Overheating amplifier

[Al ears]

I can send the op my spare phono stage..they can then try it to see? If it makes no difference? Amp is faulty! If it makes a difference then phono stage is faulty! Tape it off..never use it again..life is as simple as you want to make it?

Agreed. Whatever the problem is it's in the amplifier.

Depends if you are referring to the amp as a whole. Until the OP gets back to answer some questions all other suggestions are meaningless.

 

[BigH]

I can send the op my spare phono stage..they can then try it to see? If it makes no difference? Amp is faulty! If it makes a difference then phono stage is faulty! Tape it off..never use it again..life is as simple as you want to make it?

Agreed. Whatever the problem is it's in the amplifier.

Not if the turntable is producing the low rumble, it you cure that then you may have solved the amp. problem. Its known the the Project TT produces hum thats why later models have been modified with a better belt and motor isolation.

 

[TrevC]

I can send the op my spare phono stage..they can then try it to see? If it makes no difference? Amp is faulty! If it makes a difference then phono stage is faulty! Tape it off..never use it again..life is as simple as you want to make it?

Agreed. Whatever the problem is it's in the amplifier.

Not if the turntable is producing the low rumble, it you cure that then you may have solved the amp. problem. Its known the the Project TT produces hum thats why later models have been modified with a better belt and motor isolation.

No hum is mentioned by the OP, and the amp shouldn't overheat on any signal.

 

[shadders]

Hi,

I am looking for some advice regarding my amplifier. It is a Roksan Kandy 2 and seems to be overheating when I run my Pro-jet turntable through it. It cuts out at mid volumes when using this source and is abnormally hot (it doesn't get anywhere near as hot on other sources - PS4 or Aux with iPad/laptop). I run the TT through the inbuilt phono stage but am not sure whether this is potentially causing the overheating? Should I send the amplifier to get serviced or potentially purchase a separate phono stage?

thanks for any help offered

Ashley

It appears to be a design fault. Heatsinks are too small, and there's probably the subsonic energy from vinyl that's causing the problem.

From Stereophile

"Before I test an amplifier, I run it for 60 minutes at one-third its specified power into 8 ohms. Thermally, this worst case for an amplifier with a class-B or -AB output stage taxes its heatsinks' ability to dissipate waste heat. The Kandy K2's top panel got too hot to touch after just 20 minutes; as I could smell hot insulation after 30 minutes, I stopped the preconditioning at that point. The Roksan doesn't have quite enough heatsink area for an amplifier of this power rating".

Hi,

Thread seems to have gotten off track. I assume that your amplifier cuts out once it has heated up, and restores once it has cooled down?

If this happens only on the phono stage input, and at mid way on the volume - from memory, most power is dissipated by the amplifier at approx 1/3 volume levels - then it is possible that the phono stage has a fault. Some faults may require energy to bias the phono stage into a fault condition, which may cause high frequency oscillation (which cannot be heard).

Either way, there seems to be a fault, design, or otherwise, which needs to be examined. You may be able to test yourself if you have an oscilloscope, with the requisite attenuation when connecting to the power output, unless there are preamp outputs.

Regards,

Shadders.

If that was the case the amplifier would still overheat with no record playing, so it would be easy to prove without an oscilloscope.

Hi,

I disagree, some circuits require a specific amount of energy to cause oscillation, which may drive the circuit into the unstable region.

Regards,

Shadders.

What circuit are you talking about? The phono preamp? Sounds unlikely to say the least.

I see that this Roksan does have a small heatsink, but it also has a 5 year warranty.

Hi,

The original poster states ONLY when using the phono stage input does this occur, and that other inputs are ok. Hence, the logic that it is the phono stage.

Regards,

Shadders.

So, to recap, it appears to be a design fault. Heatsinks are too small, and there's probably the subsonic energy from vinyl that's causing the problem.

As I said above.

Hi,

No, the energy causing the overheating could be high frequency due to a fault in the phono preamp. Until the original poster conducts tests, we can only guess.

Regards,

Shadders.

Then it will still overheat without the record playing.

Hi,

No, not if the fault requires some energy to put the phono stage into oscillation. If the original poster can capture the preamp stage output using a soundcard, then they can use Audacity to analyse the spectrum to see where the energy appears.

Electronics are not either 100% stable, or 100% unstable, there is always some grey area in between where some conditions can cause instability, such as capacitive loads on the amplifier output.

Regards,

Shadders.

The energy will appear once the needle hits the record. That won't be oscillation in the preamp, it will be the roar and subsonic noise from the vinyl or turntable. Capacitance can make what unstable?

Hi,

A capacitive load can cause amplifiers to become unstable. This was just an example that an otherwise stable amplifier with an inductive load can be unstable with a capacitive load. This would be amplifier design dependent.

Likewise, the phono preamp circuit could be unstable due to the signal power from the turntable, where the circuit in its quiescent state is stable.

Regards,

Shadders.

 

[BigH]

I can send the op my spare phono stage..they can then try it to see? If it makes no difference? Amp is faulty! If it makes a difference then phono stage is faulty! Tape it off..never use it again..life is as simple as you want to make it?

Agreed. Whatever the problem is it's in the amplifier.

Not if the turntable is producing the low rumble, it you cure that then you may have solved the amp. problem. Its known the the Project TT produces hum thats why later models have been modified with a better belt and motor isolation.

No hum is mentioned by the OP, and the amp shouldn't overheat on any signal.

Ok rumble then. If you cut that out it may cure the problem. I would do the kit anyway, it should improve speed accuracy and reduce vibration.

 

[TrevC]

"A capacitive load can cause amplifiers to become unstable. This was just an example that an otherwise stable amplifier with an inductive load can be unstable with a capacitive load. This would be amplifier design dependent."

Yes, but that's in the output stage, so not relevant to this problem at all. Some Naim amplifiers were criticised for leaving out the zobel network, thus making their amplifiers unstable.

"Likewise, the phono preamp circuit could be unstable due to the signal power from the turntable, where the circuit in its quiescent state is stable."

You are talking nonsense, which really isn't helpful.

 

[shadders]

"A capacitive load can cause amplifiers to become unstable. This was just an example that an otherwise stable amplifier with an inductive load can be unstable with a capacitive load. This would be amplifier design dependent."

Yes, but that's in the output stage, so not relevant to this problem at all. Some Naim amplifiers were criticised for leaving out the zobel network, thus making their amplifiers unstable.

"Likewise, the phono preamp circuit could be unstable due to the signal power from the turntable, where the circuit in its quiescent state is stable."

You are talking nonsense, which really isn't helpful.

Hi

You have taken my comments out of context, to support your argument. You have resorted to rude responses to supplant reasoned argument, rather than state factually what I have stated as being incorrect.

You have no evidence that what I have stated as being incorrect. I have not stated that you are incorrect in your submission on what the issue could be.

I would never descend into such behaviour as yours.

Regards,

Shadders.

 

[Al ears]

"A capacitive load can cause amplifiers to become unstable. This was just an example that an otherwise stable amplifier with an inductive load can be unstable with a capacitive load. This would be amplifier design dependent."

Yes, but that's in the output stage, so not relevant to this problem at all. Some Naim amplifiers were criticised for leaving out the zobel network, thus making their amplifiers unstable.

"Likewise, the phono preamp circuit could be unstable due to the signal power from the turntable, where the circuit in its quiescent state is stable."

You are talking nonsense, which really isn't helpful.

Hi

You have taken my comments out of context, to support your argument. You have resorted to rude responses to supplant reasoned argument, rather than state factually what I have stated as being incorrect.

You have no evidence that what I have stated as being incorrect. I have not stated that you are incorrect in your submission on what the issue could be.

I would never descend into such behaviour as yours.

Regards,

Shadders.

You are trying to debate with trevc here you realise. I'd forget it.

There is not much point of continuing this thread until the OP comes back with some answers.

....says he continuing the thread.

 

[TrevC]

"A capacitive load can cause amplifiers to become unstable. This was just an example that an otherwise stable amplifier with an inductive load can be unstable with a capacitive load. This would be amplifier design dependent."

Yes, but that's in the output stage, so not relevant to this problem at all. Some Naim amplifiers were criticised for leaving out the zobel network, thus making their amplifiers unstable.

"Likewise, the phono preamp circuit could be unstable due to the signal power from the turntable, where the circuit in its quiescent state is stable."

You are talking nonsense, which really isn't helpful.

Hi

You have taken my comments out of context, to support your argument. You have resorted to rude responses to supplant reasoned argument, rather than state factually what I have stated as being incorrect.

You have no evidence that what I have stated as being incorrect. I have not stated that you are incorrect in your submission on what the issue could be.

I would never descend into such behaviour as yours.

Regards,

Shadders.

If you don't want to be criticised for posting nonsense then don't post any. Simple really.

 

[Al ears]

"A capacitive load can cause amplifiers to become unstable. This was just an example that an otherwise stable amplifier with an inductive load can be unstable with a capacitive load. This would be amplifier design dependent."

Yes, but that's in the output stage, so not relevant to this problem at all. Some Naim amplifiers were criticised for leaving out the zobel network, thus making their amplifiers unstable.

"Likewise, the phono preamp circuit could be unstable due to the signal power from the turntable, where the circuit in its quiescent state is stable."

You are talking nonsense, which really isn't helpful.

Hi

You have taken my comments out of context, to support your argument. You have resorted to rude responses to supplant reasoned argument, rather than state factually what I have stated as being incorrect.

You have no evidence that what I have stated as being incorrect. I have not stated that you are incorrect in your submission on what the issue could be.

I would never descend into such behaviour as yours.

Regards,

Shadders.

If you don't want to be criticised for posting nonsense then don't post any. Simple really.

Yet another classic statement.