All about electronic valves and hi-fi
Here are some further tests using automated measurements. Firstly I tried same configuration running the 4P1L at closely 38mA and 160V screen voltage. Second test, I dialled up the screen voltage to 171V and tweaked feedback to get current up to 40mA Interesting to see that the performance is more triode-like and has a higher … Continue reading “Robustiano: 4P1L SE Schade Feedback tests Part I and II”
Quick breadboard this evening after watching the world cup match. Increased screen voltage to 160V and dialed the feedback resistor to achieve minimum distortion without jumping back to 100% pentode mode. Nice to see 2W at less than 0.5% with a nice harmonic profile:
Introduction Building a new version of the venerable 4P1L “Siberian” was very encouraging. This belated project finally came to life after some recent work on a new set of power supplies. So why 4P1L again? I always found the 4P1L sound to be unique. Great detail, overall tone and fantastic treble. What it makes it well … Continue reading “4P1L DHT Preamp Siberian (Gen3) finished!”
Recently I finished the filament supply for the latest incarnation of my 4P1L pre-amplifier. Here is the next instalment of this project. The HT power supply was refined after builiding more than 7 stacked HT supplies for the 814 SE Amplifier. The supply design is very simple. Perhaps the selection of components and the refinement of some … Continue reading “4P1L Siberian DHT Preamp (Gen3)”
Here is the 4P1L Siberian DHT preamp (Gen3) socket board. I’m using a pair of custom made teflon sockets mounted on a PCB sandwich with a 4mm silicon rubber sheet. The lower board is mounted over 4 silent blocks: This should be a great improvement to reduce any further microphonic noise in the preamp!
Last week I did some preliminar tests with the LL2746 in 1:2 step-up mode. Despite having measured good results with it, it will be a challenge to drive grid current given that the output impedance of the 4P1L will be multiplied by 4 so about 5KΩ. Before looking at the LL1671/20mA which is suitable for … Continue reading “4P1L driver – LL7903+LL1671 tests”
After a recent discussion in the DYI Audio forum about the 4P1L drivers, I decided to do some quick tests on an idea I had around to use a step up transformer (1:4) – 4P1L and step up interstage transformer (1:2) to drive a 300B or similar using the 4P1L in filament bias. First suspicion … Continue reading “4P1L – LL2746 driver test”
Like LEGO bricks, I thought about building this module for a pair of loctal sockets for 4P1L. It can be used in PSE or PPP…
Improving the DHT model in A2 After playing for some time with the uTracer, I found that the tracer wasn’t measuring accurately A2 curves. Ronald clearly advised me (as explained on his site) that uTracer wasn’t designed for this purpose although there was a great trick to use the screen driver to generate the A2 … Continue reading “4P1L model improved”