A 40 Amolifier problems

[hiradi]

Hello,I am completly new to this ,so be patient.I bought a A40 Amp of a reputable builder/engineer and have had nothing but problems with it.
I am on Solar Power and running of a true Sinewave Inverter.
I have had no trouble with my SET Amps or a Bel Canto EVO.
When I played the A40 and lifted the record of the turntable it popped,deadly silence after that on both channels.
Back to Melbourne the amps went for repair.I was concerned it was static of the turntable that popped the amp,but could not understand why it did not happen to the Valve SET amp.
I fixed the static and now could not detect any pops on the SET amp.
On return of the A40,after about an hour of music the same thing happened to one channel.
The builder insists that it is a spike in my power supply,the Inverter ,causing the problem,blowing the fet's on the biasing circuit.The TV,computer etc all run OK.
The builder of the A40 has removed the fet ,constant current source,biasing circuit and replaced it with a resistor.He maintains that this will not affect the sound and it is a better way to go ,anyway.
Any suggestions ?

[jam]

Replace the fet with a current diode.

Jam

[GRollins]

Is this a trap to see if I'll take the bait?
I can see Jam waiting with fingers poised over the keyboard...

Actually, I'd try to track down the source of the pops. You said 'the same thing happened.' I'm assuming that you mean your system popped the second time. Something else is wrong. Yes, turntables can generate static, but if you've grounded the turntable so that it no longer pops you'll need to look somewhere else to find the problem.
You might check through the power supply on the amp to make sure that all connections are good. If the rail is intermittent, you could get some really ugly things happening.
Whether to use a resistor (which will be somewhat less delicate than active devices) or current source is up to you.

Grey

[hiradi]

Yes,the T/table is now grounded and does not pop anymore.The second time I lost only one channel and there was NO pop .
Does the resistor affect sonics ?
After the first repair,I was told,he put back to back zeners to protect the input,obviously that did not work.

Originally posted by GRollins
Is this a trap to see if I'll take the bait?
I can see Jam waiting with fingers poised over the keyboard...

Actually, I'd try to track down the source of the pops. You said 'the same thing happened.' I'm assuming that you mean your system popped the second time. Something else is wrong. Yes, turntables can generate static, but if you've grounded the turntable so that it no longer pops you'll need to look somewhere else to find the problem.
You might check through the power supply on the amp to make sure that all connections are good. If the rail is intermittent, you could get some really ugly things happening.
Whether to use a resistor (which will be somewhat less delicate than active devices) or current source is up to you.

Grey