impedence value.? amp to preamp.

05-05-09: Sidssp
The concern of resistor based attenuator is that the output impedance changes
a lot depending on the setting. That means when matched with a low input
impedance amp, your system may sound very different as you turns the volume
up and down.

I'm afraid that I do not quite agree with you. For example, here is one implementation of a resistor attenuator:
http://www.tweakaudio.com/Attenuator%20info.html
The only places where the impedance will be high & is likely to affect the sonics is at the -0.5dB, -3dB, -5dB, -7dB settings. Of these settings the -7dB setting is probably the best as the effective impedance the power amp would see in the 500 Ohms region. This is still high for a 10K input impedance power amp but it just *might* work - on the cusp.
(BTW, a digression: my calculations show the 1M resistor provides -0.008dB attenuation, the 4.99K provides -1.5dB attenuation, the 1.69K provides -4dB attenuation, etc. Am I missing something here? Is he adding some other resistor in series w/ the 1K such as the source output impedance (which is not shown)?)
More often than not, the user is going to be in the -31dB range where the effective resistance of this attenuator will be defined by the resistor to ground - which is a very small value. Thus, for even a 10K input impedance power amp this should not be an issue.
(this is all electrically speaking, which is the focus here. No idea what the in-line attenuator does to the overall sonics - my intent is *not* to discuss that here).

hi thanks for your input,i will keep interconnects short .5m,also balanced.longer speaker cables.this should help.into 8 ohms i have325rms. so power is there.also helpful.my source will be two cd transports.one arcam,,and one audio alchemy.thi should give me an edge over a normal cd unit.

05-05-09: Bob_reynolds
Sorry for being dense, but I don't understand what interactions there would be by adding a resistor bewteen the source and amp. Could you give some examples? Thanks.

Bob, 1stly, who is the question directed to? The forum in general OR to any particular member?
2ndly, not sure what you are asking - you mean what are the ill-effects of adding a SERIES resistor between pre & power?
You wrote "source" which I interpret as CDP/tape-deck/reel-reel/TT, computer, etc but the author was talking between pre & power. So, you mean between pre & power OR source & power amp, as you wrote?
Thanx.

First, start with the source impedance. Then add to it the value of your passive. That is now the source impedance (much higher) at low volumes. A tube amp has a high input impedance- 100K is common.

The result is that the high output impedance of the volume control, with the high input impedance of the amp, and the character of the interconnect cable itself will result in drive difficulties at low volume, because the source impedance will be primarily the value of the control. At higher volumes this effect is reduced. Thus it is to your advantage to not have a whole lot of voltage output (3 volts max) out of your source, so that you can run the volume control near the top! Midway down, and the control is already degrading the signal.

Most CD player manufacturers don't get this simple point, and so put **way** too much output from their players. I've seen them as high as 15 volts- making a passive control useless (if you want it to sound right).