[Docere]

Most tube amp designs can be turned on for short periods without speakers connected; not sure about the Cayin.
When a tube amp is connected without the speakers or a resistor of adequate value the output transformer starts to short circuit and warmup, what first heats up is the wiring of the windings, which can harm the protective varnish of the winding wiring. That was not a good recommendation them give to you.

I should have been clearer and not given the impression that running without a load is recommended - my bad. In a stable amp with no signal applied, the amp should be fine for short periods. That said, it is recommended practice and safest to have a dummy load or, of course, speakers attached to the speaker terminals. Mistakes and accidents happen. Play it safe. I do.

I will remove my original post.

[FullRangeMan]

I should have been clearer and not suggested running without a load is recommended - my bad. In a stable amp with no signal applied, the amp should be fine for short periods. That said, it is recommended practice and safest to have a dummy load or, of course, speakers attached to the speaker terminals. Mistakes and accidents happen. Play it safe. I do.

running without a load
Now I also was in doubt, maybe E55L2 that makes audio transformers for over 20 years can enlighten us?

[Docere]

running without a load
Now I also was in doubt, maybe E55L2 that makes audio transformers for over 20 years can enlighten us?

I think you made a good point FRM - don't run without load. If people do, they do it at their own risk.

[Kw6]

Bad news pop is actually still from both sides just that i didn't notice it because i was focusing on the right side. What to do now? My dealer says try a cheater plug and not use ground as a test. He thinks its my AC but I tell him my other amps dont do this.

[Tyson]

Try replacing all the tubes with new/different tubes.  If that doesn't fix it than I'd guess it's a DC power supply cap going bad since it's common to both channels.  You'd have to send it in to a tube tech to get it diagnosed and repaired.

[E55l2]

At the moment you switch off a amplifier you shut off the mains transformer. Physics tells you that the abrubt switch off will induce a voltage spike. If the amplifier is disigned correctly you don't get a "pop" on your speaker. Not every amplifier has enough filtering to filter out this spike

Is the mains transformer a toroid?

btw If you switch on without a load or have signal on the amplifier without a load, a penthode amplifier can cause damage to your output transforer, ultra-linear maybe a problem, triode output probably no harm for your outputtransformer

[Kw6]

It could be a Toroid but its encapsulated so not sure. The model of my amp is Cayin A-300b MK II. It's a single ended triode. I talk to another tube amp maker says on power down something in the power supply is getting through to the audio circuit  causing that small pop. What you think?

[Kw6]

At the moment you switch off a amplifier you shut off the mains transformer. Physics tells you that the abrubt switch off will induce a voltage spike. If the amplifier is disigned correctly you don't get a "pop" on your speaker. Not every amplifier has enough filtering to filter out this spike

Is the mains transformer a toroid?

btw If you switch on without a load or have signal on the amplifier without a load, a penthode amplifier can cause damage to your output transforer, ultra-linear maybe a problem, triode output probably no harm for your outputtransformer

Ok thanks!

[FullRangeMan]

The mk3 version not use a Toroid transformer seems a EI.

[Kw6]

My exact model is A-300b MkII. I wasn't aware there was a Mk III. So what in there has gone wrong? An ex dealer for Cayin says it could be the power regulator. What you guys think?

[FullRangeMan]

An ex dealer for Cayin says it could be the power regulator.
If he mean say the Two Rectifier Tubes are defective it is unlikely, I wonder why he would think that?

[Kw6]

I'm not sure. So from that image you posted what could be the culprit? The pop is coming from both speakers. So it can't be something faulty from one side as chances both sides having similar bad parts is low probability. One guy says something is getting out of the power supply and getting into the audio circuits.

[Kw6]

I'm not sure. So from that image you posted what could be the culprit? The pop is coming from both speakers. So it can't be something faulty from one side as chances both sides having similar bad parts is low probability. One guy says something is getting out of the power supply and getting into the audio circuits.

He said it was some sort of IC chip in the power supply. He did not say the rectifier tubes.

[Kw6]

Dealer got back to me saying it could be a faulty resistor which is responsible for discharging the capacitors or even faulty capacitors discharging abnormally. Does that make sense to you guys?

[Kw6]

Is the bad resistors or capacitors in the area where i have drawn a circle?

[Kw6]

.

[Kw6]

I read when you switch off the power to your amplifier, its power supply will collapse asymmetrically which will cause the amplifier’s output to be at an indeterminate state when it should remain at zero DC.

This results in the switch On or Off thump.

Most amplifiers will contain an output relay to negate this problem - the relay is energized or de-energized only when the amplifier’s output is stable. In the pic do you see such a relay on the Cayin amp?

[FullRangeMan]

Dealer got back to me saying it could be a faulty resistor which is responsible for discharging the capacitors or even faulty capacitors discharging abnormally. Does that make sense to you guys?

Iam not an tech but by the little I know yes it make sense.

[FullRangeMan]

.

Probably its right there.
I dont know how relay are looking today.

[dB Cooper]

We can speculate until the end of time but if you want answers that are helpful, have it checked out by a tech (assuming you have, or can obtain, a copy of the schematic).