable zeners?
Quote from: DougH on September 10, 2012, 01:26:41 PM
There's been some speculation that this may be related to the onboard fuzz built into the Messenger guitar used on the early Grand Funk albums.
That was discussed some time ago, and confirmed that it wasn't the Heathkit fuzz. The Messenger fuzz is completely different.
Quote from: Mark Hammer on September 10, 2012, 02:41:12 PM
By the way, I'm curious. What does the contemporary pedalboard user power this with? Do you rely on an AA, or use an external supply and drop it, via suitable zeners?
I've seen at least one person use a AA battery. When I can get back to working on this circuit I plan on using 9v with diodes, both so I can use external power, and because I still think it needs a booster stage on the end.
Mark, what's your opinion of adding a buffer to the front end to increase input impedance?
i'm just using an AA battery on mine.
i don't know enough about diodes to run it at 9v, would i use a 1.5v zener or something?
i AM gonna probably add a small pf cap to nuke the rfi i'm getting....
that said, here's the corrected, verified vero layout:
(http://i605.photobucket.com/albums/tt137/pinkjimiphoton/HEATHKITTA28FUZZBOOSTER-1.png)
ok, boxing it now...
gotta definitely do a little mod... it's just below unity when pegged.
can't run an led, either!! 1.5 v just barely turns the led on. ;)
Quote from: pinkjimiphoton on September 10, 2012, 06:06:23 PM
ok, boxing it now...
gotta definitely do a little mod... it's just below unity when pegged.
can't run an led, either!! 1.5 v just barely turns the led on. ;)
I would do a Zener mod, as Mark suggested. Actually, two standard 1N400X diodes in series (roughly 0.7V each) is a 1.4V zener. Close enough. Just set it up like the Vocalizer. Then you can either use a 9v battery, or power supply, and have your LED as well.
Cake, fork, mouth, eat.
I agree with doing the diode thing. Look at the Fuzz E-One at Small Bear and see how Steve did the power supply: https://www.smallbearelec.com/Projects/FuzzE-One/FuzzE-One.htm (https://www.smallbearelec.com/Projects/FuzzE-One/FuzzE-One.htm)
Quote from: Electron Tornado on September 10, 2012, 08:56:33 PM
I agree with doing the diode thing. Look at the Fuzz E-One at Small Bear and see how Steve did the power supply: https://www.smallbearelec.com/Projects/FuzzE-One/FuzzE-One.htm (https://www.smallbearelec.com/Projects/FuzzE-One/FuzzE-One.htm)
Poifect!!
I threw one together on perf. Took all of a half hour. I used a 2N3391 with an hfe of 330 or so, and a BC308B of unknown hfe (legs too short to make contact with meter socket). Input cap was .1uf, and 10k resistors to ground on tone control. Sounded okay - aggressive and hairy - but very sputtery unless you played a chord.
I had used a pair of 1N4001 and pair of 1N5817 in series as my fake zener to get close to 1.5V, and it seems the 5817s did not like that one little bit. They got very hot. I'll go back to a trio of 1N4001s and see if that holds up better.
> fake zener to get close to 1.5V, ... got very hot.
What value resistor in series with the zener and battery?
If you put a lo-volt zener right across a 9V battery, sure it will get HOT, and the battery will go flat real quick.
I posted this IDEA in the past for an adjustable 9VDC to 1.5VDC
(http://www.aronnelson.com/gallery/main.php?g2_view=core.DownloadItem&g2_itemId=39853&g2_serialNumber=2)
Quote from: PRR on September 10, 2012, 10:55:36 PM
> fake zener to get close to 1.5V, ... got very hot.
What value resistor in series with the zener and battery?
If you put a lo-volt zener right across a 9V battery, sure it will get HOT, and the battery will go flat real quick.
Unfortunately, I didn't use ANY resistor, not having looked at the suggested example from Steve Daniels beforehand ( :icon_redface: ). What resistor value would you suggest?
thanks guys, i will look into it and see if i can work it up today while g is at school..
looks easy enough, i gotta run to rat shack and get some 914's tho, i can't believe i am out of 'em.
i DID use it last nite, just to try it out, it's not real dynamic, and seems to suck ALOT of tone out of the signal chain when engaged.
even with the 2 10k's replacing the 1k's in the tone circuit (and i paralleled another 10k under the circuit board on the 10 k feeding the tone stack) it's still not quite ballsy enough.
real close...i may try putting maybe a 2.2k there instead of 5 k.
but that said, it's a much nicer distortion than i expected, very very vintage sounding....pretty impervious to guitar knob changes, but great sustain and a different "sag" than 9 v pedals.
i will try to do the SPT video today while she's at school.
thanks brothers . :icon_mrgreen:
Quote from: pinkjimiphoton on September 11, 2012, 10:57:35 AM
even with the 2 10k's replacing the 1k's in the tone circuit (and i paralleled another 10k under the circuit board on the 10 k feeding the tone stack) it's still not quite ballsy enough.
real close...i may try putting maybe a 2.2k there instead of 5 k.
try it with 0K (removed or shorted). you'll get way more volume and more high end
Heres a clip of mine that I did a while back. Probably my Tele on the middle PUP selection, 1st time round both controls halfway, then tone to the bass side, tone to the treble side. Like Jim says, it doesn't turn right off on the fuzz control. I find that it sounds much nicer over the 1st 3rd turn of the fuzz dial, but I'm not into massive distortion, I just like a bit of grit and edge.
http://www.mediafire.com/?e1tz6wvdj3c44gn
Looking at my notes I'm using the 10ks to ground off of the tonestack. I have two of these myself and have sold a couple (one up on ebay at present), one with an LM317T regulator (mostly because I wanted an indicator LED) and one that I run off of battery. Its had the same battery in it for about two years. If I do another it will be battery with a power off switch. If anyone knows how to light up an LED from a 1.5v battery that would be neat :) Voltage doubler maybe?
Sounds daft, but I found it hard to fit an AA battery into a smaller sized box, so I build them in these:
(http://inlinethumb18.webshots.com/49489/2782194660102672897S425x425Q85.jpg)
(http://inlinethumb47.webshots.com/48942/2339148500102672897S500x500Q85.jpg)
Thats the one with the regulator. This is the battery one.
(http://inlinethumb26.webshots.com/49305/2940756150102672897S500x500Q85.jpg)
Quote from: LucifersTrip on September 11, 2012, 05:12:18 PM
Quote from: pinkjimiphoton on September 11, 2012, 10:57:35 AM
even with the 2 10k's replacing the 1k's in the tone circuit (and i paralleled another 10k under the circuit board on the 10 k feeding the tone stack) it's still not quite ballsy enough.
real close...i may try putting maybe a 2.2k there instead of 5 k.
try it with 0K (removed or shorted). you'll get way more volume and more high end
to my ear, 3.3 is perfect
check the link in this thread about using diodes
here's the vero i worked up...now can run from 9v batt or power supply
(http://i605.photobucket.com/albums/tt137/pinkjimiphoton/17vpowersupply.gif)
Quote from: kaycee on September 11, 2012, 05:48:09 PM
If anyone knows how to light up an LED from a 1.5v battery that would be neat :)
there are many ways...as I mentioned earlier in this thread, I use the easiest (they're not super bright but cool enough for an indicator):
http://www.futurlec.com/LED/Red_2mm_LED.shtml
then there's:
http://www.metacafe.com/watch/943296/one_aa_battery_led_lamp/
this:
http://farm4.static.flickr.com/3622/3324388279_83b9a99623.jpg
and this (which looked the best, but couldn't find em in small quantities...haven't looked recently):
http://www.muzique.com/news/not-a-joule-thief/
So I changed the supply arrangement on mine to the same thing Steve Daniels uses for the Fuzz E-One ( https://www.smallbearelec.com/Projects/FuzzE-One/FuzzE-One.htm ): a 100k resistor and three 1N4001s in series to ground.
The sputter is absolutely gone. The distortion intensity is toned down a lot, though, so I may opt for a smaller current-limiting resistor as well as reducing the 10k just ahead of the tone control.
Effective tone control, though, I must say. Worth exploring for Big Muff users or other circuits using the same sort of tone control. Sometimes you don't want searing to be replaced by muffled. Sometimes you just want a little more body without quite as much sizzle.
mark, try a 10k resistor there like in the vero i posted instead of 100k.
i have ZERO change in tone, other than being slightly brighter on a wart than on a battery...the distortion stayed remarkably the same.
i used a 4739 zener or shotke or whatever them things are called. worked like a charm.
i took out the AA battery holder and batt right out of the equation, just hooked up a normal 9v 2.1mm jack, and opted for a 9v battery snap as well as the little daughter board..can run on battery or standard power supply.
it is a lot BEEFIER sounding on 9v imho...probably just because with more power, it's a more stable supply i'm thinking?
i noticed i could overload the AA in it and make it sag some when i was really beating on it.
all that said, a 3.mm led will light just enough so you can almost see it in a dark room at 1.5v.. just a dim glow. but ya don't need a CLR for it. ;)
Quote from: pinkjimiphoton on September 12, 2012, 12:52:02 PM
all that said, a 3.mm led will light just enough so you can almost see it in a dark room at 1.5v.. just a dim glow. but ya don't need a CLR for it. ;)
Try powering the LED from the 9v section, not the 1.5v.
lol...no worries, ET, i got it powered from the 9v supply. but i DID try to power it from 1.5v..before converting it yesterday to 9v.
at 1.5, it just barely glows...almost imperceptibly! ;)
100k changed to 10k, and its AOK. :icon_biggrin:
Removed the 10k just ahead of the tone control and got more output.
The tone is decent now. Pitted it against the Tonebender Mk III I made, and while it sounds a little different, is every bit as agressive and a little woolier, compared to the Tonebender's "throatier". I just need to figure out how I'm going to adjust the volume.
Thanks for all the tips, folks.
This past year has been a real Heathkit year/ Last year I bought a TA-16 amp, and a couple months back I bought a TA-17 amp that needs a little bit of work. And now I have a TA-28 clone. Sheesh, all I need is a Harmony Rocket and it's 1968 all over again!
mark, try about a 3.3k just before the tone stack...or a 5-10k trimmer...you'll find the sweet spot where with the fuzz control off, it's unity gain, and then you can roll up the filth.
i am really digging this little pedal!!
i gotta thank the guy on ebay for posting it!! lololololol!! :icon_twisted: :icon_twisted:
here ya go, another episode of STUPID pedal tricks...
today's attractive little device is the heathkit fuzzbooster...
QuoteSheesh, all I need is a Harmony Rocket and it's 1968 all over again!
Mark, shouldn't that read "
Hasheesh, all I need is a Harmony Rocket and it's 1968 all over again!"
:icon_lol:
I was thinking that at 1.5v q1 is biased close to 2/3 vcc, but at 9v q1 operating point is close to vcc, ie 8.4v, so I'd expect different distortions in both cases.
Near vcc distortion "looks like" octave up. Just a thought.
mac
Quote from: LucifersTrip on September 12, 2012, 05:08:41 AM
Quote from: kaycee on September 11, 2012, 05:48:09 PM
If anyone knows how to light up an LED from a 1.5v battery that would be neat :)
there are many ways...as I mentioned earlier in this thread, I use the easiest (they're not super bright but cool enough for an indicator):
http://www.futurlec.com/LED/Red_2mm_LED.shtml
Thanks, I'll have a look around.
mac, that's way over my head...are you suggesting that at 9v you could get an octave up effect?
i DID try it at 9v, but it sounded real farty, and i didn't want to have to change the circuit to get it to bias.
total hack newb here bro!!
You know, I thought that the TA-28 was the same distortion a high school buddy of mine had made back in the day, to go with his Heathkit amp. But trading e-mails with him today, I learned that it was NOT, in fact a Heathkit fuzz, but an Allied Radio unit he had bought from Chicago. At the time, from what I understand, Allied and Knight were effectively the same.
The effectsdatabase shows a Knight fuzz here. Clearly not the same. Note the diode pair off in the corner. can't see the transistor or caps clearly but do those resistor values ring any bells?
(http://files.effectsdatabase.com/gear/pics/knight_kg-389_003.jpg)
ff with a diode clipper?
Not with a pair of 2M2 resistors in there.
I'll keep looking through my files of 2-transistor fuzzes for something using those values.
Quote from: Mark Hammer on September 14, 2012, 04:32:09 PM
Not with a pair of 2M2 resistors in there.
I'll keep looking through my files of 2-transistor fuzzes for something using those values.
I had this bookmarked
(http://www.ampage.org/schematics/knfuzz.gif)
Wow! If that isn't it, I don't now what is!
The transistors still remain unidentified, but there aren't all that many candidates in the button style from that era. I'm guessing 2N3565 or maybe even the EHX favourite - 2N5133.
Thanks. I owe you one....and I think I'm gonna build one tonight.
Okay, built. For some reason, the 2N3565 button-types I had in the bin had hfes under 100, so I thought better of it and simply used a pair of 2N3904s that were in the mid-100s. I'm kind of kicking myself that I didn't wire up sockets to swap out transistors, but so be it. The diodes are unspecified type that I believe are germanium (I think from a Radio Shack "variety pack") but have a forward voltage around 350mv or so. The input has a 470k fixed resistor feeding the input of a 100k pot. I figured I'd make it a little more sensitive by using a 250k pot with a 330k fixed resistor in series.
An interesting sound. Not a fuzz, as such, but certainly not a conventional overdrive sound. Really more of a growl than a fuzz...and that's using a Tele. Thicker-sounding with humbuckers. Listening to it again, the sound that immediately came to mind was Stephen Stills' (or maybe it was Neil Young's) distorted tone on the Buffalo Springfield tune Bluebird http://www.youtube.com/watch?v=55q2rRh5UUU&feature=related (Jeez what a great tune; holds up well).
I thought I might want to stick a cap in parallel with the diodes to tame any potential excessive treble but the 1500pf base-to-collector cap takes care of all that. An input pot and volume pot are just fine.
Not for everyone, but worth building.
Put a cap on the first transistor between collector and base and it kind of looks similar to a BMP with the diodes at the end. What does a BMP sound like with hard clipping?
Here's a question - the schematic doesn't show what transistors are being used. Assuming they are both being used simply as amplifiers to get maximum gain, and that most (if not all) of the clipping is meant to come from the diodes, and given the other compnent values, input power, and input signal level, can one make an educated guess at the transistors' specs and use those to come up with likely devices to use?
L ooking at the schematic, I'm guessing both transistors are the same.
I hate typing on an iPad.
Quote from: Mark Hammer on September 14, 2012, 08:41:09 PM
Wow! If that isn't it, I don't now what is!
excellent...
Quote
The transistors still remain unidentified, but there aren't all that many candidates in the button style from that era.
Okay, built. For some reason, the 2N3565 button-types I had in the bin had hfes under 100, so I thought better of it and simply used a pair of 2N3904s that were in the mid-100s.
Definitely not nearly as many candidates as metal can, but I must have at least 15-20 different button numbers. Most that I have are form the mid to late 60's (I have one bag labeled 1964) and are one color, black. The hfe's of mine generally tend to be on the lower side (<100). But, I believe the ones in the pic you posted are a bit newer, which are black & white. When I have both black colored ones and black & white colored ones in the same #, the black & white ones are usually higher gains....and do have a newer look. The ones in my garage sale (#36) actually have gains 300 - 500:
http://www.diystompboxes.com/smfforum/index.php?topic=90624.msg864111#msg864111
Quote
An interesting sound. Not a fuzz, as such, but certainly not a conventional overdrive sound. Really more of a growl than a fuzz...and that's using a Tele.
Not for everyone, but worth building.
thanx for posting a report...I don't think I ever did breadboard that one, but might try real soon. Again, it would be cool if you could post your voltages as a reference. Did you screw with the biasing?
ps: we might consider a new thread instead of infiltrating TA-28
Quote from: Electron Tornado on September 14, 2012, 09:03:21 PM
can one make an educated guess at the transistors' specs and use those to come up with likely devices to use?
probably someone as good as PRR or RG could, but honestly, with those type of silicon fuzzes, it's pretty much all about the gain...and when you get to a certain point (~150-200), it doesn't make as much difference going much higher...
after building a sh*tload of vintage fuzzes, it's very common that the higher gains will just give you a bit harsher sound. every circuit is different, but many times I get a warmer sound with hfe's under 100, the best sound with vintage fuzzes in the 100-200 range, then an increase in harshness over 200...with, as I wrote before, small changes after that. Ie, there'll be a bigger difference in sound between hfe 50 & 200 and very little difference between hfe 300 and hfe 500. You can actually see this by taking voltages. You'll realize that there is a sharper curve from 50 - 200, then a much slower curve after that...
Quote
Looking at the schematic, I'm guessing both transistors are the same.
yeah, probably...check the pic above
Thanks, LucifersTrip, that's some interesting info on older fuzzes. I have a feeling that the design formula was to use cheap garden variety transistors and bias to taste.
Quote from: pinkjimiphoton on September 14, 2012, 03:37:12 PM
mac, that's way over my head...are you suggesting that at 9v you could get an octave up effect?
Someone posted long ago about transistors biased near vcc. Spice graphs showed how a transistor distorted the signal into something "similar" to 8-up. I use "..." because it was not exactly 8-up, just think of a cousin who is far away.
Besides I guess q1 has not enough gain to exhibit this "8-up".
If you want to hear the difference just breadboard a single transistor circuit sitting at 8.5v or so. Then take the output from HK q1.
Quotei DID try it at 9v, but it sounded real farty, and i didn't want to have to change the circuit to get it to bias.
total hack newb here bro!!
Use this values for 9v:
q1 - 270k, 56k, 27k, 5k6, 33k
q2 C should be near 6v or so.
mac
Quote from: LucifersTrip on September 14, 2012, 04:48:03 PM
Quote from: Mark Hammer on September 14, 2012, 04:32:09 PM
Not with a pair of 2M2 resistors in there.
I'll keep looking through my files of 2-transistor fuzzes for something using those values.
I had this bookmarked
(http://www.ampage.org/schematics/knfuzz.gif)
I could be wrong, but I think the input jack wiring is wrong. The tip seems to be going to the supply. ***in his best Sgt. Schultz voice "Ahhhh, but I know NOTHING!"***
I always ignore the jack wiring since I've done it so many times, but yeah, I don't think that would be the standard way of drawing it. I remember an old one that also caused confusion
http://www.montagar.com/~patj/mfuzrite.gif
Hey jimi, I built one of these way back in the 60's. It sucked. Might have been the way it was put together... :icon_razz:
it is what it tis... lol
Finally got mine done last week. I used a Radio Shack enclosure since it was cheap and available, and seemed to work out well with a previous build.
(http://imageshack.us/a/img594/6007/ta28.th.jpg) (http://imageshack.us/photo/my-images/594/ta28.jpg/) (http://imageshack.us/a/img39/7203/ta28andfuzzwright.th.jpg) (http://imageshack.us/photo/my-images/39/ta28andfuzzwright.jpg/)
Playing hard with the 0.1uf input cap in the circuit and the drive on full it will not only sag, but will actually cut out at times. Halving that cap might help prevent that, though 0.1uf is stock and can get some nice full fuzzy sounds playing single notes. Switching to the 0.0047uf cap is more crunchy, but less sustain, but playing with the tone control can give some great tones.
I used 100k pots for the tone and volume since I already had them on hand. If I were to build another I might go for 50k for the volume, but 100k works well for the tone control.
I eliminated the 10k resistor on the output of Q2 for more output.
The pedal plays well with others and plays great with a wah.
Here's my final schematic:
(http://imageshack.us/a/img33/9916/heathkitta28modschemati.th.jpg) (http://imageshack.us/photo/my-images/33/heathkitta28modschemati.jpg/)
cool, thanks for the build report!!
if you run it on a 1.5v battery, it will indeed sag as you report...
if ya use the little daughterboard so you can run it at 9v tho, it probably won't...mine doesn't, anyways.
it is a nice little fuzz...so glad them peeps on ebay posted it. :icon_twisted:
Quote from: Electron Tornado on October 07, 2012, 01:47:33 PM
Playing hard with the 0.1uf input cap in the circuit and the drive on full it will not only sag, but will actually cut out at times. Halving that cap might help prevent that, though 0.1uf is stock and can get some nice full fuzzy sounds playing single notes. Switching to the 0.0047uf cap is more crunchy, but less sustain, but playing with the tone control can give some great tones.
(http://imageshack.us/a/img33/9916/heathkitta28modschemati.th.jpg) (http://imageshack.us/photo/my-images/33/heathkitta28modschemati.jpg/)
I'm kind of dragging up an old thread, but I'm still stumped about something.
After some fiddling, I opted for a 0.01uf cap for the input cap. With a 0.1uf, as used in the original TA-28, it will cut out when playing hard, especially on low strings. I ran it from a One Spot. Tested an original TA-28 using a fresh AA battery and it did the same thing.
Does anyone have any idea why it will cut out with a 0.1uf cap on the input?
Quote from: Electron Tornado on March 14, 2013, 03:00:21 PM
Does anyone have any idea why it will cut out with a 0.1uf cap on the input?
Mine doesn't cut out, but it does sag when that 50K up front is jacked. That was my only complaint when I first built it, so I wound up putting a switch between the original and .033, which is the smallest cap I liked before the tone changed too much.
The explanation was given by PRR:
http://www.diystompboxes.com/smfforum/index.php?topic=90489.msg769424#msg769424
"I suspect it would handle chords better (not great) if C1 0.1uFd were much smaller, even 0.01uFd. This with the treble-loading would bandpass a narrow slice of guitar spectrum, so the wide spread of partials on guitar chords did not intermodulate all over the audio band."
...and you're in that thread, too
Thanks for that link! I recall the discussion going over more than one thread, but when I searched, that one didn't come up. I still don't understand why it happens, though.
Quote from: Electron Tornado on March 15, 2013, 09:01:18 AM
Thanks for that link! I recall the discussion going over more than one thread, but when I searched, that one didn't come up. I still don't understand why it happens, though.
I think you can get the answer by reversing the above, but I'm not good enough to explain it.
.1uF is not bandpassing a narrow slice of guitar spectrum, so the wide spread of partials on guitar chords will intermodulate all over the audio band
I'm still not sure if that explains what's going on. It depends on what Paul meant by "handle chords". I took that to mean in the same way that a fuzz can sound bad when playing chords due to intermodulation distortion. The problem I'm having is that the signal will actually cut out briefly. Somehow the trons stop flowing for a millisecond.
Hmmm, come to think of it, I wonder if this is somehow an impedance issue, since impedance is frequency dependent.
You are just playing too hard. The simple transistor circuit will rectify large signals and de-bias itself.
Quote from: PRR on March 16, 2013, 09:56:15 PM
You are just playing too hard. The simple transistor circuit will rectify large signals and de-bias itself.
I don't think I'm playing particularly hard. I can turn the drive control down quite a bit and still have it cut out. The fact that the pedal is OK with an input cap of 0.01uf and cuts out with a 0.1uf cap sounds like a frequency dependent issue. Still a bit of a mystery to me.