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Turntable Hmmmmm

I could use some advise, here, please. I recently bought some new equipment and have been setting things up a bit at a time. I have a McCormack DNA-225, Kora Eclipse preamp, a Sony CD player, a Pioneer CD recorder, and a old Sony analog tuner all hooked up and running fine. Then, I introduced a Nottingham Spacedeck TT with Tracer #3 cartridge to the system. I had the TT and cartirdge in an another system with no problemes at all. Now, in this system, I get a very low frequency hum, barely audible at low volumes but which gets progressively louder as I add gain to the preamp. Amp and preamp are connected to one wall outlet, the rest of the components on a power strip run through a second outlet (neither dedicated). I have checked the RCA connections, the ground connection, moved the ground, swapped out outlet connections in every combination, and tried a cheater plug - all to no avail. Anyone have a sugestion on what to try next? Thanks
4yanx
6 responses Add your response
lugnut
1,190 posts
 
If this is a regular household circuit that provides current to other lights, appliances, etc. you may wish to shut off all the other stuff one at a time to find the culprit. Assuming you are using a light source to illuminate the tt you may first want to turn that off and see if it is causing the hum. Basic advice, I know. Others with more electrical knowledge will probably post other suggestions.
Good luck,
Patrick
sean
6,231 posts
 
Try checking this thread out. If you don't feel up to the task, try reversing any non-polarized two pronged power cords in the outlets. AC polarity is VERY critical with phono systems. Sean
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http://forum.audiogon.com/cgi-bin/fr.pl?htech&1014011751&read&keyw&zzac=polarity
4yanx OP
1,576 posts
 
Thnaks for the advice. Well, I did two things. I switched a couple of the two-pronged plugs AND moved my amp a bit further from the TT. The hmmmm is GONE, but there is still a most annoying hiss (instead of blackness as with my CD). I assume this is a result of phono stage performace. No?
bob_bundus
1,834 posts
 
yes due to the very high gain of phono stages you'll always hear some background thermal noise (hisssssss) but at typical listening levels it's buried well below music signal
4yanx OP
1,576 posts
 
Thanks again for the response. The 'Not now sounds every bit as good (and more) in this system as in the other. Love that vinyl!
sean
6,231 posts
 
The amount of hiss that you hear will vary from system to system, primarily from preamp to preamp. Some preamps will produce no noise to very little with the gain cranked all the way up while others will have a much higher noise floor at any gain setting. The art of designing a versatile, accurate and quiet phono stage that sounds good is one of the toughest things known to audio engineers. There are some "oldies" that still compete ( and easily beat ) some of the current "recommended" phono stages for this very reason. That is "typically" why some of the better ones garner so much money and people don't want to part with them. This includes some "full function" preamps too.

Other than that, i'm glad that you were able to get things resolved and back on track. I would suggest checking component polarity some time down the road if you already haven't. This could reduce the noise floor even lower than it already is. Sean
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