One more 4P1L SE

[Jaime]

Hi Anatoliy
I Like an amp Takuma-san style, 4P1L to 4P1L.
Some day I'm going to try.

http://www.tchernovaudio.com/media/1252920192.jpg

[Wavebourn]

Originally Posted by Jaime

Hi Anatoliy
I Like an amp Takuma-san style, 4P1L to 4P1L.
Some day I'm going to try.

http://www.tchernovaudio.com/media/1252920192.jpg

Good luck!

Paralleled output tubes would give lower output resistance, for better speaker damping. But you will loose 20W of idle power dissipation instead of 10W needed for 2.5W of output power. With 2K2 transformer with paralleled tubes you can get 5W of output power.
You may use -9V bias for the driver, and -18V for the output stage, such a way plain stock batteries may be used.

[kevinkr]

I ordered some 4P1L from rutubes.com yesterday, it will be interesting to build an SE amp around them. Anatoliy your comments about the tube and picture you posted were my inspiration..

I guess I was not the only one as they are now showing no stock..

Incidentally rutubes is not the same as tubes.ru - sorry for the confusion..

[Wavebourn]

Originally Posted by kevinkr

Anatoliy your comments about the tube and picture you posted were my inspiration..

Which picture do you mean Kevin: with triode curves, or with breadboard on top of Magnavox boombox?

[kevinkr]

Originally Posted by Wavebourn

Which picture do you mean Kevin: with triode curves, or with breadboard on top of Magnavox boombox?

The Magnavox..

The triode curves were impressive, but the whole maggie thing looked like FUN..

The radio article was kind of cool too, I looked at the whole magazine although obviously I couldn't read the articles unfortunately.

[Wavebourn]

Oops... Answering the first time I have not seen you had your post edited.

Originally Posted by hihopes

Are those light blue caps I see underneath there? They are huge!

No, they are on top.

Do you put all of your trafos and chokes underneath in your pyramid design?

No, they are on top as well, in a transformer compartment that is usually shielded from hot toobs by mirrors. 4P1L generate only 20W of heat all together, instead of 4x40W GU-50 in Pyramids generate, so I used a peace of dark Lexan.

The front portion of the chassis is vacant: I will put there motorized remote control, and ladder-type input attenuator, with input selector using miniature Japanese relays.

The front panel will be ordered in Germany.

Currently I breadboard it, so it stays upside-down on top of the boombox. Transformers are not bolted, I tried them when took that picture.

[Wavebourn]

Originally Posted by kevinkr

The triode curves were impressive, but the whole maggie thing looked like FUN..

The Maggie looks nice, but it is too boomey; I build some sandwiches for this amp.

Memory Foam, Linoleum, MDF, concrete, and oak veneer layers, and still the same Maggie drivers, plus a pair of naked piezos additionally.

[kevinkr]

Originally Posted by Wavebourn

The Maggie looks nice, but it is too boomey; I build some sandwiches for this amp.

Memory Foam, Linoleum, MDF, concrete, and oak veneer layers, and still the same Maggie drivers, plus a pair of naked piezos additionally.

Wow! Looks good, bet those cabinets will be nice and rigid, and non-resonant. How are you joining and sealing the corners?

Also can you point me to a good data sheet for the 4P1L as Frank's doesn't seem to have it..
I do have a Russian only djvu format data sheet and I can figure out some of the parameters, but not others.

What I think I understand:

Plate dissipation: 7.5W
Screen dissipation: 1.5W
100K grid circuit resistance in fixed bias
Recommended max plate voltage 250V,
Transconductance ~6mA/V
10.5K plate resistance (pentode mode)
Filaments 650mA @ 2.1V or 325mA at 4.2V (I'll use 2.1V connection probably with CCS)

I believe an OPT suitable for the 45 ought to work pretty well for 4P1L in triode connection? (I'll have to work out the load line, haven't done that yet.)

Operating point tbd, but somewhere around 200Vp and 45mA total Ip as a swag. I'll drive it with a 5842/417A..

[Helmuth]

Tip

About 2W and good spl here a nice speaker plan idea.

To get 104dB and 30Hz with low power SE. It is a basreflex with tractrix horn of 133 liter volume.

Back Loaded Horns

[Wavebourn]

Thank you Helmuth;

your avatar looks very similar to my folded horn that I made for my Waybeyond bass guitar rig.

Originally Posted by kevinkr

Wow! Looks good, bet those cabinets will be nice and rigid, and non-resonant. How are you joining and sealing the corners?

I took MDF boxes from disco speakers and glued concrete layers on top of their carpet. Corners are sealed by tile glue. On top of concrete layers I glue oak veneer, corners will be covered by oak angle profile from Home Depot, glued by epoxy. I did that already before, it looks well:

http://pics.qip.ru/301nkjh.jpg

Also can you point me to a good data sheet for the 4P1L as Frank's doesn't seem to have it..
I do have a Russian only djvu format data sheet and I can figure out some of the parameters, but not others.

What I think I understand:

Plate dissipation: 7.5W
Screen dissipation: 1.5W
100K grid circuit resistance in fixed bias
Recommended max plate voltage 250V,
Transconductance ~6mA/V
10.5K plate resistance (pentode mode)
Filaments 650mA @ 2.1V or 325mA at 4.2V (I'll use 2.1V connection probably with CCS)

I have Russian djvu archive as well, probably the same. Also, I have curves from old Radio magazine, they are here in the topic.

I believe an OPT suitable for the 45 ought to work pretty well for 4P1L in triode connection? (I'll have to work out the load line, haven't done that yet.)

4K-5K OPTs work well.

Operating point tbd, but somewhere around 200Vp and 45mA total Ip as a swag. I'll drive it with a 5842/417A..

Mine is 220V on plate (some drop on OPT primary), 50 mA. Also, since I drive it via cathode follower, I am getting up to 2.5W of clean power.