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Old 10th May 2010, 08:44 AM   #1
lauret is offline lauret  Netherlands
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Default Aleph P with balanced shunt attenuator

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:
Click the image to open in full size.

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!
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Old 10th May 2010, 10:10 AM   #2
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It should work OK, I would try 1k for starters.
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Old 10th May 2010, 02:21 PM   #3
lauret is offline lauret  Netherlands
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Quote:
Originally Posted by Bill Fuss View Post
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?

Last edited by lauret; 10th May 2010 at 02:30 PM.
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Old 10th May 2010, 09:07 PM   #4
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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.
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Old 11th May 2010, 02:13 AM   #5
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Maybe a little higher - 5 to 10k

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Old 11th May 2010, 06:19 AM   #6
lauret is offline lauret  Netherlands
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Quote:
Originally Posted by Bill Fuss View Post
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?
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Old 11th May 2010, 11:20 AM   #7
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I'm not familiar with the D1, but I bet that other poster knows something about it.
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Old 11th May 2010, 02:41 PM   #8
daly41k is offline daly41k  United States
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Default 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
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Old 12th May 2010, 08:47 PM   #9
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Go to Uskok_Preamplifier. There you'll find exellent balanced attenuator. Some text is Croatian, but drawings are in English.
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Old 13th May 2010, 01:54 AM   #10
DiyFan is offline DiyFan  United States
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This site: Shunt Pot Volume Control - World-Designs-Forum shows how to calculate values for shunt controls.

Sean
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