Big Muff Ram's head low gain question

[BramP]

Hi, so one of my recent builds is a Ram's Head Big Muff based on the layout on the Tagboardeffects site.

Now it sounds really wonderfull and creamy and all, it's just really low gain compared to sound clips I hear of this pedal.

The voltages on the transistors seem fine (could post them on request), they are 2N5089, as far as I understand the HFE of these transistors can vary between 400-1200 so could this just be a matter of having a 'bad' batch of low HFE ones? I currently don't own a transistor tester unfortunately.

Or are there other things I could try to get some more gain out of this pedal?

Hope to hear from you!

Bram

[pietro_moog]

I don't know what kind of sound you're after, but in my build i used 2n2222 hfe between 180 and 220.
It is very creamy and heavy, and it sounds much better that the others i had with higher gain transistor.
You should try

[bumblebee]

Hi, so one of my recent builds is a Ram's Head Big Muff based on the layout on the Tagboardeffects site.

Now it sounds really wonderfull and creamy and all, it's just really low gain compared to sound clips I hear of this pedal.

The voltages on the transistors seem fine (could post them on request), they are 2N5089, as far as I understand the HFE of these transistors can vary between 400-1200 so could this just be a matter of having a 'bad' batch of low HFE ones? I currently don't own a transistor tester unfortunately.

Or are there other things I could try to get some more gain out of this pedal?

Hope to hear from you!

Bram

Very unlikely it’s the transistors.

Go over your work, orientation of parts, and wiring with a magnification lens and check for mistakes, from first component to last. Trace it out. If it’s vero board then the likelihood of a solder bridge or misplaced cut etc is highly likely.

Big Muffs, even with 2N3904 and 2N2222 which are lower gain than 2N5089 and 2N5088 etc make high gain Big Muffs.

You can increase or lower the gain by choosing specific values of both the collector and emitter resistors but if there’s a problem, as there seems to be, this won’t fix that.

Also, please post the schematic you used. If you changed values of anything in the layout then post them as well.

I don’t post here with any frequency so I may or may not reply to you again. You should still do the above anyways as it’s standard debugging procedure.

[BramP]

Thanks for your reply, I've been doublechecking for solderbridges and resoldered any potential dead spots but so far not resulting in more gain. Now I've followed the veroboard layout as included. I also added a schematic of the Violet variant, which I know might slightly differ in some component values and a schematic from electrosmash that shows the biaspoints.

This last one is also a slightly different variant but I would assume that the measurements of the transistors are roughly the same for all variants? The biggest difference I found is that on the first transistor (named Q4 in the schematics and as far as I can tell is the bottom left one on the veroboard) the collector measures about 3.6 volts instead of the 7 mentioned.

How those the distribution of the 9V exactly occur here? It looks like it gets 'fairly' distributed through those four 12K resistors to the four transistors but that's where my understanding of electronics stops I'm afraid

[bumblebee]

Thanks for your reply, I've been doublechecking for solderbridges and resoldered any potential dead spots but so far not resulting in more gain. Now I've followed the veroboard layout as included. I also added a schematic of the Violet variant, which I know might slightly differ in some component values and a schematic from electrosmash that shows the biaspoints.

This last one is also a slightly different variant but I would assume that the measurements of the transistors are roughly the same for all variants? The biggest difference I found is that on the first transistor (named Q4 in the schematics and as far as I can tell is the bottom left one on the veroboard) the collector measures about 3.6 volts instead of the 7 mentioned.

How those the distribution of the 9V exactly occur here? It looks like it gets 'fairly' distributed through those four 12K resistors to the four transistors but that's where my understanding of electronics stops I'm afraid

Firstly,
Are all you transistors in the correct way? Have you used the correct value resistors in the right locations? Have you included every jumper wire that is shown in black on the vero layout? Some of them go over the cuts in the back but are one piece. There’s 5 in total. Have you counted your cuts to be 17?

Secondly,
On Kit Rae’s schematics he has labeled the transistors backwards on all of his schematics compared to the logical way and everyone else’s schems. Q4 is actually Q1; Q3 is actually Q2.

Q1 is always the first Q on the left at the input stage, and so on.

Here’s a few stock voltages I’ve recorded from some of my pedals.

Voltages from 1981 American 3034:
Transistors are 2N5088.

Q1
E B C
.03 .63 3.98
Q2
E B C
.03 .64 4.00
Q3
E B C
.03 .63 4.00
Q4
E B C
1.22 1.82 4.00

Voltages from 2000s American 3003-A:
Transistors are 2N5088.

Q1
E B C
.05 .65 4.34
Q2
E B C
.18 .77 4.71
Q3
E B C
.16 .75 4.62
Q4
E B C
.99 1.57 4.28

Voltages from mid 90s Version 1 Green Sovtek Big Muff
Transistors are KT3102EM (white/green paint dots)

Q1
E B C
.14 .73 4.56
Q2
E B C
.13 .74 4.68
Q3
E B C
.13 .74 4.55
Q4
E B C
.90 1.49 5.60

If your voltages are inline with these then maybe your expectations vs your build differ? It’s hard to say without hearing the thing on full sustain. I’ve never once had to bias a big muff when built to a schematic. It’s not like the fuzz face which can be finicky.

If you want to increase gain then swap those 10/12k collector resistors to 15k and the emitter resistors to 100R…on the first three transistors only. The 100R resistors are already on the layout so you only need swap the three collector resistors.

I will say I’ve never liked anything under 15k on the collectors of the first three transistors as it sounds different to me. However, I did build one that has other values and it is my second favorite big muff. There’s a lot of variables in this circuit and many many sounds to be had.

If you could upload audio of sustain on full, tone on half, and at decent volume while just strumming a few chords and letting a few ring out as well, then it would help us out a lot.

[pietro_moog]

Thanks for your reply, I've been doublechecking for solderbridges and resoldered any potential dead spots but so far not resulting in more gain. Now I've followed the veroboard layout as included. I also added a schematic of the Violet variant, which I know might slightly differ in some component values and a schematic from electrosmash that shows the biaspoints.

This last one is also a slightly different variant but I would assume that the measurements of the transistors are roughly the same for all variants? The biggest difference I found is that on the first transistor (named Q4 in the schematics and as far as I can tell is the bottom left one on the veroboard) the collector measures about 3.6 volts instead of the 7 mentioned.

How those the distribution of the 9V exactly occur here? It looks like it gets 'fairly' distributed through those four 12K resistors to the four transistors but that's where my understanding of electronics stops I'm afraid

How much gain do you want ? My ram's head is MASSIVE and THICK.
check the resistors of the first transistor. This aside, are you sure you didn't make any error in the vero ?

[BramP]

Ok so here are my measurements for the transistors:

Transistors (C,B,E)
Q1 3.8V, 0.68V, 42mV
Q2 3.8V, 0.63V, 43mV
Q3 3.6V, 0.64V, 42mV
Q4 4.9V, 1.7V, 1.2V

I've also included a short snippet of first a clean sound (strat through a vst) and then with the circuit engaged with sustain on full, tone about half, maybe 1 o'clock. I think it sounds nice but I would have expected something even more saturated I guess, having never owned a Big Muff and going by demos I heard.

In the screenshot you see the waveforms of the clean sound and the Big Muff engaged, that waveform being asymmetrical, would that imply that we're looking at asymmetrical clipping and might that suggest there's something wrong with one or more of the diodes in the circuit? Or am I on the wrong path here?

Thanks for all the help and suggestions so far!

[pietro_moog]

Something is very wrong.
Check the resistors with a meter, all of them. Look at the vero to see if you skipped a cut or if there's a solder bridge

[BramP]

Yes, I'll check all the resistor values again although I'm pretty sure I checked them all with a dmm before soldering them in...

I'll also triple check all the cuts and links

Emitter values seem a bit high compared to the other examples that were posted here right?

[pietro_moog]

I don't know. What kind of transistor did you use ? Did you check the pinout ?

[BramP]

Í used 2N5089 transistors

[pietro_moog]

Ok. Are they oriented like that on the vero ?
Did you check the line cut with this image ?
Something is very wrong with that sound, but it's not the voltages

[bumblebee]

Ok so here are my measurements for the transistors:

Transistors (C,B,E)
Q1 3.8V, 0.68V, 42mV
Q2 3.8V, 0.63V, 43mV
Q3 3.6V, 0.64V, 42mV
Q4 4.9V, 1.7V, 1.2V

I've also included a short snippet of first a clean sound (strat through a vst) and then with the circuit engaged with sustain on full, tone about half, maybe 1 o'clock. I think it sounds nice but I would have expected something even more saturated I guess, having never owned a Big Muff and going by demos I heard.

In the screenshot you see the waveforms of the clean sound and the Big Muff engaged, that waveform being asymmetrical, would that imply that we're looking at asymmetrical clipping and might that suggest there's something wrong with one or more of the diodes in the circuit? Or am I on the wrong path here?

Thanks for all the help and suggestions so far!

That sound is very, very wrong.

To check your resistors, since they are soldered in, best to use a color code deciphering tool. Don’t enter the colors backwards or you’ll get the wrong value and it will have you second guessing yourself.

https://resistorcolorcodecalc.com/

If you have electrolytics make sure they are in the correct way.

When going over it you need to be 100% methodical and have the concentration of a zen Buddhist.

That’s what I do when I build and it’s also why I never make mistakes. I approach it calmly and logically, counting every single thing every time for the next component. I made mistakes once or twice and so I decided to never do it again by using this method as debugging takes a very long time in simple builds for beginners. It’s a pain in the ass.

[Intripped]

Debugging plays a big part in the learning process, anyway
it's not just wasted time, not always at least.... But I do agree with you Bumblebee: it's good to devise a method for avoiding debug!

[bumblebee]

Debugging plays a big part in the learning process, anyway
it's not just wasted time, not always at least.... But I do agree with you Bumblebee: it's good to devise a method for avoiding debug!

Yeah, it does for sure. However, a lapse in concentration for a few seconds can cost you hours in debugging and take all the fun out of it. For me at least.

I’m not into electronics as much as I used to be and aside from being quite familiar with just a few favorite circuits from messing with them so much I’m still just a novice-amateur hobbyist at best…as far as I know anyways.

I know there’s some very knowledgeable guys involved in DIY and some of them are also EEs or build pedals professionally, or have been doing it for decades and so know far more than I do. Most of these guys are members here. Some at the other place as well.

There’s always people who know either less or more than you and so each person can help others who know even less still. We all help each other rise to the next level, which is great!