First may I say that it would not be damping.first I used a kit. It did buzz. Then I got the schematic of that kit and made my own layout. Buzzes as well. It did buzz at the old flat in Europe and still buzzes here in Australia.
You reckon, the speaker cables feed back, not enough dampening?
I would not advise going for a switch mode power supply.found an 8.2 ohm resistor, the buzz gets a bit less but its still there. Power consumption in both cases is identical. Even when the speakers are not connected.
The easiest way out will be a switch mode power supply. As its quiet when powered by the lab supply. When on the lab supply, the pure 50Hz tone, I have to be 5cm away from the driver to just so hear it.
The amps are at 30dB amplification, I will wind dit down to the minimum they do, about 22. When switching them on for split seconds there are 2 V in the bass drivers (2 in bridge), that nearly pushes the membrane out of the driver. I reckon I should wind down the supply voltage. Its not about being loud, its about producing a clear sound.
No reservoir capacitors or are they underneath?top left supply for the relay that switches mute on/off
top right supply for crossover
below transformer 3pass crossover
underneath crossover the power supply
Wow! nice power supply.the accessories are on the line of 100mA or less. The relais draw something like 10mA at 5 Volt, the crossover no idea, worst case 100mA at +-15V. I did not want to run them off the main transformer.
Here power supply. The Cs across the diodes are film, have to replace them with ceramic.
I disconnected the 2 small transformers, does not make a change.
OK no rush- I have to do some building work pretty soon anyway.I messed up the supply, transformer has 2 centre and 1 each end, so I had to do some magic. Anyway, that was my next plan. 22:30 in here now, see if I get it done
Hmm, interesting, but not unusual.ok, did that, transformer about 1m/3 feet away. any other transformer inside the housing disconnected. Power for mute in/out relays from lab supply.
Hum is still there. But, when I switch the mains transformer off, mute is off (as in speakers running of the power supplys caps while they are discharging) the hum is still there.
Can you also confirm this. With the configuration above, if you disconnect the two cables connecting the xover to the monoblocks, the hum stops and all you can hear is some background noise. Is that background noise normal and acceptable to you?Now remember, the crossover sits over /on top of the power supply. When I disconnect the cable from the xover to monoblock in, there is small white noise, cable back on, buzz is back.
I hope you do not mind me saying this, but it would be best to avoid considering any solutions at this stage until the root cause of the problem is established.So next step is replace foil caps parallel to rectifier diodes in power supply with ceramics, as that seems to add some resistance and it acts as a snubber. But still, without transformer, why is it still oscillating? Crossover is not powered.
With monoblocks in mute, it draws 1.6 or so W, monoblocks on 12W. The transformer does not get louder wirh more load.
diodes are these
**broken link removed**
thread on bypass resistors on diodes
OK. Can you try this:the earth is still connected to the chassis as I am a bit scared to have it completely floating, voltage wise
the xover I did, ther ceramic caps are 100nF in the rails for the +-15 V to the opamps. The xover is not connected to anything, excapt that cable to the input ot the mono block. This amp is just 1 channel, no need to worry about other speakers.
There is a power cable in the wall about 600mm away, goes vertical. And the only thing it does is power my experiment, so not much magnetic field there.
its all MKPs and metal resistors, opamps are OPA134, then a bunch of Mundort tin caps.
Ok remover all the clutter around and listen to it again. But the buzz kept going with the lab supply for the mute relays unplugged, until its caps dischaged and the relais tripped.
For prices, does Reichelt supply to the UK, everything in there feels like half price.