3 stage DC - any thoughts?

[JMFahey]

There´s 2 transformers and an inductor in the circuit; any of them has WAY more complex and unpredictable impedance and phase shift than even the cheapest capacitor, let alone a good one, which is WAY easier to properly understand and , if needed, correct.

I presume the intention was to make a better amplifier, but it got loaded with unpredictable problems in the way.

May work, but it´s outdated (to say it kindly) and looks needlessly complex, without an exceptional result for such an effort.

 

[TheGimp]

I noticed that Jensen does not specify breakdown voltage of that transformer.

You potentially will have over 300V across primary to secondary during power up, before the input tube begins to conduct.

I recommend requesting breakdown information on that transformer before using it in such an application as this.

 

[Ludwig Haus]

I noticed that Jensen does not specify breakdown voltage of that transformer.

You potentially will have over 300V across primary to secondary during power up, before the input tube begins to conduct.

I recommend requesting breakdown information on that transformer before using it in such an application as this.

I think given a slight misunderstanding, the best candidate so far presents as www.lundahl.se/wp-content/uploads/datasheets/1570_0xl.pdf

 

[Ludwig Haus]

There´s 2 transformers and an inductor in the circuit; any of them has WAY more complex and unpredictable impedance and phase shift than even the cheapest capacitor, let alone a good one, which is WAY easier to properly understand and , if needed, correct.

I presume the intention was to make a better amplifier, but it got loaded with unpredictable problems in the way.

May work, but it´s outdated (to say it kindly) and looks needlessly complex, without an exceptional result for such an effort.

Yeah, what did they know about voltage amplifiers in the 1930's ?..

 

[kevinkr]

It actually sounds just fine, my only issue with it which IMHO is addressable with fuses is what happens to the output tube if one of the driver tubes fails. The water's fine as they say.

 

[DF96]

Yeah, what did they know about voltage amplifiers in the 1930's ?..

They faced different problems from us, so adopted different solutions. For example, they used interstage transformers because the valves they had were very low mu; the transfomer boosted the voltage gain. They put up with the weaknesses of transformers because they needed the gain. I'm sure that if they had higher mu valves they would have used them instead of transformers; they would find it amusing that we try to copy them when it is now quite unnecessary.

 

[Ludwig Haus]

They faced different problems from us, so adopted different solutions. For example, they used interstage transformers because the valves they had were very low mu; the transfomer boosted the voltage gain. They put up with the weaknesses of transformers because they needed the gain. I'm sure that if they had higher mu valves they would have used them instead of transformers; they would find it amusing that we try to copy them when it is now quite unnecessary.

DF96 - I think they would find it amusing that after 90 odd years the early DHT's are still at the very top of the most linear voltage amplifiers. The self rejuvinating thoriated tungsten types last for decades+ when used within their limits (before the age of built in redundancy) and btw theres no interstage transformer or transformer configured for voltage gain in the circuit - so they'd be suitably impressed I'm sure ;-)

kevinkr, thanks for the reply - I'm diving in !!


LH/S

 

[JMFahey]

Some people are SO impressed by old technology that they keep it running, no matter what :
https://youtu.be/Cv3LNNwSx6M?t=2m33s

 

[DF96]

btw theres no interstage transformer or transformer configured for voltage gain in the circuit

Yes, my mistake. There are input and output transformers, which will somewhat degrade the linearity of an old low mu valve.