Long time ago I developed a CCS board which provides full flexibility in terms of FETs/MOSFETs used. It was a 2-terminal CCS, a very well known circuit.
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Tag: IXTP08N100D
3 versions of the gyrator board
From left to right: 1) Standard Rev08 PCB with full flexibility of FET and TH components. 2) Rev 1.0s board with SMD except Rmu, protection drain resistor and LED as well as space for any nice big PIO capacitor. 3) the smallest version of all, all SMD except Rmu, film cap and standard TO-220 top FET and multiturn trimmer.
Very happy with the results in the board development. It does take more time and precision (you will need a microscope) to work with the MELF resistors and the SMD components in general. However, it’s worth the trouble if you’re looking to reduce the footprint.
Tracing (MOS)FETs to be used in the gyrator PCB
I took out the Locky Tracer and remove some dust, it was about time. One of the most popular lower FETs I use in the gyrator PCB is the now obsolete BF862. Here is the tracing output:
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UV-201a DHT Preamp Revisited
I previously implemented a preamp with the UV-201a. These are very old globe valves, somehow fragile and hard to get in good shape. Despite all this, it’s a superb valve. I have managed to acquire a decent set of them to pair the best valves to use in my preamp.
Recently I developed a prototype PCB for the source follower circuit. The source follower is ideal to place at the output of this preamp due to its low driving current. My 4P1L PSE amplifier will be pleased with more current to pump the Miller capacitance effectively.
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:
Slew Rate (Part IV) and the Tale of the three Source Followers
Some of you may be a bit fed up already with these slew rate posts, however I find this fascinating as is taking me through different routes of experimentation.
On my last tests, I abused the DN2540 to an extent which meant the dead of it. So I ended up adding the appropriate back to back protection zeners on the gate:
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