Burning Amplifier BA-2

One thing that i have notice also is that the transformer of the unregulated supply is bazing excessively and this mechanical noise is audible thru the speakers.
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What current and voltage is your transformer primary winding designed for? Buzzing can be caused by saturation i.e., transformer can't cope with the primary voltage.

Does it buzz when connected to the house power supply but with the secondaries unconnected?

Dear Backbones,

The transformer is rated at 1000VA / 220VAC primary and it bazing without a load on the secondary

I have 1,5-2VDC in the AC line this must be the route cause for this mechanical noise.
 
Have you bypassed the soft start?
Dear JimM
I have bypass the soft start this is not the problem.
Today i have tried another approach

I have bypass all the front end regulated psu everything is dead silent no any noise what's so ever.
I thing that the problem lies with the regulated psu transformer secondary winding.
I will try to hookup separate transformers and report back.
 
nikosgrdr,

I haven't got a wiring diagram. However, let's try and do it with words.

The 8 wires from the output of the Salas reg are joined to make two wires for the +ve, four for the ground and two for the -ve. I'm running it at -25-ground-+25.
The BA-2 board then receives these three connections.
I then also connect the ground of the BA-2 board to the star ground of the separate power supply which supplies the power boards (the design of this is identical to Nelson's circuit diagram in the BA-2 build including the CL60 thermistor connecting ground to the amplifier's chassis which is mains earthed).
If you don't connect the front end ground to the power board ground you will get a hum (from the loudspeakers not the transformers).

What is the voltage rating for your front end transformer? You may get saturation of your transformer due to poor manufacture or because it can't cope with the voltage input or both which can set up harmonic interference that can cause other transformers within the circuit to hum or buzz.
 
Humm Problem

Dear all,
The hum problem when both front end inputs where connected with the outputs of a pre amp has been resolved by using two separate transformers (one per front end regulator also the main psu transformer for the output stage has been changed having now (4) separate secondary windings).
The amp now is silent.
One additional question.
Can someone advise were we can find very closely matched IRFP240-9240 (i cannot find any in tech diy).

Thanks
 

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Hi NoSmoking,

one BA-1 output board works as one channel (= 1 mono), if you want stereo, build two. Of cause you can operate them as stated in the F4 article.
As the BA-1 is a single-ended amp, there's no need for complementary devices.
BA-2 is push pull, so you have n-channel and p-channel devices.

Thanks for the wishes, I would be glad if we'll get some sun and warmth here in Germany where I life, but the last days we had so much rain you could get the idea it's already november.
Have a nice day!
Matthias