New member, first post (not counting intro) so please be gentle. I have acquired two Hashimoto transformers, HW-25-8 (25W, 8k, PP) and PT180 (multiple 6.3V, 280,250,0,250,280V) and I am looking for advice or suggestion what to build. Medium size room, 15x20, speakers will be around 90-93db efficient. I have EE degree but experience from industrial electronics, nothing audio related and zero knowledge of tubes. Have necessary test equipment and can do pcb or ptp, Hopefully, with your knowledge and experience I will succeed at producing (famous or not) tube sound.
The OPT would work with EL84s or 6V6s. Maybe something like a Tubelab SPP or Baby Huey EL84?
The power transformer is not an ideal match being a bit overspecified with quite a high power output. Do you plan to use a tube rectifier?
The power transformer is not an ideal match being a bit overspecified with quite a high power output. Do you plan to use a tube rectifier?
Not tube, I am more comfortable with ss devices and can design ./build power supply to necessary specs. As for transformer, isn't it better if it will operate below max wattage to avoid saturation?
It won't hurt, but the operating point that it was designed for would have assumed 300mA, so voltages might be a bit higher than planned with the lower demand of EL84 PP. But with those two taps, SS, maybe a choke, you should be able to dial it in. For planning the PSU PSUD2 on Duncan Amps is a great tool, if you have not seen it before.
I was looking at the Hashimoto power trans data sheet and noticed they have 100v primaries. Not the end of the world, just something to be aware of.
http://www.hashimoto-trans.co.jp/frame/tubecateng17a.pdf
jeff
Thanks for link, I am totally new and not familiar with all the goodies so definitely will check it
I have version 180F which is 120V, anyway I can build regulator to get what is needed.
What will be the input level from your source. If it's not too low then you might be able to get enough gain from 2 stages.
Are you wanting to experiment with different ideas or build once and forget it. There are some good books and blogs to help you on your way if you want any recommendations, I'd point you to the Bartola Valves blog and the books by Morgan Jones and Merlin Blencowe.
Are you wanting cheap obscure tubes or the traditional 300B. Directly heated tubes like the 300B ideally need a clean DC filament supply.
Are you wanting to experiment with different ideas or build once and forget it. There are some good books and blogs to help you on your way if you want any recommendations, I'd point you to the Bartola Valves blog and the books by Morgan Jones and Merlin Blencowe.
Are you wanting cheap obscure tubes or the traditional 300B. Directly heated tubes like the 300B ideally need a clean DC filament supply.
With the UL taps on the output transformers you could also consider a design like Dynaco ST35. You will have to tweek the GNF and compensation components for your Hashimoto’s, but the PCBs that Dave Gillespie offer will be an excellent starting point. His EFB biasing scheme works very well.
Check out the articles and material in his store: http://tronola.com/html/daves_store.html
With your power transformer his EFB for grid bias modulation might work better than the SCA35/ST35 cathode bias scheme. You can see how he modified the Fisher SA-100 in this thread: https://audiokarma.org/forums/index.php?threads/improving-the-fisher-sa-100-with-efb-ii.476431/
Post 35 shows his EFB grid-bias scheme with the modulated screen supply, which you don’t need if you go the UL route.
Check out the articles and material in his store: http://tronola.com/html/daves_store.html
With your power transformer his EFB for grid bias modulation might work better than the SCA35/ST35 cathode bias scheme. You can see how he modified the Fisher SA-100 in this thread: https://audiokarma.org/forums/index.php?threads/improving-the-fisher-sa-100-with-efb-ii.476431/
Post 35 shows his EFB grid-bias scheme with the modulated screen supply, which you don’t need if you go the UL route.
Thanks everyone for advise and suggestions, let me check all proposed solutions, hopefully I can make decision. I have Morgan Jones book but it's a brick so going through slowly.
You might look at the Western Electric 124. Only has local feedback so no global feedback to tune on your first build. There is a thread running here:
https://hifihaven.org/index.php?threads/building-a-western-electric-124.5851/
BTW, I’m a retired EE with all industrial experience. Tubes are learnable without too much trouble. Even for EE’s with no tube training.
https://hifihaven.org/index.php?threads/building-a-western-electric-124.5851/
BTW, I’m a retired EE with all industrial experience. Tubes are learnable without too much trouble. Even for EE’s with no tube training.
After little research I have decided to go with ST35 and ordered boards, let's see how it will go.