Mechanical Hum from Class A Amplifier Clayton

Hi All,

Need some advise,

I have a paid of Clayton M300 Monos,

Speakers Tested on were Danley SH50 Horn 100db and Legacy Audio Whisper XD 94db

I noticed one of the mono block has a louder Mechanical Hum and tends to get hotter. The amps are giving off a Hiss sound with some mechanical buzz noise in the midrange drivers.

The other mono block has hiss and slight hum with a much lower Mechnical buzz from the amplifier. What concerns me is the Hiss noise. Its not only a hiss but some buzz mixed into it.

I tried connecting the amps directly to the wall socket and to a AC Regenerator and nothing seems to sort the issue out. Is this normal noise for a Class A amplifier to make a loud hissing noise? My Tube amps have a lower noise floor specially the Bob Carver which are dead silent, The ATI amplifier is Also Dead Silent.
I would think both amps should have similar characteristics in the noise floor. I had a Plinius amp that had two large toroid trannies that made a hum, and it had a hiss in both channels. It was just a big, powerful amp, that was noisier than most, but still sounded great.

That one of your amps is noisier and runs hotter, is an indicator of an internal problem of some sort. I would have it (or both) checked out by a technician.

Best of luck, regards,
Do you run them both off the same circuit? If so, then any residual noise or mechanical hum/buzz should be the same (w/in normal piece to piece variance). If they are not on the same circuit, you may have some DC offset on the circuit w the noisier amp. Class A vs AB should have nothing to do w it, other than a hot/warm idling Class A amp may put more thermal stress on internal components and cause faster wear.
Large torroids are susceptible to mechanical noise. The torroidal transformers and capacitance of these amps are huge. The M300s are fully balanced so the first thing is to give them a balanced input signal. A single-ended signal with rca-XLR adapters will not work due to ground issues. If you are coming out of a single-ended preamp you will need to use Jensen rca-XLR transformers, which work great and are very quiet. Do not use a power conditioner - run them straight from the wall. If you still have noise I suggest contacting Wilson Shen (owner/designer at Clayton) directly as he is one of the nicest people I have worked with in audio. He does offer a power supply upgrade for M300s that he did to my amps. I believe the upgrade includes better torroids, increased capacitance and other improvements. The result was an improvement to the already great SQ and elimination of any mechanical hum. Unfortunately the upgrade was not inexpensive but I am happy to own the M300s because I have heard nothing SS that sounds better (although there are many I have not heard).
my Preamp is fully balanced, Even when no source is connected the amplifier is very noisy. I am speaking to Wilson now probably going to send them back. Mines were purchased this year and came to me with a fault, I shipped them back to Wilson for repair and it came back faulty and noisy again. I assume its the power transformers are not designed well for the 220-240 voltage.
With speakers as sensitive as yours, a bit of noise shouldn't concern you too much. The difference in the heat output is a concern and should be looked at. Probably just a bias setting out of adjustment, but worth having it looked at.
Good points Timrhu, my speakers are only 90dB sensitive and need the high power to drive less than 4 ohms impedence at lower frequencies - I missed how sensitive the partnering speakers are. While these are great sounding amps in my system, Clayton makes smaller amps that may work better with such sensitive speakers. Regarding temp., here is a link to an interesting post where someone measured their heat sink temperature over time to document how long it took a pair of these amps to achieve full operating temperature
I owned a pair of M-100's a few years ago and thought they sounded excellent when playing music. However, they had a mechanical buzz coming from transformer hum that I never could get rid of, no matter what I tried. Changing cables and cords didn't help, even a PS Audio Humbuster did not work. I eventually gave up and sold them.

If one of your monoblocks is running hotter though, it sounds as if the bias needs to be adjusted too. I would send them back to Wilson Shen to see if he could solve your issues. Good luck.
I stressed the amplifier todays and they keep cutting off at some point, something don't seem right, My Bobs and ATI drive them at insane levels yet the claytons are cutting out when the volume bar is up at 48. The bobs pass 60 easily at points my ears cant handle them and the speakers are dynamic. Even testing on the Danley the Amps just drop out signals. Both are behaving this way I assume the power designed for the 220-240 voltage is not ready yet.
If the Class A bias is higher on one amp it will be hotter, and if it is bias higher than the specs then it will stress the transformer and cause it to hum.
It needs to be looked at, do not play it. I have seen a transformer damaged because the bias was too high.

Cheers George
I have removed them and they going back to Wilson, The Midrange from the mono amp is distorting.
Getting a Refund, This unit was sent back to Wilson for repair as the first time it was noisy and the sound was distorted. Came back and still got problems. Not taking the risk again. Already spent thousands of dollars on shipping, Tax and Agent Fees. Going down another route. Possibly MSB 203 Mono Blocks.
That is a shame, though I can not blame you, I know what a hassle it can become. As I posted earlier, I gave up on my M-100 monoblock amps too for transformer hum. These are great sounding amps when the music was playing, but that constant hum during quiet passages eventually drove me to sell them.

Many folks don't have issues with these amps, so they just seem to be very sensitive towards the electrical lines, which is very unusual for solid state designs. I've had issues like this before with tube equipment, but outside of Clayton Audio, I have never had issues like this from solid state designs.
No matter what I did, the noise and distortion is always present. The fact that the midrange and upper frequency was very distorted during higher spl levels drove me to think something is seriously not right. Both Monos had noise which I find it way above normal use. Yes my Speakers are all sensitive but this is no excuse. a Very well built amp should not make too much noise. This sort of noise was not your average hiss. It was a multiple frequency buzzing noise with background hiss. Something I have never heard. It is a shame as the amps have potential but a loss of just under 3000 dollars in all shipping and agents, Tax, Duty and clearance at 2 ports just really too it too far. I was hoping the second time round they were shipped back to me it will be fixed yet it felt like nothing was changed. Wilson is a nice person, its a shame that my units turned out to be like this. Guess it was not for me and I cant run the risk of taking another chance.
Don't overlook the CODA 15.0 amp. I can't say enough good about it. Tons of juice and NO hum or vibration. You can always get 2 of them and bridge into a dual-mono configuration. That is the amp I use with my Purity Audio Design preamp, and it is superb.
Yep, and it will knock your socks off. But only if you listen to it. If you are really concerned about wattage, either bridge it in mono (as I had suggested) or try the Model 33.0. Legacy has told you how good they are, I am sure.
Rtilden, re-read Dragon_vibe's post, the Coda 15.0 only runs in Class A bias up to 100 wpc. The 33.0 that you recommend next only runs in Class A bias up to 15 wpc. He was using the Clayton Audio M-300's, which were 300 wpc of pure Class A power. Coda doesn't have a model that does that. I don't know of any other amp that provides this much Class A power, but I do understand his desire to stay with a pure Class A amplifier. Pass Labs XA200.5 puts out 200 wpc in pure Class A, that is the most that I know of.

FWIW, I do enjoy Coda as well, I am using a Model 11 amp, 100 wpc of pure Class A power is plenty for my application.
What am I missing here? 300watt amps to drive 100db efficient speakers. If you listen at levels requiring that kind of power, your hearing is in trouble.
Do as you wish but be warned.
Timrhu shares my thoughts exactly. My room is 30'x31'x12'h, and my speakers are 4 Ohms, about 87db efficiency. Plays difficult classical louder than any sane person can take it and sounds great while doing it. Playing Pink Floyd even louder calls the cops. The CODA 15.0 punches well above its specifications. Gents, I do not make this claim lightly. I live in Winter Park, FL in case anyone wants to hear it himself.
My theatre speakers are 100db, The ATI Amplifiers run them.

My 2 channel are 94 db.

I like to keep head room on the amp rather then driving them to certain aspect of there limits.
Pass Labs compares very favorably to the Coda house sound, in fact I wish I could afford the Pass Lab amps. Those 200 wpc pure Class A XA-200.5 monoblocks will set you back over $34K!!! They should sound awesome at that price!!

I haven't heard the MSB amps.