cartridge imbalance help please

Hi all,

I'm calling over to a friend of mine tomorrow to help him out with his TT - project RPM5/9C arm with a ortofon MC25 cart. He reports a channel imbalance with the TT - he has checked cables/phonostages etc and has narrowed down the cause of the imbalance to be either the cart or the way its set up. I should say that the imbalance is not that bad, but say when something should be front dead centre its actually off to the right or left a bit (can't remember which way but its constant).

What are the kind of things I should watch out for? I have the HFNRR test record, multimeter, balance etc. I'm looking at antiskate and possibly azimuth, but is there anything else I'm missing.

Is there any check I can simply do on the cart, eg check a resistance or something with the DMM that would help diagnose if the cart is off?

many TIA,

The imbalance is most likely in the Cartridge as apposed to how it's setup. I say this because of the specs of that cartridge for channel balance can be as high as a 2dB difference and still be within spec. This, of course, is a manufacturers spec and in practice the cables, and phonostage will contribute to that number possibly being greater along with the any non-symmetrical harmonics or distortion.

This is not unique to this cartridge. Many manufactures post specs for channel balance and the practical measurements in system can sometimes be off.

The best way that I know of to handle this, if it is really the cartridge, is to use the balance control on your preamp. Trying to correct for this with setup is not going to give best results.

I don't think it's a good idea to put the DMM directly on the cart to measure resistance. Some DMMs put out enough voltage during the measurement to burn through the coils.

The best way to check the channel balance, that I know of, is to use the phonostage outputs to measure the voltage of a signal. You can use track 3 (channel balance) of the HFNRR test record to measure the output of both channels and see the difference in volts. If this channel output is not high enough for your meter, then you can use track 6 (+12dB 300Hz Bias Tone)of the HFNRR test record.

After you have this measurement, swap the left and right channels of the phonostage input and remeasure the outputs. This will let you know the effect the phonostage makes.

Next, I'd suggest verifying the phonostage balance by using a single output (Say the left channel of the Cartridge output) from the cartridge and feeding that into both phonostage inputs. measure the voltage levels on the output of the phonostage. Hopefully thay are very close.

Armed with the measurement information above, you will be able to determine which channel of the cartridge has the highest output. You will also know which channel of the phonstage has the lowest output. you can then use that to compensate, as best you can, for some of the difference.

Ultimatly, you want to correct for channel imbalance caused by the cartridge through adjusting gain in the phonstage or preamp by using a balance control. If you don't have those options, you can search for a cartridge with better channel balance (If it is the cartridge and not the phonostage).

There is other option I could walk you through but I would need to know the exact input impedance of the preamp that the phonostage feeds.

Hope this helps,
just to close this thread out, the problem was down to speaker placement. The TT was more resolving than the CDP and so the slight imbalance showed up more clearly there.


I posted to Agon before your post showed up. Glad to see it was something else and not what was stated in the original post above. The good thing is you don't have to dig this deep in your situation. Maybe this will be useful for someone else in the future.

Thanks for the input anyway. Although I'm new here, I hate to leave threads hanging - so I "try" to report back to close out/update a thread.