Modifying a Surfybear for separate dry and wet pots

[andare]

Hi,

years ago I built a Surfybear kit. It's a Fender 6G15 reverb unit with transistors instead of tubes. It features the same drawback of the originals: dry and wet signals are blended in the Mixer pot, which means the dry signal gets quieter and darker as the wet signal increases aka massive tone suck.

Here's the schematic:



I read on a forum somewhere that it's possible to connect caps C10 and C17 to separate pots to control dry and wet level, respectively, wired as standard volume pots with lug 1 going to ground, lug 3 to the caps and lug 2 to output. However I read that resistors are needed to prevent crosstalk between the pots before they reach the output. Is that so? And what value would I use? The SF uses a B250K pot for Mixer, should I use two of those as well or a smaller value like 50k?

Thanks

 

[andare]

Bump!

 

[jwin615]

A MN taper pot would work well here.
Would be offboard. I believe you would wire it like bassists do for no load pots

 

[andare]

A MN taper pot would work well here.
Would be offboard. I believe you would wire it like bassists do for no load pots

You mean replace the Mixer pot with an MN pot? I've never heard of those.

I thought no load tone pots simply had no resistance CW and were wired normally.

 

[jwin615]

Not, different pot. These are dual gang. Each taper you see above is each gang. Your dry and wet would feed in each gang individually.
Center is full on both signals.
Think of them as half the travel is zero ohms then from center through the other half is the taper.
May need a resistor in series after though to prevent it from being too loud.
A 250k at dk as example

https://www.digikey.com/en/products/detail/bourns-inc./PDB182-GTRB1-254MN/3780712

Bassists use them as pickup blends as they only load down the pickup you want quieter. I believe it's common practice to omit the ground in that instance and use as a variable resistor(instead of voltage divider).

 

[jwin615]

Note, make sure if you, or anyone else gets one, that it is truly MN taper and don't trust the part number. Check the data sheet. Per here:

https://www.talkbass.com/threads/balance-pot-vs-blend-pot-same-or-different.1299814/

Need MN taper not balance taper which is just B and revB.