6P45S PP, simulation frustration.

[MadsKaizer]

Hey All

I have spent a couple of days trying to wrap my head around why my simulation is acting up weird, I have come to the conclusion that I have made some small rookie mistake that I am blind to see.

It is two ECC83 tubes and 6P45S output tubes. OPT is a Generic14K model.

I have cut the circuit up in all kind of smaller parts to make it behave like I expected, no luck. Even just the input stage by itself gives the same result, without NFB.

Blue trace is input -500mv to 500mv. Green trace is from anodes of U1a/b.

I expected a amplified signal, not a amplified signal with a huge DC offset.

Help a blind man see

An externally hosted image should be here but it was not working when we last tested it.

 

[45]

The bias V4 looks wrong. Shouldn't it be the other way around?
The offest on the plate is normal as you are at plate potential, there is no DC decoupling there.

 

[MadsKaizer]

The bias V4 looks wrong. Shouldn't it be the other way around?
The offest on the plate is normal as you are at plate potential, there is no DC decoupling there.

It does give out -50V.

This is by the way my first time simulating a tube amplifier, seems like you are right about the plate potential, just got my mind wrapped around that I would get a signal out crossing zero. I feel rookie again

 

[artosalo]

I am not sure what you have tried to simulate.
I attached one simple 6P45S PP output stage.
It should work.

 

[artosalo]

Concerning your schematic, there are no grid leak resistors at tube U1.

 

[JonSnell Electronic]

Concerning your schematic, there are no grid leak resistors at tube U1.

Likewise U2 has a very high cathode resistance.

 

[MadsKaizer]

Thanks Artosalo, I can see that I am miles from simulating correctly I have only plotted the schematic and thereby not taken reality into account.

The phase splitter a reuse from my current working amp, schematic at page 19: http://www.lundahl.se/pdf/ovrigt/amplifier_30wpp.pdf

What I tried out here was to improve the APX-100 amplifier with the similar improvements Claus Byrinth made to the Mullard design in his paper.

 

[heavil]

I can say without a simulation, but a large number of experiments: 6P45S - this lamp is not for music. It gives the power and sound but not the music.

 

[dave slagle]

The DC offset you are seeing is simply the B+ of the first stage. Looks to be about 105V with your amplified signal going +-25V from that baseline.

to see it ground referenced you can either subtract the B+ from the waveform with an equation or cap couple off the node to a 10 meg resistor to ground.

dave

 

[artosalo]

Thanks Artosalo, I can see that I am miles from simulating correctly I have only plotted the schematic and thereby not taken reality into account.

The phase splitter a reuse from my current working amp, schematic at page 19: http://www.lundahl.se/pdf/ovrigt/amplifier_30wpp.pdf

What I tried out here was to improve the APX-100 amplifier with the similar improvements Claus Byrinth made to the Mullard design in his paper.

Did you get my ciruit to work ?

 

[MadsKaizer]

Did you get my ciruit to work ?

Yes, it works very nicely. Only had to remove the tube library link.