What I thought might be a good reason for looking at direct (DC) coupling between driver and output stages in the particular case of a 300B amp might be the fact that we require a rather large voltage swing into the output tage. So slew-rate requirements between driver and output tube are bigger.
Furthrmore, since the output power is a bit limited, we would be pushing the amp into the upper regions more often as compared to higher powered amp. Consequently, good overload recovery would be an important design goal.
My understanding is that direct coupling of the output tube can. help with both of these aspects.
Furthrmore, since the output power is a bit limited, we would be pushing the amp into the upper regions more often as compared to higher powered amp. Consequently, good overload recovery would be an important design goal.
My understanding is that direct coupling of the output tube can. help with both of these aspects.
Cool thanks. I see so many posted simulations, it's nice to see an actual >measured from a real live amplifier< one 🙂
It was the best (low THD) pair of 300B (gold grid EH300B) which I have for decades. Sadly one of them died (filament interrupted) after few years.
Nowadays the SQ is much worse, so it's probably unrepeatable.
Nowadays the SQ is much worse, so it's probably unrepeatable.
Too bad for you, Euro21. Why not buying one of the new WE 300B tubes instead?
Will they sound not good enough compared to those gold grid replica tubes?
Just asking for curiosity as I'm not into the 300B game any longer..its only for the rich kids.
Will they sound not good enough compared to those gold grid replica tubes?
Just asking for curiosity as I'm not into the 300B game any longer..its only for the rich kids.
None of all 300B type suitable for A2.
Most of them reacts with growing distortion if grid swing approaching or exceeding 0V.
Robust metal anode and grid wire types (for example old ValveArt, Electro-Harmonix or JJ) can be used.
I'm not sure, that "boutique" production tube (NOS or replica WE, Elrog, EML etc.) worth it for testing.... as you can say it's only for rich kids. 😛
With triodes, using an excellent IT is most often the better way for achieving maximum signal quality. Especially as driver for a precious 300B boutique tube. Nobody wan't to harm this.
I will try this one myself someday
Direct coupled SET proposal – wauwatosa tube factory
I will order and use Rod Coleman's new shunt cascode kit. I'm not sure if it is ready yet or not.
Direct coupled SET proposal – wauwatosa tube factory
I will order and use Rod Coleman's new shunt cascode kit. I'm not sure if it is ready yet or not.
Last edited:
because it has tubes and output transformers. I also have interstage transformers amps. I guess that I just don't care about tube purity anymore.
Last edited:
Popa Marius:
Have you actually built this driver circuit you posted?
Is the Vout 70v rms, peak or peak to peak?
THD+N figure posted is measured at what output level?
Is the THD+N figure shown on the schematic measured value or simulated?
Art
Have you actually built this driver circuit you posted?
Is the Vout 70v rms, peak or peak to peak?
THD+N figure posted is measured at what output level?
Is the THD+N figure shown on the schematic measured value or simulated?
Art
This is basically Alan Kimmel Fig.4 Mu follower circuit.
http://www.fetaudio.com/wp-content/uploads/2003/09/Mu-Stage.pdf
Art
http://www.fetaudio.com/wp-content/uploads/2003/09/Mu-Stage.pdf
Art