Convert cartridge output voltage to db gain

Thank you Doug, Kal and Al for your very informative replies. I think I have some ideas of were to head here. First let me make a few points of clarification. Kal, you are right, I looked it up, and the preamp stage in my integrated amp has 11 db more than the gain of my seperate preamp. So more gain may be a bad thing.

Secondly,I have owned this integrated for over a year now, but due to personal reasons, have not listened to analog for about the last 8-9 months. As I recall, the last I listened to this setup regularly, the noise was more apparent than with my seperates, but not nearly as loud as the noise floor is now. Doug, the noise sounds like surface noise, steady hiss, easily audible from the listening chair when I turn the volume up to my normal listening levels (70-90 db). Also thanks for the JJ tube reco Doug, I may try that.

Here are my current thoughts. First, my phono stage is the Walker Audio Signature. Walker recommends that the DC offset be adjusted monthly. When I had the rig running regularly, I checked it about every 3 months, no issues after the original adjustment. However, I have lost the manual, and can't recall how to adjust the DC offset using the supplied DMM. I sent Lloyd an e-mail yesterday and I'm awaiting a reply. I think I should check the DC offset before tube rolling. Second, once I have made sure the Walker phono preamp is in spec, if the issue still exists, change out the preamp tubes. As far as everyone has said, and I tend to agree, one of these two steps should solve my problem.

I do not expect a $6500 integrated amp to be as quiet as $20K seperates, but I do remember it being enjoyable before, so I should be able to make it enjoyable again for much less than buying a new cartridge or phono stage.

I'll keep you posted once I've heard Lloyd's reply. Thanks again for all of your help.

Cheers,
John

BTW, all cabling is single ended, not balanced.

"Kal, you are right, I looked it up, and the preamp stage in my integrated amp has 11 db more than the gain of my seperate preamp. So more gain may be a bad thing."

Bingo. The key thing here. Your system in its new incarnation is amplifying the noise resulting from the slight mismatch (slightly too much gain) you have with the phono stage and cartridge.

Get your gain on the phono stage into the 63 db area or get a cartridge with an output of .17 mV and your noise problem will disappear. Things will sound better as well. Getting the gain right will be much easier, less costly, and less time consuming than coming up with a new cartridge!

Hdm, I respectfully disagree. Lowering the cartridge output will make things worse. It will result in the signal being lower relative to the level of noise that is being summed onto it, presumably in the preamp stages of the integrated amp. The lowered signal level will result in John setting the volume control at a higher setting than he is presently using, which will further boost the noise (assuming the noise is being introduced at a point in the system that is prior to the volume control, which appears to be the case).

What is called signal-to-noise ratio (s/n or snr) is what is important, and what needs to be improved, either by raising the signal level prior to the point at which the noise is being introduced, or by reducing the amount of noise that is being introduced, or both.

Too much gain or too little gain is only an issue if the volume control ends up being used near the top or bottom of its range, or if the input of a component is overloaded, neither of those situations being present here, or if the additional gain comes at the expense of degraded s/n ratio in the particular design (which may be the case here).

Regards,
-- Al

Correction. The last paragraph of my previous post should have read:

Too much gain is only an issue if the volume control ends up being used near the bottom of its range, or if the input of a component is overloaded, neither of those situations being present here, or if the additional gain comes at the expense of degraded s/n ratio in the particular design (which may be the case here).

Regards,
-- Al

Al: In this case, lowering the cartridge output (or reducing the gain for that matter) would indeed result in John having to run the volume pot higher with phono, but as you point out in your last paragraph that is only an issue if he's running full out on the volume pot of the integrated and that is (and IMO won't be the case with a reduced gain of 3 db at the phono stage) not the case.

IME, the noise or hiss that he describes is totally consistent with too much gain at the phono stage. In effect, the phono stage is either on the verge of being overloaded, or is being overloaded by the cartridge which has too much output for the amount of gain on tap. That manifests itself in the hiss which he's describing as well as a bit of hardening up in sound quality and a collapse of soundstage, particularly front to back.

Not having enough gain can also create noise problems as well as totally squashing dynamics and giving the effect of listening through about 3 wet blankets.

Particularly with low output MC's having outputs in the .15 to .35 mV range, dialing in the gain is critical. Get 3 db in either direction on the wrong side at the phonostage and you have problems, 4-5 db wrong or more and it's not worth listening to. And those problems cannot be rectified further on down the line than the phonostage.

Changing tubes may indeed help. I don't have much experience with tubes to be candid. But I would expect that if that was to help that the tubes themselves might, in fact, be altering the overall gain that the phono stage is ultimately providing.

I would be curious to hear what Lloyd Walker would recommend in this situation, but I do think it is a gain issue and that the phono stage has too much gain for the cartridge being used.