All about electronic valves and hi-fi
I upgraded the DHT filament regulators to version 4. Rod has released a new kit which introduces temperature compensation for high current filaments. This is a key feature in my 4-65a design and I shall explain why:
If you are looking to test your precious valves and you don’t have the equipment, I can now offer this service for you which includes:
Some examples of a lovely EL34 Mullard tested on request:
My fees are very competitive and this service is worth if you are looking to sell your valves or match them.
Terms and conditions:
My apologies but due to pandemic and lack of free time, I’m not offering this service anymore.
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 curves and also measure grid current. Measuring grid current is key in A2 mode so a better grid current model can be derived to better simulate the non-linear and low impedance behavior of the grid in positive bias.
My incarnation of the uTracer is not neat. I’m using my existing analogue curve tracer. As shown in the pictures below, my current tracer have a plethora of sockets and just adding right jumper cables for anode, cathode, screen and grid connectors will still give me the flexibility I had with my analogue tracer
The process of generating the A2 curves (and SPICE model) starts by plotting the normal curves. The uTracer is great for this. Then you have to overlay the A2 curves in Excel (or whatever tool you prefer) to combine both set of curves.
Just finished the digital tracer project uTracer V3. Did some further tests this morning, now with my favourite DHT: 4P1L.
Started with a well known bias point for triode-strapped operation:
After a stupid mistake which blew the PIC, I finished today my version of the uTracer. A quick trace of an CX-226 RCA Radiotron can be seen below. This is an incredible digital tester. I need to test it properly and do some comparisons against my analogue tracer, but as everyone would expect,the digital tracer has superior capabilities in terms of data manipulation and representation.
Highly recommended. Ronald provides a sterling service and specially when I damaged the PIC and send me a replacement at no cost!
More to come shortly…
A great record shop in Edinburgh. Highly recommended. Came out with some Thelonious Monk LPs. Even brewdog house is 5 min away. Enjoyed a 14% ale so can’t get better than this!
Raised arm board flushed to the plinth so VTA and arm position was optimised. Great sound indeed 🙂
Listening to Mingus Band. It sounds really nice on the Lenco turntable!
As discussed previously, I replaced the gyrator’s polypropylene caps with better ones I had at hand which are 1uF 450Vdc Mundorf Mcap EVO Silver Gold Oil Cap (EVOSGO-080). I should look at lower value. A 220nF or even 100nF one should provide a 1Hz -3dB point with the 4M7 resistor. Anyway, the sound is a tad better in the bass I would say. Nice upgrade but should listen to it more to find what other changes has this capacitor made to the amp:
