PL84 triode

TV-Roehre-PL84-Telefunken-m--Raute-ID1497-1497

The PL84 pentode is very well known out there. I’m not going to write about it as there is plenty of information about the use of this pentode in push-pull amps, etc as well as comparisons with the EL84, EL86 and Russian equivalents such as 6P14P, 6P15P and 6P43P. I recommend you to check Klau’s work here.

I have a nice set of Telefunken PL84 which I may be using in triode mode as part of a Spud project I’ve been working on the design for some time. I’m interested in triode-strapped curves but also will be looking at tracing the Schade-feedback curves when I get the time to do so.

I quickly found a sample valve that was close to the pentode specs at 90%. Good enough for my purpose so I proceed to trace the triode curves quickly in uTracer.

Continue reading “PL84 triode”

LME49830 Amp starts!

Oh yes, a lot of sand! My good friend Tom recommended me to build this amp instead of an F5. Objective is to get baby-proof in 6 months. All HT valves will be removed unfortunately 🙁

300B will be built for a separate room….

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Testing the MOSFET rectifier board!
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LME boards just need the MOSFETs and are ready to go!

 

4P1L Siberian Gen1 upgrade

Some of the DIYAudio fans have built this version of the 4P1L with great success. There are several upgrades that can be easily implemented to improve this. I haven’t tried this myself, but my recent experience with the Gen3 and the 01 preamp gen2, I think are worth trying:

  1. Replace the gyrator FET for a cascoded pair (M2 and M4 below) to improve PSR
  2. Replace voltage reference by a cascoded LND150 for better HF and PSR response
  3. Optimise the LF pole of the gyrator load by increasing R4 to 4.7 MΩ and reduce C1 to 220nF
  4. Bias 4P1L to about 30mA. This will reduce distortion

Hope this is useful

Ale

4P1L Siberian Gen1b v01 4P1L Siberian Gen1b v01 THD