• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Passive line stage with tubes

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Hey...

Sort of juggling around some equipment here, and most likely going DIY for my next preamp due to budget constraints. I've read a lot about passive "preamps" as being highly transparent and introducing nothing to the signal chain, but I've read quite a few negative comments about them at the same time. Articles such as this: http://www.enjoythemusic.com/magazine/equipment/0801/coolaudio.htm tend to make me confident that it can be done with tubes, but I figured I'd ask you all before I went out and bought anything.

Here's my situation. As the signature says, I'm going to be keeping my SV811 monos - they use a 6EA7 input stage. I'm not sure of the input impedance, but I've heard that anything from 25k to 100k is the value to use for a vacuum tube passive system. I found this on Ebay: http://cgi.ebay.com/DACT-CT2-Stereo...ryZ58164QQssPageNameZWDVWQQrdZ1QQcmdZViewItem ...seems to fit the bill and my budget quite nicely.

My sources are going to be mainly a phono preamp (not decided exactly what model yet) and a CD player or tuner.

Thank you for any help in advance.
 
Thank you both for your input.

One more question...I've found the DACT for the main volume control, but I'm planning on mounting a balance control on the rear of the unit, as a sort of "set and forget" control. More intuitive to my preferences than dual mono controls, and is cheaper :) Any suggestions on, well, good pot? :rolleyes:

I'm sure Radio Shack probably has something that will work, but I doubt the quality will be up to par...I'm not looking to spend $100 on a balance control, but middle-of-the-road quality wouldn't be a bad thing.

Thanks.
 
I'm still not completely sure what you are building. And I'm not sure what is the point of using a switched attenuator but then still putting a pot in the signal path for the balance. BUT, since you asked, I would probably look for either an ALPS or one of those PEC mil spec conductive plastic pots that were the rage a while back. A quick search should find you a good price.
 
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