terataz

Uneven volume in amps??

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Hi expert members of the Wam,

I've got a dilemma here that require some attention please:

On my two integrated valve amps, a Trafomatic Audio and a Croft Camaleon, the right channel sounds several db higher than the left one.

THE TESTS DONE SO FAR:

- Swap speaker (685 B&W) left to right and viceversa: no changes, right higher

- Listening close (10 cm) from the speaker or further away (2-3m): no changes, right higher

- Swap IC/channel: no change, right higher

- Swap IC/speakers: no change, right higher

- Checked for phase in IC black/black-red/red: they are fine

- Changed from HF to LF: no changes.

- Changed source (digital,analog): no changes

...I'm at loss. I read somewhere this is somehow considered "normal", but in my opinion that's simply not true. I also can't believe two amps , from different brand/previous owners might have a "balance" problem on the same channel.

Any idea of what this might be due to? All suggestion greatly appreciated.

Thank you

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I am unclear: Did you swap left and right channels from the source to the amp to see if the imbalance moved? I mean JUST the left and right source interconnects?

Sent from my GT-I9195 using Tapatalk

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Have tried swapping speaker cables left to right. Could be a poor connection/ joint on the Banana plugs.

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What you need to do is measure the signals in and out.

By far the best way. Play a mono signal, preferably a tone from a signal generator...you can use Audacity to create a 1kHz test signal and play that, or burn it to a CD.

Play that from your source, and measure the output of the PC or CD player. Then measure the output of your amplifier. Both channels should be equal, to within 2-3dB, ideally 1dB (say 10%).

You can use a normal digital multimeter costing £10 from Maplin or whoever to do the measurement. They're not particularly accurate at 1kHz, but you're not looking for a specific measurement, just whether they're the same, within 10-20% which is close enough.

S

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Also, turn your back on your system and listen.... Just in case it's your lugholes!

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Thanks for all the replies.

Just changed digital source (playing from simple mobile phone out) and the story is the same. That should roule out the source, including the source IC

Also, swapped the speaker cables, amp side, and the right left speaker is now louder. This seems to confirm that it's somehow at the amp level (left is now connected to right out on amp).

Played a 1Khz tone from a signal generator (there's an app for that of course) fairly loud, and it is still clearly louder on whatever is attached on right out of amp. (wife confirmed each time in a sort of blind test).

I then took a multimeter and measured the output on each channel of the Trafomatic : 0.1 on the left and 0.8 on the right (the loud one).

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Thanks for all the replies.

Just changed digital source (playing from simple mobile phone out) and the story is the same. That should roule out the source, including the source IC

Also, swapped the speaker cables, amp side, and the right left speaker is now louder. This seems to confirm that it's somehow at the amp level (left is now connected to right out on amp).

Played a 1Khz tone from a signal generator (there's an app for that of course) fairly loud, and it is still clearly louder on whatever is attached on right out of amp. (wife confirmed each time in a sort of blind test).

I then took a multimeter and measured the output on each channel of the Trafomatic : 0.1 on the left and 0.8 on the right (the loud one).

It would then seem that the Trafomatic has a fault, probably in the tracking of the volume control, but could be elsewhere. You mentioned that your other amplifier does the same. Is that still the case?

Whilst it's possible two amplifiers have the same fault, it's pretty unlikely so you should confirm that first.

Just for completeness, you should check with your multimeter that the output of your signal generator has identical output on the two channels.

If only the Trafomatic has the fault, it should be fairly easy to find and fix.

S

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Thanks Serge,

tried on the Croft and the different is there, just less prominent it seems 0.9 vs 1.0.

I'm not sure how i can check the output of the signal generator? It's a simple jack to rca cable from my phone to the amp.

Appreciated

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Thanks Serge,

tried on the Croft and the different is there, just less prominent it seems 0.9 vs 1.0.

I'm not sure how i can check the output of the signal generator? It's a simple jack to rca cable from my phone to the amp.

Appreciated

Just put the multimeter across the RCA connectors. You should measure something like 1-2 volts with the phone's volume at maximum. I would be surprised if there was any difference between Left and Right, but one of the guiding principles of making measurements is never assume anything, always check.

The difference between 0.9 and 1.0 is about 1dB so is about as close as you'll get with conventional rotary volume controls.

S

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I find this depending on which rotation of equipment is in use (usually a bit of it is being looked at by Serge, because I always pick the most reliable gear...)

Edd9000's advice is to generally listen for an hour or 2 - the brain will get used to a balance discrepancy after some time, especially one as minimal as you have measured on your Croft amp.

That said, the only time I cannot get used to it, is if I have my speakers positioned so that the mid and tweeter drivers are next to the wall - the reflection from the left makes me feel sick because it beams so much, it is bizarre, so I swapped them so the mid and tweeters are on the inside.

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Possibly a bad interconnect or RCA plug?

Unlikely 2 amps could have similar fault on the same channel.

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Seriously... Are you sure this is not your ears ? "Several" db is very substantial and the power required to notice is meaningful,

just find a mono source (iPhone tone generator, line in etc) and turn around. Still louder, but now on what was the left (still your right) then you have to suspect.

Try headphones.. Mono source.

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How does the room look? Could be the acoustics? Have you tried re-positioning your speakers?

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