Channel Imbalance with Turntable Setup

I've noticed with my setup that there one channel is louder than the other. I have been testing with a mono record by Semprini. Recording were made via an RME 9632 and Audacity.

With the turntable connected normally to the phonostage, the right channel is 1.5dB RMS louder than the left. If I swap the left and right connections to the phonostage, the left channel is 0.9dB RMS louder than the right (not 1.5dB as one might expect if the channel imbalance was due solely to the turntable). The comparison was made with the same track.

Would it be a correct conclusion to say that the channel imbalance is being caused by a combination of both the phonostage and the turntable? When connected normally the phonostage imbalance is adding to the overall imbalance, and when reversed it is subtracting from the overall imbalance? That would mean the phonostage is contributing to 0.3dB of the imbalance and the turntable is contributing 1.2dB, if my logic is correct?

To try and check this, I performed a recording straight from the turntable to the RME, missing out the phonostage. Obviously, the signal was a bit weak and no RIAA curve is applied. The right channel is 1.1dB louder than the left channel with this test. This may be within a margin of error of 1.2dB and therefore seems to confirm my hypothesis.

Could someone please confirm or refute my thinking? Are these acceptable values for channel imbalance?

The chain is:

Technics SL1210Mk2 --> Nagaoka MP110 --> Pioneer SA-940 -->RME 9632

Many thanks.

 

Have you tried swapping the cartridge leads?

 

Could be an azimuth issue as well if your cart's stylus isn't properly aligned.

 

Thanks guys. I will check the azimuth and think about swapping the cartridge leads tomorrow.

Obviously, the majority of the imbalance is upstream of the phonostage. But from my experiment is it possible to conclude that a smaller amount of the imbalance is due to the phonostage? I guess I should repeat the experiment after fixing the turntable issue to be sure.

I've had the headshell off recently. And when I put it back on the left channel wasn't working. I had to remove the headshell, blow on the contacts and reattach. I did this a couple of times because the first time there were crackles during playback. Not normal playback crackles but very severe, regular, sharp crackles coming from the tone arm. But that's fixed now.

 

I swapped the cartridge wires over and this reversed the channel imbalance. The problem is either with the cartridge or the way it is set up. Good to know it's not the tonearm wiring. I'm a bit of noob with all this and don't have the necessary tools to set things up properly, will have to get educated. Eye-balling the azimuth is inconclusive, it looks straight but not really possible to be certain - makes me go cross-eyed!

The imbalance is down to 1dB now, I'm not sure how I managed that.

 

I had a look at the specifications for the Nagaoka MP110 and channel balance is quoted at 1.5dB or less. I guess this answers my question that this a normal amount of imbalance. I'm probably not going to get much better than 1dB? I will have a go at setting up turntable and cartridge again sometime (I managed to accidentally move the cart in the headshell when swapping over the wires) to see if I can further improve it.

I knew that vinyl required high tolerances compared to CD / digital, but now I understand why the top-end stuff is *so* expensive. To me, a 1dB channel imbalance is noticeable on headphones. At least it can be corrected in Audacity when creating a needle drop. And definitely sounds much better when corrected.

 

1dB may or may not be audible as a volume change, but I can believe that it is audible as quality change.

Take heart. Back in the day when we were all listening to to LPs, we didn't know that we had to spend lots of money on that high end

(Actually, back then, even a cheap hifi was expensive compared to ten or twenty years later.)

 

Yeah, my next suggestion was going to be to use a DMM to check the tonearm wires. I'm guessing that the problem, such as it is, is the cart: using a mono LP should exclude most of the setup parameters as the reason for the imbalance. It would be interesting to see what another test shows when you adjust your cartridge again, paying particular attention to antiskate, and using a stereo LP.

The lowered imbalance after the cartridge lead swap may be as simple as the pins/connectors being 'cleaned' from being put on and off, and perhaps a tighter connection.

At any rate, I, myself, probably wouldn't notice 1db from listening, so I'd be ignorantly happy. I'd wager that you'll find many, many LPs that have at least that level of imbalance simply from the recording/engineering/mastering process. I do like your analytical approach, well done and I hope you're having fun!