My tube amp power supply is buzzing away Help

My tube amp - Mcalister Audio has an outboard power supply that buzzes quite loud. Not through the speakers, but the unit itself makes a buzzing noise I can hear 15 feet back - very obvious.

I have read there is some material you can buy to place under the transformer to help. The transformer does not seem well mounted - kind of lose. Can anyone tell me the name of the anti-vibration stuff and where to buy it. I think I am going to tweak it before calling the manu to replace.


I don't know about that anti-vibration stuff, but PS Audio makes some products to prevent transformer hum (Hum Buster, etc).
Before you do anything, try tightening the transformer down. You may find you need to go no further. And, if the design is not great, look into fixing THAT first.

Trying these other products is good, but unless you first batten down the hatches, you are surely putting a band - aid on the real issue, and your results will not be maximized.
The hum is probably from too much DC in the power line (DC Offset). Blame your power company. While you can issolate the hum with "anti-vibration stuff"; fixing the power is the real solution.

The various power regeneration, balanced power, power issolation devices that use their own transformers to produce clean power will probably do the trick. However, the cheaper ones might hum themselves since they'll be getting the same lousy outside power (LOL!!).

Never tried the PSA Hum Buster, but I assume it works.

Power "conditioning" or "filtering" will not work.
There are a few things that might work, first off check the nuts and bolts connecting the power supply to the chassis as I had a bit of hum in an amp and by tightening the nut just a tiny bit did away with the hum completely as I think over time they work there way loose. One other thing as mentioned above is the Humbuster. If the hum is in the component and not coming through the speakers it's most likely dc on the line.
The unit is plugged into a BPT 2. I am going to try this. Open up the unit and place the transformer on four cut strips of hard rubber. I will then tighen down the bolts using the rubber as both a washer and underpad.

I called Pete from Mcalister and he feels this will do the trick. This power supply is said to be very quiet. Seems mine had been dropped during shipping as the underside is bashed in about 1 inch under the transformer. All else looks fine, but the bottom metal plate in bent and I am pretty sure this fix will work.

I will write a full review of this amp soon. But I will say this now. It is easily the best buy I have ever run accross in high end audio. $995 new and I paid $600 used. One of the very best amps I have had the pleasure of owning. Does not take a backseat to any amp I have owned costing up to $9500. Pure and simple.

I will let you know if this fix works. Pete said there is no need to buy that expensive stuff that comes in sheets. Just use the rubber from a $5 black bunge cord. I like that!
I fixed the issue by buying a $5 hard rubber bunge and cutting into strips and placing it under the transformer. I then tightened the whole thing down.Now it is much more quiet. Cant hear it from where I sit.

Neat way to qiet down transformers.

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I have a McAlister PP150S amp. My power supply appeared to have been handled roughly as the bottom panel was bent. This magnified the induction noise from the power supply when I first powered it on.

I removed the panel and straightend it. Then I installed four neoprene isolation mounts under the transformer. These are small, cylindrical mounts with a stud in each end. The mounts prevent most of the vibration from being transmitted to the chassis. This modification required adding a jumper ground wire from the transformer frame to the chassis since the neoprene mounts act as insulators.

These mounts are available from McMaster-Carr, part number 9376K114. Go here and type the part number in the "Find" box. They are available in 1/4"-20 USS thread and M6 X 1 metric thread. They cost $1.39 US each and are 1/2" high. I had to enlarge the holes in the transformer and lower panel for the 1/4" USS thread studs. Metric would have been a better choice, but I had a supply of 1/4" USS nuts/washers.

I also put some dynamat on the inside of the top/bottom/front panels. I did not block the side air vent slots. These mods resulted in a considerable reduction in the inductance hum.

I suggested he work on better packaging in the future that would support the underside of that heavy power transformer. Despite having to go through this mod, I remain very pleased with the sound from this amp.
Thanks Scompracer. My method is more crude and I my try yours. Funny thing is my bottom plate was also bent from shipping. I love the sound of this amp. Have you found tube rolling helps or changes the sound. The amp has very detailed highs and good sparkle and killer transparancy. Is that what you find?

Bass is very tight and fast. The mids are not as ripe as my past CJ MV60 amp and I did like that about the CJ. The PP150S beats the CJ in every other area of sound in my system. Great amp!
Scompracer, I did the mod the exact way you outlined and the results were fantastic. Wow! Most pleased. I am going to do the same thing for the transformer in my Powervar line conditioner as it also makes some noise.
Hi Grannyring,

I'm glad the fix worked out for you too. I had expressed my comments about Peter's amp in this thread and still feel the same way about it.
I am waiting for a custom tube pre amp from him and expect it to be shipped shortly.
2019, great thread. I will try this on an outboard power supply for my PreAmp.