Tube amp buzz (amp, not speakers)

The most likely cause is DC offset. Many common appliances connected anywhere in your house can be a cause, making it seem random. https://www.pooraudiophile.com/2015/03/how-to-fix-dc-offset-and-transformer.html

AC quality is usually brought up and probably for good reason. Some transformers can tolerate it and some buzz. It would be worse at certain times of the day than others.

Wouldn't hurt though to check the transformer screws and mounting.

Some transformers are rubber mounted to reduce the noise since it also can get the chassis buzzing.

Tube amp buzz (amp, not speakers)

Hello -

Almarro a318b makes buzzing sound at random: sometimes it does, sometimes it doesn’t, completely unpredictable. The buzz comes out of the amp itself, like a transformer buzz; the sound out of speakers is completely clean.

I’ll appreciate any ideas - what causes it, what to do? boriso

I also would say DC offset on the mains power if the amplifier uses a toroidal power transformer in its’ power supply.

Here are some pictures of the bottom side of the amp.
https://www.audiocircle.com/index.php?topic=138713.0


I have no idea what kind of power transformer that is in the picture. You might want to check the supporting bolts and nuts for tightness. Do not over tighten. Unplug the unit from the wall outlet the night before you stick your fingers inside to assure the DC high voltage has completely discharged.
.

Run with the cover off and when buzz starts, touch various parts of the transformer and chassis and see if you can identify what is vibrating. Once you locate that, you can address it. 

Your a318b uses extremely high voltages.

As there is no guarantee that it is not still holding such high voltage, even days after being powered off/unplugged, only knowledgeable people should access the inside for diagnostics/repair.

DeKay

I used to own that amp. Holographic sound for sure. I always got a system "hum" when switching it on, even with a dedicated line and a power conditioner. Occasionally a transformer would buzz and I'd just unplug the unit and power up another time. I owned the Almarro about 3 years.

Thank you all so much. I don't know the first thing about electronics, so it seems like I have two options: getting an Emotiva CMX-2  or taking it to a technician, at least for a comparable cost if not more. What would your inclination be? 

@tuberist - what does "holographic sound" mean in this context?

Have you checked to see if there are sources of noise like a worn refrigerator compressor motor or dimmers coincident with the buzzing? What about trying a direct run to the house breaker panel?

Boriso,
Holographic IMO means spatial characteristics where the instruments and voices are clearly delineated. If you go Emotiva you will regret it if you value those traits I described. I found the Almarro easy to tube roll by swapping out the 6SN7; the 6SL7 not as much. It was a fun amp but the biasing was tedious and somewhat dangerous.
regards,Larry

Descent sized toroidal power transformers are usually the ones that buzz, vibrate, from DC offset on the AC mains. As a rule EI transformers do not buzz, vibrate, because of DC on the mains.

I think the power transformer in the OP’s amp is a bobbin transformer. I couldn’t find any info on how they react to DC offset on the mains.

.

Thank you all so much. I don't know the first thing about electronics, so it seems like I have two options: getting an Emotiva CMX-2  or taking it to a technician, at least for a comparable cost if not more. What would your inclination be?

This is another one that is known to eliminate DC offset transformer hum

https://avahifi.com/products/humdinger-dc-line-blocker

Well, after all, the AC is 60 cycles. Hmmmmm. The other troublesome thing about transformers is the rather significant magnetic field they produce.