I’ve been using these boards for many years now. Haven’t offered them as is required for anyone to be experienced well enough in SMD soldering to get these done effectively. I have a reflow oven so work at scale is easier this way. I’ve been doing a lot of SMD board design and building over the past few years though.
On a busy time regardless, I found the space to build these four commissioned boards for D3a drivers like the ones I used on my 300B amplifier. There seems to be a lot of interest and build work done around this design, so happy to see this happening.
Saweet
Definitely interested in 2 of them
Nice! What are the active/sand devices on this board?
The usual suspects in SMD version: LND150 for voltage reference and the ubiquotus IXTP08N100D2
Thanks.
I am using 3A5 tube connected in parallel as an input tube for my amplifier. Would be nice to try those. Bias is fixed and I run 9-10mA @ 95V.
This would work right?
Thanks
Hi, yes sure. You just need to dial the bias voltage of the hybrid mu-follower board down to 95V. Cheers, Ale
Ok, what is the recommended B+ for input of the board?
Thanks
Hi, The board can operate up to 450V. However the supply has to be at least the sum of the operating point, plus your positive output voltage swing and at least 25V for the MOSFET to operate optimally. That means for example if you have 95V at the anode and let’s say the output swing is 100Vpp (50V peak) you will need 95V+50V+25V = 170V.
You can operate with higher voltage, that’s the minimum your circuit will need. The higher the voltage the more dissipation the top MOSFET will have to handle. Let’s say that if you feed it with 200V and the operating point is 95V, then the dissipated power is just over 1W for 10mA of anode quiescent current. A small clip-on TO-220 heatsink does the job perfectly well.
Hope this helps.
Cheers
Ale
To be honest, I think I have one 170VAC secondary on my transformer that is not used! This should be enough, right?
CLC filtering and right to the mu follower, exactly?
What is the price? You will not believe me, but for now I am using 850V B+ and 100K anode resistor. I tried a lot of combinations, but this one works (sounds) excellent. With this mu follower gain would be better and everything from technical aspect, correct?
I am a fan, I do not know what I am looking at? I build 1950’s circuits and work at RTX and solder surface mount all the time. Are you selling these boards and what do they do? This post did not explain. Thank You, Jonathan
Hi Jonathan,
If you are just getting started on this fascinating audio journey and want to know more about this, have a look at the ETF.18 DHT Preamps Lecture and also there are plenty of stuff to read on this blog. Hope this helps.
Cheers, Ale