For more than 10 years I’ve been experimenting, designing and enjoying DHT pre-amps. Without over-dwelling on this subject, to me DHT preamps bring the unique sound transparency and detail we all seek for. They can make night or day difference in any system. And is not about gain, hence I’m focusing on sharing this blog entry.
Tag: 4P1L
Monolith Magnetics S9
Now fitted on the 4P1L PSE stage:
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!
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:
- Ravel Feria (Cleveland/Boulez)
- Janacek The Cunning Little Vixen Act 3 Scene 7 “A vixen’s running through the woods” Prague Theatre/Gregor
Andy Evans
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.
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.
Continue reading “DHT Audio Shootout @ London”6Э6П-ДР (6e6p-dr) preamp / driver
With a quick mod on one of my active preamps, I managed to implement very quickly the 6Э6П-ДР (6e6p-dr) driver in my system. Here is how the circuit looks like:
4P1L PSE Class A2 Amplifier
It was mentioned here, so I decided to chip in with my previous experience from back in 2013. Here is what I tried myself:
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.
eTracer Build and Review
Tracing valves: an obsession
Since my early days of valves and DIY audio, I developed an obsession around testing and tracing valves. This led me to design and build my analogue curve tracer which I used for many years successfully until I build my uTracer, which was a great innovation in curve tracing. I do have many valve testers (some which I made myself) so why building another one?
Well, Chris Chang from Essues Technologies developed a fantastic new digital curve tracer for valves, the eTracer. There are a few things which will grab anyone’s attention on this curve tracer. Firstly, the power supplies can accommodate a large range of valves which the uTracer can’t. HT can go as high as 750V @ 300mA and the grid supply down to -170V! This is exactly what you need to test your transmitting valves or even a 300B. Secondly, the tracing speed is surprisingly fast. This is a nice feature, specially when you want to trace pentodes at various screen voltages to develop a Spice model for example.
Build process
4P1L / 4П1Л Siberian Gen4 in Screen mode (part 2)
Last time I wrote about the 4P1L in screen mode. It was great to see some DIYAudio member (Blitz) to post about his work on the 4P1L with screen as anode. I call it screen mode but probably is incorrect.
His post about G3 structure remind me to post this, I have tested it but never blogged about it. Yes having G3 as part of the anode structure will increase conductance and will form a nice “mesh” anode. Here it is how I implemented:
The pin 4 (G3) is now connected to 3 (G2) to form the anode. I reduced the anode voltage down to 110V to get 10mA. It could be increased, sure within the Pd limits.
The response is very good:
Here you have the distortion at 1kHz:
How does it sound?
Well, I wrote about it before. The 4P1L is one of my favourite valves. In this mode it sounds great, with a particular clear detail in the treble. I like this valve and will play it for some time to get further impressions.
4P1L / 4П1Л Siberian Gen4 in Screen mode
Some time ago, I did some initial experiments with the 4P1L (4П1Л) with the screen performing as anode instead. Some DIYers claim the improved sound of the mesh type anodes. Kees Brakenhoff kindly sent me some PL519 to test in screen mode. He has done multiple builds with this mode of operation with great results. Unfortunately I’ve not had the chance yet to build such an amp.
What I could do instead though, was to mod very quickly my 4П1Л preamp to screen mode. It was a very easy and fast modification. I kept the same heating wiring and just adjusted the screen (anode) current down to 10mA: Continue reading “4P1L / 4П1Л Siberian Gen4 in Screen mode”