An application of C-Vac: the SolidGlass amplifier

[kenpeter]

if the current gain is sufficiently high to begin with, then the dynamic loading on the tube plate can be insignificant compared to its plate resistance at all times.

Did I say operate the triode at constant current? Yes, I did...

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Even more linear to load the plate slightly beyond constant, with a negative resistance slope.
Not that going there ever makes any sense for stability...

Some type of dynamic bias scheme could also be conjured up which would help to maintain the impedance seen by the tube more constant, by increasing the cross-thru current near crossover.

Did I say just Circlophone it? Yes, I did...

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It has proven more stable to add bias current to a C crossing than shunt the excess
from an AB crossing. Elvee's Circlophone doesn't oscillate. My shunt tailed pair does.
Though they "should" be equally effective ways to dynamically bias the same class B
result, somehow they are not.

I suspect again the negative resistance devil hiding in the details somewhere.

 

[JZatopa]

Well I don't own an OTL amplifier and I have way to many projects to try building this amp so I must. How does it sound? Or better yet, how does it sound when compared to a traditional OTL and SS amplifier?

I would be curious to hear how some of the more modern improvements to tube circuits affect this one as well (CCS, LED bias, etc.). If an amplifier like this could give me the best of both worlds (ss + tube) I would be really interested to see an optimized version.

 

[gingertube]

I like your current mirror / multiplier circuit.
We guitar amp types have been calling this gm multiplication and using it (in a simpler form) to get the characteristic sound of our little EL84 or 6V6 amps and boosting it to "stadium crusher" ear bleeding levels. Of-course we still need the BIG Output tranny and its generally so damn loud that whether we have achieved our aim remains entirely debatable. What is left of the hearing maybe able to tell once the ears stop ringing.
Cheers,
Ian

 

[Elvee]

Well I don't own an OTL amplifier and I have way to many projects to try building this amp so I must. How does it sound? Or better yet, how does it sound when compared to a traditional OTL and SS amplifier?

To my tin ears, it doesn't sound very tubey; probably partly because it has no magnetics.
But it doesn't sound "neutral" like a good SS amp either. That's probably because it has a low feedback, and therefore preserves some of the tube character; THD is about 0.5% after all

I would be curious to hear how some of the more modern improvements to tube circuits affect this one as well (CCS, LED bias, etc.). If an amplifier like this could give me the best of both worlds (ss + tube) I would be really interested to see an optimized version.

This amp is just an application example of the C-vac concept. Probably not the best of what's possible with it, and you are free to experiment, to "magnify" the tube you like best: why not try a 500W nuvistor amp for example?