Making a Mud into a Muff

Every so often I get a challenge that I love and while I don't really have time for this sort of thing, sometimes it's just gotta be done.
This customer bought one of my "Vintage" Triangle Big Muds to replace his original EH Triangle BM so he could keep his original good and not feel too uncomfortable taking it out and using it live. His is in really nice condition and it's always nice to see pedals this old, that have been used, but still in great condition. 
It's had work but just the usual things that are done to lots of these old pedals like a new stomp switch but was basically intact as far as components went.

The customer had said the Mud had "too much bottom end", which is common on early vintage Tri's but this circuit varied SO much in it's original form that it's hard to pin down an actual "Triangle tone". From his description by email I said "it sounds like it might be more of a Ram Head tone?"

I plugged it in and ............ WOW. This was nice. I've heard, repaired and made quite a few Tri's (including the Lyle and Foxey Lady) now and this was one of those BM's you plug in and go "OK, this is nice". The top end was almost the same. Very (very) close in top end sizzle and saturated gain and a similar mid scoop but the Mud definitely had more bottom end.
Running them side by side I could hear my Mud in there, but it was too "fat" to match the original. I then put my Ram Head next to it and again, it was in there, but not ........ triangly enough.


I opened it up and there it was. It's a "later" Triangle from around late '72/early '73 (pots date 34th week, 1972) so it was on the cusp of entering into the Ram Head era. I gave the circuit a quick perusal to check cap values and transistors. At a glance cap values, which was my first thought, were the same as mine. Transistors are the "legendary" rare FS3700 PNP Fairchild Semiconductor transistors. While these transistors are sought after in BM circles, I personally don't believe they are the "magic" to the tone of these units. 


Carefully removing the circuit board from the pedal was going to necessary to work out what was going on so I dove in.


I've traced out a lot of these old BM's now and you get used to seeing things straight away that you go "oh, there's the issue/answer" but this one looked pretty ....... standard ?
I checked all the caps again and all looked normal except for two caps on the clipping stages that were slightly different to my Vintage Big Mud. I was sure it was going to be a input/output/coupling cap values to let less bass through the circuit. I was thinking it was going to be my Tri with my Ram Head cap values ?
I started checking resistor values and found some different from mine, but normal for this circuit and not integral to the bass response of this circuit so I started running a signal generator into my scope on different parts of the circuit to have a look what was going on.

Some resistor values had drifted slightly to values unachievable with standard values so I started experimenting with sections that make a difference in the bottom end without effecting to many tops as it was spot on. After some trail and error and changing components in the Mud I eventually came up with a VERY close approximation of the original BM, albeit with different values from the original vintage BM.
I emailed the customer and asked them where they normally ran the knobs on it as I really wanted to get close here, rather than through the entire sweep of all three knobs.
I fine tuned the Mud a little more around their settings and ended up with what, to my ears sounded almost perfect.


With the knobs on his original where he described where he ran them (scope on the left) I could achieve the same signal on the Mud (scope on the right). The Mud goes further and with the volume and sustain on full, it's louder and more distorted, but you can dial in my Vintage Triangle Mud to replicate his vintage Triangle BM.
After a certain point on the sustain on the Mud the signal starts to change significantly enough to hear the clipping change, and you could see it on the scope, but with the sustain only run up to about 9, it shows identical clipping characteristics and sine wave shapes.


This is a very nice sounding and original early 70's BM and although it was made to be used, I have no problem with replacing it on a pedal board with something similar sounding that you don't have to be precious about. After all, my Mud has a Boss style 9V adaptor, an LED and true bypass and is smaller so you can jam more onto your board. It kinda just makes sense ?
While I wouldn't want to do this with every Mud I sold I actually enjoyed this challenge and really, most people buying my Muds can't afford or don't own originals to compare them to so they trust me to keep consistently making my favourite versions of these very erratic and inconstant pedal. It just goes to show yet again that you can spend silly amounts of money on vintage BM's and sometimes (like this one) you get gold, and sometimes you don't.


I'll find out soon how close I got. Both pedals are in the mail heading back to their owner.


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