BMP Opamp modding help (answered)

[Anonymous]

I just finished my first ever pedal build the BMP Opamp with the tonestack bypass mod. I was thinking of making use of the A B connections on the pcb. I presume you could use it to connect a different sets of diodes on a exterior board and switch between them via a toogle. Exactly how you go about this via the A B outlet, I’m not quite sure. I also heard that you can change a resistor for a pot to boost and control the mids. Any help or pointing in the right direction would be greatly appreciated and maybe suggested diode alternatives to the stock ones.

[Barry]

Hi Tommie,

The main mods are listed in the Build Document.

Be sure you have the latest depending on where you got the document.

You can use a Tone TwEQ for proper Active 3 Band tone control which is the best of all mods using the A/B pads. To me that would be better than any other mod as it would offer full tonal flexibility superior to any scoop or diode mods.

Additionally you can view the DPDT Wiring Board document for ideas on using that instead. Also you probably want to look at the Guides Page for even more ideas in photos and writing using layman terms. The Guides Page can always be accessed from the Home/Landing page by hitting the Green Button or on the main Forum Page by also hitting the Green button at the bottom. There are many innovative ideas you can try with examples and diagrams.  🙂

 

 

[Anonymous]

Thanks for the advice Barry,

I’m too tight on space to incorporate the tone TWEQ (125b enclosure). I put in the 9v battery compartment just for the sake of it, but I generally use DC. So that’s where I was thinking of putting another set of diodes to offer different clipping. But I assume from what you said it would be so subtle a change that it wouldn’t be worth it. By the way, the pedal seems to be working fine, a real early pumpkins wall of sound, but is it normal for such a volume increase when the tone switch is off?

[Barry]

You would be surprised how little room you actually need to put a Tone TwEQ in. If you use 9mm on-board pots the finished and mounted circuit will literally hug the inner top of the enclosure leaving plenty of room to lay the main board over top of it in a 125B because of their extra height. Admittedly it would be even easier if there were no battery so you could add a little extra vertical room by moving the footswitch down a little but I have done it with a pre-drilled enclosure meant for a battery several times.

This example is not your exact scenario however the height available in a large Muff is similar in height to a 125B and basically gets my point across I hope.

 

This example features two circuits using a 125B enclosure and while the foot switches are lower that was more of a preference than needing the vertical room.

To answer your question anytime you have different forward voltage in clipping diodes the result will yield different volumes. For example Germanium Diodes are quieter than Silicon and Silicon are quieter that LEDS but if you remove the clipping Diodes altogether then you will certainly get a volume increase. Since this is not a mod you would use on the fly in the middle of a song it really is not a problem for most players to make a minor volume adjustment and use a specific favorite tone for an entire song or even set.

I hope that helps.

[Anonymous]

Cheers Barry,

I forgot you would be taking out the tone pot, but it would still take a lot of moving about. I have the two jack sockets halfway up either side, the DC up top and the pots in a v shape with the toggle under the middle pot. I’ll have a look at the weekend to see if it’s doable. Thanks again for all the info.

[Anonymous]

Hi Folks,

I just build a >BMP OP AMP v2 with Tone TWEQ. I just wondering if I can also get 2 other diodes clipping options.
Could anybody tell me, were I should connect a Dual Clipping Switch with a ON-OFF-ON Switch to have standard and 2 other clipping options
while Pad A is still in use for the Tone TWEQ?

Do you have other suggestions fore nice mods according to my muff?

Thanks and best regards

Smellslikebleach

[Author]

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