Little/no sound from the left channel of my amp.

[admin_exported]

 

[Mooly]

We need a bit more to go on than that. Make/model ?

Have you tried swapping the speakers over ?

Is the problem on all inputs or just one input ?

 

[Anonymous]

Hi, I'm the OP. I'm new here and having problems simply posting my topic or reply. It seems I have to select "smiley's" or other font styles before it allows me to post anything other than the topic of my thread.

Anyway, if this works successfully, then my problem is that the left channel of my amp produces little to no sound. The right channel is fine but when I rotate the balance to the left speaker, I notice the degraded sound in that channel. When this happens, it can be corrected by switching the speakers off and on several times, or when I increase the volume, the channel will come into play at normal level. I'm wondering if the problem could be caused by a dirty left speaker terminal on the amp, or maybe the speaker relay is dirty/corroded or is simply reaching the end of its life and needs replacing. My amp is a Denon PMA-350/II from around 1993, if something needs replacing I don't know how difficult it will be to find a part that would be a suitable replacement. Thanks for the inputs 🙂

 

[Anonymous]

Hi, I'm the OP. I'm new here and having problems simply posting my topic or reply. It seems I have to select "smiley's" or other font styles before it allows me to post anything other than the topic of my thread.

Anyway, if this works successfully, then my problem is that the left channel of my amp produces little to no sound. The right channel is fine but when I rotate the balance to the left speaker, I notice the degraded sound in that channel. When this happens, it can be corrected by switching the speakers off and on several times, or when I increase the volume, the channel will come into play at normal level. I'm wondering if the problem could be caused by a dirty left speaker terminal on the amp, or maybe the speaker relay is dirty/corroded or is simply reaching the end of its life and needs replacing. My amp is a Denon PMA-350/II from around 1993, if something needs replacing I don't know how difficult it will be to find a part that would be a suitable replacement. Thanks for the inputs 🙂

 

[drummerman]

Could be anything from a dodgy volume pot, rectification (unlikely), supply and/or the relay. If you have access to a meter head over to DIY audio and ask for a schematic. If there is distortion with lower volume I'd probably concentrate on supply. No fuse has blown so nothing has gone to ground but you really need to test from input capacitors to the relays, especially passive components.

If you can't do this yourself get some contact cleaner in spray form and use it on the volume control and relays with the amp disconnected from the mains. The tops of the relays should unclip.

regards

 

[Anonymous]

Hello drummerman. I'm no expert in electrical equipment, but my amp has two speaker systems A and B, both channels are healthy with the A speakers, as is the right channel with the B speakers, so I came to a conclusion that it was something specifically to do with either that left channel, or the B speaker relay, as oppose to something like the main volume control. Also since there's no distortion at all (just weak unbalanced sound from that one channel) I'm gonna concentrate mainly on the speaker relay. Thanks for the input. Others (elsewhere) have said similar, but I thought I'd get a second opinion before taking any action. I hope it just needs a clean and nothing too serious nonetheless. I was proud of myself to pick up this denon amp for £60 (used) but in the great condition it generally it was/generally is now, and the problem has only just started before christmas last year, so hopefully there's nothing too badly wrong. Thanks again I'll be looking into it.

 

[drummerman]

Yes, they make decent amplifiers. .

If the issue are the relays, contact cleaner may solve it for a while but they will likely fail. Sourcing replacements would be a good idea if you plan to keep the amplifier.

regards

 

[dumbledore]

Stating the obvious, but if you stack, just wire everything on A to get you going.

Also you need to confirm you have relays. This is easy as when you mess with the A/B switch you should hear some relay noises.

Relay cannot be easily cleaned with a contact cleaner as they are sealed usually. Replacement is the only cure. Also it may be possible you have a dry joint near the B speaker terminal/relay that needs attention with the soldering iron.

 

[Anonymous]

Drummerman - I'll get some contact cleaner for the ready, and providing I can access the parts in question, I'll give it a go. To be on the safe side though I'll take it to an electrical consultant for them to take a look at, and see if they can tell me about any replacement parts that would fit for the amp.

Dumbledore - I'm not sure exactly what you mean by relay noises. I've read numerous places online people referring to the two buttons that activate/deactivate the two speaker systems, as a relay. The buttons on mine press in and latch on to keep them in position, and the speakers activated. Is a relay something different? Maybe when you push one button in it cancels out the other one next to it? I'm not very knowledgeable on the bits and bobs inside amps, I've only really picked up basic knowledge of how to set up and operate audio equipment over the years, but never on the assembly/dis-assembly side of things lol.

 

[drummerman]

Karl 1983, the relay/s are not the buttons on the front of the amplifier but are components near the speaker outputs internally.

Perhaps best to leave this to a service professional.

regards

 

[dumbledore]

Don't actually think the pm350 has any relays for speaker selection, but if it has you should hear clicking noises when you press the A/B buttons. Relays are used in more expensive amps as they are more durable then a standard switch when the switch is asked to handle a few amps of load as is the case with speaker connections.

 

[Anonymous]

An electrical 'Click' occurs to indicate power going to either or both the speaker sets when activated. Anyway, I think I'm gonna leave it to a professional to look at. Even if I get some cleaning stuff I wouldn't begin to know where to look for the offending part(s) that need the attention and I don't wanna make things any worse.

Thanks for all the replies.