X-202 - hum when using Phono

[ssouci]

I have a Fisher X-202 integrated tube amp that sounds very nice

have been playing only CDs so far, using the Aux input... sounds great, nice and quiet

just hooked up my old turntable, a vintage Dual 1209 idler wheel unit (with Ortofon VMS 5E Mk II cartridge)

seems to play fine, however, I'm getting a pronounced HUM/BUZZING sound, which I'm guessing is 60Hz

the buzzing is volume dependent, and comes from both channels

I've tried touching the gray ground wire from the turntable to the X-202's chassis, and I get no change in buzzing sound, only some minor scratching noise as I move the wire against the chassis

I've tried connecting via both RIAA2 and RIAA1 inputs, but get the buzzing with both

Q1: what is this buzzing, and how can I get rid of it?

Q2: do I use RIAA2 or RIAA1? (to play standard old LPs)

thank you!

 

[RUmad]

I’m sure the folks that KNOW the answer will show up shortly, but it sounds to me like a grounding issue. I would probably clean the rca jacks and check that the actual ground wire from the ‘table isn’t bad.

 

[dcgillespie]

If the unit does not hum without the turn table connected, then that pretty well defines the culprit as the turntable. Little things like plug orientation (of all the connected pieces) can make a difference, as can keeping your turntable away from sources of magnetic energy (power transformers). Check also that the cartridge is installed and grounded correctly in the turntable.

Both the RIAA 1 and RIAA 2 settings offer a standard 47K load to a connected cartridge.

Dave

 

[ssouci]

UPDATE:
- I cleaned all the RCA jacks on the Fisher amp (both #1 and #2 terminals) using Dexoit 100% followed by 5%, scrubbed with a skinny cotton swab and small nylon brush, followed by inserting/removing and rotating an actual RCA plug... then blow out with compressed air
- did the same for the RCA terminals underneath the Dual turntable (the RCA cables are not hardwired to the turntable, they are removable)
- unfortunately the buzzing could still be heard... did NOT seem to change much if at all

- noticed that removing the RCA plugs from the amp caused the buzzing to completely stop (in both RIAA2 or RIAA1 input positions)

- the hum is not a deep, even, low frequency hum like from a big electrical transformer... it is somewhat higher frequency and more irritating (ie., more of a buzzing than a hum)... I'm only guessing that it's 60Hz

 

[RS Steve]

Maybe you can double check your wiring to the cartridge and RCA cables coming out of the table.

 

[larryderouin]

Clean the contacts on the Cartridge sled, and the tonearm. tighten and clean the contacts on the SLED to the Cartridge. Loose pins can contribute or cause the Buzz.
Underneath, check, tighten and clean all the RCA Connections solder connections from the tonearm.

 

[dcgillespie]

Make sure you are using good quality shielded cable for your interconnects with the turn table if it requires their use. This sounds like a silly statement to make since it should be obvious. I have found however that most of the cheap RCA interconnects offered with various SS components you buy, or even that separately available at home improvement stores and the like are no longer shielded cable at all! Many of these interconnects (up to as long as 6 ft) are little more than two conductor wire that looks like shielded cable -- of course we assume it is shielded cable -- with colored RCA plugs on the end. They can get away with this because of:

1. Their relatively short length.
2. The low impedance that SS equipment operates at (which minimizes susceptibility to hum pickup).
3. The high signal level that RCA cable operate at with modern SS equipment (Modern boxed theater systems typically don't have phono inputs).

So make sure you are using quality interconnects to connect the turntable. If your table has permanently connected audio leads then this likely won't be an issue. But if it doesn't, be sure to check that your interconnect cables (even if you think they're "good") aren't the source of the problem.

Dave

 

[fred soop]

If you want to purchase the lowest price cables, simply buy one. Cut it apart and see if it has a legitimate shield. If so, then you can go buy another. Total cost would still be low. Save the cut cable as it may be useful in testing someday. A slightly higher price but not outrageous cable is sold under the AR (yes, Acoustic Research) name. These have very good, but quite tight, connectors. They have 2 signal wires with a foil shield (100% coverage) connected at the source end.

 

[ssouci]

thanks everyone for your replies and suggestions!

I will try a few things, research a bit on Dual turntable forums, and then post back with an update

 

[ssouci]

SOLVED -- it was the cables!

I had been using skinny cheapo RCA cables because those were always with that turntable, and the small diameter allowed them to pass under the turntable base (a rather narrow opening because of the small rubber feet)

also, they had apparently been playing fine at my parent's home just last week, and previously for years there with several different amps... but obviously not now at my place... that is why I had never given them a second thought

I swapped in some thicker, old-school shielded cables and the hum disappeared... pretty quiet now, and I can only hear a very faint hum at a very high volume setting

now, to move onto restoring this turntable and maybe putting in a new cartridge.........

*thank you* Dave and everyone else!

 

[dcgillespie]

Glad that solved it for you! I found out that little factoid about a year ago when I was temporarily using some of those same type cables between the output of an active preamp, and a power amplifier of high sensitivity (requiring only 0.5 vac for 50 watts/channel) driving my 101 db Cornwalls. Even though the preamp had an output impedance of about 1KΩ, I noted that just bringing my hand near the cable caused a notable hum in the speakers. A little investigation found that the "shielded" interconnects between the pre and power amps were not actually shielded at all.

Those short little cables are nice in keeping cable clutter to a minimum, but at best, if they must be used, are only good for use with the output of a SS device, where the output impedance is known to be 100Ω or less, and the signal level is 1 volt or more.

Dave

 

[gadget73]

I've got some cheesy cables between the two sides of my console at the moment, and it also has a hum because of it.