Balanced Crack

[Karl5150]

While I'm collecting the parts to try building the 3D pre-amp it occurred to me that a balance control on my Crack (?) would be nice. Using the Stereomour II as a guide I came up with this scheme. Please be kind enough to point out errors.
Thanks,
Karl

 

[lth1]

I use two mono pots most of the time, makes things a lot easier but more costly, always thought that a balance pot was just unneeded wire that could possible effect the sound.  If I do not use two mono attenuators I replace the Bottlehead alpha pot with two mono PEC pots, have a box full of unused A100K pots.

Either way you are using two pots and modifying the top plate, just believe that the better solution is two mono volume pots or attenuators.

 

[Karl5150]

Thanks for the input Lee, I hadn't thought about the extra wire involved. Dual-mono is the way I went on my SEX amp at work, but it gets a bit fiddly to lower the volume for a phone call then turn it back up again and re-center the image.

 

[lth1]

I do not know what is involved in installing a mute switch, but this would solve the phone or other interruptions problems.  Just a two pole on/off inline switch would probably work.  Let the experts answer this question.

 

[fullheadofnothing]

Why do you need a mute switch? Just take off the headphones.

 

[Karl5150]

Josh, the Crack is at home. Thinking about the balance option to make up for my uneven head / hearing, I have to wear headphones slightly askew to center the image.
The SEX amp with the dual-mono volume is at work, no headphones allowed there. If the Stereomuor based balance works on the Crack without perceptible sonic penalties I might give it a try on the SEX too.
I really started the thread to make sure the resistor value was ok for the Crack and I hadn't transposed any wiring.
Thanks
Karl

 

[richmi]

I have the same problem as you.

I did not use the potentiometer that came with the kit, but 2 mono ones.

The extra aluminum plate is there because I made a mistake when I bored the second whole. I had used the knobs as a guide; I should have used the potentiometers instead. Working with a template is a good idea.

Here are photos of my build.

Richard

 

[photoduo]

I want to experiment with dual mono pots as well.
Found some info on Cosmos TOCOS Carbon Mono Trimmer Potentiometers 1 Turn 100K Ohm .5W
There are a few comparisons online about these and old Alps Black Beauty similar sound quality for whatever that is worth.
There is a choice between a .5W and 1W version on fleabay.
Any suggestions as to which wattage would work with crack or crackatwoa?
Thanks
Charlie

 

[Paul Birkeland]

The wattage won't matter, but the physical form factor can be pretty important.  Pots that are much smaller than the stock pot won't fit the holes in the chassis very well, while pots that are much larger could run into the wood base or other parts of the amp.