Aleph P with balanced shunt attenuator

[lauret]

Hello all,

I'm using my Aleph P1.7 right now single-ended with a 10K 41-step 1,5dB-per-step series attenuator on the output from Acoustic Dimension. Would it be possible to use this attenuator in a balanced series-shunt attenuator like shown on the right side in this picture:

An externally hosted image should be here but it was not working when we last tested it.

Ok, I have three questions regarding this setup:
Any drawbacks in this configuration? Is the Aleph P1.7 up to this config? And lastly what should be the value of the series resistors?

Thanks!

 

[Bill Fuss]

It should work OK, I would try 1k for starters.

 

[lauret]

It should work OK, I would try 1k for starters.

Just for learning purposes: what is the reasoning behind 1k?

BTW, can I still use it SE when configured in the balanced shunt way?

 

[Bill Fuss]

That's a good question. Referencing the signal to ground, it would surely change the response. After thinking a minute, no, it wouldnt work correctly single ended. A simple DPDT switch would work though, switching the bottom of the att. from ground to the other output.

1K is just a guess as you are using it as a variable voltage divider.

 

[Nelson Pass]

Maybe a little higher - 5 to 10k

 

[lauret]

That's a good question. Referencing the signal to ground, it would surely change the response. After thinking a minute, no, it wouldnt work correctly single ended. A simple DPDT switch would work though, switching the bottom of the att. from ground to the other output.

I see that the D1 also uses such a volume control, but there it is squeezed between active circuitry. So that would be the condition for both the functioning of SE and balanced without a switch?

 

[Bill Fuss]

I'm not familiar with the D1, but I bet that other poster knows something about it.

 

[daly41k]

balanced attenuator

If you go to Erno Borbely's web site you will find a tweak for a balanced volume control that looks very similiar to yours that he recommends for use with his equipment. You can compare the resistors used in the balanced arrangement. I have tried it and it works fine. dave

 

[dobrivoje]

Go to Uskok_Preamplifier. There you'll find exellent balanced attenuator. Some text is Croatian, but drawings are in English.

 

[DiyFan]

This site: Shunt Pot Volume Control - World-Designs-Forum shows how to calculate values for shunt controls.

Sean