Low volume imbalance

lazyfly · 25th June 2004, 01:46 PM

Hi folks.

I've got a pair of 50W modules running and have used the 'Better Volume (and Balance) Controls' - Rod Elliott - ESP / Bernd Ludwig. http://sound.westhost.com/project01.htm

It's definately smoother than the 50kOhm log pot I was using but at very low volume levels there's a definate bias to the right channel (in a cheesy 1 - 10 scale, anything below 1 the right channel is clearly lourder!). Can anyone explain what's happening here. I'm an aspiring electronic buff novice

or something.

The only clue I have in regards to the bias is - aside from a cheap pot! - the speaker outputs on the modules show different measurements. The left channel shows 24mV the right 28mV. Is this anything to do with it?

It's not noticable at normal listening levels but at night when folks are sleeping the < 1 (on that cheesy scale) is an ideal level... but for the bias!

Thanks in advance to any replies and just for reading.

Kendal.

p.s I made two volume controls and matched the resistors on both to as best I had. The bias was there regardless.

sreten · 25th June 2004, 03:37 PM

Add a -10dB or or -20dB pad switch to your volume control
so you never have to use below 1, will work a treat.

sreten.

carlosfm · 25th June 2004, 03:54 PM

The problem is the cheap pot.

If you have some of those, measure them and use the pot that has smaller difference between channels.

lazyfly · 26th June 2004, 01:37 AM

sreten... what?? eh? Keyword here is 'novice'

carlos, thanks, I'll try that but I've problem I didn't notice yesterday that is taking precedence over the bias thing. When changing music tracks there's a mild thud in the left channel, argh! The right channel doesn't make a sound but the left has this little 'skip track' - 'dink' - 'track begins' noise. It's like the noise of very briefly touching the source (input) terminal. Any suggestions as to what would/could be causing this?

Oh yeah, I tried a different volume pot to cure this but no luck there.

Thanks again fellas!

Kendal.

lazyfly · 26th June 2004, 05:23 AM

Hi folks - ignore my last post as I found the culprit. A dodgy RCA socket

rabbitz · 26th June 2004, 01:31 PM

If you need a balance control use the design from Rod's project 88. Works a treat and is not in the signal path...... nice and simple.

http://sound.westhost.com/p88-f3.gif

http://sound.westhost.com/project88.htm

Some of these pots are real crap. Bought one from Jaycar and was really scratchy. Ended up using an Alps from Farnell.

Cheers

anatech · 26th June 2004, 06:33 PM

Hi lazyfly,
Almost all pots suffer from tracking problems at the lower end. A -10 / 20 dB switch is a realistic approach. The only other way to get around this is to use a switch with a audio taper resistor network. I will consider a DAC to be the same approach. Personally, I like a -20dB switch and good audio control.
Life is too short to get freaked about channel matching at really low levels.
-Chris

25th June 2004, 01:46 PM	#1
lazyfly diyAudio Member Join Date: Jun 2004 Location: Melbourne	Low volume imbalance Hi folks. I've got a pair of 50W modules running and have used the 'Better Volume (and Balance) Controls' - Rod Elliott - ESP / Bernd Ludwig. http://sound.westhost.com/project01.htm It's definately smoother than the 50kOhm log pot I was using but at very low volume levels there's a definate bias to the right channel (in a cheesy 1 - 10 scale, anything below 1 the right channel is clearly lourder!). Can anyone explain what's happening here. I'm an aspiring electronic buff novice or something. The only clue I have in regards to the bias is - aside from a cheap pot! - the speaker outputs on the modules show different measurements. The left channel shows 24mV the right 28mV. Is this anything to do with it? It's not noticable at normal listening levels but at night when folks are sleeping the < 1 (on that cheesy scale) is an ideal level... but for the bias! Thanks in advance to any replies and just for reading. Kendal. p.s I made two volume controls and matched the resistors on both to as best I had. The bias was there regardless.

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25th June 2004, 03:37 PM	#2
sreten diyAudio Member Join Date: Nov 2003 Location: Brighton UK	Add a -10dB or or -20dB pad switch to your volume control so you never have to use below 1, will work a treat. sreten.

25th June 2004, 03:54 PM	#3
carlosfm Banned Join Date: Mar 2003 Location: Lisbon, Portugal	The problem is the cheap pot. If you have some of those, measure them and use the pot that has smaller difference between channels.

26th June 2004, 01:37 AM	#4
lazyfly diyAudio Member Join Date: Jun 2004 Location: Melbourne	sreten... what?? eh? Keyword here is 'novice' carlos, thanks, I'll try that but I've problem I didn't notice yesterday that is taking precedence over the bias thing. When changing music tracks there's a mild thud in the left channel, argh! The right channel doesn't make a sound but the left has this little 'skip track' - 'dink' - 'track begins' noise. It's like the noise of very briefly touching the source (input) terminal. Any suggestions as to what would/could be causing this? Oh yeah, I tried a different volume pot to cure this but no luck there. Thanks again fellas! Kendal.

26th June 2004, 05:23 AM	#5
lazyfly diyAudio Member Join Date: Jun 2004 Location: Melbourne	Hi folks - ignore my last post as I found the culprit. A dodgy RCA socket

26th June 2004, 01:31 PM	#6
rabbitz diyAudio Member Join Date: Jul 2003 Location: Newcastle, Australia	If you need a balance control use the design from Rod's project 88. Works a treat and is not in the signal path...... nice and simple. http://sound.westhost.com/p88-f3.gif http://sound.westhost.com/project88.htm Some of these pots are real crap. Bought one from Jaycar and was really scratchy. Ended up using an Alps from Farnell. Cheers

26th June 2004, 06:33 PM	#7
anatech diyAudio Moderator Join Date: Jun 2004 Location: Georgetown, On	Hi lazyfly, Almost all pots suffer from tracking problems at the lower end. A -10 / 20 dB switch is a realistic approach. The only other way to get around this is to use a switch with a audio taper resistor network. I will consider a DAC to be the same approach. Personally, I like a -20dB switch and good audio control. Life is too short to get freaked about channel matching at really low levels. -Chris