Yup the bias points are spot on but instead of a mu of 3. What I’ve found is that this was in the filament supply. I think you have about the highest quality interstage transformer available. The current interstage in there is a Hirata Tango NC but I might be willing to try something else here since there are lots of high quality interstages offered these days and I could probably make quite a bit selling them off. Thanks again for the inspiration.

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I didn’t want to further confuse the situation, and wasn’t buying into the deceptive marketing scheme. Now it pentdoe better! You can post new topics in this forum You can reply to topics in this forum You cannot edit your posts in this forum You cannot delete your posts in this forum You can post attachments in this forum.

• View topic – GM with 4P1L pentode DRD driver

pentore So here is the first circuit draft: Here is schematic attached. There is an interesting H3 contribution to this output beam tetrode triode strapped.

Had 6sn7 as the driver when I first got the amp. Bearing in mind that the 4P1L has a healthy gain of around 10, what we have here is a 2 stage amp that can drive reasonably sensitive speakers with 2v in from a DAC.


Kinda depends on whether you want to go with 2 or 3 stages. I am not using a preamp, so source voltage is 2 vrms max from DAC How about the 10 family? Feel free to ask questions.

More power can be obtain by driving it harder above 1kV or swinging it into A2. I’m building something with a 4p1l filament bias driver – FlyCast Think of all the folks that love their ST 45s. With a quite large choke input and a good quality Pentodr transformer the sound got smoother.

I may try this configuration in my a SE amp, but am not urged by this at all.

As having neither the CAD nor a drawing board with me, I made a layout drawing with a steel square, rules and a caliper on the graph paper at an exact size.

Driver tube suggetions for B amp, posted on February 14, at Sat Dec 29, 7: The Spice model I developed for the see above seems to match reasonably well the hand plotted curves. I managed to get 0.


Driver tube suggetions for B amp – Caucasian Blackplate Here in Texas, bidness is a contact sport, in China it’s war. Pentoxe is serious stuff.

Driving big transmitting valves like,or GM require a large swing of volts for the driver which should do this linearly. I use it in the output stage in preference to b or I intend to use this tube for quite a while.

There are draw backs to this- The circuit has to be tweaked for each tube. I optimised the operating point to reduce distortion at maximum swing i.

I will have soon PCBs available for power supply designed for Pyramid amps. Sound is up there with the best DHTs like 2a3, 10Y, 46, b. I guess its max plate dissipation in triode connection should be around 8W.

Tag: 4P1L pentode

It is more than enough for PP amp. Photo and Image Files. The measured THD was: