Hello all!
I have just started my DIY pedal journey and been playing around with some different Bazz Fuss type circuits. I have access to a lot of old electronics at my work and have build this pedal out of completely recycled components (except the vero and case), I ended up settled on a nice sound using two BC337 transistors in a darlington configuration.
A friend suggested I design it so the effect has a wet/dry blend with the clean guitar signal so I preceded the Bazz Fuss circuit with a Split 'n' Blend found here:https://tagboardeffects.blogspot.com.au/2012/02/split-n-blend.html (https://tagboardeffects.blogspot.com.au/2012/02/split-n-blend.html) it mentions there that it will not work properly with inverted signals so I added another recycled transistor (2n4400) in order to un-invert the signal at the end of the Bazz Fuss circuit which worked great.
'
My only issue now is that it sounds like I have lost some of the balls of the original Fuzz, I don't believe it is the 2n4400 as I used an audio probe and it sounds the same before and after it. From my research the Bazz Fuss likes to have a high impedance input and the original home-wrecker page suggests using one side of a small audio transformer on the Bazz Fuss input. One side of the 42TM018 transformer has an impedance of 10k and according to here http://www.freestompboxes.org/viewtopic.php?p=148640#p148640 (http://www.freestompboxes.org/viewtopic.php?p=148640#p148640) the primary winding of the 42TM019 (also 10k) has an inductance of above 2H.
I have access to lots of small (680mH) inductors that I can recycle, my question is could I achieve the same effect of the audio transformer by having fourh of these smaller inductors in series on the input?
A transformer doesn't really have an impedance per se, but rather a turns ratio. The impedance ratio is the square of the turns ratio. But that's using both the primary and secondary.
(http://home-wrecker.com/dbf.png)
If you use only the primary as above, it's only an inductor, not a transformer.
Quote from: thermionix on February 13, 2018, 12:18:36 AM
A transformer doesn't really have an impedance per se, but rather a turns ratio. The impedance ratio is the square of the turns ratio. But that's using both the primary and secondary.
(http://home-wrecker.com/dbf.png)
If you use only the primary as above, it's only an inductor, not a transformer.
OK thank you, if I were to use that transfomer and only use the primary winding as show in the schematic, will that create a higher impedance input for the bazz fuss? I am unsure why else it would be included in the schematic.
Sent from my SM-G950F using Tapatalk
Yes. I'm sorry I should have quoted "One side of the 42TM018 transformer has an impedance of 10k" as I was only replying to that particular phrase. But yeah, the series inductor adds to the total impedance the circuit input "sees." And yes, I think you can add the 680mH inductors in series to mimic that. There's also DC resistance to factor in, but it quickly goes over my head at that point.
Quote from: thermionix on February 13, 2018, 12:34:56 AM
Yes. I'm sorry I should have quoted "One side of the 42TM018 transformer has an impedance of 10k" as I was only replying to that particular phrase. But yeah, the series inductor adds to the total input impedance the circuit "sees." And yes, you can add the 680uH inductors in parallel to mimic that. There's also DC resistance to factor in, but it quickly goes over my head at that point.
Awesome thank you! Yes I am aware of the small DC resistance that occurs in inductors.
Sent from my SM-G950F using Tapatalk
You quoted my "parallel" before I was able to edit it to "series"...I meant series, I guess you knew that.
Quote from: thermionix on February 13, 2018, 12:52:27 AM
You quoted my "parallel" before I was able to edit it to "series"...I meant series, I guess you knew that.
Yes I did pick up on that haha, thanks for your help.
Sent from my SM-G950F using Tapatalk
In theory, 3 X 680mH in series result in 2H equivalent inductance..
But you need some amount of impedance rather than a "bare" inductance value..
A reactive element, like inductor, exibits frequency variable impedance XL= 2*π*L*f, hence about 1k at 80Hz, 10k at 800Hz and so on..
At low to medium frequencies, 2H inductor adds practically nothing on 100k Thicknes pot at high pot value..
Instead of messing with 3 bulk/heavy/unpredictable transformers, place a phase inverter in your clean signal path..
(an amplifier with unity gain and input impedance similar to your own Bazz Fuss should do the job..) :icon_wink:
Quote from: antonis on February 13, 2018, 04:16:14 AM
In theory, 3 X 680mH in series result in 2H equivalent inductance..
Upon further inspection it looks like the inductors I planned to salvage are actually 680uH which is not going to cut it...
So are you saying that if I add another unity-gain transistor similar to the 2n4400 I added at the output of the bazz fuss, but on the clean input coming from the Split 'n' Blend, then it will provide the bazz fuss with a high impedance input signal?
If I am not mistaken this will also invert the input signal, which means the darlington pair bc377s will un-invert it, so I can just move the 2n4400 from the output to the input in order to not have phase cancellation with the clean signal blend.
;D
No, I'm saying to delete the "phase correction" transistor from Buzz Fuss output and place it to clean signal path..
Buzz Fuss (as any single/one stage BJT/FET amp) inverts signal (180o phase difference with income/clean signal..)
If you place such an inverter somewhere on clean signal path you'll result in same phase (0o/360o) singnals blending/mixing..
P.S.
If you place that inverter on Buzz Fuss input you maybe increase input impedance but you also add series frequency shift which may lead to oscillation problems..
If you want to raise input impedance, place a buffer in front of Buzz Fuss..
Quote from: Voltzy on February 12, 2018, 11:14:58 PMFrom my research the Bazz Fuss likes to have a high impedance input and the original home-wrecker page suggests using one side of a small audio transformer on the Bazz Fuss input. One side of the 42TM018 transformer has an impedance of 10k and according to here http://www.....org/viewtopic.php?p=148640#p148640 (//http:///viewtopic.php?p=148640#p148640) the primary winding of the 42TM019 (also 10k) has an inductance of above 2H.
I have access to lots of small (680mH) inductors that I can recycle, my question is could I achieve the same effect of the audio transformer by having fourh of these smaller inductors in series on the input?
Yes, the 680 microH that you have will be too low in value for proper operation. The inductance needs to be much higher. Most any small 10k:10k (or 10k:600) transformer should do the job, even if it is not the Mouser part.
The original article on the design that suggests using a small transformer is here: http://www.muzique.com/lab/pickups.htm
Best regards, Jack
My understanding is that the transformer helps to mimic pickup behaviour in case there was a buffered pedal in between the guitar and the bazz fuss, thus basically shelving off the highs and recovering some emphasis on a resonant frequency.
If you're playing guitar straight into the bazz fuss circuit then the transformer coil won't do much.
At least that's what I experienced.
And to be honest, when I put the bazz fuss after a buffered pedal, the transformer coil doesn't do much besides shelving off the highs. I don't really experience any balls recovering
Quotewhen I put the bazz fuss after a buffered pedal, the transformer coil doesn't do much besides shelving off the highs. I don't really experience any balls recovering
Oh right how interesting, it feels like before I had installed the buffer effect into the pedal the fuzz was huge and nasty where as now it sounds like the gain knob has been turned down half way (if I had a gain knob).
Here is a rough sketch of what I have built:
(https://s10.postimg.org/emu7sixd1/bass_f_v2.png) (https://postimg.org/image/emu7sixd1/)
The 15k res and 50nF shunt cap on the fuzz input form a low pass filter of around 245Hz (I hope), so when you say shelving off the highs I assume you mean it cuts them somewhat, which I am already doing with the low pass filter so I don't know if it would actually help.
QuoteNo, I'm saying to delete the "phase correction" transistor from Bazz Fuss output and place it to clean signal path..
OK now I understand what you are suggesting, I should move the 2n4400 and its two 10k resistors from the end of the fuzz to in between the split 'n' blend and leg 3 of the pot? Will this help?
I am beginning to suspect I am hearing the original fuzz tone through rose-tinted headphones, hopefully I will get a chance tonight to build the original Bazz Fuss again on my breadboard and I will compare the two.
I built another bazz fuss, without the extra phase inverting 2n4400 and the buffer/blend and compared the two and it does have a lot more fuzz and bite to it.
I thought that maybe I had not biased the phase inverting transistor properly, so I upped the collector resistor to 50k and left the emmiter resistor at 10k... And it did develop a more fuller sound but not the same crunch as the original circuit. I suspect it was boosting the signal a little. I was getting around 6.5V on the collector and 0.6V on the emmiter.
Could it be the 100K blend pot is actually letting through some small amount of clean signal, even when it is turned all the way to the fuzz side? Is 100Kohms enough to completely block the clean signal?
I will be picking up a small mouser audio transistor with a 10k winding tomorrow after work hopefully this fixes the problem.
Sent from my SM-G950F using Tapatalk
Quote from: Voltzy on February 13, 2018, 05:25:54 PM
QuoteNo, I'm saying to delete the "phase correction" transistor from Bazz Fuss output and place it to clean signal path..
OK now I understand what you are suggesting, I should move the 2n4400 and its two 10k resistors from the end of the fuzz to in between the split 'n' blend and leg 3 of the pot? Will this help?
I suggest something like this:
(more or less..)
(https://i.imgur.com/Z6yV6zc.png)
Items marked with red asterisk may be omitted in case of 33k input impedance for phase shifter is acceptable..
Clean Volume Pot may be part of 100kA dual gang one, also used for Buzz Fuss output Volume..
In case of you want to also use the low-pass filter for clean signal, split signals after the filter..
(cut-off point should be calculated taking in mind further effects impedance..)
Use of active FET splitter, like above posted, is left upon your taste.. :icon_wink:
edit: 50nF cap ground erased by mistake.. :icon_redface:
Frankly I'd rework the pedal to work well with whatever impedance at the input, equipment which is sensitive to impedance is a pain in the arse. I suspect that reworking the input filter may suffice, and anyway, instead of using just the primary of a small transformer, I'd rather actually use the transformer as such, it can be an interesting idea. Maybe at the output instead of the input too.
Quote from: fryingpan on February 14, 2018, 09:01:39 AM
instead of using just the primary of a small transformer, I'd rather actually use the transformer as such
Have you asked your guitar coils..?? :icon_wink:
Quote from: antonis on February 14, 2018, 09:07:36 AM
Quote from: fryingpan on February 14, 2018, 09:01:39 AM
instead of using just the primary of a small transformer, I'd rather actually use the transformer as such
Have you asked your guitar coils..?? :icon_wink:
Well the sound will change due to both inductance and capacitance (and, depending on where it is placed, on possible core saturation). My Epiphone Jack Casady has a transformer wired after a low impedance pickup (it measures around 13 ohms, not kohms, I think), it drastically changes the sound and it's actually nice (makes the sound warmer and thicker). Trying a small transformer (with a low primary to secondary ratio, such as 1:3, or selectable ratios even) after an input buffer (= low output impedance) could have nice effects on the sound. At the output it's probably even more interesting.
Quote from: antonis on February 14, 2018, 08:23:46 AM
Use of active FET splitter, like above posted, is left upon your taste..
Ah I see now, you were suggesting I remove the splitter all together, thank you.
If I had a non-inverting effect instead of the Bazz Fuss, then could I wire the effect output to leg 1 and the clean signal coming straight from the input jack to leg 3 with the output jack to leg 2, and it would work the same way? Why even have a FET splitter, what does it even do?
I am still going to pick up one of these transformers and I am thinking of recording some short clips to compare the different circuits.
Quote from: Voltzy on February 14, 2018, 05:14:03 PM
If I had a non-inverting effect instead of the Bazz Fuss, then could I wire the effect output to leg 1 and the clean signal coming straight from the input jack to leg 3 with the output jack to leg 2, and it would work the same way?
As far as we only deal with signal(s) phase, yes..
(see below..)
Quote from: Voltzy on February 14, 2018, 05:14:03 PM
Why even have a FET splitter, what does it even do?
It settles to "equilibrium" possible currents difference due to different paths impendance..
(it actually makes each path input(*) to be "seen" from other path's output(*) as a high impedance one..)
(*) Splitted signals should be considered in pararell so any individual input "sees" it's own load in parallel with other individual inputs impedances - same also stands for outputs on blending point..)
Ok thank you for your explanation I am beginning to understand. I have recorded a couple of different samples, I want to rebuilt it as you described above with just a phase inverter on the clean path and no FET splitter and then record one last sample.
If I build it like that, what can I do to protect the circuit from low impedance input? For example if I have a seperate buffered-effect pedal before it in the pedal chain (other than always having it first in the chain).
Sent from my SM-G950F using Tapatalk
QuoteOne side of the 42TM018 transformer has an impedance of 10k and according
Last time I tried to get the Inductance on that I ended up with an estimate of 2.65H and some people on the web were quoting 3H. Unfortunately I have not measured it.
OK I have finally made it sound like the original, with a blend knob.
Here is a video of the different sounds and the parts/layouts I went through:
https://youtu.be/BnGVQvV13M4
Quote from: antonis on February 14, 2018, 08:23:46 AM
I suggest something like this:
(more or less..)
This is exactly the circuit that I went with except I added the mini transformer between the input cap and where the signal splits.
:icon_wink: :icon_wink: :icon_wink:
Well done, Voltzy..!!
I'm trying to understand this datasheet, so I can decide which of my small transformers can be used here:
(https://i.postimg.cc/sBnDj300/hammond.gif) (https://postimg.cc/sBnDj300)
So it seems that 10k transformer has inductance of 6H? But why is this called 10k transformer, when it has 45.4k inductance at 1.0kHz???
I have a small GM328A transistor tester which can measure inductances too, and it shows 6H on a small transformer I got from an old modem. Will it be OK for this purpose?
QuoteSo it seems that 10k transformer has inductance of 6H? But why is this called 10k transformer, when it has 45.4k inductance at 1.0kHz???
The measured impedance of a transformer is always higher than the impedance spec. If the transformer was an ideal transformer it would have an infinite inductance and an infinite impedance. It would also have zero DC resistance as this represents a loss. That way the transformer has no effect on the circuit other than the change in voltage at the input and output due to the turns ratio.
For practical reasons transformers do have an impedance. The measured impedance of the transformer itself is always larger than the specified impedance. The inductance is usually worked out so it produces 1dB drop or so at the lowest frequency of the frequency spec. However you might seen anything from 3dB to 0.3dB. That transformer is 1.5dB.
Another weird thing you might notice is the inductance spec is 5.89H whereas if you calculate the inductance from 45.4k ohms you end up with 7.2H. I can't explain it. Normally differences can explained because of losses and DC resistance but it seems a large difference and both tests are done at 1V 1kHz. Another angle is one spec is typical and another max. Normally the impedance would be *min* and you would end-up with a smaller inductance than the typical.
God answer as always, Rob, but I'm still unsure about mini TF choice for bass fuzz and similar cirtuits? Is 6.0H OK, or we can go with some other inductance value, to achieve 10k impedance?
QuoteGod answer as always, Rob, but I'm still unsure about mini TF choice for bass fuzz and similar cirtuits? Is 6.0H OK, or we can go with some other inductance value, to achieve 10k impedance?
The final behaviour of the circuit will depend on the inductance and not the nominal impedance.
My best information is the inductance of the 42TM018 transformer is about 3H. That could actually be wrong.
If you have a 10k impedance transformer which is the same size and same DC resistance as another transformer there's a good chance the inductance will *roughly* be the same. It's very rough. Like the transformer you have fits this matching profile but the inductance is 6H which is quite a way off (assuming the 3H is correct.)
So you could just try it but if it isn't quite right it's obviously going to affect the sound. However that transformer gives you some tricky options. (Many are the same and there is little reason to choose between them without complicated hair-splitting measurements.)
Connection Inductance (approx)
1 & 3 6H
1 & 2 6H * (1/2)^2 = 6H * (1/ 4) = 1.5H
2 & 3 6H * (1/2)^2 = 6H * (1/ 4) = 1.5H
3 & 6 but join 2 & 4 6H (1/2 + 1/15.5)^2 = 6H*0.32 = 1.9H } in all cases
2 & 6 but join 1 & 4 6H (1/2 + 1/15.5)^2 = 6H*0.32 = 1.9H } we are joining a dot to a non-dot winding
1 & 4 but join 6 & 4 6H (1/2 + 1/15.5)^2 = 6H*0.32 = 1.9H } and the connection goes
2 &4 but join 3 & 6 6H (1/2 + 1/15.5)^2 = 6H*0.32 = 1.9H } between the outer dot and non-dot
1 & 4 but join 3 & 6 6H (1 + 1/15.5)^2 = 6H * 1.13 = 6.78H
6 & 3 but join 1 & 4 6H (1 + 1/15.5)^2 = 6H * 1.13 = 6.78H
The 15.5 is an estimate of the turns ratio. It's some where in the 15 to 16 mark.
So you can get 1.5H, 1.9H, 6H. You can't get exactly 3H.
So you could try 1.9H and 6H and see if you can hear a big difference.
Beyond that you could tweak the 1n and 2.2uF caps to compensate for the different L
A rough guide is to calculate: W = 1/(L_old*C_old) then C_new = 1/(L_new*W)
Hard to know if leaving the C's or tweaking to new ones will make a difference.
I honestly think the 1.9H option and maybe a cap tweak is going to be the closest option.
Thanks Rob, I actually didn't think to use THAT Hammond TF, just used datasheet as an example, but you however described the process in detail. I have few different small transformers, most of them are 600:600 isolation TFs. I will measure inductance and see if there's anything near 3H mark.
Quotemost of them are 600:600 isolation TFs.
If you find any have 0.75H on one winding you can connect the windings in series and get 3H.
One series connection will give a high inductance (~ 3H) but if you flip one of the windings you will get much less than 0.75H.