Russian EL509 / 6KG6 quality question??

[Parafeed813]

Looking at that Svetlana data-sheet, the heater draws 25% more power than the western originals (6,3V@2,5A VS 6,3V@2A/40V@0,3A).
Something to consider when using these as replacements.

 

[GUNFU]

6P42S and 6P45C are much larger lamps and dissipate more power than indicated in comparison with datasheet.
Nevertheless, the heater of the updated 6P42C compared to the 6P45C is a bit more economical (1.26 W), the slope S is nevertheless higher. They and EL509 are more advantageous to use as OTL.

 

[multi]

Are there any circuits using EL509 in class B zero bias? I have 6P45C's. Plate dissipation is only 35 watts so max voltage would be 350 to 400 volts to get good sound.
thanks
Phil

 

[artosalo]

max voltage would be 350 to 400 volts to get good sound.

To what this assumption is based on ?
Usually zero-bias circuits have high supply voltage.
Try to connect all grids of 6P45S together to form a high-mu triode and some 600...750 V supply voltage. I have tested such SE-amplifiers some years ago.
For example with GU50 and 750 V +Ub, some 15 W is available.
The driver stage should have low source impedance, of course.

 

[multi]

Zero bias

Thanks Artosalo

The late Nobu Shishido designed many amps using Zero bias tubes SE 805, 811,833, low voltage high current.
All the record cutting amplifiers using 805’s, 811’s use low voltage high current the 811A’s run as low as 550 volts 70ma per tube; I built the GEC zero bias amp using KT88’s 10 mills current per tube, 750 volts Terrible sound, may be ok for PA; Tube lab built an amp based on the GEC KT88 using 1625 Zero bias. I rebuilt the GEC amp using the 811A 600 volts 70 mills current draw, excellent sound. The Gotham zero bias amp claims 40 watts class A
Tube Lab” wrote the following, about the GEC zero bias KT88 class B amp

That's the circuit that I recall from the PA amp. I think I found a version exactly like this, and another where the grid choke was replaced by a driver transformer with a CT secondary.

The grid resistors are 22 to100K in the GEC design. Those are intended to keep G1 from melting as they are driven positive. This however causes distortion, and lowering the value improves the distortion up to the point where the output tubes go into nuclear meltdown. I think I settled on 10K with the 1625 tubes.

I went back to the class B circuit with 1625 tubes since I had a few hundred and made a "working" amp, but I didn't like the sound. I finally got something I liked using a pair of 6LW6 sweep tubes in a conventional circuit.

All of these experiments were done with a guitar amp in mind, since that's what I was making back then.

I will stay with real Zero bias triodes don’t want to melt the grid of an EL509 or KT88, 811a's are cheaper any way
__________________
Tubelab, it's 5 year mission. To explore strange new tubes, to seek out new circuits and topologies, to boldly go where no tube has gone before......

 

[Wavebourn]

To what this assumption is based on ?
Usually zero-bias circuits have high supply voltage.
Try to connect all grids of 6P45S together to form a high-mu triode and some 600...750 V supply voltage. I have tested such SE-amplifiers some years ago.
For example with GU50 and 750 V +Ub, some 15 W is available.
The driver stage should have low source impedance, of course.

For gu-50 you need something like +8V bias.

 

[Perfectusaudio]

EL Tubes EL509 have you any comments/ experience on their reliablity ? Thanks

Christoph,

I specialise in electron tube applications (high power transmitting). My company Australian Electric Valve distributes electron tubes. This will explain my stock of 100+ tubes.

Audio is my hobby. So I design audio amplifiers as well.

I have been stocking Russian tubes since 1990. Tubes that I have in stock are marked in Russian. My comments refer to these. I have not purchased Svetlana branded ones yet. My comments apply to the original Russian production.

I used to have stocks of EI tubes-PL519. These are tonally very pleasing in Tim de Paravicini’s EAR amps. If you use these tubes you may need replacements every two years or so.

More dynamic than the EI tubes are the Tugsram PL519. They are also quite reliable and will last a few more years than EI tubes.

I hope that this answers most of your questions.

Mohan