Single-ended-series amp with a "1 winding" transformer

[woody]

I don't think this is single ended.

 

[tubee]

Is it single ended or pp? Here is a comment on this (solid state example though)

http://www.tcaas.btinternet.co.uk/jlhoutput.pdf

The rail voltage is single for sure

 

[smoking-amp]

"Is it single ended or pp?"

With matched current drives, as in the JLH output, or with matched voltage drives, as in the bootstrapped drive (Yvesm schematic), the even harmonic distortion products will cancel (for matched output devices), so they are obviously P-P.

Don

 

[tubee]

It is a pseudo push-pull design. At around 1969 it was difficult to make complementary transistors, so they designed (iron or no-iron) pseudo-pp amps, no need for expensive transistor-couples (and matching) Philips and others came with some of those designs.

PP indeed eleminates 2nd order harmonics. The use of a triode in the first stage creates some even harmonics, all together the amp could sound very neutral due to the combination of "even" & "odd" stages. But i am unaware what the bootstrap will do to the harmonic distorsion., (bootstrap = positive feedback)

 

[smoking-amp]

The splitter bootstrap guarantees equal grid to cathode drive voltage on the top output tube. Since it references the equal voltage drop on the top 82K (versus the bottom 82K) splitter resistor to the top tube's cathode (which the bottom drive already does too).

Since the splitter bootstrap is not increasing the top grid drive versus the bottom grid drive, it should not be creating any additional distortion here. Really just has the same effect as one would get using an interstage transformer with two floating secondaries. (Remind me not to buy any interstage transformers, how stupid!)

Don

 

[tubee]

Talking about interstage transformeres: had 2 identical ones with special mu core, one i demolisched as study-object, i am now sorry i did.

Did some thinking to add a cap and a autotransformer, not easy with the bootstrap.

 

[tubee]

Is this gonna work?

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

 

[tubee]

Little improvement, speaker on one side grounded

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

 

[tubee]

giant topic kick

well well, looooong time ive been here. Long story too: my class D amp in PC speakers broke up and made a germanium amp for it wich i had laying around, AD161 amp. This made me think could it not be done with tubes and that reminded me on my first attempts. Spend a few hours on a soldering session and first design idea of a SEPP with EL34 penthodes is done. Sound not available (yet) but keep you posted.

Did not use the bootstrap idea but used this schem:

This has less coupling caps, and the bootstrap to upper EL34 is not needed, simply the voltage swing of lower EL34 drives the upper, simple as that.

 

[tubee]

some pictures or it did'nt happen