2. amps-preamps
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Passive & Tubed pre-amps to power amp at same time?

Would any harm be done by using a Y-splitter to simultaneously connect a passive pre-amp and tubed pre-amp to the same power amp? The idea would be to use the passive for volume control and run signal from a CDP to the power amp. The tubed pre would be used for sending other inputs (e.g., phono) to the power amp. All devices would be "powered up" at the same time but only one input at a time would be used. Thanks in advance.
128x128ghosthouse
ghosthouse's avatar
ghosthouse OP
4,319 posts
 
Thanks for the idea George. What I am trying to do is introduce volume control
for the CDP without any addition boost in gain while leaving other sources
unaffected that run through the tubed pre-amp. Your idea does seems like
something to explore. No tape out...but sub out. However, I am going with Al's
suggestion of attenuators. Ordered a couple of Harrison Labs -12dB RCA plugs
from Parts Express. Much less expensive than those from Rothwell and Parts
Express allows returns if they don't work out. Others on A'gon do report
satisfactory results using these. Thanks again to all for the suggestions.
ebm
9,311 posts
 
Very bad idea splitters are bad quality.
almarg's avatar
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almarg
9,670 posts
 
Ghosthouse, if you happen to have a multimeter it would be interesting to know the values of the two resistors that are presumably used in the Harrison Labs attenuator. The values aren't particularly critical, but knowing them may provide added confidence in their suitability for the application.

You would take two resistance measurements, one between the input center pin and the output center pin, and one between the output center pin and its ground sleeve.

I've measured those values in the Rothwell 10 db attenuator as 22K and 10K respectively, which seem like reasonable numbers for most (but not all) applications. Especially, as in your case, when used between a solid state signal source (presumably having low output impedance) and the input of a tube-based component (presumably having high input impedance).

Also, thanks very much for the nice words. Best regards,
-- Al
atmasphere's avatar
atmasphere
11,979 posts
 
PlanB: place the passive between the CDP and the preamp input.
Adjust to suit, but keep your cables short as passives have been shown to be quite sensitive to cables!
ghosthouse's avatar
ghosthouse OP
4,319 posts
 
Al - Have multimeter. Will measure.

Atmasphere - Good one. That would allow me to do what Zd suggested 6 posts above yours. He was thinking my CDP had a volume control (at least, that's how I read it). Re passives' sensitivity to ICs, I assume this would be to ICs on the output side of the pre-amp?

Everyone - thanks. Lots of stuff to try.
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