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4P1L DHT amp

77.126.130.143
Posted on July 26, 2014 at 21:26:18
airairy
Audiophile

Posts: 43
Joined: July 19, 2008
 Hi all
I read a little about DHT base amplifiers
Would you consider building around 4P1L tube instead of 2A3, 45, 50, and 52?
Anyone had tried it?
What about using 4P1L as a driver tube into 4P1L power?
Thanks

 

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Andy Evans is your man (nt), posted on July 26, 2014 at 23:50:31
danlaudionut
Audiophile

Posts: 5480
Location: Schenectady
Joined: June 6, 2002
 DanL



 

And for a 4P1L Preamp... , posted on July 27, 2014 at 10:11:51
Gerry E.
Audiophile

Posts: 2192
Location: Saratoga Springs, NY
Joined: February 19, 2000



Bottlehead are your men! Check out their new Smash preamp using the link below.

Gerry

 

And here I am...., posted on July 27, 2014 at 10:51:10
andy evans
Audiophile

Posts: 4382
Joined: October 20, 2000



I've been using a 4P1L into 4P1L PSE amp for 2 years and no desire to build anything else. I'm that satisfied. Bought 150 tubes so I'm future proof. It all has to be in filament bias - you're throwing away quality if you don't use filament bias right through. Lundahl iron - LL1660/25mA and LL1620/80mA. No coupling caps or cathode bias caps. Simple 2 stage design, but complex power supplies!

I've built 2a3, 6B4G and 300B amps and this is better than all of them, mainly because I only need 2 DHT stages since mu of 4P1L is over 10. And with filament bias you lose the cathode bypass caps which I hate. Apart from the gain favouring the 4P1L they're all good tubes, but you can't use the 2a3/6B4G/300B in filament bias. Or rather you'd be nuts to try.

 

And for some more 4P1L Preamps... , posted on July 27, 2014 at 16:04:09
andy evans
Audiophile

Posts: 4382
Joined: October 20, 2000
 Very nice looking kit indeed. I hope it makes many friends.

For myself, I'd prefer Rod Coleman filament regs, filament bias and a Lundahl OPT like LL1660/25. There are several variations, though, like Ale's active load one on his Bartola site. Also plenty of discussion on DIY Audio on two threads:

- "One more 4P1L SE"
- "4P1L DHT Line Stage"

You'll get all the building instructions over on DIY Audio. Very active threads.

 

RE: And here I am...., posted on July 28, 2014 at 19:39:05
Tropical Triode
Audiophile

Posts: 9
Joined: October 21, 2004
 Andy, what does the PS circuit look like? I'm interested in building one of these.....

 

RE: And here I am...., posted on August 30, 2014 at 11:15:56
Fitero
Audiophile

Posts: 119
Location: Portland, Oregon
Joined: August 23, 2002
 Hello Andy,
I have been searching for a schematic for a new project, and I stumbled upon your post here.
Would you be willing to share any pertinent information with me regarding your amplifier build?

Please send me a message or email if the spirit moves you.

Thank you and regards,
Pierre

 

RE: 4P1L DHT amp, posted on September 1, 2014 at 12:59:42
Al Noakes
 It's a lovely sounding valve but I find it a tricky candidate as an output stage . You'll get around 1.8 watts out of one in SE so sensitive speakers required . I find this valve to be microphonic , the microphonics can be tamed but there are limits with regards to suitable speaker sensitivity . I built a DC coupled 4P1L-4P1L amp and found it too noisy and with four separate filament supplies , very bulky . I would suggest an upper limit of 100dB/1w , 4P1L are too noisy for compression drivers . If you only need a fraction of a watt , I'd suggest building such an amp to see what these things can do . The filament supply is the difficult part but the Rod Coleman filament reg kits are excellent . I can't remember the exact component values I used but with a 6SN7 driver with two stacked red LEDs in the cathode with CCS top loads running 6mA and the 4P1L running 240mA/35mA with 5k OPTX , you should get a very good sounding amp

Al

 

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