All about electronic valves and hi-fi
Feedback was that more pictures were preferred. So here they are. I have little time, but slowly I will make progress I hope. The main chopping board is what is left now. Layout is tricky as have not enough space given the size of the OPTs 😀
I made a set of useful PCBs. They are intended to mount large (big really big) film capacitors: WIMA DC Link ones!
I use the cost-effective 45μF/600V (MF Part No. DCP4I054507ID2KYSD) in many of my boards as the last capacitor in the filtering network. This is a 2 pin device, however when you go larger like the 80μF/900V (MF Part No. DCP4N058009JD4KYSD), this one has 4 pins and bigger size. The PCB for the later can also accommodate the smaller DC Link of 45μF/600V. The boards have turret or 2mm banana plug connections and an INS-1 Nixie indicator with its associated resistor. Finally a bleeder 3-5W resistor can be added.
The smaller board has the size of the Source Follower PCB. It can be mounted below it or can be used independently. Can fit a variety of PIO/Film capacitors for decoupling or for AC interstage coupling.
Speaking about the Source Follower PCB, I made also a new batch of PCBs as run out of the original ones. I made a minor modification and improvement by adding an LED indicator before the top MOSFET drain. This works in the same way as the gyrator Rev08 PCB. Can be used for normal operation or for A2 current source indicator. Also added an extra PIO/Film 100nF decoupling cap to be mounted under the PCB to decouple the high impedance node to the power supply:
It didn’t take long (or at least as long as I thought it would) to finish the driver board. It has a D3a hybrid mu-follower with SiC cathode bias arrangement:
The board is mounted on top of this previous board.
Back at the beginning of the year I purchased a pair of Emission Labs 300B for my new amplifier version (still working on it). I own several 300Bs but was keen to try these out given their reputation.
Jac from JacMusic sent me a matched pair which I traced them with the eTracer:
As part of my 300B SE project design, I looked into various fixed bias arrangements and regulators. Rod Coleman has developed another fantastic circuit after the success of his DHT filament regulator which is now the preferred filament supply kit within the DIY audio community. After many years of refining the DC filament regulator, Rod came up with a clever design for fixed bias using the same concept: a gyrator and a temperature-compensated CCS. Instead of feeding a current through the DHT filaments, in this case the current is used to generate a clean bias voltage across a “bias resistor”. The bias resistor is bypassed by a capacitor as the high impedance loop formed by the regulator and the bias resistor is sensitive to pick up HF noise which could be amplified by our system.
The kit is of the same quality you would expect from Rod’s boards and very easy to build. It takes less than an hour to build the boards:
