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Does phono stage noise drive you crazy too?

After using high output moving magnet cartridges for many years, I recently purchased a .5mv output Grado Master 1. I thought that it would be a decent match with my Acoustech Ph-1p phono stage. Reviewers all claim to have used this phono stage with lower output cartridges and had no noise issues that bothered them. I'm just wondering if I'm unduly sensitive to electronic circuit noise, as I find the pairing to be obnoxiously noisy. There's no hum issue, just a "white noise" kind of circuit noise. When I have system volume set to normal highest level listening, I can hear the preamp hiss from the listening seat nine feet away from the speakers. It's not louder than lead-in groove noise, but it contributes to an electronic haze that obscures low level micro-dynamics. I've got the preamp set to 61db. of gain (53db. A weighted noise it turns out.) The Master sounds lifeless and anemic at the lower 52db. gain setting.
Is this state of affairs common? Do many of you just learn to listen through this low level noise haze? At present, it seems that I either need a cartridge with .8-1.0 mv. output to be able to use less noisy gain if I stick with the Acoustech, or I need a phono stage with a better S/N ratio. It surprised me when I started looking for A-weighted phono stage specs, not too many manufacturers seem to want to list that spec.
photon46
almarg's avatar
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almarg
9,670 posts
 
Sounds like you've made some good findings.

A 100 ohm load in conjunction with a 2mH cartridge, though, will result in significant rolloff of the top octave (10 to 20kHz). You can see that by plugging those numbers into the calculator in the section labelled "MC Cartridges" near the bottom of this page at the Hagerman site, which indicates a bandwidth of only 8kHz for that combination. (To a reasonable approximation, I don't think the fact that the Grado is not a MC is relevant to that calculation). My impression is that it is capacitance that the Grado's are pretty much insensitive to.

With respect to deciding whether to replace the cartridge or the phono stage, keep in mind that going to a LOMC having significantly less inductance than the 2mH may lower the noise levels even further than they are with the Grado and 100 ohms, even if the same 100 ohm load is used. 2mH at 20kHz corresponds to an inductive reactance of about 250 ohms. A LOMC having an inductance of say 50uH or less would be only a few ohms at 20kHz, and so would be equivalent to a near-short across the phono stage inputs. Although that benefit would trade off against lower signal levels for cartridges having output levels significantly below the 0.5mv of the Grado.

Regards,
-- Al
stringreen's avatar
stringreen
6,467 posts
 
I'm using an Ayre unit which is DEAD quiet. It sounds to me as though your pre is working too hard. Try reducing the output level and turning up the volume control on your preamp instead. The less hard phono stages work, the better they are.
photon46 OP
1,082 posts
 
When I reinstalled the Grado, the first thing I did was to try it at the lower 52db. gain setting again. It did not sound "weak and anemic" anymore at that gain setting, so I surmise that I must have underestimated how long it was going to take for a brand new cartridge to break in. When I adjust the phono gain to either 52 or 61db. gain and then set system volume to a measured 79-80 db. playback level, the background circuit hiss sounds pretty much the same to me. Don't know what to think about that, confounds my expectations as well.
Thanks Al for all the advice. It would be interesting to run a frequency analyzer on this combo to see what the frequency response is. If there's a severe roll off above 8khz., my middle aged ears aren't hearing it yet.
almarg's avatar
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almarg
9,670 posts
 
When I adjust the phono gain to either 52 or 61db. gain and then set system volume to a measured 79-80 db. playback level, the background circuit hiss sounds pretty much the same to me. Don't know what to think about that, confounds my expectations as well.
That's not surprising. Assuming no special problems such as ground loops are present, overall noise performance will usually be pretty much determined at the front end of what comes first in the chain, because signal levels are lowest at that point, and any noise that is generated or introduced there is amplified by everything that follows. That is particularly true if the gain of what comes first is high compared to the gain of what follows, as it is in this case even at 52db.

So I would not expect noise levels to be affected in any major way by how the overall system gain is allocated among the various amplification stages in the system.

Regards,
-- Al
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yogiboy
5,656 posts
 
Give Grado a call and ask if they can bump up the output. I think they can add some coils.
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