Pre-Amplifier Aleph P 1.7 - why Attenuator Network after the Gain Stage? - diyAudio
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Old 1st November 2010, 01:33 AM   #1
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Default Pre-Amplifier Aleph P 1.7 - why Attenuator Network after the Gain Stage?

What is the reason for the location of the relais controlled volume control behind the gain stage (instead in front of) ?

Actually I must take into account the same disadvantage by this model than by passive pre amplifier with volume control commonly usual:
Volume-dependent low-pass filtering due to the following cable capacity.

Are there at least one advantage, if I use a connecting lead, that have ultra low capatitance ?

have a look also to post #14 about
Aleph P 1.7: 2k pot is in the signal path?

BTW - all PDF-URL's of service manuals from the Aleph series are death in the meantime - e.g.
http://www.passlabs.com/pdf/aleph/apserv17.pdf
since the sites "www_passlabs_com" get new design.
Who knows an other PDF-URL therefore ??
Attached Files
File Type: pdf Aleph P Volume Control.pdf (17.1 KB, 339 views)

Last edited by tiefbassuebertr; 1st November 2010 at 01:40 AM.
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Old 1st November 2010, 05:55 PM   #2
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I'm no expert but it attenuates both noise and signal, leaving only random electron noise at full attenuation.

It has been said that it can drive almost any load. Mine IS as quiet as death.
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Old 3rd November 2010, 09:24 AM   #3
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Quote:
Originally Posted by Bill Fuss View Post
I'm no expert but it attenuates both noise and signal, leaving only random electron noise at full attenuation.

It has been said that it can drive almost any load. Mine IS as quiet as death.
I see. But a better way it would be to avoid voltage gain in the line preamp. Then I would use a small power follower (basicly low noise character through Unity Gain). This means no audible disadvantages regarded noise by using the attenuator in front of that stage and no parasitic interferences through certainly cable characters at the same time (by Aleph P 1.7 still a problem, especially by long wires to mono block devices near by the speakers).
A good ciruit design for such a stage would be Andrea Ciuffoli's power follower but with lower supply voltage and idle current
http://www.audiodesignguide.com/my/Follower_99c.gif
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Old 3rd November 2010, 10:18 AM   #4
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Quote:
Originally Posted by tiefbassuebertr View Post
...But a better way it would be to avoid voltage gain in the line preamp...
That's why there is the B1. http://www.passdiy.com/pdf/B1%20Buffer%20Preamp.pdf
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Old 7th November 2010, 04:48 PM   #5
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Quote:
Originally Posted by tiefbassuebertr View Post

BTW - all PDF-URL's of service manuals from the Aleph series are death in the meantime - e.g.
http://www.passlabs.com/pdf/aleph/apserv17.pdf
since the sites "www_passlabs_com" get new design.
Who knows an other PDF-URL therefore ??
Try http://www.diymania.net/pass/project...h/apserv17.pdf
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Old 7th November 2010, 04:54 PM   #6
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Maybe also the SUSY-efect works better when there is a larger voltage ..............
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Old 7th November 2010, 05:26 PM   #7
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Quote:
Originally Posted by Rodeodave View Post
yes, a good solution for small cable capacities (i. e. short connection to power amp). If there is a multi amping system in use with several long leads to the power amp inputs, more idle current in the line stage is necessary to avoid unwanted low pass character.
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Originally Posted by generg View Post
thank you for this URL - at whole interesing things to find about
http://www.diymania.net/

Last edited by tiefbassuebertr; 7th November 2010 at 05:29 PM.
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