Big Muff Ram's head 1973 "violet #4" vs Stomp 75

E

EGRENIER

Well-known member
So first of all, let's make a few bullets about me:

- I'm a total newbie at building pedals
- I'm a total Pink Floy nuts ! (Hence a David Gilmour wannabe !)
- I know nothing about electronics
- I sometimes over research and over think stuff that I should ignore (I have a doubt I'm not alone !)

So, while I'm waiting for my first 2 PCBs to arrive, a Parasite Wah and a Delegate Compressor (Boneyard), I've been researching the Big Muff and trying to figure out what variant of the Muffing Fuzz I should build to get as close as possible to a DG sound. (I know it's all about the fingers, but still).

My research lead me to conclude that DG was using a Ram's head 1973 violet edition #4. If anyone think differently I will oblige. BTW, the era I target is the obvious late 70's early 80's...

Anyway in that research effort I landed on this diagram about the pedal and tried to figure out what would match:

Ram's Head 1973 Violet #4

So after being told that this should be a Stomp 75, (Thank you Dali and Robert), I made a full analysis of the circuits. Here's the results.

1611710083408.png

There isn't much difference. Let's see what I found out...

The Obvious:
- The diodes variant is only a matter of old vs modern. From what I can find, a 1N914 and 1N4148 is the same just from different era.
- Transistors: the original 2N5133 was highly inconsistent, replacing with a 2N5088 should provide an equivalent gain without the risk of purchasing a 2N5133 with low gain value.
- Capacitor C9 (C10) is probably so close to make no noticeable difference (3.9 vs 4nF)

The not so obvious:

- R23 (R6) is presenting a interesting variant (560 Ohms vs 1K)
- R4 (R2) is presenting a interesting variant (2.7K vs 4.7K)

As you can guess (see context above) I have no clue what those variants could cause in sound, tone, sustain or whatever...

I'm curious to hear from the forum if they feel that this could lead to a closer sound to the original and what such difference could have on the sound.

Thanks !

Eric
 
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Thank you Sir...

But to clarify, I'm more curious to understand the potential impact of the difference of R23 and R6 to the sound which is probably a theorical exercise as I'm guessing my old ears wouldn't see the difference in a blind test.... or would they ?

Although I greatly appreciate the pointers to other new potential builds in the quest to replicate a DG sound...

E.
 
The page you link to is one of the best resources about the different parts and designs for the BMP. You can see there that parts substitutions were common even within the same version within a year, creating a real collector's niche market.

For the parts you have highlighted in your chart, R23 probably won't make a difference in sound, just in the relative position of the pot that feeds it. R4 will interact with Q1, so different values there will mostly depend on the specific specs of that transistor. The transistor subs you suggest are not going to get anywhere close to replicating the Gilmour sound because of the type and output from them. You can still get the 5133 transistors from Small Bear, or equivalent ones at least. Also not hard to find 1N914 diodes either, but using 1N148 diodes probably would not make a big difference in the sound.

The BMPs probably had a lot of variation in their sound even when they were new, due in part to some wide tolerances in the performance of the parts, but also due to the changing inventory of parts used to assemble them.

You will probably have a lot of satisfaction building the different PCBs that are chasing those sounds.
 
zgrav said:
The page you link to is one of the best resources about the different parts and designs for the BMP. You can see there that parts substitutions were common even within the same version within a year, creating a real collector's niche market.

For the parts you have highlighted in your chart, R23 probably won't make a difference in sound, just in the relative position of the pot that feeds it. R4 will interact with Q1, so different values there will mostly depend on the specific specs of that transistor. The transistor subs you suggest are not going to get anywhere close to replicating the Gilmour sound because of the type and output from them. You can still get the 5133 transistors from Small Bear, or equivalent ones at least. Also not hard to find 1N914 diodes either, but using 1N148 diodes probably would not make a big difference in the sound.

The BMPs probably had a lot of variation in their sound even when they were new, due in part to some wide tolerances in the performance of the parts, but also due to the changing inventory of parts used to assemble them.

You will probably have a lot of satisfaction building the different PCBs that are chasing those sounds.
Click to expand...
Thanks and I agree... I thought the pedal build community was a sub-culture, I now realize that the BMP is a sub-culture within this sub-culture... LOL

For the 5133 found on small bear, they only guaranty 50 hfe, so I'm inclined to go with the suggested replacement, the Fairchild SE4010 that has a minimum hfe of 140... From what I read the target would be more 200 hfe for a similar gain.

What a lot of people seems to be doing is buying a large batch and test until they get 4 5133 with at least 200 hfe. Again, as i'm a newbie, i'm using these acronyms without really knowing what they mean to the sound itself...
 
If you're wading into the pool, go ahead and jump in the water. Enjoy hands-on building along the way and don't think you have to first come up with a definitive version. Use sockets for the transistors and try out a few different things to see what sounds right to you.

I think that most pedals I have built with PNP geranium transistors have HFEs less than 120, and probably less than 100. If your goal is to build "the" pedal that make your ears happy, plan on building a bunch of pedals along the way for the experience and fun that comes with it.
 
Well, if you REALLY want to dial in a Muff to your liking, here's what I'd do to go all in:
1. Buy 3-4 Muff PCBs
2. Take two and use sockets for every component.
3. Use a 1590XX enclosure to build a 2-in-1 with both the socketed PCBs to make A/B tests easy.
4. When you have a version you want to make permanent, you can just take the components out of the sockets and solder them onto another blank PCB.
 
Thanks all, I appreciate the support... keep the comments coming I like them...

@zgrav : I'm starting to feel the water to my knees, if my PCB can finally arrive (been waiting 20 days now), I'll be able to experiment on my first build and really see if I want to keep on building !

@jubal81 : This is hardcore, but an a very interesting thought... My building skills may be a bit limited to go there.. yet ! But I will keep this suggestion in my back pocket. Appreciate it !
 
Found this thread while looking up which muff variant to build for a friend who wants a gilmour ram’s head. Don’t really want to do a danube just because I’d rather be lazier and use a 3 knob tayda enclosure without drilling for the additional switch. Could just do it internally I suppose (lol)

Curious what you ended up doing @zgrav.

From what I can tell: R23 prevents the sustain pot from killing the sound entirely, R4 biases Q1, which I imagine is due to the transistors being different.
 
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@finebyfine, if you're interested.... I built mine to match of the Violet 1973 and the spec I had researched starting this thread. Except a few differences:

Substituted the 2N5133 with SE4010 (Based on Small Bear recommended replacement)
Use a 3.9nF for C10, I couldn't find a 4nF on Tayda.

I also build a Skreddy as per @zgrav recommendations. I play them side by side the Skreddy and the Muff and my wife told me the Muff sounded more Pink Floydish :)

I'm happy with both...
 
EGRENIER said:
@finebyfine, if you're interested.... I built mine to match of the Violet 1973 and the spec I had researched starting this thread. Except a few differences:

Substituted the 2N5133 with SE4010 (Based on Small Bear recommended replacement)
Use a 3.9nF for C10, I couldn't find a 4nF on Tayda.

I also build a Skreddy as per @zgrav recommendations. I play them side by side the Skreddy and the Muff and my wife told me the Muff sounded more Pink Floydish :)

I'm happy with both...
Click to expand...

D'oh, didn't realize you were OP and not zgrav. My bad! Very happy to hear you like both! I think I'll start with the Stomp 75 values but socket or use trimpots for the differences. I don't have any 2n5133s or SE4010s on hand but I have a ton of 2n5088 and 2n5089s and really like how they sound in the other variants. I've only used 3n9's in my muff builds that call for 4n, I've never seen a 4nf in my life.

Wish the muff board was in stock, I got one last week but I'm building another foxy lady build on that one

Edit: What did you end up using for the clipping diodes on your muff board?

Appreciate your feedback and guidance! Thank you
 
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I used the 1N914 for diodes...

I'm not sure if there that much difference between the SE4010 and 2n5088... I had both, but I was just too lazy to fool around and make test. I played it with SE4010 and like it, so even if I had them socketed, I didn't try the swap... It could be an interesting experiment but I suspect that if you don't play them side by side, it may be difficult to see a difference.

You can find my build report here: https://forum.pedalpcb.com/threads/the-big-violet-muff.6513/#post-54719
 
EGRENIER said:
I used the 1N914 for diodes...

I'm not sure if there that much difference between the SE4010 and 2n5088... I had both, but I was just too lazy to fool around and make test. I played it with SE4010 and like it, so even if I had them socketed, I didn't try the swap... It could be an interesting experiment but I suspect that if you don't play them side by side, it may be difficult to see a difference.

You can find my build report here: https://forum.pedalpcb.com/threads/the-big-violet-muff.6513/#post-54719
Click to expand...

Thank you so much!
 
Lotta cork-sniffing going on in that thread. Unless you perform a double-blind test, you will not know what effect, if any, varying transistor HFE has on the tone. Even then, the perception of tone is subjective. You can listen to the same pedal, same settings, same looper input on two different days and it might very well sound different.
The statement equating HFE with amplification factor in a BMP is incorrect.
 
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