Does phono stage noise drive you crazy too?

53db. A weighted noise it turns out

What does this mean? Are you saying that at the listening position you measure 53db A-weighted noise with an spl meter, with the volume control at a setting that you would use for listening? If so, that would definitely sound like there is a problem somewhere.

I'm wondering if the hiss could be caused by rfi pickup. Have you tried unplugging power to everything that is not necessary for phono playback, especially the video stuff? As well as turning off any dimmer switches and fluorescent lighting that may be in the area. Also, it would be interesting to know what the noise level would be with shorting plugs connected to the phono stage inputs, at the same gain and volume control settings.

Regards,
-- Al

The 53db. A weighted noise figure was provided by the factory

Assuming it is based on one of the commonly used test conditions and reference levels, a 53db A-weighted s/n ratio is in a ballpark that I would expect to result in the audible hiss levels that you seem to be describing.

In addition to trying the shorting plugs, it might also be worthwhile assessing the hiss levels with the cartridge and cable connected and with loading set to 100 ohms or thereabouts, while you are not playing a record but with the volume control set to where you presently use it.

Perhaps the reason for the better noise performance that Tom reported is that the heavier loading (lower resistance value) that he was probably using in conjunction with a LOMC improved the s/n performance of the PH-1P, relative to what it would be with a 47K input impedance. That possibility would seem consistent with Lloyd's observation, as well. 47K input loading would also seem likely to increase rfi susceptibility, compared to a low value such as 100 ohms.

Also, I note that the Grado's inductance is 2mH, which is considerably higher than that of many and I believe most LOMC's, and would not come close at high frequencies to being the near-short across the phono stage's input that those LOMC's would be. The near-short would presumably reduce both self-generated noise in the front end of the phono stage and rfi susceptibility.

Just some thoughts. Regards,
-- Al

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

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