Buff n Blend and a Loud Pop from Foot switch

[Robert]

So I added a Buff n Blend to a BYOC Lil Russian Beaver aka Big Muff. Both circuits work great but there is a LOUD POP when the footswitch is activated on/off. I isolated the fuzz circuit from the BnB audio and power and see the pop is still present, but much less. The buff n Blend is making the existing pop louder. The original build has 10k at R5 and this build has the jumper. I don’t feel the FX circuit is overpowering the Dry, but maybe a larger value there can help quiet this pop. But how can it without making the whole fuzz circuit lower?… So, any thoughts? Any reports of this? Oh…. and I should add, I did not wire the BnB to a footswitch as I always want it in the circuit. I jumpered the upper and middle pads of the 3  channels left, center and right. Everything else was wired as build docs say. Wait… I also remember my pcb was a little different than then the build docs. Everything looks the same as in the pics on the build doc as they have a spot for R8, but the build doc says CLR. R8 IS the CLR but maybe I was using the wrong doc? Any thoughts?

[Robert]

Also… I have since gone over this, isolated the fuzz from the Buff n Blend from power and audio. The Buff n Blend is creating the loud pop when the other circuit’s foot switch is turned on/off. What might this be? These are the 2 schematics… And here is a new thought. Someone looked at the BnB schematic and said that the send part of the blend has dc on the send-signal. Might be causing the pop. Try to put in a cap between. Why would he say this? Is it because the send is fed from the MP102 Tranny Emitter? Do we have more than just boosted signal coming out of the 102?

[Barry]

The BnBlend circuit does not have a blocking capacitor installed on the SEND line from the J113/MPF102.  This is because most effects circuits to be installed in the effects loop already contain a blocking capacitor at their input.  Therefore any DC on that line will be blocked before it enters the effect circuit.  AND, most folks will not bypass the effect by using the effect’s switch but rather by using the BnB bypass switch.

In this case, the BYOC effect installed contains a bypass switch BEFORE the signal reaches the blocking capacitor in the circuit.  This could cause popping when that switch is actuated.

If you leave that switch active and use the BnBlend bypass switch as intended to activate or bypass the effects loop, you will not hear any popping.

Another solution is to install another blocking capacitor in series with the SEND circuit.  A 10uF can be installed right at the SEND jack.

 

[Robert]

BOOM. Thanks Barry! YEs all of this came to be and we have a few solutions on hand for if this arises again. For a BYOC, I have to use the pcb integrated footswitch and move the SEND of the BNB to after the 10uF cap. But with most other PCB’s I can use the BnB as intended with its footswitch. Thanks for the confirmation.

[Author]

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