Buddy's Breadboard and Circuit Design Notes

[BuddytheReow]

It does! I stumbled upon this on the net a while ago. The circuit was called "Bigger Muff" and also had the AMZ presence control in it. I took it out and worked just like a regular BMP stack! I had no idea what C2 is doing in there or what it was trying to accomplish. But, I was happy with the result

 

[Chuck D. Bones]

FYI, C2 is for DC blocking.

OK, yeah, I fucked up my sim too. See below for correction.

 

[Chuck D. Bones]

Please update the schematic, then I'll run a new sim.

Also indicate which way is CW on the TONE pot.

 

[BuddytheReow]

Sorry, Chuck. I put the schematic together right before bed last night and realized what I did. The TONE knob pinout top/bottom is 1,2,3. Horizontal pots are left/right 1,2,3.

 

[Chuck D. Bones]

Here we go! NB: the VOL pot influences the TONE knob's response a little. This is with VOL at noon.



BTW, you could better use the 4th opamp as an active VOL stage between U1.2 and C2/C3 by duplicating the 1st stage and jumpering the resistor that corresponds to R3. It also undoes the overall inversion, which matters to some.

 

[BuddytheReow]

BTW, you could better use the 4th opamp as an active VOL stage between U1.2 and C2/C3 by duplicating the 1st stage and jumpering the resistor that corresponds to R3. It also undoes the overall inversion, which matters to some.

But, wouldn't that just make the control a boost control instead of just volume? It's already decently loud enough as is compared some of my other pedals out there.

 

[Chuck D. Bones]

No. That's an advantage of an inverting stage. We can make the gain less than 0dB if we want. Use 100K for the input resistor and 100K for the VOL pot. The gain goes from 0 to 1x (-∞ dB to 0 dB). For less gain, make the input resistor bigger.

I would also put small resistor, 2.2K is good, in series with C3 to limit the high freq gain when VOL is dimed.

 

[BuddytheReow]

In my head I had switched up inverting and noninverting gain calcs. This is definitely a better use for that last opamp. I'll try it on my board and circle back here. There probably won't be much difference in sound, but all the parts will be utilized.

What are your thoughts on the HARMONICS control? I started with 1k and kept upping the value until I could hear a difference during the sweep. It is on the subtle side though...

 

[mybud]

Lurking and learning so much from your discussion. Thanks gentlemen.

 

[Chuck D. Bones]

In my head I had switched up inverting and noninverting gain calcs. This is definitely a better use for that last opamp. I'll try it on my board and circle back here. There probably won't be much difference in sound, but all the parts will be utilized.

Agreed. The biggest improvement is it will remove any unwanted interaction between VOL & TONE.

What are your thoughts on the HARMONICS control? I started with 1k and kept upping the value until I could hear a difference during the sweep. It is on the subtle side though...

When I tried something similar, I ended up with a large pot. Try 100K or larger.

 

[Chuck D. Bones]

That is a pretty cool tone control and I'll keep it in mind for future designs.

 

[BuddytheReow]

Thanks, Chuck. Just something I found while wandering the net a while ago and wanted to try it out. I wonder if this method could work on other passive filters.

So, here's version 2 with an increased HARMONICS control and the active Volume control. TBH, I tried the volume control and it didn't work. Turns out half the tl072 didnt work so I swapped it out for a 4558. Like I said before, I see no reason why any quad opamp won't work here. 2 duals are easier to breadboard. I haven't had enough time to play around with the harmonics control so that value might change.

Anybody wanna design me a PCB? Please?

 

[Chuck D. Bones]

Maybe wait for someone else to breadboard it too.

I think a 1uF cap in series with R10 would be a good idea, especially if you're going to use a 4558 or other bipolar-input opamp (NE5532, LM833, JRC2680, etc).

what's with everyone running out of TL072s? BTW, they are cheaper at Mouser than at Tayda if you buy 10.

Quads are harder to breadboard and harder to layout. It's unlikely that a quad will save any board space over two duals.

 

[Sturdag Lagernathy]

I think a 1uF cap in series with R10 would be a good idea,

I'm not seeing R10, although there is 2x R8..

 

[Chuck D. Bones]

Oops, I meant R4.