Super Noisy Phono Pre--Help?


I have a Fosgate Signature Pre. I feed it with a Lyra MC cartridge mounted on an SME V arm. Until last week, all was bliss. Then the preamp started producing a random popping sound and a motor sound like there was poor electric motor plugged into the same outlet. I thought it was a tube, but swapping out tubes didn't change it. I took it to my local service department. They cleaned and resoldered some of the connections. Now the popping sound is gone, but the constant motor sound persists. The motor sound goes away if I disconnect my turntable. I can influence the sound by moving my interconnects around. I cannot change it by relocating my preamp. It seems like it might be some sort of interference, but I can't understand why it has shown up all the sudden after a couple of years of perfect sound. Suggestions, please. Could there be something wrong with my interconnects or my cartridge?
jmmorford
I have the V.2 version, and it's very quiet. If you've done the obvious things like simply disconnecting/connecting connections and swapping, maybe time to call the distributor(Musical Surroundings)for an R/A. Their quite reasonable and if it's within the 2 year warranty period,
they should even provide the UPS shipping label to send back to them.
I had a futzy right channel that I was able to isolate to an inferior solder job to the output jack. A quick touch up, no problems.

Have you compared the Foz to others in the price point? I'm curious if the Manley Chinook exceeds rip its performance. I may demo one just to hear the differences. Mine is tubed with NOS,and plumbed with Nordost Heimdall 2 power/interconnects into a VPI Classic. No complaints here!
Trying different cables would seem to be the next logical step. What are you using now?

Have you tried plugging it into another outlet? Maybe with an extension cord from another room. I also have a Fosgate V1 and it is very quite.

I had an intermittent hum in my tube preamp. I could not figure out what it was. It would come and go sometime after hours of listening. It turn out that it was the light in the dining room. We had replace the bulb with a compact florescent. Every time the light was on there was a hum in my preamp. Since the dining room is not visible from the room my stereo is in it took me a while to figure it out. We have now gotten rid of all the compact florescence in the house.

Does anyone know what the actual differences are between the Fosgate V1 and V2?
Lostbears, when it was on the market I believe it's mentioned power supply enhancements for even quieter performance along with replacing the blue LED's under the tubes to a shade that blends with the glow of the tubes.
Never was a fan of the blue LED, reminds me of cheesy made in China gear. I've been tempted to unplug the blue front display.
Unplug your cartridge leads and report back how much noise was present.
Could be an errant IC cable. Try swapping cables. Sounds like it could possibly be a ground problem to me.
Then the preamp started producing a random popping sound and a motor sound like there was poor electric motor plugged into the same outlet. I thought it was a tube, but swapping out tubes didn't change it. I took it to my local service department. They cleaned and resoldered some of the connections. Now the popping sound is gone, but the constant motor sound persists. The motor sound goes away if I disconnect my turntable.
I would not assume that the phono stage necessarily has anything to do with the problem. You didn't mention what turntable you have, but a possibility that occurs to me is that a capacitor associated with the AC wiring within the turntable has become leaky or otherwise defective. And it could be that the cleaning and resoldering that was done on the phono stage had nothing to do with the elimination of the popping sounds. Perhaps they just went away, probably temporarily if my theory is correct, as a result of the turntable being unpowered for some period of time, allowing the capacitor to temporarily recover to some degree.

Just a guess, but a possibility to consider. Good luck. Regards,
-- Al
Al, I had/have an issue with my Aesthetix Janus full function preamplifier that may be very like the one described by the OP. When the tt is "on", I heard a sound on the speakers that was very like that of a motor, the turntable motor. The sound was only present when the tt motor was running and immediately ceased when I shut it off, and only when the Janus was set to "phono". Extensive investigation suggested that the tt and the Janus were very well isolated acoustically from one another, so I tend to rule out the idea that a microphonic tube was picking up actual motor vibrations. Further, the tubes were not demonstrably microphonic in the first place. Switching outlets and grounding vs ungrounding the tt also had no positive effect. Finally, I faced the possibility that the coupling capacitors in the Janus, which I had force-fit onto the PCBs using longish leads, might be picking up motor noise "through the air". I then replaced those caps with smaller ones that allowed the use of much shorter leads, and this cured the problem. But it was very odd; I would not have thought that EM radiations from the motor could manifest as "the sound of a motor". I wonder whether something similar is going on here.
Sounds like Lewm and Jmmorford both have the same problem, and in both cases no evidence whatsoever that the preamp is at fault.

If getting a lot of motor noise the culprit likely has something to do with the tone arm wiring. Perhaps a bad ground so the arm tube isn't able to shield the cartridge from the noise of the motor. If one is using a belt drive turntable, the best designs will have the motor opposite of the arm in order to minimize noise pickup from the motor. But if the motor isn't grounded properly and if its not opposite the arm, the noise from the motor might be getting into the preamp through the cartridge itself.

If the preamp is silent when the turntable is disconnected but on, this is a good indication that the preamp is not at fault.

This would also explain the sudden nature of the onset and why its not tubes (if it was tubes, the problem likely would not have manifested in both channels at once...). All it would take is one bad connection in the turntable and you've got your noise problem.
Dear Ralph, I neglected to mention that the phenomenon I encountered was not present when either of two other entirely different preamplifiers were substituted for the Janus. Further, the noise was present when the tonearm/cartridge was not in use; all one had to do was turn on the tt motor to produce the noise, in both channels. Waving the arm wand back and forth across the surface of the platter also had no effect, good or bad. And finally, as noted, the problem was cured by reducing the lengths of the leads on the coupling capacitors (or cannot rule out that there was a weird defect in one or more of the coupling capacitors themselves, since I replaced the couplers when I arranged for shorter lead lengths). The situation you describe, would, I expect, result in hum or other mixed frequency noise. What I heard was the actual sound of a motor running.