One more 4P1L SE

[tcqanh]

My plan of 4P1L is in progress.

My 3.5K- 8 0hms OPT has separate winding for G2 (say G2 winding). There are some options:
1. G2,3 connect to anode.
2. G2,3 to G2 winding.
3. G2 to G2 winding, G3 to anode.
4. G2 to G2 winding, G3 to cathode.

Which is better ?

 

[tcqanh]

3. G2 to G2 winding, G3 to anode.

I did choose plan 3 for my amp: 5Y3 rectified tube, Mullard E180CC driver runs 95V 4.5mA, Svetlana 4P1L (date 6x) runs 235Vak 37.5mA with auto bias. Sound is wonderful. It beats many penthode tube SE amps that I've built before, like 30P1s, El84, 6V6, 6L6GB... even El34, 6550.

I feel new amp has sound quite likes Hytron VT52 amp's sound. One Vote is for them.

PS: I don't know why unable to post pictures and insert emotion icons. Maybe my computer has problem.

 

[stajo]

Would a 4P1L with an LL1660/18 4:4,5 (alt S) drive the grid of an 6B4G properly?

 

[andyjevans]

I've used exactly that to drive a 300b. I didn't measure anything, however. I swapped fairly quickly to PSE 4P1L because I thought it sounded better.

I've used push-pull 4P1L with interstages to drive PP 2a3 and 6B4G and that worked very nicely.

 

[stajo]

Thanks Andy. I'm thinking of trying. What is the approximate amplification factor of a triode connected 4P1L with 150 V?

 

[regal]

I've used exactly that to drive a 300b. I didn't measure anything, however. I swapped fairly quickly to PSE 4P1L because I thought it sounded better.

I've used push-pull 4P1L with interstages to drive PP 2a3 and 6B4G and that worked very nicely.

There is a caveat, you need a preamp with at least 2x gain to get the most of a 2A3/300B driven by a 4P1L. Or a third stage. For the same reason the 4p1L driving the PSE 4p1ls's keeps things 2 stage and could be why it sounds best., but its not going to give 300B power levels.

Personally think a IDHT with gain of 25-30+ giving a 2 stage amplification is more elegant for 2a3/300b tube types.

The "all 4P1L" amp to beat is the P-P as described above, they were designed for this application, but I'm just not into p-p.

Just letting you know that a triode 6e5triode-300B is going to be an much easier possible more elegant build.

If you really are a DHT purist a VT51 is a tube to investigate.

 

[palmas]

Would a 4P1L with an LL1660/18 4:4,5 (alt S) drive the grid of an 6B4G properly?

Yes, it would be quite perfect. I have that same driving a 300B (that drives a GM70). Go for it

 

[stajo]

Has anyone set up a 4p1l in an avoIV and know what parameters to use?

 

[rotaspec]

Has anyone set up a 4p1l in an avoIV and know what parameters to use?

Try this (as I did on my Mk.III):
Thumbwheels: 265144300

Filament: 4 volts
Anode: 150 volts
Screen: 150 volts
Neg Grid bias: 8v

I saw 5.5mA/v and 21mA on a sample just now.

 

[IslandPink]

There is a caveat, you need a preamp with at least 2x gain to get the most of a 2A3/300B driven by a 4P1L. Or a third stage. For the same reason the 4p1L driving the PSE 4p1ls's keeps things 2 stage and could be why it sounds best., but its not going to give 300B power levels.
Personally think a IDHT with gain of 25-30+ giving a 2 stage amplification is more elegant for 2a3/300b tube types.
Just letting you know that a triode 6e5triode-300B is going to be an much easier possible more elegant build.
If you really are a DHT purist a VT51 is a tube to investigate.

There is the other option of using 4P1L in pentode as a driver , which I have mentioned before, and found to be extremely successful both with 6B4G and 300B .
For an example of the set-up, see circuit attached - just finished building this one for our meeting in Yorkshire last week . This happens to be a two-channel amp to drive two horn drivers , with internal crossovers, but the set-up and principle of the 4P1L driver is there - just build the upper 6B4G channel with a more suitable coupling cap and grid-leak .
This driver retains the 'direct-heated' sound, but achieves more gain without going to three stages or the inevitable low-end time constant of an SE interstage .
Gain on this driver as shown is about 22 , rising to around 32 if you use a cathode by-pass cap .

audio-talk :: View topic - A 2 or 3-channel SE 'Horn-amp'

 

[IslandPink]

Circuit

Circuit ... try again ...

 

[stajo]

Nice IP. On a 1660 with primarys in series I might even try UL.

 

[Pano]

I'm still using the 4P1L triode strapped to run my horns. Battery bias, single 6SN7 input with LED bias. Nothing changed at all. I'm happy.
https://production.diyaudio.com/community/index.php?posts/3400631/

 

[tcqanh]

Here is my favorite amp, very simple, easy to build, quite cheap, output ~ 3W, deadly quiet with noise 0.6-0.8mV. Sound is so sweet and It beats my 300B on midrange

 

[Skip Pack]

Could you clarify the impedences on the primary of the output transformer? Is it
3.5k on each primary or 1.75k adding up to 3.5k? I haven't seen separate coils
used to achieve what looks to be an ultralinear setup. Very interesting,

Thanks for posting this,

Skip

 

[tcqanh]

These opt are diy product from a friend. Plate and g2 winding are the same turns and have same 3.5K impedance. I guess it operates like something between triode and ultralinear, so I can get more power than one in triode.

 

[Pano]

Interesting. It looks like one winding of the primary is simply acting as a feedback loop.

 

[stajo]

Interesting. It looks like one winding of the primary is simply acting as a feedback loop.

Feedback? Its a normal 50 percent between pentode and triode to me. Ultra linear concept. Evolve plz

Edit. I see now, its on G2. Sorry. Yes please?

 

[Pano]

Yes, and that's a form of feedback, right? Ultra-linear is usually at 43% tap, that's all.

 

[yagoolar]

Feedback? Its a normal 50 percent between pentode and triode to me. Ultra linear concept. Evolve plz

Edit. I see now, its on G2. Sorry. Yes please?

If two windings were in series and its center point were connected to G2 it could be UL, but they are in parallel.