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al3700 22nd October 2009 03:38 PM

Yaqin MC-100b channel imbalance
I bought a Yaqin MC MC-100b second hand off ebay and right out of the box it was much better than my previous SS amp:) I then noticed an imbalance between right and left channel:eek:, left channel louder than right. I put on my trusty set-up CD and played a steady tone and used a volt meter to measure the voltage at the speaker posts. The right speaker voltage was about a third lower than the left so I measured the voltage out of the amp and got a similar reading:confused:.

Thinking it must be the valves I replaced the Chinese KT88`s with Electro Harmonix matched quad from Watford valves and that made no difference but sounded fantastic:). I have since replaced the 12 ax7`s again no difference and I have a set of 6sn7`s on order.

The sound from this amp is simply superb although I do need to replace my CD player (Micromega Concept on its way) I am currently using a Pioneer PD-S07 through a Shek D1 NOS DAC (plugged into the front sockets) and the DAC makes the CD player sound much sweeter it can`t give it the deep sound stage that I am after.

Sorry I digress! Can anyone help? What do you think could be the cause? I am building a preamp with indipendant left and right gain control so that will sort the balance but I am a bit concerned that the channels should not be that much different to start with.


toufu 22nd October 2009 06:35 PM

Sorry for stating the obvious but you might want to switch the 6sn7's between the channels to see if they are the problem. Or check your bias for each output tube.

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