turntable noise

[tgourlie]

In an attempt to eliminate as much noise as possible from my 2 channel setup, I am tracking down the source of each noise I hear.

With the volume almost all the way up, I get a lot more hiss on Phono than I do on Line inputs. I have tried numerous phono preamps Tube and SS, and numerous amps with the same noise present. That points to the TT. A dual 1229Q

Ground point seems ok, but I did notice that if I touch the + leads (outter jacket) from the tone arm to RCA female connection, the noise does get louder. Taking the Headshell off completely I get a very loud hum.

Any thoughts on how to eliminate it...? Or is that just the nature of the beast?

[3dzapper]

It's normal to have more noise from the very high gain phono stage. The phono stage compared to 11 on the line stage would be like 33.[]

Maybe more info would be helpful. The output from say a CD player could be as high as 2.5V. In that case your pre-amp section would actually be acting as an attenuator since an amp can put out full power with as low as 0.5V to 1.0V. A high output moving magnet cartridge puts out maybe .0045V. As you can see, it takes a great deal of gain to even get that MM to 0.5V. Any electrical noise at all will be amplified as well. Since we don't normally run the volume control wide open when listening to LPs, the noise floor of the pre-amp is hidden well below the the level of the music and the noise floor of the LP itself.

Rick

[djk]

Noise in a phono preamp is dominated by the source impedance of the cartridge.

A typical moving magnet design will be 66dB.

It does not matter that the preamp may be rated for 100dB, one you hook up the cartridge it becomes 66dB.

Moving coils have lower source impedance, and thus less noise, the main reason they sound better.

[garymd]

My system's background noise is at its quietest when playing an LP. It took a really good table/LOMC/Preamp combo to get to that point as explained above.

[maxg]

Ditto on that Gary.

The single biggest change going from my rather modified project to the Clearaudio is in the background noise. It has gotten to the point that the sound comes out of such a black background it is really quite eerie.

TT's generically are problematic. They are entirely mechanical systems that output electical charge. Potential sources of noise are myriad. With the old project I noticed that moving the cartridge over the vinyl the background noise got louder. This was coming from the motor that was mounted on the opposite side to the arm. The nearer the cart got to the motor the louder it got. Pulling the motor and mounting it in a separate box - some distance away, was probably the single most effective (and one of the cheapest) upgrades I ever made to that rig.

Otherwise - what Mark said. It is interesting to note that if your amp amplified as much as your phono stage does you would be able to kill people with your system - at some distance too...