4P1L PSE Amplifier for Sale!

Firstly, my apologies to all readers for not writing much over the last year. Things have gone a bit crazy between work and family commitments. Also, modular synthesiser work has taken a lot of interest lately to me. Finally, this blog was hacked twice and have been painful to get it back up again. Needless to say, I’m not an IT expert so I do the best I can!

Selling my beloved 4P1L

All good things come to an end. In this case, my loved 4P1L PSE Amplifier. I moved listening rooms with the growing family and space is now an issue. I no longer can store this beauty and I think it would be wise for someone else to enjoy it rather than collecting dust somewhere my attic (which is mostly full).

This amplifier gave me a lot of joy and sums up a “no-compromise” approach to DHT considering the design and component selection of the power supplies. It’s a very flexible beast as the power supplies (HT and LT) can be used in many different configurations – all the way up to a 300B and more.

4P1L PSE Output Stage
Full 4P1L PSE Amplifier
For the ones who remember my 814 amplifier, I reused the amazing power supplies which were feeding the 46 driver stage. The DHT filament raw supply is similar to these:
One PS per channel (2 boxes on the right in the picture above)
It’s a no-compromise design here. Best custom-made JMS transformers designed to fit this amp supplies with split-bobbins and copper screening.
The HT supply is my design for 300B and 4P1L PSE. It has a lot of capacity which can be reused and is very flexible with its design. It has a surge protection start up circuit and two current meter (one per channel).
I will dig out the circuit and share all documentation for whoever buys this  amplifier.
The amp use MM OPTs, 4mm plate machined by Schaefer.  Filament bias and circuit as per own my design.
All cables provided.
4 valves selected and matched to gm and Ia by me with eTracer
You will need a preamplifier / driver – which isn’t included. Anything with gain of x8 will work (preferably a DHT stage like 01a, 26,4P1L, 2P29L, etc.) – this isn’t included.

 

This is “the one and only” Bartola 4P1L amplifier. It has gone back and forth to ETF.18 and got into quarter finals on the competition (personally and a few others think it could have gone further but listening levels and setup were not the best).

Needless to say:

  • No reserves
  • Payment upfront
  • Only collection in London, UK.  No deliveries
  • Sold as-is. You need to know what you’re doing here 🙂

I haven’t got idea of what price to ask, need to think about it.

If you are interested, ping me.

Cheers,

Ale

Tuning the system for ETF

This year I entered the shootout competition and will bring my DHT system to the European Triode Festival in France. It’s comprised of the ER801a stage plus the 01a (if extra gain is needed) and the 4P1L PSE output stage

I will have to swap out the amorphous OPT for the Monolith Magnetic ones as the speaker load is 5R.

It’s going to be interesting!

ER801a Driver Stage

ER801a as Driver in my system

Received the ER801a today back from Thomas. They were working fine, it was a faulty UX-4 socket pin of my tracer which annoyingly made the grid to appear faulty and open at certain voltage level. I need to replace it.

Either way, they are now in my system and I can only say how much I was surprised with the sound of these. They take the detail and timbre of the VT-25 to a next level. Amazing result, happy to have these as part of my driver stage. The preamp is the 201a feeding the ER801a into the 4P1L PSE

Highly recommended valves, worth the price indeed.

DHT Audio Shootout @ London

Here’s the summary of the shootout day we had yesterday at my place with  Tony Rees and Andy Evans

Test Music

For testing the pre-amps Andy suggested the following 2 tracks:

  1.  Ravel Feria (Cleveland/Boulez)
  2. Janacek The Cunning Little Vixen Act 3 Scene 7 “A vixen’s running through the woods” Prague Theatre/Gregor


The Ravel is orchestrated for a large orchestra and percussion, and listening was particularly for the timbre of strings, brass and woodwind and the clarity of the percussion. The Janacek is for several different voices and chorus, and listening was for the tone and character of the voices and how well they were differentiated from each other. In both cases the overall clarity, life and crispness was considered.

Andy Evans

Although I wasn’t familiarised enough with these 2 tracks myself, I found them to be an excellent choice and a reflection of Andy’s musical experience and knowledge as musician. 

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NP Acoustic Transformers

This is a long overdue post which I never had the time to write about. I was hoping to get my measurement gear down to where my system is to take a final FR sweep analysis of my 4P1L PSE amplifier, but never got around to do it.  However, after the recent posts in DIY Audio, it was time I shared the measurements made and my listening impressions of the NP Acoustic Transformers.

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2P29L DHT Preamp

The Mule saga continues and it was time to modify the 3B7 preamp and to test the 2P29L valve. This was quite easy as they both have loctal sockets. I had to modify the Rod Coleman filament regulator to set the filament current down to 120mA. Then a bit of wiring work, and in less than an hour a new preamp was ready. Job done, this is why I built the Mule:

The circuit is quite close to my original design time ago. I modified the filament resistor to use an existing Russian NOS wirewound part I had in stock and suit this preamp quite well. Added grid and screen stoppers as well:

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VT-25 DHT Preamp Update

Well, it was just a question of time to make an update to the VT-25 DHT preamp. I wanted to try the BSH111BK as lower FET as shown below:

The result is visible on the frequency response. It does have an improved FR and the bandwidth gets up to 800kHz on same testing conditions. If you increase the HT to 280-300V you can increase the anode current to 30mA which should be good as well. 

I love the sound of this stage driving the 4P1L PSE output stage. It has a deep bass as well as clear treble. Dynamics on the system are fantastic. 

The bass on my system is fantastic now. Stronger than with previous setup. That is what you get when you marry low ra (4P1L pair) with a high-quality OPT.

I have a pair of pre-soldered BSH111BK boards (which are painful to solder) so I will give them away on a first come first serve basis

Weather is really nice today in London, so I’m going out right now…

C-299/CX-299 DHT Preamplifier

The start of a different DHT experience with the Mule

I built the “Mule” to provide enough flexibility to test other DHTs as pre-amplifier / line stage. Using the gyrator board, the flexibility is fantastic. Can share same HT and dial the right anode voltage. The LT supply can also be shared amongst many DHTs and Rod Coleman provided me with a set of different resistors to test the list of 9 or 10 DHTs I have in mind which haven’t listed carefully on this design. 

The C-299

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