• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

4P1L DHT Line Stage

Just for laughs I measured the distortion on a few #26 and 4P1L (with a IXCP10M90S load). Guess which had the lower distortion. :)



One strange thing about 4P1L is, it is very linear in triode mode, while in pentode mode screen grid draws relatively high current. Like, Germans designing it's prototype RL2,4P6 took some triode project adding extra grids.


Here is interesting web page: Google Translate

Here is a picture from there:

RES164E-5.jpg
 
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Hello

Excuse me, I give minimum comments. But I answer concrete questions.
This VA characteristic correspond tube made in USSR. Tube is very best!
You must correctly choose working conditions. In SE this tube return 1VA,
for extremely sensitive acoustics .

aeandm
 

Attachments

  • 4P1L - 5K.GIF
    4P1L - 5K.GIF
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Hello

Excuse me, I give minimum comments. But I answer concrete questions.
This VA characteristic correspond tube made in USSR. Tube is very best!
You must correctly choose working conditions. In SE this tube return 1VA,
for extremely sensitive acoustics .

aeandm

Hi,
Those curves are for pentode mode and I'm planning to run the valve in triode mode. Have plotted the triode curves before but don't have them here right now. On previous distortion measures some of us found that THD was minimised at 80V and 25mA. Haven't tried how it sounds at different op points yet....

I will etch the PCBs over the weekend if I get some time
 
Hi,
Those curves are for pentode mode and I'm planning to run the valve in triode mode. Have plotted the triode curves before but don't have them here right now. On previous distortion measures some of us found that THD was minimised at 80V and 25mA. Haven't tried how it sounds at different op points yet....

I will etch the PCBs over the weekend if I get some time

Hello, I don't translation many. This tube in triode mode is good, but out power smaller . I is opinion by VA characteristic. But and pentode mode is super (S1=S2).

aeandm
 

Attachments

  • 4P1l.GIF
    4P1l.GIF
    31.7 KB · Views: 1,134
He In SE this tube return 1VA,
for extremely sensitive acoustics .

I was getting, as I said before, 5W from 2 tubes in parallel, in triode mode. Load was 2K4, that means about 5K per tube. However, I was driving them with cathode follower, up to 12V positive peak. For preamp that is discussed in this topic such power is not needed, so the higher is dynamic load resistance, the less distortions you are getting from it. That's why we discuss gyrator load here.

Let me translate for you, if you have troubles reading English.
 
I was getting, as I said before, 5W from 2 tubes in parallel, in triode mode. Load was 2K4, that means about 5K per tube. However, I was driving them with cathode follower, up to 12V positive peak. For preamp that is discussed in this topic such power is not needed, so the higher is dynamic load resistance, the less distortions you are getting from it. That's why we discuss gyrator load here.

Let me translate for you, if you have troubles reading English.

Yes, translate for me, а сможете?

HI-FI and semi-conductor ??
 
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Без проблем. :)

Hi-fi + semiconductors = High-End. I mean real high end, not fetish. Semiconductors help to preserve each bit of smoothness of transfer functions of tubes.

HI-FI с полупроводниками не понимаю! Максимум ЦАП и фильтр(?),
После того как послушал настоящий HI-FI.

Fetish is 10K $
 
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