Sony Ps-X600 With Hum

by **PilotSkier** » 09 Sep 2011 23:09

Due to a death in the family, I had to place all of my projects on hold; thus, I still am looking for scrap metal dealers as a source for the requisite aluminum plate. After reading the second to the last posting, I just thought it informative that B&K never warned its consumers during that time period about the potential for hum. I still have the original manuals and marketing brochures and separating components to prevent hum or interference was never mentioned. In fact, B&K's sales brochure shows the pre-amp sitting directly on top of the power amp. I should also point out that both units are designed to be "rackmounted."

by **Coffee Phil** » 12 Sep 2011 06:43

PilotSkier wrote:Due to a death in the family, I had to place all of my projects on hold; thus, I still am looking for scrap metal dealers as a source for the requisite aluminum plate. After reading the second to the last posting, I just thought it informative that B&K never warned its consumers during that time period about the potential for hum. I still have the original manuals and marketing brochures and separating components to prevent hum or interference was never mentioned. In fact, B&K's sales brochure shows the pre-amp sitting directly on top of the power amp. I should also point out that both units are designed to be "rackmounted."

I am sad to hear of your loss. Your family issues now are certainly more important than audiophile tinkering other than what is necessary for your therapy.

It is possible that the power transformer in your amp leaks more flux than typical. Some years back I worked on a Carvin mixing board. It had hum due to leakage from its power transformer. I had a toroid built to replace the OEM E-laminated transformer. That gave me a 13 dB improvement in the hum level. While Carvin isn't the highest level stuff I can't believe the the board I was working on was typical.

Phil

by **PilotSkier** » 18 Sep 2011 19:32

I sent in both the B&K Pro10mc preamp and the Pro600 power amp to B&K's servicing facility in New York to have them bench checked together as a unit. As of this posting, the test results are not in. The Pro600 has a toroidal transformer.

I found a commercial supplier of aluminum which sells 24"x24" sheets with a thickness of 0.249" for $100 per sheet. This is for Alloy 1100 which is 99% pure aluminum. There are other aluminum alloys on the market, but this alloy is listed as being non-magnetic and being an excellent conductor of both heat and electricity.

by **Coffee Phil** » 19 Sep 2011 20:46

PilotSkier wrote:I sent in both the B&K Pro10mc preamp and the Pro600 power amp to B&K's servicing facility in New York to have them bench checked together as a unit. As of this posting, the test results are not in. The Pro600 has a toroidal transformer.

I found a commercial supplier of aluminum which sells 24"x24" sheets with a thickness of 0.249" for $100 per sheet. This is for Alloy 1100 which is 99% pure aluminum. There are other aluminum alloys on the market, but this alloy is listed as being non-magnetic and being an excellent conductor of both heat and electricity.

Hi PilotSkier,

The power amp having a toroidal power transformer yet being the cheif offender is a surprise. I would like to see B&K's report.

$100 strikes me as a lot of money for the aluminum sheet. Hopefully you can find a scrap metal dealer who can supply the metal at a better price.

Phil

by **PilotSkier** » 23 Oct 2011 22:46

Both the B&K pre-amp and the power amp were found to meet factory specifications. The unit's original design engineer, after the bench check, suggests the hum is either from a "dirty" AC power source or from the cables. What is perplexing is that the hum is present even without any other component (other than the two B&K units) being "plugged" into the AC wall outlets - this includes the turntable, and no other piece of equipment is plugged into the pre-amp (except of course for the cables carrying the signal and the ground wire from the turntable). As I am typing this posting, I can clearly hear the hum from ten feet away from the speakers. Out of frustration, I pulled the pre-amp off of the top of the power amp. As the pre-amp was being moved the hum got louder (the same as it did with the 1" coil probe), then diminished, got louder, but then started to diminish as the pre-amp was removed from the amplifier's vicinity. When the pre-amp was about six inches away from the amplifier, the hum was almost gone. (So much for marketing hype!)

by **Smengy1** » 24 Oct 2011 05:25

So why don't you just get a cabinet and put the amp on the bottom and the preamp
on top? I would suggest you put the amp and preamp in a area where you can move them about up to 3 feet from each other, then move them around until they quiet down. Figure out the length and get a appropriate stackable cabinet.

100 for aluminum plate? Don't do that!!! Why not buy that stuff they make
the truck toolboxes out of in Loews? That is thick and it steel and chrome.

by **Coffee Phil** » 24 Oct 2011 06:49

Hi PilotSkier,

There probably is no spec for stray magnetic flux from the power amp or the sensitivity to magnetic flux for the preamp so the units could very well be in spec.

Of coarse the simple solution is to isolate the two units by physical seperation and the aluminum "eddy current plates" I would probably be curious as to why the amplifier is so loud even though it has a toroidal power transformer. I would probably take the top cover off of the amp and sniff with the loop around the transformer to find the hot spot. It could be the wiring or traces from the transformer through the rectifiers to the input filter caps. Those traces and their returns should be as close to each other and parallel to avoid making a radiating loop. If it is wire you may be able to move the wire to reduce the area of any loop formed. If it is circuit card traces it may be more bother than it is worth compared to the eddy current shield and spacing.

Phil

PilotSkier wrote:Both the B&K pre-amp and the power amp were found to meet factory specifications. The unit's original design engineer, after the bench check, suggests the hum is either from a "dirty" AC power source or from the cables. What is perplexing is that the hum is present even without any other component (other than the two B&K units) being "plugged" into the AC wall outlets - this includes the turntable, and no other piece of equipment is plugged into the pre-amp (except of course for the cables carrying the signal and the ground wire from the turntable). As I am typing this posting, I can clearly hear the hum from ten feet away from the speakers. Out of frustration, I pulled the pre-amp off of the top of the power amp. As the pre-amp was being moved the hum got louder (the same as it did with the 1" coil probe), then diminished, got louder, but then started to diminish as the pre-amp was removed from the amplifier's vicinity. When the pre-amp was about six inches away from the amplifier, the hum was almost gone. (So much for marketing hype!)

by **PilotSkier** » 13 Mar 2012 02:29

Hum issue resolved. Separating the units vertically by two feet resolved most of the hum issue. There are three solid wood shelves between the power amp and the preamp. The pre-amp is now just below the TT so the TT's leads never go past any other electrical component. Presently, the level of hum is only slightly louder than the normal "line" hum of the amplifier [which is less than or equal to the ambient room noise]. I have not yet added the aluminum plate to shield the units further. The question now becomes: Is it more effective to place the aluminum sheet directly below the pre-amp or directly on top of the offending power amp? My thought process is that by placing the aluminum panel directly below the pre-amp, I would be shielding both the pre-amp and the TT from all of the units situated directly below them.

by **Coffee Phil** » 13 Mar 2012 05:10

Hi PilotSkier,

I would try the aluminum plate in both spots. If the result is equal, the decision can be which looks best. You could also put a plate in both spots.

While you are doing this check the continuity from the turntable ground to the shields of the phono cables. I prefer that they be isolated but on some tables they are not. If they are not be sure the ground takes virtually the same path as the phono cables to avoid current being induced in the cables from the stray field from the amp. You might also try a 100 Ohm resistor in series with the ground lead at the preamp to reduce the ground current if it proves to be a problem.

Phil

PilotSkier wrote:Hum issue resolved. Separating the units vertically by two feet resolved most of the hum issue. There are three solid wood shelves between the power amp and the preamp. The pre-amp is now just below the TT so the TT's leads never go past any other electrical component. Presently, the level of hum is only slightly louder than the normal "line" hum of the amplifier [which is less than or equal to the ambient room noise]. I have not yet added the aluminum plate to shield the units further. The question now becomes: Is it more effective to place the aluminum sheet directly below the pre-amp or directly on top of the offending power amp? My thought process is that by placing the aluminum panel directly below the pre-amp, I would be shielding both the pre-amp and the TT from all of the units situated directly below them.

by **gfedorowicz** » 01 Jun 2012 12:01

I HAVE BEEN AROUND TURNTABLES FOR A LONG TIME, WHEN I ENCOUNTER HUM FROM MY TURNTABLE IT IS BECAUSE THERE IS INTERFEARANCE HAVING TWO PREAMPS. IF YOUR TURNTABLE HAS A BUILT IN PREAMP TRY CUTTING IT INTO THE OFF POSITION. YOUR RECEIVER MAY HAVE A PREAMP FOR THE RCA PHONO JACK ALL READY AT WORK OR YOU CAN LEAVE YOUR PREAMP TURNED ON YOUR TURNTABLE AND USE ONE OF YOUR AUX INSTEAD OF THE PHONO JACK. WITH A ACTIVE PREAMP IN YOUR TURNTABLE YOU CAN ACCESS YOUR CD INPUT OR TAPE 1 AND OR TWO WITH NICE RESULTS. OTHERWISE TOSS THOSE RCA JACKS AWAY AND REPLACE THEM WITH A NEW SET AND THAT OFTEN CAN BE THE PROBLEM AS WELL. THE OLDER GERRARD TURNTABLES REQUIRE YOU SECURE THE GROUND WIRE PROPERLY ON YOUR AMP OR RECEIVER. WHEN ALL ELSE FAILS CHANGE YOUR CARTRIDGE TO CERAMIC AND I KNOW YOUR HUM WILL GO AWAY.I HOPED THIS HELPED SOMEBODY-GREG3325