No problem - by todays standards I'm now fully trained. £120/hour ok? No guarantee of it working but it'll look great after I dust and polish it. If it doesn't work after, it'll be your fault sir, it was perfect when it left our fully equipped workshop.
There go you, Rich, not to be out done. British full wave ructumfrier in all it's glory, some nutter on the Bay of E might make my day for a matched pair.
My, that is a big one . Got some of similar size/profile, but they’re RF jobs (with anode connection on the top, perfect for giving yourself an almighty belt).
A-ha! Eureka moment. "starved plate tube preamp". Not only is it a "thing" it's been going on for decades using tubes from ex-military low voltage equipment that had a wide operating window. Usually used to add colour and often used for guitar distortion pedals to imitate old style tube amps, but also used more gently for mic pre amps and the like in conjunction with op amps if you actually want amplification.
Indeed. No amplification from mine. In fact when I look at the original spec for my Little bear, someone has changed the tube if I'm not mistaken. You can get mic pre amps designed like this and mic preamp users want colour but certainly don't want distortion so I'm going to go with that and try not to think too much more about it. I bumped into the starved plate term completely by accident - I'd already put this in the "baffled" section of my brain (there isn't much room left in there!).
Lots of valves are actually similar, some physically, some electrically and physically, "tube rolling", to get the sound you want, is also a "thing".
I can remember running an ECC83 as an electrometer, with the heater run of 12 volts and the anode run off 12 volts. It provides a heck of a lot of power gain, going from effectively volts at infinite impedance, to a few more volts at 10k ohms impedance .. With a transformer on the anode, there is nothing stopping a valve working like that. The Russian radio equipment has a major advantage over Western stuff. One EMP high altitude nuclear weapon, the valves absorb the EMP in the worst case with a little spark, and carry on. The Western radios stop working. If you want a "hard" radio, you might start with a valve then go on to a software defined radio downstream, mixing 1940's and 2020's tech.
And you're right. It's just a unity gain buffer, doing...nothing. No "starved anode" about it, as it's not configured with the load in the anode circuit, so isn't working as a conventional amplifier. Nowt to do with choice of valve. You could chuck the valve in the bin, connect the input directly to the op-amp, and it would sound exactly the same. People will buy anything.
I wouldn't subscribe to the doing nothing bit, it won't sound the same, tho less is often more. Said device is probably adding some second harmonics.. nice...and possibly reducing output impedance versus whatever is the input; there will be measurable distortion
They're all hiding behind other things. The circuit board has IRF630 written on it. https://uk.farnell.com/stmicroelect...d-1428566262|&CMP=KNC-GUK-GEN-SKU-MDC-Test760
