One more 4P1L SE

[mogliaa]

I did some tests using the 4P1L as a driver in filament bias. Linearity is outstanding in triode mode as measured before, but was keen to see the performance in pentode mode. I tweaked my breadboard to run in pentode albeit it wasn't optimal but still got THD=0.58% @ 200Vpp which is really good for a driver!

4P1L Driver Tests | Bartola Valves

Improved Pentode driver by adding a parallel resistor to the gyrator output and managed to halve distortion: THD=0.27% @ 200Vpp, 4P1L is a great driver candidate indeed!
http://www.bartola.co.uk/valves/2013/01/12/4p1l-pentode-driver-test-2/

Ale

 

[regal]

Using a 4p1l in the first stage but a 307A (triode connected) in the second stage gives you this. Not much of a difference. Of course, this is just simulation, not reality.

That looks really nice, unfortunatey the supply of the 307A is rather hit or miss I have often wondered if there was a russian equivilant. Any chance you could point us to the 307A model you are using ?

Improved Pentode driver by adding a parallel resistor to the gyrator output and managed to halve distortion: THD=0.27% @ 200Vpp, 4P1L is a great driver candidate indeed!
4P1L Pentode Driver (Test 2) | Bartola Valves

Ale

Is there an advantage of a DHT pentode, vs a 6c4pi ? I guess I always considered the little space tube as being a better driver.

 

[mogliaa]

Some will argue the sound of a pentode driver is better. I haven't tested the 4P1L pentode driver in filament bias, but it looks promising on the bench at least!
Ale

 

[regal]

Some will argue the sound of a pentode driver is better. I haven't tested the 4P1L pentode driver in filament bias, but it looks promising on the bench at least!
Ale

For my 4p1l-4p1l idea it would be interesting to have a switch to throw the driver into pentode mode for low efficieny headphones that need more gain, or is the bias too different ?

 

[mogliaa]

When Listened to 4P1L-4P1L made me think I wanted a different sound, too clean perhaps 🙂
Either way, you could bias driver on Vgk=-5V and operate the 4P1L in both pentode and tetrode with filament bias.

 

[regal]

When Listened to 4P1L-4P1L made me think I wanted a different sound, too clean perhaps 🙂
Either way, you could bias driver on Vgk=-5V and operate the 4P1L in both pentode and tetrode with filament bias.

Just check your website wow a lot of interesting new stuff.

I guess the next logical question would be does the 4P1L Pentode driver stage have the kuhnas to drive your 4-65a directly, making it a 2 stage amp instead of three stage could be beneficial ?

 

[mogliaa]

Thanks, I've been working a lot lately on my 4-65a Amp.
I thought about 4P1L as a driver, hence all the testing lately. eBoz used D3a in triode and others used pentodes. However, I already built the filament bias supply for the 46 and the 46 driver in filament bias (yes, hefty thing I know) is very promising....
Ale

 

[cotdt]

Some people believe that others prefer tube amps because of added distortions, despite experiments don't prove that. You can't model result of absense of nasty distortions adding something that is irrelevent. Like water from a glass cleaned by gasoline may look better than from glass cleaned by water that contained some clay, but it will not taste better. Adding to the glass of water cleaned by gasoline a bit of clay you can't improve it's taste.

best analogy ever

 

[cotdt]

4P1L is too clean, too much like SS. I like 26 better. (in my preamp)

 

[Wavebourn]

4P1L is too clean, too much like SS. I like 26 better. (in my preamp)

Hmmm... If SS was as clean as best tubes, why would I need tubes at all? 😀

 

[Pano]

Ale, you're killing me! 😀 I wanted to be in there first with the 4P1L pentode driving the 4P1L in triode mode. Alas, it took a month for my tubes to arrive, then I was out of town for a week. Grrr.....

So I'll be following in your footsteps on this path.

 

[matejsirk]

Improved Pentode driver by adding a parallel resistor to the gyrator output and managed to halve distortion: THD=0.27% @ 200Vpp, 4P1L is a great driver candidate indeed!
4P1L Pentode Driver (Test 2) | Bartola Valves

Ale

Hi,

what is the gain of Pentode driver 4P1L? Operation point is 256V/-3.6V?

 

[mogliaa]

close to 150...

@ Pano, I just did some test, you can take it from here...
Cheers,
Ale

 

[Pano]

I will, Ale, I will. This week.
Thanks for the gain info in pentode mode. Far more than I'll ever need to drive the output stage.

 

[mogliaa]

Good, keep us posted!
Gain is determined by the RL in parallel with the 4P1L when loaded with the gyrator (or CCS). It may be a bit high, you can reduce it by reducing the RL, but distortion will increase...
Ale

 

[RajkoM]

Hi Anatolij and others.
Trying to find a cheaper, but good, pentode driver as a replacement for my existing C3g, Im here.

Based on Anatloij first post in this thread I simulated this 4P1L pentode driver. Works good to me.

I have no experience with 4P1L or another DH pentode. My plan is connect pin 1 and 7 to 4.2 Vdc then LED string from pin 8 to ground.
Correct?

Thanks to Ale for very good 4P1L pentode spice model.

Rajko

 

[Wavebourn]

Hi Raiko;

looks doable, except I personally would reconfigure your CCS into gyrator, for better regime stability of anode voltage.

 

[RajkoM]

Hi Raiko;

looks doable, except I personally would reconfigure your CCS into gyrator, for better regime stability of anode voltage.

Tnx Anatolij

 

[Pano]

Max Voltage?

I'm having some trouble with my PSU. Trouble is the B+ voltage is too high (I think). Even with 80mA of draw it's up over 300V. Unloaded about 320V.
How high a voltage can the 4P1L take? I was thinking not going above 250V on the B+.

Still working with it, trying to insert some R into the line to drop the voltage. The series resistor would dissipate a lot of power. Maybe a 15W light bulb?

 

[palmas]

You should pay atention to the anode voltage, 250V should be OK.
The B+ you can have much more (400V, 500V...) depends on the anode resistor or CCS or whatever you're using.