V8 Black Russian Big Muff Pi bypass scheme confusion

[j_flanders]

Last night I had some great, warm, mellow, soft, round tone but today after setting up it was gone, being louder and harsher.
It took me a while to realize the key ingredient missing was my Black Russian BMP in bypass.
Now, I've always found my small box, 4 screw, 2006, second edition, V8 Black Russian Big Muff Pi a tone sucker in bypass, although in some cases/setups I kinda liked what it did to my tone, but everyone on the internet, and more importantly kitrae the muff master himself, says they are true bypass, so it must be, right?
http://www.kitrae.net/music/big_muff_history2B.html#SmallBlackRussian

So, today I finally opened it up and checked myself.
This is what I came up with, after double and triple checking, both visually and with the continuity tester on my DM, because it was so different from what I expected.



As far as I can tell, it obviously uses the typical 3PDT switch which you expect to find in a true bypass scheme, but it seems to be wired as 'hardwire bypass', leaving the input always connected to the circuit.
This leaves me with a couple of questions to which the experts here may know the answer:

1)Does everyone (including kitrae) simply assume it's true bypass because they see that typical blue 3PDT switch?

2)Is the reason for not actually using true bypass (although they have the switch for it) that the input jack is soldered to the PCB and (thereby) directly connected to the input of the circuit (R2), so there is no way to make it true bypass without changing the PCB layout?

3)Why would it connect ground to the middle lug of the sustain pot???

4)Suppose I like the way this pedal loads my pickups in bypass, but I don't want this big box on my board just for that, what would a circuit minimally look like to emulate this effect?
Or put otherwise: what part of the circuit is still 'active'/involved in bypass.

I also have some questions about the schematics on kitrae's site:




1)Can someone confirm that the schematic, as far as bypass is concerned, based on my findings, is incorrect on kitrae's site?
2)Can anyone explain why one side of the LED is connected to the tip of the output jack when in bypass, and why input on output jack tips would be grounded in bypass???
I simply don't understand the sw 1a,b,c part in any of his schematics...
When I do true bypass I ground the input (and the output) of the crcuit, not the jacks and I disconnect the led from power or ground, not from the tip of the output jack.

One final question:
I notice the transistors in my Big Muff Pi are labeled "c547c". Are these the same as "bc547c".
Locally I can only find "bc547 LF", would that be the same as well?

[duck_arse]

the only big muff I've ever handled (please don't think less of me for it) is a black russian version, and I too was surprised by the bypass wiring, so much so that I traced it out. and yes, it is not true bypass, it does have the input stage always connected. to emulate this accurately, you'd just need the first transistor stage.

as for the transistors, "c547c" does not sound like the most usual way of marking BC series transistors, but would be from the high-gain buckets if they were bc's. (look up 2sc547 see if you get any hits.) there is little difference between a BC547C and a BC548C, and between a BC547C and a BC107C. same goes for the BC548C.

what confuses you about the switch dia? the three poles can be labelled a, b and c, and they are all kitrae drawn in the same position, so there will be no connection confusions.

the sustain pot wiper also connects to the input of the second stage, so grounding here makes sense to kill noise in following stages. won't hurt the first stage either.

[j_flanders]

to emulate this accurately, you'd just need the first transistor stage.
the sustain pot wiper also connects to the input of the second stage, so grounding here makes sense to kill noise in following stages. won't hurt the first stage either.

I found that the position of the sustain pot affects the volume/highs of my guitar signal when the pedal is in bypass:
Sustain maxed out gives the most volume/highs (this position grounds/eliminates/bypasses the resistance of the sustain pot)
Sustain at minimum gives the least volume/highs (seems to add the extra 100k of the sustain pot in parallel, and/or forms some kind of LP filter)

what confuses you about the switch dia? the three poles can be labelled a, b and c, and they are all kitrae drawn in the same position, so there will be no connection confusions.

I'm confused that the input and output jacks (and thus the signal?) is either connected to the circuit or to ground. To me this either means big muff sound or no sound (instead of bypass sound)
I'm confused that the led is either connected to ground or to the output jack. That alone doesn't make sense to me, and in his schematic the a and b parts are drawn as if the pedal is active, so the c part should be connected to ground to let current through the led from batt+ to ground instead of to the output jack.
I'm confused why all the arrows point inwards from jacks to the circuit instead of outwards from circuit to jacks.

[thermionix]

the only big muff I've ever handled

[brianq]

I remember an article over at singlecoil.com about converting a Russian muff to true bypass? It's got a few pics if I recall? in fact I remember there being instructions for converting  all the muff models, check it out


Sent from my iPad using Tapatalk

[goo]

just looked at the other schematics on the BigMuff page and i think the drawing you made needs to be fixed as true bypass.
1 - 2 - 3
4 - 5 - 6
7 - 8 - 9

so, let's do this!

1 - LED ("-" cathod)
2 - Guitar Input - jumper to 9
3 - PCB out (Volume 2)
4 - Ground
5 - PCB Input (39K resistor)
6 - Guitar Output
7 - jumber to 8

that's true bypass with circuit grounding when effect is Off.

[j_flanders]

I finally figured it out last night!
See my comments below the schematic.




On Kitrae's schematic (the one I posted above):
1)The word "ground" at the bottom left on the grey coloured line should be removed. It's not a ground line but simply the connection between input jack and output jack when in bypass.
2)The 'sw 1c'-part of the 3PDT switch should NOT be an arrow going from led to either ground or output jack. It should be an arrow from ground to the led or the middle lug of the sustain/DIST pot.
3) the upper line going to the middle lug of the volume pot/output jack should be going to the middle lug of the sustain/DIST pot.

As far as the real life circuit/wiring versions, there are not 2 but 3 versions:
- version 1: pcb labeled BM-1-01.00.001 using a DPDT switch and this one is not true bypass, not even an attempt to be.
- version 3: pcb labeled RBEM 3.000.001 using a 3PDT switch, this circuit has no trace between input jack and R2 and is wired for true bypass
- version 2: a transition version where the pcb is already labeled RBEM 3.000.001 but the trace between input jack and R2 is still there.
It uses a 3PDT switch and EHX wired it for true bypass and manually cut the trace bewteen input jack and R2.
On some of these (mine for example) they forgot to cut the trace, so you end up with a confusing pedal that is clearly wired for true bypass, having a wire from the input jack to the switch and then a wire going from the switch to the circuit input, but it isn't TB because they forgot to cut the trace and thus, despite the extra wiring for TB, the input jack will always remain connected to the input of the circuit.

If I'd want to make my pedal true bypass, all I'd have to do is cut the trace between input jack and R2, which EHX forgot to do.

[duck_arse]

j_f - don't be confused. if we accept that the kitrae diagram doesn't match the build you have at hand, it doesn't really matter which way his arrows point. the connections I traced from the unit makes sense, led connections and ground-wise.

I wrote down the board version [using the correct characters] I "handled" as pbnm3.000.001 [using incorrect characters]. and, further looking at my dia, is there a chance there is not 3 but four versions? my tracing (not the entire circuit, only the bypass arrangement) shows only a dpdt switch, input connected full-time, output switched, led//sust wiper switched.

I can't prove any of this; the pedal is long gone, leaving only my scribbles.

[j_flanders]

j_f - don't be confused. if we accept that the kitrae diagram doesn't match the build you have at hand, it doesn't really matter which way his arrows point.

It kinda matters to me.
I like things to be correct, even on the internet. I also often quote from his site or send people links to his schematics.
It's not so much about his diagram differing from my build, it's about it being technically incorrect. (his diagram would put 9V into your guitar and amp input for example, his led would never go out, and would have no sound at all in bypass)
Also, the way arrows point matters because they represent what is being 'thrown' in a XpoleXthrow switch.

In the mean time I also think I got an idea why he made these mistakes (I'm calling these mistakes because he does seem to know a thing or two about electronics).
Unlike normal people like you and me, EHX rotated their DPDT and 3PDT switches 90 degrees inside their boxes.
This way you're not looking at:

123
456
789

but at:

369
258
147

If you don't pay attention to this 'detail', then suddenly the led connects/switches to the volume pot/output jack instead of to ground

I wrote down the board version [using the correct characters] I "handled" as pbnm3.000.001 [using incorrect characters]. and, further looking at my dia, is there a chance there is not 3 but four versions? my tracing (not the entire circuit, only the bypass arrangement) shows only a dpdt switch, input connected full-time, output switched, led//sust wiper switched.

Yes, that would mean there are 4 (wiring) versions.
I simply copied those 'characters' from his site because I don't know Russian but if I would write them down, I'd put what you have there:  pbnm3.000.001

Thanks for your replies btw!

[duck_arse]

replies? no problem. it's nice to have someone as pedantic and picky.

to the kitrae dia you have posted. first - disregard the "ground" shown on the grey line, that is the audio, tip_IN to tip_OUT line.
at the input - if you connect battery (-) to the jack ring, and the sleeve to circuit ground, that leaves the tip to connect to the switch common, the "arrow". this is what his dia show, and is correct/makes wiring sense - it may not be what EHX actually did, but it is drawn 'right'.
the led switch - you are right, it is wrong. it is drawn wrong for bypass because the led "will be off"** in the position drawn, (and the input is connecting to circuit,) so - wrong.
and at the output - you are right, that connection to SW1c is wrong as drawn. minus that line/connection, the bypass is correct - with that connection it puts DC onto the vol pot and whatever follows.

perhaps we should draw Mr kitrae's attention to?

** actually on in both positions, but brightness will follow the vol pot setting when the circuit is active/on/in/not bypassed.

[j_flanders]

perhaps we should draw Mr kitrae's attention to?

Now that you've explicitly confirmed my findings, I can finally do so.