• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

6P45S PP, simulation frustration.

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 :)

[IMGDEAD]http://gratisupload.dk/billede/thumb/692227/full/[/IMGDEAD]
 
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 :)
 
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.
 
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

Member
2010-02-16 9:00 am
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 ?