4P1L DHT Line Stage

[andyjevans]

BTW, I'm looking forward to one of Thomas Mayer's great tube deconstruction photo sequences of this tube.

In the past Thomas never wanted to use this tube - I don't know if he's changed since then!

 

[KevinC]

He posted on this thread a few pages back that he had bought a box of 100 4P1Ls, because you guys had convinced him of the sound worthiness of the tube!

 

[andyjevans]

Ah! That's good to hear.

The irony is that it was originally A German Wermacht tube - it's going home!

Buying 100 is a very wise move.

 

[Abszero]

Wow, this tube is starting to become famous. Soon we'll see a shortage worldwide...😉
The reality is that it sounds is amazing. I am building now the third amp using it.
Just that one needs a high sensitivity speaker..
Cheers,
Radu

 

[mogliaa]

Indeed. I'm going after my third incarnation of the "Siberian" preamp. I will run the 4P1L rather hot at 35mA with an LL1660 in 4.5:1 to provide low output impedance and drive to my system.
Just started filament supply - choke input

Siberian DHT Preamp Gen3: filament supply | Bartola Valves

cheers
Ale

 

[Bas Horneman]

Spent emission

I hope not!

In pic three and four I cleaned the glass with some toothpaste.

 

[Abszero]

Indeed. I'm going after my third incarnation of the "Siberian" preamp. I will run the 4P1L rather hot at 35mA with an LL1660 in 4.5:1 to provide low output impedance and drive to my system.
Just started filament supply - choke input

Siberian DHT Preamp Gen3: filament supply | Bartola Valves

cheers
Ale

Hi Ale,
In my last built PSE I tried it at 40 mA and was the best sound right there.
My OPs were 70 mA so I had to let them run at 35mA, 250V.
I am curious to find out how long they will last running them at 10W.
I have to figure out how to run a accelated test at 40 mA. I dont want to spend 6 months to figure this out.
Best,
Radu

 

[simon2a3]

Talk of questionable 4P1Ls reminded me that I bought some a while back but I've never used them. I've just had a quick look at them and wonder if some might be a bit dodgy. They were sold as NOS but at least half of them look a little "milky", perhaps like Bas', though it looks to be internal. In the attached photos the valve which looks good is on the left and the dodgy one on the right. Might they be less than perfect?

 

[Bas Horneman]

I'm convinced mine are new. They look almost identical too the ones posted on Siberian shop's versions. Why would they post ones with visibly spent emmision. The base and pins also don't look tarnished whatsoever...as is the case in one of Kevin's 4p1l's.

 

[andyjevans]

Sockets FOR Tube 4P1L 4P1? RL2 4P6 Wermacht X 2pcs | eBay

This could offer opportunities to add sound-dampening material to the cylinder of the socket.

 

[rickmcinnis]

Did not see anything there

Sockets FOR Tube 4P1L 4P1? RL2 4P6 Wermacht X 2pcs | eBay

This could offer opportunities to add sound-dampening material to the cylinder of the socket.

Are these bottom mount phenolic mounts?

I found some made by EDISWAN that seem like they could be good.

Reminds of when Harry Pearson's favorite 12AX7 was made by EDISWAN.

I like the idea of phenolic better than ceramic.

Ordered some 4P1Ls today along with the COLEMAN filament regulators.

 

[andyjevans]

If the sockets doesn't come up here's the ebay.pl reference:

 

[rickmcinnis]

You must be an EBAY expert

and I am not.

I have no idea how to access that!

But I will keep trying.

Thanks,

 

[rickmcinnis]

I found them

but am not sure they are worth twenty dollars a piece.

Think I will start out with the phenolics.

Think they might have some advantages isolating the tube.

 

[andyjevans]

No I'm not an ebay expert - far from it. Just the link doesn't load here properly.

Just go on "www.ebay.pl" and enter the item description as it appears in the image I posted. Or just search on "4P1L" and it comes up

 

[mogliaa]

A new improved loctal socket board to reduce microphonic noise in the preamp. Using silicone rubber layer between PCBs and silentblock. Looking forward to implement it soon:

 

[merlin el mago]

Looks promising Ale.

 

[Magz]

A new improved loctal socket board to reduce microphonic noise in the preamp. Using silicone rubber layer between PCBs and silentblock. Looking forward to implement it soon:

Looks a bit like what I used on my 26 preamp. Works great...

 

[mogliaa]

Yes indeed. 26 are very quiet though, specially when run at around 850-950mA starved filaments. 4p1l on the other hand is a real singer

 

[Bas Horneman]

Sorry to intrude on this 4p1l thread. But I am busy building an 801A pre. Using Rod Coleman's boards. And wish to implement filament bias. What voltage should I be aiming for...and what value resistor would suit an 801A preamp?