[jonnywolfet]

hello all,
im a little baffled, resistors should make volume lower right? well apparently not for me.
my preamp to my speakers is far too loud, and i thought that putting a 2.2k resistor on the output to quieten the volume and allow more play on the pot... no difference. so i put 3 in series on one channel to see if i could hear any imbalance. no difference.
what is going on? im confused!

 

[AndrewFischer]

Quote:

Originally Posted by jonnywolfet /img/forum/go_quote.gif hello all, im a little baffled, resistors should make volume lower right? well apparently not for me. my preamp to my speakers is far too loud, and i thought that putting a 2.2k resistor on the output to quieten the volume and allow more play on the pot... no difference. so i put 3 in series on one channel to see if i could hear any imbalance. no difference. what is going on? im confused!

The input impedance of your amp is likely much higher than 6.6K so the voltage divider isn't doing much.

 

[AndrewFischer]

Try connecting your 2.2K resistors like this:

If possible, it would be better to reduce the gain of your amp or preamp.

 

[jonnywolfet]

thanks for your reply andrewfisher. could you explain that image for me please? i dont really know what im looking at.

 

[Awk.Pine]

Are you placing resistors before the amplifier or before the speakers? I'm assuming they're between the preamp and amp {or between the amp and speakers}.

Andrew's diagram shows the positive signal wire on the top, the negative wire on the bottom. "In" is out of the preamp {or amp}; "out" is the amp {or speakers}. The green wires show what was there before any changes. The squiggly lines are the resistors. Place one resistor (R1) in series with the positive wire; place the other resistor (R2) after the first resistor and bridging the positive and negative wires. This is called an L-pad, if you want to google it.

Now, I only think I know what I'm talking about here, so grain of salt and all.

 

[jonnywolfet]

is an l-pad strictly for the output to speakers? because my issue is with my active pre-amp and not my power amp. is it worth a try on my pre anyway?

 

[kklee]

The circuit is a simple voltage divider and works the same way a volume controls works in adjusting input level to an amp. A very simplfied explanation (without factoring in output/input stage impedances) is that the output voltage a fraction of the input voltage. The ratio is determined by the value of the top resistor versus the bottom resistor.

Output = Input * (Rtop/(Rtop+Rbottom))

The example shows equal values for both resistors so you get 1/2.

So if Rtop is 2K and Rbottom is 1K, the output would be roughly 1/3 of the input. A volume control works the same way by changing the ratio as you turn the knob.

You would use this circuit in the amp's input.

 

[jonnywolfet]

awesome. ill try that tomorrow.
Thanks!

 

[jonnywolfet]

cool, i learned me a new trick! that works awesomely, thanks very much!