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Old 9th February 2005, 11:50 AM   #1
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Default Which pass preamp for unbalanced in/out ?

For driving unbalanced power amplifier, which of these preamps is better option? Sound quality is very important.

Aleph 1.7 or Aleph L

Thanx
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Old 9th February 2005, 03:34 PM   #2
azira is offline azira  United States
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What exactly is a passive preamp?

Basically it's an attenuator right? as in a potentiometer?

I suppose then that there are several very high quality stepped attenuators (the chipamp evangelists all use them). Or you could choose to go with a relay powered resistor ladder and then it's a matter of resistor quality.
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Old 9th February 2005, 05:40 PM   #3
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Hello Supernet,

Personally I like the Aleph P for what you are trying to do. There has been a lot of discussion in the forum about using a BOSOZ or Aleph P verses a Passive preamp.

There is a wonderful warmth and romance to the sound when using one of the Pass active preamp circuits. If you use a balanced source and an unbalanced amp, you should expect great results.

Good luck,

-David
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Old 9th February 2005, 06:02 PM   #4
eLarson is offline eLarson  United States
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I don't know where "passive" came into the conversation. But I'm going to ignore the binary choice of the original question and recommend a BOSOZ.

You can delete the drain resistor and associated components on the non-inverting input's MOSFET since you are going to use a strictly single-ended in to single-ended out. Take the output from the other MOSFET's drain. And ground the inverting input.

Presto: signal goes in one side, comes out the other side noninverted.
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Old 9th February 2005, 06:44 PM   #5
azira is offline azira  United States
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Looks like I should just eat my words for lunch today.. I misinterpreted the title to mean passive instead of Pass. Sorry folks. Too much time reading the chipamp forum I guess.
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Old 9th February 2005, 11:02 PM   #6
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Hi Azira,

Don't feel too bad.... The Aleph L is a passive Preamp until the attuenator is set to about 75%, then the active components kick in.

Most people who have an Aleph L use it as a passive preamp.

Here's a link to the L's description.

http://www.fullswing.com/passlabs/alephl.html

-David
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Old 10th February 2005, 11:33 AM   #7
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Thanks for reply.

I was thinking that Aleph P 1,7 Susy concept will not work so good with unbalanced inputs and outputs as balanced. So my idea of Aleph L come in.

Anybody knows when X2 service manual will come? Mr. Pass said that it should come out to the end of last year. I am a little bit impatient
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Old 11th February 2005, 08:46 PM   #8
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Hi Supernet,

I asked earlier about the X2 Service manual... Here's Nelson's reply. Essentially he is waiting for patient approval for the attuenator.

Any word when the Pass X2 preamp Service imanual is available?

-David
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