RC-1550: left channel has a lower gain than right at low volume.

[dxL]

I sent this message recently to Rotel Support Europe (no answer yet), but it seems interesting to me to post it on this forum too:

Two weeks ago I bought a new Rotel combination consisting the RC-1550 and the RB-1552. I'm very pleased with the overall sound quality, but today I noticed a minor problem...

When I listened to music at a low volume it seems that the right channel was louder than the left. I was not sure, so I decided to do a test. I linked the output from the RC-1550 to my DAC. Now it was possible for me to recieve the signal of the preamplifier on my computer and to visualize it with Adobe Audition. I used a 15000 Hz sine wave to this test at different volumes. These are my findings:

When the volume knob was set between "7 and 8 o'clock" I found a diffence of 4dB between left and right channel (right was indeed louder). When I increased the knob to 9 o'clock I could measure up to 1dB diffence between the two channels. When increasing the volume even further, the difference was negligible.

Now I could read on the internet that small volume differences of analog volume controls are normal in greater or smaller extent. But in my opinion, 650 euros costing preamplifier has to perform perfectly, certainly volume balance.

So my question to you is: would it be possible to solve this issue easily?

Thanks,

dxL
Belgium

[madmac]

That's really odd??. I assume you have checked all wires and connections and source feeds?. Most Rotel products allow you to set speaker levels via the speaker setup area of the menu via the remote using test tones and a SPL meter.

[srb]

Most Rotel products allow you to set speaker levels via the speaker setup area of the menu via the remote using test tones and a SPL meter.

The RC-1550 is a two channel analog preamplifier, not a digital surround processor or receiver.

Steve

[dxL]

The RC-1550 is a two channel analog preamplifier, not a digital surround processor or receiver.

Steve

Indeed, and that is also the problem I think. An analog volume control will never be perfect, but in my opinion a 650 euros costing unit should be close to perfection when it comes down to volume balance.

Rotel sent me recently a mail that they have noted my comments and that they investigate it further .

Last week I noticed a second problem, I would even say a huge failure! After switching on my RB-1552 it wasn't possible to get any sound out of it. I noticed that the red led in the front panel didn't work at all . Normally the power amp first goes in protection mode (led lights up) and after a few seconds the protection switches off, but in my case only the power button lights up. It seems that the protection mode is damaged this way of another. The RB-1552 is now back to the dealer for repair...

[blackholesun]

dxl I had a few Rotel amps and pre-amps, 9xx series. The problem you are describing was, unfortunately, quite prevalent. On some amps more, on some less audible. Exactly as you are describing, audible on low, disappearing at higher volumes.

[Audio_ElF]

I assume you checked that reversing the input connections didn't reverse the channel where the lower level was.

Eloise

PS. I assume you connected the output of the RC1550 to an ADC (analogue to digital converter) and NOT to a DAC (digital to analogue converter).

[dxL]

Yeah, of course I connected the preamp to an ADC, otherwise it would not be possible to record the signal on my computer

Rotel mailed me last week. This is an extract of the message:

The specification of the volume control is as follows:

Below -70dB within 3dB
Over -60dB within 2 dB

Particularly at the low setting, there is always likely to be a difference between the two channels; indeed the Balance control is fitted to compensate for this.

However, if you wish to take this further, please contact our local Distributor, details below. Please be aware that If the volume control is replaced with a new one, a match between the channels cannot be expected to be better than that specified above.