Phono Stage Hum

The Zu Xaus is shielded. I think that I need to:

1: Play around with the cable from the phono pre to the integrated.

2: I've heard that using a three to two prong adapter on the phono pre power cord at the power conditioner can help.

The problem is volume sensitive. That leads most to think that this is not a ground issue. I don't always get the radio broadcasts which is strange but also seems to support the idea that it may be driven by external interference. I guess the challenge is figuring when it is introduced.

I've swapped the cartridge to confirm that makes no difference--it did not.

Any other thoughts? Anybody know the acoustic revive equipment?

Tim

It might be those Zu Xaus cables. Are they shielded?

See this recent thread for some ideas about what to try with respect to the radio signals:

http://forum.audiogon.com/cgi-bin/fr.pl?htech&1230309974

HTH,

-- Al

I think it might be something external. I have slowly dismantled and reassembled my system. I also reset the impedance on the phono preamp. I have reduced the noise/hum significantly but just discovered that at very high volume levels (with nothing playing) that it is picking up radio signals!?!?! It does not happen when I run my turntable directly into my Creek. It does happen over either amp when I introduce the Jolida phono preamp.

Right now, I have the gain set to the factory recommend and I'm running out on the "low" line out. The sound is great, and I never really get to the 50% point on that amp with the Druids, but it seems like there *should* be someway to clean up that noise.

I did recently read a review on 6moons of a device that is supposed to clean up external fields (if I remember correctly).

Tim

The phono pre-amp seems to be the suffering piece.

Hopefully it is just external magnetic fields that can be taken out of the equation (like kryptonite with SUperman) rather than some inherent problem with the piece itself.

Good luck.

One more update:

-I ran the turntable directly into the phono stage of my Creek 5350 SE. No hum.

-I then ran the turntable into the JD 9A and the JD 9A to the Creek. Hum.

It seems to me that it is clearly something in the phono preamp. Right? or in the connections/settings.

Off to play around with the placement and settings on the 9A.

Tim

On the Jolida: There is a high output and a low output. Both seem to be line level. I have been running the high output to my integrated. Maybe I will run the low output to the integrated, and then set the gain for the MM cartridges. That might be the best way to start.

In the manual, it says that the "low" is for preamp separates and the "hi" is for integrated amps or line stage preamps. That is why i have been using the high.

I just pulled the phono cable out of the phono pre. I still get some low level hum (actually a noise more like wind blowing across a mic) but I have not put the shorting plug in yet. That strikes me as potentially noise around the tubes.

Might be the nature of the beast. I have the 9A and also have a low level hum. It is not audible unless it is very quiet or I put my ear to the woofers. I have tried all the suggestions mentioned above with no luck. Play with your cartridge settings as I was able to reduce, but not eliminate the hum.

I'm totally confused by what the dealer told you. As I indicated, 70db phono stage gain for your 4mv cartridge does seem a bit excessive. But "no gain" is absurdly too low -- that would say that on loud passages only about 4mv would be going into your integrated amp -- WAY too low.

Also, how physically was the gain adjusted to 0 or whatever it was set to. Based on the JD9A description at their website it just seems to have 3 settings -- 70, 85 or 95 db.

Re RIAA equalization, as you may know records are cut with non-flat frequency response (20 kHz boosted around 20 db; 20 Hz cut around 20 db, relative to 1 kHz, with boosts or cuts for other frequencies corresponding to a specified curve). The phono stage has to apply an inverse frequency response curve, to restore a flat response relative to what was recorded.

The JD9A description at the Jolida site says something about "Two Outputs RIAA, Line stage." Not sure what that means, but it sounds like one pair of outputs might not have the RIAA equalization in the path, for whatever reason. If not, and if that is the output you are connected to, you will not get good sound to put it mildly (although that may be unrelated to your hum problem).

Regards,
-- Al

Check all connections including those to the cartridge first.

If still a problem, check proximity of the phono stage to other components and any other devices emitting magnetic fields. The power amp is a prime suspect. Move it around physically and see if hum increases/decreases. Try to locate it where hum is minimized or hopefully gone.

If that is it, I have been treating a similar issue with my phono. Check my system postings for more info on solutions involving adding additional magnetic shielding, if needed.

The gain was high for MM cartridges. I talked to the Jolida dealer, and he said that they typically recommend no gain for MM cartridges. I'm not sure what you mean by the riaa equalization in the path.

The hum is roughly equal in both channels and they are all plugged into a Shunyata Guardian.

I have had a small fear that there is a bit of crowding around the cabling. That is part of what I will experiment with this weekend.

I do get the hum when the turntable is not turning. I also occasionally get a pop when I turn it on... Something I just remembered.

Good advice on the shorting plug. That might be my first test.

Thanks,

tim

Not sure what you mean by having the phono stage set to no gain. The specs at the Jolida site show 70db gain for moving magnets (which seems like a lot, btw). And I assume you have its riaa equalization in the path.

Is the hum equal in both channels?

Do you have the turntable, phono stage, and integrated amp all plugged into the same outlet or power strip or surge suppressor? If not, I'd suggest trying that, to make sure that ground offsets between differing ac sources aren't causing the problem.

Are the components physically some distance apart, so that for instance ac fields from the power xfmr and associated wiring in the integrated amp aren't being picked up through the air by the phono-level wiring.

I'm not familiar with the cables. Do they by any chance have directional markings, which might signify that their shields are grounded at only one end? If so, try them the other way.

It could also conceivably be a tube problem, such as a filament-to-cathode short.

Do you get the hum when the turntable is not turning? If not, it would suggest Grado-like pickup by the cartridge of 60 Hz emi from the turntable motor.

Also, if possible disconnect the turntable from the phono stage, and put a shorting plug on the phono input, and see if you still get the hum.

HTH,
-- Al