Amplifier (B&K 200.7) Hiss in ONE Channel when Powered OFF

scubalab

I've been meaning to post on this for some time now. Since I installed the B&K 200.7 amp in my HT, one channel (I believe channel 2 of 7) has a very loud, distinct hiss when I turn everything (including the amp!) off. It lasts a LONG time (like days, if not weeks). I'm wondering if it's some sort of capacitor power drain (if that's a correct term). The amp plays beautifully from all channels when powered on. As soon as it powers on, every speaker goes dead silent (i.e. no hiss whatsoever from any channel) and is crystal clear, even levels, and sounds beautiful.

I suppose I could just leave it on 24/7, but I'd prefer to power it down when not in use. As soon as the Processor triggers the power down (yes, I have it set with a 12v trigger), it clicks off, and the one speaker starts hissing. It's not deafening loud, but it is definitely noticeable from anywhere in the room. As time goes by, it does seem to dissipate and become quieter. However, we use the HT enough though that I can't say that after a week or two weeks, or a month if it would entirely go away.

All I could find in some quick Google searches refer to one channel hissing when the power is ON.

Any idea what this is, what might be causing it, and if there's anything that can be done to eliminate it?

Thanks in advance,
-Al

heiney9

Ghosssssssssssssssssssssstsssssssssss

H9

EndersShadow

@mantis

I also have this issue with my 200.5 but only if connected to the 12v trigger. Without it, no biggie.

And even once initially connected still no problem, but after 1 or 2 days connected it shows up as well.

Curious if there is a fix for it as I'd love to use the 12v trigger myself. But I'm ok leaving it on 24/7 since I installed the surge protector at the breaker and its on a dedicated line.

scubalab

Boooooooo Brock!

scubalab

Any other ideas?

I setup a FLIR camera and took some EMF readings last night and have ruled out paranormal activity...

mark090852

Sometimes the paranormal "activist" is smarter than a FLIR camera. I don't know...just sayin'.

lightman1

Check for snakes.

mhardy6647

Snakes on the plain!?

(or is he in the foothills?)

Probably goes without saying that I have no clue as to what the root cause might be, unfortunately.

mantis

So let me get this straight. If you power on and off the amp with a 12v trigger you get a hiss?
I don't see how they relate unless the 12v is leaking into channel 2 and then it dissipates that energy when you power down. The 12v is gone when you turn off your preamp and on all the time when it's on. The 12v is constant.
I'm gonna assume something is wrong with the trigger circuit. I suggest not using the trigger and see if that fixes it. If it does and you want to use the trigger, then get it repaired.
Another way around this issue is to use a Surge Protector with a 12v trigger outlet turn on. Most higher end surge units do this. You can also get a stand alone unit one outlet from Niles or anyone you want to to do that same thing if you don't want to use a surge on your 200.7.
This might be a cheaper solution then the repair.
https://www.crutchfield.com/p_190CS12V/Niles-CS12V.html?tp=9103&awkw=75639146425&awat=pla&awnw=g&awcr=104893312585&awdv=c&awug=9007229

tonyb

I've never heard of a cap discharging and taking weeks to do so.....as described by the OP. Almost sounds like line noise or a grounding issue recirculating back in from something else on the same circuit.

scubalab

@mantis I'm going to have to try taking the 12v trigger out of the setup. I do want to clarify that the hiss is only there when everything (Marantz 7702 pre and B&K) is powered off. The B&K also did this when I was using my old Anthem MRX-500 that Dan (EndersShadow) has now. That's why I assumed it was the amp and not the pre. I don't think Dan is using the Anthem with his B&K that does a similar thing. I think he's using his Denon as the pre for his amp.

@tonyb - Additionally, the B&K did this on a different circuit in the past. I now have everything set up with a dedicated 20A circuit to the B&K. Currently (no pun intended), the B&K is the only thing on that circuit. I'll have to try some things later today. If I have to leave it on 24/7, I can. Just prefer to power everything down if I could.

I'll post what I find once I try thing with the 12v trigger out of the mix.

Thanks for the help.

scubalab

Wait... it was a snake! Russ nailed it!

Seriously, will do some troubleshooting later today and update. (It wasn't a snake... )

Mark (mhardy6647) - I'm in the valley - Happy Valley!

scubalab

Update... It is not the 12v trigger. I just unplugged the trigger cable from the back of the amp. Instantly, it powered on (as expected). But then I manually powered the amp off (without the trigger cable installed) and yep, the hiss started again on Channel 2... sounds like faint static. By faint, I don't mean you have to have your ear next to the speaker... You can definitely hear it from just about anywhere in the room.

I also tried unplugging the amp entirely from power and the his is STILL there. Therefore, I have to assume it's some sort of current drain or something. Either that, or it is in fact ghosts as H9 suggested. I think my only option to eliminate it is to leave it powered on all the time...

EndersShadow

Try this. Turn the amp off manually and let the hiss go away overnight.

Then leave the 12v disconnected and power it back on and use it for the day. Then when done turn it off manually and see if it happens again.

For me, without the 12v the hiss goes away, but I'm using diff speakers.

I will verify mine don't bias when turned off tonight.

Ricardo

scubalab wrote: »

I also tried unplugging the amp entirely from power and the his is STILL there....

OK. Definitely ghosts.....

mantis

I think it's a leaky Capacitor on channel 2. I think you should find a repair shop that can fix it in your area.

scubalab

Yeah - I may take it in to a local shop. Only problem is he's the only repair place within an hour drive. Additionally, I dropped over $200 on another amp that had a couple low channels and he didn't completely fix the problem. Amplifiers and mid-higher end gear seem to stump him... kind of lost a little trust when he called me and said he fixed the 5-channel amp with the low channels. His fix? He said he cleaned the volume pots and then adjusted them until they were all equal. In other words, he just turned the normal channels down. I told him that was not an acceptable fix and he then replaced some caps and resistors. It helped, but one channel is still a little low.

FTGV

My guess is that some residual power is still reaching the channels even in standby mode.The mute circuit in ch 2 may be faulty thus allowing noise to reach the output.

scubalab

Yeah, for now, I'm just leaving it on. I'll have it looked at eventually... just need to swap my B&K AV-5000 (that I use for outdoor movie nights in the summer) into the setup. It's our main tv in the house and hate to be down entirely.

EndersShadow

You will leave it on unless changing speakers right

scubalab

But of course. Lesson learned!

DaveHo

Faulty relay on that channel not disconnecting when the power gets turned off?