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!
Goodluck!
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?
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?
- ...
- 18 posts total
>>"My guess is that there is also a relationship between the preamp output voltage"<< That's the relationship you want to look at not impedance The Aragon 8008 amp has an input sensitivity of 1.68 volts according to the factory spec That means a signal of 1.68 volts will drive the amp to it's full rated output of 200watts Your Parasound JC2 pre can put out as much as 8 volts which is 4 times more than you need to drive the Aragon It seems that the Parasound's output voltage is directly related to it's input sensitivity From the Parasound site it states that a 200MV input signal will output 1 volt at the JC2's output ... so if your source (Dac) is putting out 400MV it would probably be just about right to drive the pre so the pre would output about 2 volts and not drive your amp into overload But your PS Audio dac probably puts out 2 volts to the JC2 pre and causes the JC2 to output the full 8 volts This 8 volt output from the JC2 is way to much for the 1.68 volt input sensitivity of your Aragon ... so you have to turn the volume control on the Pre down, so as not to dive the amp into overload This is probably why you can't turn the volume control on the Pre up pass 9 oclock Simply put the 2 volt output of your dac is driving the JC2 pre amp to full gain and outputs 8 volts to your amp which is way to much ... so you turn the volume control down to 9 oclock so as not to over drive the amp Volume controls are attenuators and can only turn volume down by adding resistance ... the more you turn the volume down the more resistance you add to the circuit The more resistance added the less transparant the signal will be So ideally you would like to have your volume control turned all the way to 1 oclock where there is little to no attenuation or resistors in the circuit to reduce transparency Here are two links which may explain it better than I did http://www.rothwellaudioproducts.co.uk/html/attenuators.html http://www.rothwellaudioproducts.co.uk/html/how_attenuators_work.html HTH Dave |
Ska_man, your problem is not uncommon, and is easily fixed without changing any of your major components (although I recognize from your posts that you appear to want to do that anyway). Just get a pair of Rothwell attenuators (made by the company whose website Dave linked to). An Audiogon seller (with whom I have no connection) is offering them here: http://www.audiogon.com/cgi-bin/cls.pl?accstwek&1260621019&/Rothwell-10-dB-attenuators--rc. Contrary to what has been said, DO NOT address the problem by selecting a component with a substantially lower input impedance. That will most likely introduce frequency response irregularities into the system, because the output impedance of the component driving that input will most likely not be constant with frequency. Given that the problem is simply that your volume control needs to be set at a non-optimal point, and that there is no indication of clipping or other severe distortion, I would add that the root cause of the problem is that the overall combination of preamp voltage gain, power amp voltage gain, output voltage from the source component, AND speaker efficiency/sensitivity, is too high. In other words, it is not generally possible to assure that this kind of problem will be avoided simply by constraining the relationship of preamp output voltage to power amp input voltage, or by focusing just on any other specific interface between components. It is a system-level issue. Good luck! -- Al |
Dave makes really good points, and 8v seems like an awful lot of output for a preamp. The parameter you want to compare, when considering amps, is the input sensitivity. Start looking at different models and see how they vary from the Aragon. If they don't vary much, the issue may be with the output of the JC-2. In any case, I would call Parasound to discuss this. I hear the JC-2 is a very good pre. Sometimes there is an easy adjustment to reduce the output of a pre, but hopefully you can find an amplifier with a higher input sensitivity. Perhaps Parasound can recommend the spec you should be seeking. |
| Post removed |
- 18 posts total