passive preamplifier newbie question

Jamh · 1st December 2003, 05:00 AM

I needed to build a passive preamp with just one source. This is a totally newbie question. I bought 2 10Kohms pots from radio shack, put them in a box, and soldered 2 sets of wires, the input set going to the CD player, and the output set going to the power amp. I tested everything, the resistance varies between 1 ohm and 9.2 Kohms. But when I hook everything up, nothing happens. When I turn the pots, they have no effect! What is going on? Shouldn't 10kOhm make some difference?

Thanks, and sorry if this is too basic.
Jam

Richard C · 1st December 2003, 02:04 PM

The wiper (centre pin) of the pot goes to the amp, of the two remaining pins connect one to 0V (screen) and the other to the CD player output. If the volume works in reverse swap the end connections.

I guess you,ve just connected them in series, this won't work.

sreten · 1st December 2003, 02:12 PM

When its correctly wired up (but not connected) :

The input resistance will not vary - will stay at 10k.

The output resistance will vary from 0 (min) to 10k (max).

The through resistance will vary from 10k (min) to 0 (max).

/sreten.

Jamh · 2nd December 2003, 05:38 PM

Thank you for your responses. I had indeed installed it in series.

1st December 2003, 05:00 AM	#1
Jamh diyAudio Member Join Date: Dec 2003 Location: sacramento	passive preamplifier newbie question I needed to build a passive preamp with just one source. This is a totally newbie question. I bought 2 10Kohms pots from radio shack, put them in a box, and soldered 2 sets of wires, the input set going to the CD player, and the output set going to the power amp. I tested everything, the resistance varies between 1 ohm and 9.2 Kohms. But when I hook everything up, nothing happens. When I turn the pots, they have no effect! What is going on? Shouldn't 10kOhm make some difference? Thanks, and sorry if this is too basic. Jam

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1st December 2003, 02:04 PM	#2
Richard C diyAudio Member Join Date: Jul 2003 Location: Nottingham, England	The wiper (centre pin) of the pot goes to the amp, of the two remaining pins connect one to 0V (screen) and the other to the CD player output. If the volume works in reverse swap the end connections. I guess you,ve just connected them in series, this won't work.

1st December 2003, 02:12 PM	#3
sreten diyAudio Member RIP Join Date: Nov 2003 Location: Brighton UK	When its correctly wired up (but not connected) : The input resistance will not vary - will stay at 10k. The output resistance will vary from 0 (min) to 10k (max). The through resistance will vary from 10k (min) to 0 (max). /sreten.

2nd December 2003, 05:38 PM	#4
Jamh diyAudio Member Join Date: Dec 2003 Location: sacramento	Thank you for your responses. I had indeed installed it in series.