Will an Iron Shield Work?

[Paul Birkeland]

To short an XLR input, connect all the pins together.

[Jamier]

PB, would PS ripple from a half-wave rectified PS be 60Hz? And from a full wave, 120Hz?

Jamie

[Paul Birkeland]

Yes, a half wave rectified supply will have predominately 60Hz noise.  I'm not sure I've ever seen a solid state amplifier with half wave rectification for anything. 

[Jamier]

PB, I'm sure  this amp is full wave rectified. I spent quite a while listening to tone generator samples and I really can't say what I hear anymore. The amp noise sounds like a 60Hz tone, but it does have a slight buzzing character to it. It definitely doesn't sound like 120Hz. 120 has a higher pitch than what I hear from the amp. My ground is as good as it can be. I crawled under the house and traced the wire to a 1/2 inch copper pipe. Where that pipe enters the ground I can't say but I do know that there is a bonding strap on the exterior hose bib at the back of my house. I suppose all that could be meaningless if my water main is schedule 80 PVC, which it might be. But if that were the case why does my diagnostic plug indicate positive ground. I have a raised foundation so those pipes probably only ground at the main. Any way, I removed the toroid mounting bolt and tilted the toroid on it's side which allowed me to pull it back from the channel boards a bit. I didn't think this would solve it, but I figure if it is the transformer the noise would change, get better or maybe worse, some change to indicate that the toroid was the cause, but the noise was unchanged. So, now I wonder if it is power supply ripple. I know you said the ton of feedback in SS circuits generally prevents this, and I know I said it sounds like 60Hz, but it could be 120 Hz noise, I'm just not sure. I think I did mention that the Power Supply Caps are on the board with the audio circuit. I don't know if this is bad or not, but in the First Watt Clone builds the PS is completely separated from the channel boards.Those are my only SS experiences. Oh well, I'll have to put this aside for a while, it's Tax time.

Jamie

[Paul Birkeland]

How about taking the amp elsewhere to see if it still makes the noise. The manufacturer is still in business, how about contacting them?

[Jamier]

PB, I did contact Cary about this. They are making a new version of this amp. They offered to install a new version of the input board and make some other, unspecified, upgrades. They wouldn’t confirm a definite cost but the estimate started at $450 plus $125/hr labor. When I calculate shipping for a 75 pound amp both ways, it starts to look pretty pricey. I’m thinking it gets close to the price of the BP2 I want, so, honestly, I think the BP2 is a better place to spend the money. I do have other amps, too many other amps. I will take the amp to another location at some point, but it’s just not convenient at this time. Also, I really don’t think that the input board is the problem, but when I questioned the Cary Tech about that, he inferred that the other, unspecified upgrades, would take care of that. I don’t feel good about the prospect of spending a grand to get the amp back with the same noise it left with.

Jamie

[Paul Birkeland]

Yeah, that is a tough choice to make.  Shipping monster amps is very pricey.  Heck, I get a lot of inquiries about fixing Foreplay I/II preamps, and I always warn that the shipping costs will be more than the cost of the preamp.

If Cary said they have a fix for the noise you're getting, then I wouldn't worry too much about doing anything else on your end. 

[Jamier]

PB, My gut feeling is that the noise is the result of a fundamental flaw in the design of the amp. It had this noise 5 years ago when I lived in another local where I had a confirmed positive earth ground. I think they have probably redesigned the amp to address this problem and now they are willing to upgrade my older version but they won't tell me exactly how they will accomplish this.  If I knew, with certainty, that they could correct the problem, if they gave more detail on the unspecified upgrades, I might consider sending it, but without something to base that certainty on, I just can't pull the trigger on that.I guess, for me anyway, when someone tells you they will replace something that doesn't seem to be a problem, and then they are going to do some other stuff, but they won't tell you what that stuff is, it doesn't inspire confidence.

Jamie

[Deluk]

Test it somewhere with known good earthing. Someone elses modern house, anywhere. Yes you want it to work in your house but tick off this box first. Did You buy it new? You say it has been like it since new. If so it should have been sorted under warranty. I note that you have talked to them. They will add a $50 card for $450 plus.............

[Jamier]

I bought this amp about 8 or 9 years ago. At that time, I thought the noise was due to my sources and that I would sort that out in time. Shortly after the purchase, I began preparations to move, so I boxed it for the move and all these years later, I pulled it out to re-evaluate it as a possible mate for a BP2. I thought the input impedance was a little low, but PB assures me that it will be OK, especially with the upgrades. So, yes, if I had, had more sense at the time, I would have pursued this then. I should have opened it up and pulled the inputs out of the channel boards at that time to diagnose it, but I just didn’t take the time to do it.This is the only big class AB amp I own and for some speakers you just need that power, so I would like to get that noise out. The cost of the upgrades isn’t so much the issue, but, as I mentioned before, the shipping will actually be much more, and the total cost is just not worth it to me at this point.I will try a few other things before I give up on it.

Jamie