Totally baffled !!
default -- Wed, 12/30/2009 - 18:56
Let me start by saying that I am an avid fan of not neccasarily "Vintage" audio equipment, but pristine, older stuff., as newer, affordable, solid state Sony and the like is just not "good" sound to me. I purchased a Harmon Kardon 6650 Integrated amplifer new around 96'? and it provided me with years of perfect service until the L channel on the amp section went south a year and a half ago. I preferred the sound of the HK so I opted to switch it out of "integrated" and into "seperate" and use the preamp section to drive a Carver TFM-15 I picked up reasonable off ebay. About 6 months after using the Carver, my system developed a series of "Pops" through the speakers (Both) and sometimes (pushing the speakers "out" and holding them there for a moment) upon turn on... for about a min or so then it would be fine. This issue got progressively worse, so I tried changing the HK Preamp for a Carver CT-3 which helped for a short time then did the same thing until it got so bad it was causing the amp to start "clicking" in series with the "Pops" and got to the point where I actually saw "lightning, for lack of a better desciption" from inside the amp. At this point I had to assume the amp was bad and replaced the amp with a Harmon Kardon PA2000 (This is an isolated amp with 45x4 or 90x2 bridged, I set it to the bridged mode, hooked it up to the Carver Ct-3 Pre and the speakers and life was good for a day! Now it's doing the same thing... I'm at a loss guys. I am using this system off my PC and used desktop speakers with no problem while I waited for the HK PA2000 to arrive. My logic tells me I have extremely bad luck with amps (I NEVER abuse them) or a problem "short?" with the speakers (Floorstanding Mirage Omni550s") But if it was the speakers, wouldn't only one side (the bad side) misbehave? they both pop the same. Unless they both mysteriously have the exact same problem... ANY suggestions or thoughts would be appriciated!
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I don't think that your source is the problem. The fact that the power amplifier pushes the speakers out & holds them there says to me that there is direct current (DC) at the amplifier output. DC is NEVER supposed to be present at the amplifier output and the fact that it is says that (probably) a capacitor in your amplifier is leaking. Leaking capacitors are also the most typical cause of pops.
Because both your Carver Ct-3 preamp and your Carver TFM-15 are giving problems, I would suspect that both (manufactured at about the same time?) got a batch of the same capacitors that are now entering their "wear out" cycles. Try hooking an iPod or something to your HK PA2000 & see if you have the same problems. If so, then the HK is about gone too; if not, then the bad components are isolated to the Carver equipment only.
If you're handy with a soldering iron, you could probably replace the Carver's capacitors yourself unless the equipment is new enough to use "surface-mount" technology circuit boards in which case, it's a throw-away. Good luck & be sure to get this equipment OUT of your system before you damage your speakers!
A good sense of humor makes it ALL sound better!
Thanks Boom, Update.. Went back to the HK 6650 as a preamp and am using the HK PA 2000 amp... so far so good. Now, if all stays good, what to do with the Carver TFM-15??! May retest it and if all checks out, ebay it.. not sure
TJC - Unless you have the equipment to test the amp & to be POSITIVE that it isn't leaking DC, I wouldn't advertise it or sell it at all. Although YOUR speakers tolerated the DC leakage with no ill effects, the customer's speakers may not be so robust. A customer who buys your amp on eBay and then has their speakers blown immediately by the amp is likely to hold you responsible (and rightly so). If you advertise the amp, you must disclose the possibility of DC at the outputs. As I said, someone handy with a soldering gun may be willing & able to make the fix. Since you know of the possibility of that DC leakage, though, a cursory "retest" doesn't justify selling the amp without mentioning the problem.
Of course, I'm sure you know all this and would never dream of advertising the amp without disclosure, but it bears mentioning for others who read the forum. In the audio gear world, and particularly with power amps, the biggest speaker hazard is DC on the audio outputs. If one even suspects such a condition, the problem must always be disclosed.
Cordially - Boomzilla
A good sense of humor makes it ALL sound better!
No Boom, It wasn't my intention to pass on something with a possible problem. Only that I assumed the TFM-15 amp was prob fine because the CT-3 preamp is the only unit that stayed in the system throughout the problems...now that it's gone, the prob is solved (Still is btw..knoc wood:). Frankly I wish it had been the Carver amp that was the problem, they seem to be more abundant than the sonic holigraphy preamps.. Never the less, overall I'm pleased with the present 2 HK units tho the PA2000 is a little bright over 10:00 which requires a tweek of the tone controls.