toroidal buzz – ideas?
My newly built Aleph J has been sounding great, and all signs point to a successful build. That said, I started noticing a faint buzz coming from the transformer. I went with an Antek 400va 18v x 2 toroidal, and I've checked all wiring and connections twice now. It's almost inaudible with the cover on, and only slightly more prominent when I remove the cover. The amp is measuring great and sounds fantastic. I think if the buzz had been there from the start it wouldn't even bother me, but its something that developed over the last 2-3 days and its going to drive me crazy.
Any ideas? Happy to upload measurements or pictures – just not sure what I'm looking for, if anything.
My newly built Aleph J has been sounding great, and all signs point to a successful build. That said, I started noticing a faint buzz coming from the transformer. I went with an Antek 400va 18v x 2 toroidal, and I've checked all wiring and connections twice now. It's almost inaudible with the cover on, and only slightly more prominent when I remove the cover. The amp is measuring great and sounds fantastic. I think if the buzz had been there from the start it wouldn't even bother me, but its something that developed over the last 2-3 days and its going to drive me crazy.
Any ideas? Happy to upload measurements or pictures – just not sure what I'm looking for, if anything.
Hehehe...not so hot as to get a burning amp. 
mpa: Your resistor won't last long. You're running over 10W into a 3W resistor.
If you have a bunch of them, you can try wiring 4 of them in series to get 80 ohms.
Then with 19V from your PS, you are now looking at around 190mA and now
each resistor and the mosfet will each dissipate less than 1W. Even then they will
feel warm.
Hope this helps.
Dennis
mpa: Your resistor won't last long. You're running over 10W into a 3W resistor.
If you have a bunch of them, you can try wiring 4 of them in series to get 80 ohms.
Then with 19V from your PS, you are now looking at around 190mA and now
each resistor and the mosfet will each dissipate less than 1W. Even then they will
feel warm.
Hope this helps.
Dennis
Hi Dennis. I just tried a different cord and receptacle on a different circuit, but buzz remains. The overall volume of the buzz seems pretty consistent. Once in a while I can hear what's best described as a light sizzle, but that's pretty irregular.
Pass DIY Addict
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I've had similar problems with various transformers. I've even had intermittent buzzing out of the same transformer. What I found to make a pretty large difference is adding a good snubber, guided by Mark's Quasimodo circuit.
If you don't have one of his boards, or just want to experiment with the impact, you can do a quick and dirty approximation. Place both a (0.01uF cap) and (a 0.15uF cap in series with a 20-80R resistor) across each secondary just before the rectifiers.
If you don't have one of his boards, or just want to experiment with the impact, you can do a quick and dirty approximation. Place both a (0.01uF cap) and (a 0.15uF cap in series with a 20-80R resistor) across each secondary just before the rectifiers.
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Thanks for including a recent picture. I just went searching back in this thread to see if there were any. ;-)
Chasing mechanical hum or buzz in a power transformer can be difficult an frustrating. The root cause can be either inside or outside your household wiring. Some of the more obvious culprits can be lighting dimmer switches and refrigerators. But it could just as easily be coming from somewhere else.
I have gotten into the habit of using some mechanical cautionary measures in each of my new amps. The first is to use rubber stoppers inside the center hole of the transformer, along with a nylon bolt to hold it in place. The tension on the bolt need not be very high, and some experimentation may worthwhile. I also sometimes add neoprene washers underneath the transformer between the unit and the large circular rubber mounting pad that comes with the Antek products. I don't use the metal mounting disc. When I am being extra cautious, I mount the transformer onto a slab of acrylic and bolt the acrylic separately onto the chassis.
I've included a picture of an early F4 build that I did with a 400VA Antek. This had the neoprene washer underneath in addition to the rubber mounting pad, but no acrylic slab. I followed the general recommendation for using a pair of NTC thermistors as inrush current limiters, plus a 4.7 nF X1 capacitor on the primary side. I also added a large ferrite core that was salvaged from the AC inlet of a defunct UPS. I generally use a large ferrite core on the primary AC feed into each of the power transformer(s) in my amp. The idea is to filter out higher frequency components that may be riding on the 60 Hz power.
Chasing mechanical hum or buzz in a power transformer can be difficult an frustrating. The root cause can be either inside or outside your household wiring. Some of the more obvious culprits can be lighting dimmer switches and refrigerators. But it could just as easily be coming from somewhere else.
I have gotten into the habit of using some mechanical cautionary measures in each of my new amps. The first is to use rubber stoppers inside the center hole of the transformer, along with a nylon bolt to hold it in place. The tension on the bolt need not be very high, and some experimentation may worthwhile. I also sometimes add neoprene washers underneath the transformer between the unit and the large circular rubber mounting pad that comes with the Antek products. I don't use the metal mounting disc. When I am being extra cautious, I mount the transformer onto a slab of acrylic and bolt the acrylic separately onto the chassis.
I've included a picture of an early F4 build that I did with a 400VA Antek. This had the neoprene washer underneath in addition to the rubber mounting pad, but no acrylic slab. I followed the general recommendation for using a pair of NTC thermistors as inrush current limiters, plus a 4.7 nF X1 capacitor on the primary side. I also added a large ferrite core that was salvaged from the AC inlet of a defunct UPS. I generally use a large ferrite core on the primary AC feed into each of the power transformer(s) in my amp. The idea is to filter out higher frequency components that may be riding on the 60 Hz power.
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Thanks for that info TungstenAudio! I've definitely chased mechanical hum and buzz with previous amps, and one of the first things I tried unplugging the fridge that sits on the other side of the wall. Unfortunately, all of my normal tricks have not panned out yet. I like your ideas about more isolation for the transformer, and I may start experimenting there next. The primary concern I had was whether the transformer or any of my wiring/assembly was faulty, but so far that doesn't seem to be the case. I actually just did a quick recording of the buzz and hope to upload it shortly.
Hah, yeah.
The ping pong rubber is without the actual paddle. It makes a good cushion for working on aluminum chassis.