Big muff doesn't sound like a big muff

[HeavyFog]

Well my luck lately has not been good lately. First my blue box doesn't work now this. I just finished building a big muff with a tonepad pcb using a schematic from kit rae found on this page http://www.kitrae.net/music/David_Gilmour_Big_Muff.html. It works but i get little distortion, even with the sustain pot maxed out. It sounds more like a very weak fuzz than the big muff sound i was hoping for. I tried it with 2n5088's and with bc239c's which gave me more volume, but not more distortion. I double checked the values on the emmiter resistors and they all match, so i'm yet again stuck.

Any help?

[EBK]

I double checked the values on the emmiter resistors and they all match, so i'm yet again stuck.

Did you double check everything else?

[HeavyFog]

Resistors are double checked and the caps look to be in the right place. Admittedly not the finest soldering iv'e ever done but not messy and there are no shorts i can see. Testing it as well without a switch and so that's not the problem. The 9v adapter powers an ehx big muff normally so its not that. Different transistors give the very similar results as i would expect but it still sounds like the sustain is set at minimum when its actually maxed out. The low gain sound sounds like it should with the gain low but its like it just wont go any higher. One thing i do suspect is the unlabeled spot coming off the +9v lead on the board that coects the +9v to ground. I don't have it connected now and i don't think it would change anything but i'm not sure. I also omitted the 1m resistor after the input.

[HeavyFog]

After taking a very close look at the pcb i found the problem. R10 wasn't soldered well and the patch one end was soldered to was coming loose, choking the second gain stage of the 9v, so i connected the resistor leg to that of R15 and it works!

All i can say about the sound is WOW. It has the David Gilmour sound 100% and it easily beats out any big muff iv'e ever owned, even my old russian. Il have to give te bc239c's another try and a few others to see what combo sounds best to me but 2n5088's sound fantastic. If you're building a big muff definitely try this one.

Thanks for the help!

[EBK]

Thanks for the help!

I think you really helped yourself on this one. 
Glad to hear that it is working.

[antonis]

but 2n5088's sound fantastic.

True & Correct...!! 

Super high gain transistors tend to be "harsy" when working with feedback loop clipping arrangement...
(even with decoupling caps..)

[Elijah-Baley]

In my Big Muff Ram's Head clone I used 2N5088s, except for the first stage, where I used an MPSA18.

I don't know your problem with the BlueBox, but I'm building it. I write about it here: http://www.diystompboxes.com/smfforum/index.php?topic=114812.0
I'm gonna draw there the final schematic and veroboard layout.

Good luck!

[Plexi]

Like I said in my post: I can accept everything...but NOT a Muff that hasn't a colossal amount of gain.

Put sockets, and try!
I used MPSA13 in the output for high volume, and clipping stages.

[HeavyFog]

I did figure out the problem(s) with my blue box after. I missed installing a jumper, i had the jrc4558d in backwards and the transistors were in backwards. No wonder i wasn't getting any sound. Going to order some more 2sc1849's soon. May as well get some other transistors to try in the big muff while i can since i have them socketed, and i know small bear has quite the selection. Thinking of trying BC108c's or even some  BC109b's to see how they sound. Any suggestions or recomendations?

[Plexi]

I did figure out the problem(s) with my blue box after. I missed installing a jumper, i had the jrc4558d in backwards and the transistors were in backwards. No wonder i wasn't getting any sound. Going to order some more 2sc1849's soon. May as well get some other transistors to try in the big muff while i can since i have them socketed, and i know small bear has quite the selection. Thinking of trying BC108c's or even some  BC109b's to see how they sound. Any suggestions or recomendations?

There you have:
Transistor mods

Source: http://www.coda-effects.com/2015/11/big-muff-mods-and-tweaks.html The Muff uses four transistors and the type and choice of these transistors will affect the sound greatly. The higher the gain, the more the unit will focus on the high end / treble. Some known examples: The Russian Muff uses E type transistors (newer ones use BC549C's though) which has a Hfe of around 500. I used BC184's as a great replacement of these transistors. The NYC Muffs usually use 2N5088's or BC550's with a Hfe of around 800. The Little Big Muff uses 2N5962 with a Hfe of around 1500 - 2000. The Russian sounds darker due to the low gain. Knowing this, we can change the sound of a muff greatly by replacing the transistors. Small tip: use sockets when changing transistors. This way the transistors are not damaged by the soldering and swapping is much much easier. Some nice ones: 2N5133's: used in Triangle ones (the NOS versions tend to sound even better then newer ones) as FS36999's. Very nice sound, smooth, warm, open.One of my favs! Note from Coda Effects: I would not use these ones. They are really rare and expensive. I am not sure that they really sound better... I would try to find something similar in hfe (around 100-400). BC239's: also used in a bunch of Muffs around. Slight less gain as the above named but this gives the Muff quite a nice touch. 2N5087's: PNP transistors instead of the above named NPN (more usualble). To use these you need to reorient some of the caps and change the + and - of the battery (called positive ground). Although they must be identical to 2N5088's they were used in some old models and do sound different. BC141's: ultra low Hfe (around 100) and not suited for anyone out there. More bass, less gain but a very different sound. MPSA13's: ultra high Hfe (around 10.000). Nice touch for some more gain. Experiment! Use four of the same transistors or try to mix. For example I like a Muff with 5133's for the clipping stages and MPSA13's for the buffer stages. Note from Coda Effects: I also experimented with a few transistors, here is my feedback about this: The first transistor is the one that will define the most of the gain of your unit. Higher hfe = more gain, but also more trebles... I tried a few ones: 2n5089: high gain, but also gives a "gritty" touch to the muff that I do not really like. Also quite noisy 2n5088: nice sound, gainy unit, but less noisy and agressive trebles than 2n5089. I really like it and use it often. 2n2222A: low gain, gives more bass and smoother sound. Beware: polarity is reversed compared to 2n5089. MPSA18: extreme gain! I would suggest to increase emitter resistor to limit gain (especially for noise issues), but you can have a nice "doomy" muff with it! 2n3904/BC549C: great for a low gain Muff. The two transistors of the gain stages play a bit more with compression. I usually use low hfe. 2n2222 are really nice for this use. 2n5088 can also do the job. The last transistor will define the final output volume of the unit. I like to have quite a lot of output volume, so I prefer to use high hfe transistor for the last stage, like 2n5089, or MPSA18.

[teemuk]

Transistors will have very little effect on stages that are held in a tight leash by local feedback loop, like in several stages of Big Muff. Yes, Hfe will undoubtedly affect gain, but that is -open loop gain- and when local feedback is employed and engaged it is -closed loop gain- that affects things most prominently. Say, the transistor can have open loop gain of 1000x but it doesn't matter squat when the circuit enforces closed loop gain figure at much lower magnitude, say 40x. Pretty much how generic opamps work as well. Now, you can regard a generic BJT as an amplifier where base is an inverting input in relation to collector and emitter is a non-inverting input in relation to collector. Now picture an opamp in place of the transistor and if feedback loop is closed the operation doesn't differ at all assuming open loop gain is sufficent. Even overdrice characteristics like headroom are inconsequential because you have antiparallel diodes in the -closed- feedback loop that enforce their own effect to closed loop gain, negating all such effects in open loop realm. Instead of gain stages clipping to their rail limits they clip to Vf limits of the diodes, and that at closed loop gain dictated by the circuit. The transistor choice doesn't mean a thing as long as its biased within proper range and as long as the open loop gain is higher than closed loop gain.

In practice you could substitute almost any transistor there with practically any transistor with -enough- open loop gain and get nearly identical results. Heck, you could even substitute those discrete transistors with opamps and the end result would still be the same because of closed loop operation keeping things in a leash and tight control. These circuits were designed to give predictable results with any device emplyed, and those emitter and collector resistances vary from version to version merely to keep thing in proper range of bias. That's all.

Transostor choice only has distinct effects to gain stages without that feedback loop. I recall in traditional Big Muff one has just a single one of them, which is a non-distorted gain recovery stage after the lossy tonestack - the very final stage. Everything else is controlled by feedback loops and if you really want to twek the operation you tweak the  components in those feedback loops, or components coupling stages (with local feedback) together. Oh, those are naturally outside the loop to... Everything inside the -closed loop- is more or less normalized and homogenized by the feedback loop.