2. amps-preamps
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Amplifier input tech question

In my current system the volume control can only be turned
up to the 9 o'clock position or so, until the music is too
loud. The components are as follows;

cd- Rotel RCD-990 (transport only)
PS Audio DLIII with Cullen stage 4 mods

pre- Parasound JC 2

amp- Aragon 8008st

spks- KEF reference model 3

I am just starting to do my research for upgrading the
amplifier. And, would like to make certain that I select
an amp or amps that are less sensitive than the Aragon.
I have read about the minimum 10 times impedance difference
between pre-out and amp-in. But there must be more to it,
as the JC 2 output imp is stated as < 60 ohms and the
Aragon is listed as 22k ohms. My guess is that there is also a relationship between the preamp output voltage
and the amout of voltage the amp needs for full output.
Is there a formula I can use for finding a good match?
ska_man
Post removed 
ska_man OP
55 posts
 
Davehrab,
That makes perfect sense. Thank you so much for your
informative and exactly on point reply!
ska_man OP
55 posts
 
Almarg,
I have read many of your responses to other posts over the past several months, and I must say I feel somewhat honored that you replied to mine. Thank you for sharing your knowledge and wisdom, it is much appreciated!

magfan
1,583 posts
 
What is the taper of the vol pot?
The 2 most common (are there more?) is Linear and Logarithmic.

Just sounds like your vol is coming on too fast.
almarg's avatar
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almarg
8,673 posts
 
As Bob very correctly indicated, the 8 volt maximum output of the preamp is irrelevant. A preamp with a significantly smaller maximum output specification would not help the problem you are trying to address (everything else being equal), and if that number were much lower than 8 volts a new problem might even result, clipping of its output stage on high volume peaks.

What is relevant is the preamp's gain, which as Dave indicated is a factor of 5 (200mv in producing 1v out), which is a gain of 14db. That is certainly NOT particularly high.

Also as Bob correctly indicated, the power amp input sensitivity of 1.68 volts is a fairly typical number, and most power amps with similar output power ratings (200W in this case) will therefore have similar voltage gains.

Your speakers appear to have a sensitivity rating of 91db, which is higher than average but just slightly.

Therefore to the extent that it is meaningful to identify a "culprit," Bob's suspicion is probably correct. The DAC is probably putting out an excessively high voltage.

But whether it is or not, as I indicated in my previous post a simple solution is to insert in-line attenuators.

Regards,
-- Al
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