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Bypassing A Preamp With Volume Pot In Amp

I see preamps as a convenient tool to control the volume of multiple sources. It only adds another link in the chain. It also adds to the cost of your system because you will need other pairs of interconnects and a power cable.

I was thinking about completely bypassing a preamp by adding a volume pot or a resistor based stepped attenuator into the amp, greatly reducing the signal path from the source to the amp.

The only detriment I can think of, is switching the interconnects from each source which is as troublesome as switching out a disk from the CD player.

Please chime in with your opinions and especially your experiences with this "issue".

The volume control I have in mind is the Khozmo stepped attenuator using 2 Vishay TX2575 resistors in a hybrid tubed/ss amp.
c_avila1
georgehifi's avatar
georgehifi
10,312 posts
 
C_avila1
You haven't mentioned the input impedance of your poweramp.

I say 10K as a general even when direct connected, as most amps are 47kohms (industry standard) input impedance.

If you have say a Rogue tube poweramp which are 1mohm input impedance then yes a 50kohm pot will be more than fine.

Just remember it's easier to manufacture a 10kohm stereo log pot so that both channels track each other within a db or so than it is to manufacture a 50kohm stereo log pot to track that well.

Cheers George
b_limo's avatar
b_limo
2,273 posts
 
C,
Just ask George which is better. What you are considering doing OR just buying a Lightspeed attenuator and another pair of less expensive rca's to bridge the connection. I understand where you are coming from wanting to keep the rca's of the same quality within the chain, but I'd bet the lightspeed with some mediocore interconnects will sound better than what you are trying to do. I could be wrong...

Ask George what he thinks. By the way, I have no relation to George other than being one of many, many happy customers. His lightspeed thread is one of thelongest here, with glowing reviews!
lse
83 posts
 
Must be some special pot.
georgehifi's avatar
georgehifi
10,312 posts
 
Lse, it's not a pot (potentiometer).

It's just like a direct connection between source and power-amp with none of the contacts or preamps active components in the signal path, like a pots very lightweight wiper contact or switched resistor pots contacts in the signal path.
It's just a single fixed soldered resistor, that just happens to be able to change it's resistance value by being light sensitive.

It's the most transparent, uncoloured, dynamic way of getting the signal of the source to the power-amp, without any active tube or solid state components or contacts in the signal path.

You can read all about in these two threads.

http://forum.audiogon.com/cgi-bin/fr.pl?aamps&1276356977&&&/Lightspeed-Attenuator-Best-Preamp-Ever-

http://www.diyaudio.com/forums/analog-line-level/80194-lightspeed-attenuator-new-passive-preamp.html

Cheers George
jetrexpro
506 posts
 
I've installed a Goldpoint stepped attenuator in my amp and soldered my interconnects directly to it. My CD player and phono pre have no trouble driving the amp.
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