Schematic needed PL519 Class A SE

[mario2005]

Schematic needed PL519 Class A SE
Hi
Could you post a schematic for Tube Power Amplifier with PL519 Class A SE .
Does someone has some experience using the PL519 in SE A mode ?

What you think about SYNOLA SE 509 ?

http://www.jogis-roehrenbude.de/Leserbriefe/Synola-509/SYNOLA_SE509.htm

thanks

mario

 

[EC8010]

Try searching for Tim de Paravacini's EAR859(?) circuit which was offered as a kit in UK publication Hi-Fi News, so the circuit is readily available.

 

[Tubes4e4]

What you think about SYNOLA SE 509 ?

Quite famous over here, but when you analyze the peak screen grid current demands of PL509 at the given operation point when using g2 drive, the CF shown there never ever will be able to deliver the g2 peak currents being needed to drive with low distortion

But maybe this is intentional, synergistic and cancels out somehow (but how?), since this amp is reported to actually sound quite good.

Tom

 

[Tubes4e4]

Tim de Paravacini's EAR859(?) circuit which was offered as a kit in UK publication Hi-Fi News, so the circuit is readily available.

Looks rather complicated and seems to use tons of feedback to get at least some linearity.

Something like "lets do it because it could be done". Why not start with a decent audio tube in the first place, instead of doing a lot of stuff to force ends to meet somehow?

Tom

 

[EC8010]

Why not start with a decent audio tube in the first place, instead of doing a lot of stuff to force ends to meet somehow?

I suspect the reason may have been that at the time the design was published it was very difficult to get reliable audio valves.

 

[astouffer]

Screen drive is the only way to go for this tube. I tried many ways to drive it normally but never found the right operating point. Maybe the g2 voltage was too high... Anyhow I built this http://www.geocities.com/bobdanielak/technoteNo33.html and it works great.

 

[Fuling]

I´ve messed around a bit with screen driven PL519 and I ended up using Mosfet followers to feed the screens.
Much easier than cathode followers, and they require no heater supplies.

 

[Tubes4e4]

I suspect the reason may have been that at the time the design was published it was very difficult to get reliable audio valves.

Nah, can´t be. For example, there never was a shortage of good quality and reliable EL34 since its introduction about fifty-two years ago. This certainly holds true also for several other audio power tubes.

Tom

 

[EC8010]

In the early 90s there were some extremely dodgy Chinese "EL34" and "KT88" and not much else available in the UK.

 

[Tubes4e4]

Hi EC8010,

In the early 90s there were some extremely dodgy Chinese "EL34" and "KT88" and not much else available in the UK.

While this might be true (I don´t know), this is no argument, since TdPs resumee tells he started using EL509 for commercial amps in 1977 already - which is more than a decade apart from the early 90s.

Tom

 

[EC8010]

I'm not going to argue - your 1976 point is valid.

 

[richwalters]

Although deviating frm the topic, Perhaps worth mentioning that my supplier has quote < Due to so many reliabilty problems encountered with the KT90 has given up hope of getting any more and are becoming extinct. > I know that Ei aren't making them anymore.

This would seem a pity, this KT90 pencil tube never excelled as the 509's line did even though were a derivation of the same class of wacker sized anodes.
Despite some dour comments regarding the earlier EL34's and KT series, I got a recent FE replica of a KT88 and grilled it, and low behold the anode did glow evenly from bottom to top. For a change, after all this time...... SOmeone actually got the alignment correct.

In a few years time. I can see only a few power tube types being made and it will be interesting to see which ones make it.
Any guesses ??

richj