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
amandarae
512 posts
 
If I were you, check the type of volume pot you have on the preamp. If it is 250K, make it 100K. If it is 100K, make it 50K etc. For sure, you will increase the position of the volume knob without changing the output level. You have to look at the pot and determine how the voltage divider is implemented in relationship to the pot wiper.
It is cheaper and easier to do this than buying a preamp no?
kijanki's avatar
kijanki
4,450 posts
 
Attenuation/division of the volume pot has nothing to do with its resistance and depends on the angle of rotation alone. You should get full power at about 1 o'clock.
ska_man OP
55 posts
 
Tpreaves,
The JC 2 manual suggests setting the amplifier gain controls (if any) so that the volume control on the JC 2
is between 11 o'clock and 1 o'clock during normal listening. That is (according to the manual) the "sweet
spot", where the channel tracking is closest & the distortion is lowest. As stated above, I intend to purchase
a new stereo amp or two mono block amps. The intent of the
question, is to learn about the impedance and voltage measurements and what they mean, as far as finding a good match. I will ultimately choose the amp or amps by ear,
but I do want to consider getting the JC 2 into its
"sweet spot".
ska_man OP
55 posts
 
Amandarae,

Thanks for your suggestion. I think that may be a little more radical approach to this issue than I'm willing to pursue. And, I am going to purchase a new amp or amps not
a new preamp.
amandarae
512 posts
 
Ahhh, I stand corrected. Buy an amp with a volume control in the input circuit then. Or have an amp with much less input impedance instead of the 22K.

Goodluck!
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