Big Muff Plus

soggybag · Post by **soggybag** » 06 Sep 2011, 19:35

I like the idea of using a 3086 or 3046 for a BMP. How would this work with the two transistors that share an emitter? Would you connect the common emitter to ground and use these two transistors as the clipper stages? Or, use these as the clipping stages with a 100 ohm to ground?

Barcode · Post by **Barcode** » 06 Sep 2011, 20:07

soggybag wrote:I like the idea of using a 3086 or 3046 for a BMP. How would this work with the two transistors that share an emitter? Would you connect the common emitter to ground and use these two transistors as the clipper stages? Or, use these as the clipping stages with a 100 ohm to ground?

It would depend on which version you want to build, but basically you would just use them for whatever stages you don't mind having the same emitter resistor value for. for example, using Tonepad's Tri schematic, stages 1 and 3 use the same value (820R) emitter resistor. So if you used the two transistors in the chip that share an emitter as these stages, then you could just run one 820R resistor from their common emitter to ground.

soggybag · Post by **soggybag** » 15 Sep 2011, 23:59

Is it possible to modify this tone control to work with 100K pots? I have these available, I don't have a 1M and 470K on hand.

Cub · Post by **Cub** » 22 Sep 2011, 14:26

grrrunge wrote:
mictester wrote:BTW, a very "well-known" guitarist recently described this as his favourite distortion pedal, and that it was "as good as any three others put together because it's so flexible". Now it's getting serious "word-of-mouth" support in the musical community here, and I'm having to make quite a lot of them. I'm thinking about making some PCBs. If I do, I'll offer them on here for the price of the materials and the postage plus one beer!
I'm seriously up for one of those too, if you decide to make pcb's
...heck! I'll chip in for a sixpack. That 'one beer' thing never seems to work out for me anyway

Put me down for two PCBs for two six packs as well !

mictester · Post by **mictester** » 22 Sep 2011, 23:46

soggybag wrote:Is it possible to modify this tone control to work with 100K pots? I have these available, I don't have a 1M and 470K on hand.

Not really. You'd have to recalculate everything in the tone circuit, and the reduced resistances would make the filter very lossy. It's best to use the right parts!

soggybag · Post by **soggybag** » 24 Sep 2011, 17:48

mictester wrote:
soggybag wrote:Is it possible to modify this tone control to work with 100K pots? I have these available, I don't have a 1M and 470K on hand.
Not really. You'd have to recalculate everything in the tone circuit, and the reduced resistances would make the filter very lossy. It's best to use the right parts!

Thanks for the reply. I figured this might not be possible, since someone might have done it already if it were. This type of tone control was over my head. I figure I can probably sub a 500k pot for the 470K? I just built up a Box of Rock with your Big Muff Plus tone control in place of the BMP type it had.

mictester · Post by **mictester** » 25 Sep 2011, 13:34

Of course you can use a 500k for the 470k pot - just consider the % difference in the values, and you'll see that you're within the tolerance of the components!

juanro · Post by **juanro** » 27 Sep 2011, 01:57

Hi,

I made this PCB for this project.

For parts numbers use this schematic:

For values, see mictester schematic.

Attached RAR file with SCH / PCB for ExpressPCB

Regards,
Juanro

auden100 · Post by **auden100** » 10 Nov 2011, 20:24

Hey, folks. I've been working on a slightly modded (removed input buffer) perf version of this. Sounds pretty good, but like Johno I'm using a MPF102, and I'm having problems with it being just a bit to low in volume. At maximum settings and slightly lower, things sound great, but if I drop below noon on the controls, then unity volume is not possible. I just ordered some 2n3819's, the should arrive next week, but I was hoping to get perhaps some confirmation that this pedal acts this way normally, or perhaps a method to produce more volume.

I tried using a 1k resistor and a 10uF cap to ground off of Q6, but that produced a lot of noise and oscillation at full gain. Not sure if there's a good way to boost the fet. Any suggestions?

mictester · Post by **mictester** » 11 Nov 2011, 00:50

auden100 wrote:Hey, folks. I've been working on a slightly modded (removed input buffer) perf version of this. Sounds pretty good, but like Johno I'm using a MPF102, and I'm having problems with it being just a bit to low in volume. At maximum settings and slightly lower, things sound great, but if I drop below noon on the controls, then unity volume is not possible. I just ordered some 2n3819's, the should arrive next week, but I was hoping to get perhaps some confirmation that this pedal acts this way normally, or perhaps a method to produce more volume.

I tried using a 1k resistor and a 10uF cap to ground off of Q6, but that produced a lot of noise and oscillation at full gain. Not sure if there's a good way to boost the fet. Any suggestions?

What resistor values do you have in the final stage? I found that substitute FETs could give reduced output (I used BF244 because I have boxes of them!). Increase the value of the collector load resistor in the final stage. The gain of that stage is predominantly set by the ratio of the collector resistor to the emitter resistor, so you can get small increases in gain by small changes to the collector resistor.

auden100 · Post by **auden100** » 11 Nov 2011, 23:23

Exactly what was listed in the schematic on page 3. I'll play around with it a little more, but probably just wait until those 3819's arrive to finalize anything. Thanks.

atreidesheir · Post by **atreidesheir** » 08 Oct 2012, 01:10

juanro wrote:Hi,

I made this PCB for this project.

BMPlus_PCB.GIF

BMPlus_full.JPG
For parts numbers use this schematic:
BMPlus_sch.JPG
For values, see mictester schematic.

Attached RAR file with SCH / PCB for ExpressPCB

Regards,
Juanro

I had forgotten about this. Juanro, my friend, what is your feeling about this pcb and pedal?

juanro · Post by **juanro** » 10 Oct 2012, 21:37

Hi,

This PCB was a sort of exercise when I was trying to get used to ExpressPCB (and contribute to the forum as a side effect)
I never actually tryied this circuit nor really verified the PCB; I checked it as good as I could, but I was hoping to someone that built it to post their result.

Juanro

soggybag · Post by **soggybag** » 25 Jul 2022, 03:53

Here’s my build. I designed a pcb and had it manufactured at PCBWay.com. Making a pcb for prototyping has been my favorite workflow. The cost of 10 boards is $5. If I hang a couple projects together I can get the cost per board down to $1 with shipping.

Using a pcb that gets most of the parts right is an easier platform to work with if I design the boards to mount the pots and easy off board wiring it’s really easy to work with.

This sounds pretty good. I made an error and wired the treble pot backwards.

I used 1/8 watt resistor footprint to make this fit a 1590B.

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