Informartion on the Deluxe Big Muff Pi model C

[Bernardduur]

Hello all!

I just became owner of a Deluxe Big Muff and wanted to know some info people could share. The previous owner did a very bad job in rewiring / stuff as some traces are cut / overly soldered and he reomoved some cables. I did some job tracing the unit but without some info on the how's and why's I don't get any sound from this unit.

I tried to search around a bit and it turns out there are multiple versions. This is the C version with the series / parallel switch (model number EH3054C) which runs on +9V instead of the +5 / -5V supply.

Hope someone can help!

[Bernardduur]

OK; I've got it up and running again for some part. The fuzz works, the compressor works only the combiner does not function yet. I will release some parts of the unit as I try to revive it again. Just feel free to mention any additions / faults / etc.

The unit has been tampered with so I don't know if I use the values of the change or the originals.

[Bernardduur]

Part 1: The power

Part 2: The choice

[Bernardduur]

Part 3: The Fuzz

Part 4: The Comp

Part 5: The switching


The red dots are placed beside the components that the PCB showed signes of replacement
- The 1K in the Vref 2 / 3 sections are different from the 100 ohm I've seen in other units; this replacement dropped Vref 2 / 3 with 0.02 mV
- In the fuzz section, R3 and C3 looks weird. R3 seems replaced, C3 is added to the "wrong" side of the PCB and a ground connection was very badly made by scratching some of the etched lines. Also the connection between R3 and R5 (jumper) is removed (cut) on the PCB

[Bernardduur]

Touch croud!





I have some issues with it; the compressor feeds horribly back at low volumes and is therefor very hard to use. It does compres the signal but this feedback / oscillation is just bad. Could it be the 3080? I had to replace some opamps on the unit bu tI have no 3080 laying around

[Zero the hero]

Thanks for sharing!
Unfortunately I have no clue about the issue you unit suffers of...

[Yun]

Hmmmmm, how many opamps do you have laying around eh?

I've never seen the inside of a deluxe BMP, so i guess that it wouldn't be easy to socket the opamps eh?  I would suggest that you socket the opamps, if you can, and experement with different opamps. 

Or.....

Maybe try a resistor from pot-to-ground? 

[Bernardduur]

I've replaced all opamps with newer ones and socketed them all

The old ones were RC4558N's and I found em quite noisy, even in bypass mode

What do you mean with the resistor?


Edit: Some pics of the inside can be seen in this topic; it is not 100% the same as mine (mine is 1 version later) but looks very much like mine!

[Yun]

I've replaced all opamps with newer ones and socketed them all

The old ones were RC4558N's and I found em quite noisy, even in bypass mode

What do you mean with the resistor?


Edit: Some pics of the inside can be seen in this topic; it is not 100% the same as mine (mine is 1 version later) but looks very much like mine!

oh, nevermind about the resistor to ground thing;  hmmmmm, i can't really read the schematic on this small monitor, man.  dern.....

Since the compression is feeding back- that tells me that something is either peiking or clipping the compression.  For an example:  i used to have an old DOD compressor; when i would run it through any of my amps (marshall stack, peavey tube amp, vox royal guardsmen) as i pushed the compression, i'd get horrid sharp feed back. 

the remedy:

Lower the resistance of the compression control (my dod's compression control was 100K, so i changed it to 50K).  End of problems, man.  There was no drog in squeeze, or compression either.  However the output, level, or volume (whatever you wanna call it) does suffer a tad bit of a loss, but no major volume drop....

[Bernardduur]

Thanks man!

You mean the threshold control in my version?? As I don't have any "compression" control other then the threshold control

It is also a bit a voltage issue; when I run the unit with the transformer (I removed the transformer as I thought it would also run on 9V; difference of about 1V) the feedback is much less but still there!

[Yun]

Thanks man!

You mean the threshold control in my version?? As I don't have any "compression" control other then the threshold control

It is also a bit a voltage issue; when I run the unit with the transformer (I removed the transformer as I thought it would also run on 9V; difference of about 1V) the feedback is much less but still there!

Yes, this is making more scense, man.  I'm sure that you're aware of how compression works, right?

So, as i said- i can't read the schematic on this compu-terd (haha)  so.....

Try the pot "mod", "remedy", or what have you, and tell me how it goes, man. 

Also, What are the values of pin-to-Voltage?  And the values of Pin to ground?

[Mark Hammer]

You'll find some useful information about the pedal here, including some interesting modding info.   http://hammer.ampage.org/files/Device1-7.PDF

[Bernardduur]

Yeah, I've seen it........

Mine is the other version; the Device version is the Blend version, mine already has a parallel / series switch so none of the mods can be used

I will try Yuns mod soon!

Btw, what did you mean with pin to voltage / pin to ground? The unit runs on 9.98V (V+), ground = 0V. Vref = 4.88V

[Yun]

Yeah, I've seen it........

Mine is the other version; the Device version is the Blend version, mine already has a parallel / series switch so none of the mods can be used

I will try Yuns mod soon!

Btw, what did you mean with pin to voltage / pin to ground? The unit runs on 9.98V (V+), ground = 0V. Vref = 4.88V

Hmmmmmm, try a trimmer from pin-to-Voltage.  That voltage seems a bit high. 

[Bernardduur]

That is the voltage coming from the transformer's route; I run mine on just 9V

I lowered the compression pot; the oscillation is less but still there; it comes in when I hold a note long...... it will starts to ripple and then the oscillation begins until I hit another note / chord.

[Yun]

That is the voltage coming from the transformer's route; I run mine on just 9V

I lowered the compression pot; the oscillation is less but still there; it comes in when I hold a note long...... it will starts to ripple and then the oscillation begins until I hit another note / chord.

Oh, dern, dude.  Hmmmmm, i would say either lower the pot value some more, or start the trimmer solution, as i mentioned earlier, man. 

Something is still clipping the compression, man....Let me download that schematic, and try to read it, savvy? 

Do you think that something is grounded that shouldn't be eh?  Check the grounds.  i have a gut feeling that the bias is too high somewhere.  Check the voltage, and grounds, man.....let me think on this a bit more and come up with some more ideas....

[Bernardduur]

Hey all!

After a while I found this schematic of the Deluxe; is quite the same as mine! One big difference is that this unit uses 15V instead of the measured 9V so I think that is the main error in my design.

I will try it on 15V;


Another thing; my deluxe had a "weird" resistor between the - and out of IC1 (RC4558) of the compressor; on the above named schematic this is a 470 pF cap. The resistor is a carbon resistor with the marks red red white silver, which should mean 22000 Mohm........
Any thoughts on this?

[jaytee]

In your power supply schem the 9v supply is coming through the led and 560 ohm resistor. Is that right?

[Bernardduur]

In your power supply schem the 9v supply is coming through the led and 560 ohm resistor. Is that right?

In the original, yes. So the LED is a power LED

[espinete]

I've got one deluxe big muff here with the eh3054c pcb and it is very similar to that schematic. The problem is that the xe0010 is completely dead and there are two wires coming from it. They go to two zener diodes. One is going to an electrolytic capacitor and led. The other one is going to the rest of the circuit I guess . But I don't know the power of these two secundary wires coming from the transformer. This would be the first step for trying to fix the pedal. Then later I'd think about how to arrange the replacement for the transformer. If you have any idea it would be a big help. Thanks in advance