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L-R balance problem at low volume on XM4

post #1 of 6
5/23/09 at 8:46pm
Thread Starter 
Hey everyone. I recently received a Practical Devices XM4 amp and a major thing I've noticed is that at low volume, it seems that the right side is louder. I have to turn it up a little bit for it to balance out. Not really sure why, is that normal?

I noticed the same thing on my PA2V2, but it was on a much smaller scale (usually not even noticable) and perhaps it was even because of the channel-specific gain settings being slightly off.

This is a bit of a problem, especially when I'm listening at night when I'm not used to "louder" sounds anymore.

Could it be the headphones? opamp? I have the gain on low and the 9V battery still has a lot of charge.

Thanks for any help
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post #2 of 6
5/23/09 at 9:14pm
My XM5 has a slight channel imbalance but it never bothers me because it occurs at a volume lower than I need to use. Have you contacted PD with your concern?
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post #3 of 6
5/23/09 at 10:28pm
The imbalance comes from the volume pot (potentiometer), and it is very common. It is actually very difficult to find potentiometer that doesn't have an imbalance on the first few steps and this problem affects more on low impedance, high sensitivity headphone (i.e. IEM). To reduce the symptom, you will need to lower the gain of the amp so you can turn the volume pot higher up which goes beyond that problematic part. If low gain doesn't help, you can try resistors adapter too. The imbalance vary from pot to pot, so it might be a more severe case in your amp that you could ask PD to for replacement.

This is actually one of the big reason why the upcoming Pico slim and RSA amp will feature digital attenuation instead of relying on conventional volume pot.
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post #4 of 6
5/24/09 at 2:25am
Thread Starter 
Hmm.. thanks for the info guys. I'll try emailing the company and see what they/I can do. I just did a quick search for some impedance adapters and they're around $20. It seems kind of expensive to me, is that an average price?
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post #5 of 6
5/24/09 at 4:19am
$20 is about right, however you could get one made for next to nothing...well maybe $5 in parts.
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post #6 of 6
5/24/09 at 1:19pm
Thread Starter 
well, it seems easy enough to build one so I think I'll go that route. Probably won't look as professional but it'll work all the same, heh.

[edit: So, I went out and bought some 150ohm resistors and an extension cable. Wire/soldered it all up and it does help a little. The true test will be when I listen tonight.]
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