Very likely it can be DC backwashing into your AC- it makes transformers buzz and hum. PS Audio made a Humbuster to take this out and Emotiva makes an outlet strip to do the same. Both work well. DC can come from a refrig, coffee maker etc.
Audio Research Reference 150 - buzzing input transformer
Hello everyone,
I have bought a second hand ARC REF 150 power amplifier (non SE, KT120 tubes) and there was a buzzing noise coming out of the input transformer after few hours. I have detected the noise appears as the amp fully warms up - after about an hour. It goes pretty loud within another 30-45 minutes.
I have taken the amplifier to a friend, a reputable tube amp engineer. He told me the input transformer must be replaced and also that in his opinion it was poorly designed.
I live in Europe so I didn't have the chance of sending the amp to the factory, nevertheless, a new transformer is on its way and I'll get it fixed by an authorized dealer and service.
I was also told that the problem may happen again and that I should get rid of the amp.
My question is whether any of you had similiar problems and what the cause can be. I really love the sound of this amp and of course I'd like to keep it. I'd also like to do as much as possible to keep the amplifier safe.
I have found a very similiar discussion here on Audiogon, I have messaged the OP and he replied he had his transformer replaced afterall -
Is there anything that can cause the transformer to overheat and melt inside? The noise was caused by a vibration of the plates inside the transformer.
My speakers are Tannoys D700, they go down to 3 ohms and I can imagine they are current hungry even tho their sensitivity is 92dB. They worked well with a Classe CA-200 but the ARC sounds a lot better of course. I'm planning of upgrading the speakers in about a year but for now, I'm still very happy with these, it's always a pleasant surprise when I upgrade any piece of gear.
I have asked the ARC company whether the speakers won't be a problem for this kind of amp. They ensured me I'd be fine and that they test their gear with much more difficult loads.
The amp never got too hot when I placed my hand on the top of the chassis, the tubes were measured and they're fine, about 1100 hours on them. The amp wasn't in use for a few years before I bought it.
Thank you for any suggestions.
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Thanks, the transformer will be replaced soon. I'm just thinking what kind of precautions I can take so it doesn't happen again. It was quite expensive, plus shipping, custom fees and mainly, it takes time. I have a separated circuit for the living room sockets (not for the audio only, yet) but I'd say the power in my apartment is quite stable. If there's DC present it doesn't damage the traf immediately, or does it!? My guess is it can get loose but it would take some time, even weeks, right? |
If this started upon initial use have you discussed this with the seller? Did he know of the problem and not disclose the condition? If so I would try to have him help with the repair or try to get a refund. Just guessing here but did ARC ever sanction use of the KT150 in the REF150? If not perhaps the previous owner was using these tubes and they caused the problem?
No idea of the design but a simple search here seemed to find this particular model had its fair share of problems.
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@jetter Yes, we have split the new traf cost 50/50. We're not sure how that happened. It worked fine for several hours when plugged into a cheap Dynavox filter. Then I got a proper cable that reached the wall outlet and listened for the whole evening. The buzz initiated after several hours at first. I turned it off, let it cool down, plugged it back into the filter and the buzz was still there. Maybe it was just a matter of time and it was just a coincidence that it happened after plugging it into the wall. Also, it was mid August, super hot weather. I placed the amp into a custom made MDF cabinet with a space of two inches on the sides, opened back, opened front, semi-opened top (there's a shelf with preamps and TT about 20 inches above). The mesh never got hot, maybe even the LS16's mesh cover gets warmer. I didn't really listen to it for more than an hour and half until I got the power cord. Thanks for asking.
I'd like some advice what to check so I can listen to it with ease. 🙂 |
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