Mains tranformer noise

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Is this amp SE or PP?

Does it have an OP Tx?

What kind of feedback have you used?

You say you have an output with all tubes removed?
This can only happen if current is flowing in the speaker!
What is connected to the speaker when all tubes are removed?


Regards
M. Gregg
 
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Alastair,

Is this amp he's got an OTL.

With two power supplies across the speaker?

Regards
M. Gregg

Not quite, Ive deduced he has an OPT...(Dunno why if its a Circlotron though--What a waste!)

Think 'Circlotron OTL' with the two independant floating supplies--But WITH an OPT.....
--This is what 'Wiggins' did when he 'invented' the Circlotron,--He used an OPT, It was only later it was adopted to be used as OTL....
 
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If he's got an OP Tx,

Then any ripple would give a current path if they share a single Gnd connection?
Then again, a quick look on the net and most circuits have one side of each supply only connected to tube cathodes.
So in this case they should be open circuit?

I think you may have hit the answer Alastair, you say floating supplies.

Regards
M. Gregg
 
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Most often than not, the cathodes are also coupled to earth/Gnd via summit like a 250 Ohm resistor, so the supplies if noisy will affect performance--especially if One Circlotron supply is noisier than the other....

Interesting,

So if the current supply is to low or smoothing to low he will get ripple. Possibly across the speaker via Tx!

I guess forget the tubes and balance the power supplies..
 
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My design has an output transformer. This amplifier is part of a work for an academic work... I chose a Circlotron just to try something different and because i wanted to know how it sounds, taking in account the reduced output impedance and probably lower distortion than a common push pull amplifier.

Without the power tubes connected the negative terminal of the floating supplies is connected to the primary taps of the output transformer... That is sufficient to create the noise i'm talking about.
 
Hmmm...

One thing concernes me....

You say that this is the first amp you've designed and built....

And you choose one of the most complicated type formats, (Circlotron) there is!

I dunno.....

Schematic defo needed to see whats happening!

I chose a Circlotron but I built some tube guitar amplifiers before. It's the first I design.

I'm sorry for not posting the schematic but I'm not allowed to, since this is academic related.
 
So it would be interesting to see:

What type of rectifier?
What value of Cap across each rail?
What voltage on the rails and max current available?

Circuit diagram of the PSU and output stage?

Full-bridged rectifier;
2 680uF in series having two 220K resistors in parallel with each other in each floating supply;
420VDC on load and 270mA available from each floating supply.
 
I chose a Circlotron but I built some tube guitar amplifiers before. It's the first I design.

I'm sorry for not posting the schematic but I'm not allowed to, since this is academic related.



Hmm......

I dunno how you expect us to help......

If we cannot See a Schematic, we're walking in the dark.....
--sooner or later we are gonna fall over a table!:eek:

The fact is, you have a couple of faults, --both of which could have many causes, --least of all bad design and layout....

I personally Cannot see how we can help without more than just a description of the amplifier.....

Fact that 1 fault is present Without the O/P tubes fitted suggests a mistake in the design or PSU....
 
I finally solved all of my problems in the amp. It really sounds awesome now with really low noise.

I solved the oscillations putting 100nF capacitors in parallel with all of the full-wave rectifier diodes. The problem had to do with the switching of the diodes.

Also the bias current of the output stage was varying too much with the ripple caused by the bootstrap voltage into the driver stage. I solved this issue with a filter similar to the one in the circlotron that can be found on an elektor magazine, of experience electronics.

Thanks for your tips.

Conclusion, although a circlotron is a different beast, it isn't an alien. ;)

Hmm......

I dunno how you expect us to help......

If we cannot See a Schematic, we're walking in the dark.....
--sooner or later we are gonna fall over a table!:eek:

The fact is, you have a couple of faults, --both of which could have many causes, --least of all bad design and layout....

I personally Cannot see how we can help without more than just a description of the amplifier.....

Fact that 1 fault is present Without the O/P tubes fitted suggests a mistake in the design or PSU....
 
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