2. amps-preamps
  3. 1446085543

Good impedance match for Precision Fidelity C-7AR

When using my PF preamp with either my tube or SS amps, I have only two volume settings I can use, low or too loud, at between 8 o'clock to 9 o'clock on the volume pot. At the higher of the two volume settings, the preamp seems as if it is outputting full voltage. The input impedance on the tube amp is 100Kohm, and the main output impedance on the PF is 600Ohm - 7Kohm. Is this a classic case of impedance mismatching? Would it be worthwhile to see if there is a problem in the PF unit, or, should I check into locating a better matching amplifier?
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Showing 2 responses by georgehifi

georgehifi's avatar
georgehifi
10,312 posts
 

Too much gain is your problem as Al states, Rothwells attenuator plugs work but they can also create impedance matching issues.
Looks to me like the alps VC pot is on the output RCA's on this pre, and there is a tube gain stage before it.
The best bet is to either get the tube stage gain reduced that's before the alps pot by a tube tech, or sell and get a passive preamp with a logarithmic 10k pot.

7th and 6th last pic
[url]http://www.wiredstate.com/forum/viewtopic.php?f=36&t=14853&start=200[/url]

Cheers George

georgehifi's avatar
georgehifi
10,312 posts
 
"Rothwell attenuators take away some of the high and low frequencies"

That's the trouble with Rothwell Attenuators they can cause impedance mismatches if you don't do the in & out z homework.

Cheers George
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