JW

So,

I ordered one of these from ebay: https://www.ebay.com/itm/4pole-24-Step-Attenuator-Volume-Control-Pot-Log-A-10K-10KA-Stereo-Potentiometer/400675811718?hash=item5d4a23b186:g:rPcAAMXQinlRlEkz

It's a 10K, 24 position log value attenuator. Very nice quality by the way. Anyway, I wired it up for one channel, and it attenuates volume nicely about 8 or 10 switch positions, then doesn't roll off anymore.

My D to A converters are IZ Radar, which are 50 ohm outputs. The speaker amp's input impedance is 10K ohms. Both balanced connections.

First question is, would a 5K attenuator be better possibly? Or even 2.5K? Is the idea that since the top positions of the switch represent a similar load for the converter outputs as they would have had anyway (with no switch) but slight attenuation, it works nicely, but once the switch adds larger amounts of resistance there is not a low enough impedance driving the speaker amp? Or is it that the converters have even larger of a load at that point that it's hard to roll them off? Or both?

In other words, am  I correct in thinking the following? Since 50 ohms times 10 is 200 ohms, it'll def. drive a 10K attenuator, but with a 10K attenuator set closer to maximum attenuation, the speaker amp (class D) sees too high of a source impedance?

(I know it's a balancing act) This 10K switch actually accomplishes what I want in that it attenuates enough volume to take it down to comfortable listening levels and a little below, but it doesn't go all the way down to no volume.  I can live without that but thought I'd ask  . . .


squarewave

It must be wired incorrectly. What is the circuit? Is it like this:



My guess would be that you wired it as a rheostat instead of as a vol control.

radardoug

I'm with squarewave. No ground on the bottom end?

Gold

It should work. The issue to keep in mind (assuming it’s a potentiometer style attenuator) is that at mid rotation the amplifier will see a source impedance of 2k5 ohms. There could be some high frequency roll off depending on cable type and length.


 

Related Topics

  Subject / Started by Replies Last post
24 Replies
7982 Views
Last post October 22, 2009, 10:58:26 AM
by helterbelter
5 Replies
2145 Views
Last post October 29, 2007, 04:19:51 PM
by 12afael
5 Replies
3181 Views
Last post January 04, 2010, 01:56:11 AM
by syn
16 Replies
4895 Views
Last post October 18, 2010, 10:39:49 AM
by Kingston