Mystery trouble with new Shanling Integrated

[Brett A]

I bought a new integrated, a Shanling A3000, from my local shop about six months ago. After about four months, I noticed a buzzing in the right channel. This buzzing can only be heard with no music playing if I have headphones on or if I put my ear within 12” or so of the speaker (point is it’s a quiet buzz).

I’ve tried many things to make it go away, but it persists.

• I’ve disconnected all sources from it (and unplugged them while I was at it),
• I’ve disconnected the speaker cables and still heard it through the headphones.
• I’ve tried a polarity cheater on the power cable.
• I’ve tried different power cables.
• I tried reversing the tubes in the input buffer L>R.
• I have crossed the external pre amp/amp jumpers L>R.

No luck, it’s still buzzing in the right channel.

So, after speaking with the shop, I boxed it back up and brought it back to them so they could send out to Music Hall/Shanling repair on the left coast. After about a week (I was away), the shop called me and said when they checked it to verify my problem, they didn’t hear anything and that I should come pick it up. When I asked if they hooked it up to test equipment, they said they don’t have any test equipment, they were simply using their ears. So, disappointed, I brought it home, hooked it back up and it’s still doing it.

Any advice about what to do next would certainly be appreciated.

A few other things that might be helpful to know:

• I don’t have power conditioning, but my system is powered by a dedicated 20amp circuit.
• When I use the remote, the motorized volume pot has always buzzed through the speakers. (This may or may not be normal?)
• It’s still under warrantee

 

[croseiv]

I don't have a solution, but I feel your pain. I would be quite annoyed if my new 1800 amp was buzzing inappropriately.

 

[Davemcc]

Check to be sure it's not a ground loop issue.

 

[TLS Guy]

I bought a new integrated, a Shanling A3000, from my local shop about six months ago. After about four months, I noticed a buzzing in the right channel. This buzzing can only be heard with no music playing if I have headphones on or if I put my ear within 12” or so of the speaker (point is it’s a quiet buzz).

I’ve tried many things to make it go away, but it persists.

• I’ve disconnected all sources from it (and unplugged them while I was at it),
• I’ve disconnected the speaker cables and still heard it through the headphones.
• I’ve tried a polarity cheater on the power cable.
• I’ve tried different power cables.
• I tried reversing the tubes in the input buffer L>R.
• I have crossed the external pre amp/amp jumpers L>R.

No luck, it’s still buzzing in the right channel.

So, after speaking with the shop, I boxed it back up and brought it back to them so they could send out to Music Hall/Shanling repair on the left coast. After about a week (I was away), the shop called me and said when they checked it to verify my problem, they didn’t hear anything and that I should come pick it up. When I asked if they hooked it up to test equipment, they said they don’t have any test equipment, they were simply using their ears. So, disappointed, I brought it home, hooked it back up and it’s still doing it.

Any advice about what to do next would certainly be appreciated.

A few other things that might be helpful to know:

• I don’t have power conditioning, but my system is powered by a dedicated 20amp circuit.
• When I use the remote, the motorized volume pot has always buzzed through the speakers. (This may or may not be normal?)
• It’s still under warrantee

Dollars to doughnuts it is RF interference, probably from a dimmer. The right speaker lead is probably the right length to tune in the RF. The RF is picked up by the speaker leads, fed back via the negative feedback to the first high gain tube, rectified and detected, amplified down the chain and is audible as a buzz.

Try swapping the speaker leads and see if the buzz goes to the speaker on the right still. In other words connect the left speaker to the right amp speaker terminals and the right speaker to the left terminal, and see if the buzz says on the right.

If it does install an RF choke between the right positive speaker terminal and the speaker lead.

Tube amps are even more prone to this problem than solid state amps.

 

[Brett A]

Dollars to doughnuts it is RF interference, probably from a dimmer.
Try swapping the speaker leads...

Thanks for the response, but the buzz still comes through headphones even with the speaker cables disconnected. (And I have no dimmers in my house, unless I count myself.)

Check to be sure it's not a ground loop issue.

As for ground-loop issues, I think I eliminated that possibility with the various try-it-and-see practices I listed in my OP. Let me know if there is something else I should try. Also, do ground loops affect only one channel?

 

[fmw]

It could be any of a number of things. It's a little hard to diagnose things from a description by someone else. If I had to take a guess, I would point at the power transformer in the power supply - particularly if you hear the noise in both channels. The Chinese haven't elevated their quality control to the level you would find in Western countries so it wouldn't be a big stretch to imagine a transformer gone bad.

 

[TLS Guy]

Thanks for the response, but the buzz still comes through headphones even with the speaker cables disconnected. (And I have no dimmers in my house, unless I count myself.)

As for ground-loop issues, I think I eliminated that possibility with the various try-it-and-see practices I listed in my OP. Let me know if there is something else I should try. Also, do ground loops affect only one channel?

Then the amp is making the buzz. By the way NEVER disconnect the speakers from a tube amp when it is on, it blows the output tubes, and Yes, I have seen them explode. A tube always has to have load termination.

I have a feeling all the amps do this. That is another problems with tubes, it is a lot harder to eliminate buzzes and hums.

Personally I found the advent of good solid state amps a blessed relief.

A potent cause of hum in tube amps is from the LT filament circuit. This is low voltage AC, usually between three and six volts. It is high current and has the ability to induce a lot of the problems you describe. I few expensive tube amps have a rectified and smoothed LT supply.

This glorification of tubes is something I just don't understand. Buy any stretch they are a step backwards. This whole thing has come about from the writings, huffery and puffery of the high end self delusional crowd.

If a speaker needs the HF roll off, present in so many tube amps, then ditch the speaker, don't buy a tube amp!

 

[Brett A]

Then the amp is making the buzz. By the way NEVER disconnect the speakers from a tube amp when it is on, it blows the output tubes, and Yes, I have seen them explode.

I never connect or disconnect anything without shutting it down. I can't afford to replace anything!

Personally I found the advent of good solid state amps a blessed relief.

A potent cause of hum in tube amps is from the LT filament circuit.
If a speaker needs the HF roll off, present in so many tube amps, then ditch the speaker, don't buy a tube amp!

It's not actually a tube amp. It's a solid state integrated with a built-in tube buffer stage for the unbalanced inputs. (The balanced inputs go straight to the SS pre section)
And this buzz is there whether I've selected a balanced or unbalanced input, so I'm pretty sure it's not the tubes.

 

[Brett A]

If I had to take a guess, I would point at the power transformer in the power supply - particularly if you hear the noise in both channels.

Well, it's only in one channel, but this thing has separate power transformers for the left and right channels (It's a dual-mono configuration). You think this could be the suspect eh?

 

[markw]

The first thing you have to do is to get the service facility to admit there's a problem. Without that, you're screwed.

That means duplicating it there.

I would suggest you take the unit back to the shop with your headphones.

I'm assuming the headphones will provide a safe load for the output tubes. If not, someone correct me.

Can you hear the buzz with no source?

Now, connect a source, or even an MP3 or a portable CD player, and listen to your headphones.

Do you hear that buzz? If so, then make the tech listen to it and tell you face-to-face that he doesn't hear it.

If he says he doesn't hear it, you're boned. If he's on the up-and-up he should see what he can do about it.

But, these things have "specs", which allow a bit of hum and noise as normal. If what you hear measures within the stated specs, you're gonna have to get used to it.

 

[croseiv]

So, if you hear it in your headphones as well as speakers, then it must be a pre-amp/amp issue (internal). If you increase the volume, does it get louder?

 

[Brett A]

So, if you hear it in your headphones as well as speakers, then it must be a pre-amp/amp issue (internal). If you increase the volume, does it get louder?

No, it's not effected by the volume level.

 

[croseiv]

No, it's not effected by the volume level.

Now that's interesting. That makes me think it's not the amp/preamp. If you increased the volume and this were causing the buzz, then the buzz would get louder. Maybe you have some sort of electrical appliance close by that could be causing the noise? Have you tried plugging it into a different outlet to see if it's still buzzing?

 

[Brett A]

Can you hear the buzz with no source?

Yes. I can hear the buzz through the headphones with nothing else but the AC power cord attached to the amp.

I would suggest you take the unit back to the shop with your headphones.

I'm considering doing this. This would address any location-specific causes.

Here's a question that's been on my mind:
I can borrow a multi meter from the facilities department at work. Isn't there a simple test I can do with it, say, measuring for signal across the speaker terminals, so that I can go by something like numbers in addition to my ears (and the ears of the guy at the shop.)

 

[Brett A]

Now that's interesting. That makes me think it's not the amp/preamp. If you increased the volume and this were causing the buzz, then the buzz would get louder. Maybe you have some sort of electrical appliance close by that could be causing the noise? Have you tried plugging it into a different outlet to see if it's still buzzing?

No, I haven't. It is powered by a dedicated circuit from my breaker box, though.

 

[markw]

Here's a question that's been on my mind:
I can borrow a multi meter from the facilities department at work. Isn't there a simple test I can do with it, say, measuring for signal across the speaker terminals, so that I can go by something like numbers in addition to my ears (and the ears of the guy at the shop.)

Trust me, that meter won't do you any good. There is no "simple test" for this. You will need a lot more sophisticated gear and a heckuva lot of technical know-how to be able to show this visibly.

 

[croseiv]

Found this thread, maybe it can help. Seems to point to resistors or solders going bad.

http://www.diyaudio.com/forums/showthread/t-55026.html

 

[croseiv]

No, I haven't. It is powered by a dedicated circuit from my breaker box, though.

Nice set-up BTW.

 

[Brett A]

Nice set-up BTW.

Thanks, It's really been giving me a lot of pleasure. (Even with this issue)

 

[Haoleb]

You mentioned that you hadnt noticed it for a while after you got the unit. Was that because it wasnt there before or you just hadnt noticed it? I once had a problem similar to your situation where the unit I sent in for service had an intermittent problem and of course when the repair facility got it they found nothing wrong. I basically told my dealer not to send it back to me until they fixed something because I didnt just pay 90 dollars to ship it to them for nothing. Thankfully they took it back to the repair shop and they did finally find the problem the second time around.

It is possible there is a solder crack somewhere and if this unit did not have tubes I would suggest kinda knocking it around a bit to see if it changes at all. Believe it or not thats really a good way to test for solder cracks and to see if youve fixed them.

By the way the motorized volume pots do usually induce noise into the circuitry.