I know there are a million 300B amp schematics and power supplies. Most are for 350v across the 300B. My design calls for about 400v across the 300B plus a 80v cathode and about 7v drop across the output transformer. This is at 90mA. My driver will be an EL84 pentode running at about 20mA or so. So a total of 220mA.
Should i split this up into 2? and design a power supply for 110mA? I have tried PSUDII and at 220mA its hard NOT to go over the max current of any tube rectifier i pick.
The 300B heaters will be powered by DC and common mode chokes.
Maybe a hybrid power supply?
The OPT will be the Edcor 3K CXSE25-3K.
Edcor does offer some 350-0-350 and 400-0-400 power transformers.
Any help would be greatly appreciated. Or just a point into the right direction. I will post my power supply design here.
Thank you in advance.
Should i split this up into 2? and design a power supply for 110mA? I have tried PSUDII and at 220mA its hard NOT to go over the max current of any tube rectifier i pick.
The 300B heaters will be powered by DC and common mode chokes.
Maybe a hybrid power supply?
The OPT will be the Edcor 3K CXSE25-3K.
Edcor does offer some 350-0-350 and 400-0-400 power transformers.
Any help would be greatly appreciated. Or just a point into the right direction. I will post my power supply design here.
Thank you in advance.
400V+7V+80V=487V
Is this tube EML 300B-XLS?
These parameters are out of "standard" 300B operating range.
In this case the estimated power transformer is about 300VA.
If you have two individual 5V filament (at least 3A) for rectifiers, possible share the 220mA to 110, 110mA (each rectifier anodes connected together, using it as one diode).
The other problems is the rectified voltage (about 500V on the first capacitor), and the large current via the choke.
Is this tube EML 300B-XLS?
These parameters are out of "standard" 300B operating range.
In this case the estimated power transformer is about 300VA.
If you have two individual 5V filament (at least 3A) for rectifiers, possible share the 220mA to 110, 110mA (each rectifier anodes connected together, using it as one diode).
The other problems is the rectified voltage (about 500V on the first capacitor), and the large current via the choke.
i would like to get 8-10W out of it.
Do you think that reducing B+ down to 350v will allow for a simpler PS and also longer lifespan of the 300B? plus easier drive (somewhat). I think i just answered my own question.
I could try the 350+, 80mA 2.5K operating point. That's 31W dissipation.
Ok so lets do 350v, 71v bias... thats 428v required from the power supply.
Again... dual mono or stereo? Sticking with Edcor transformers and probably some ASC oil caps in the PS.
Thank you so far!!
Do you think that reducing B+ down to 350v will allow for a simpler PS and also longer lifespan of the 300B? plus easier drive (somewhat). I think i just answered my own question.
I could try the 350+, 80mA 2.5K operating point. That's 31W dissipation.
Ok so lets do 350v, 71v bias... thats 428v required from the power supply.
Again... dual mono or stereo? Sticking with Edcor transformers and probably some ASC oil caps in the PS.
Thank you so far!!
My 300B amp is over 10W in A2 mode (CCS loaded D3a, FET source follower, fix bias 300B 70mA, 5k:8 transformer, 400V B+).
I use one 5U4GB rectifier for whole amp.
I use one 5U4GB rectifier for whole amp.
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"its hard NOT to go over the max current of any tube rectifier i pick. "
The simulation assumes that all the tubes conduct immediately and so the surge in current is not real. That's why PSDUII gives you the option of a "stepped load." Use the stepped load function to start the 300Bs at a small current, say 10mA and then after a .5 second or so apply the full load. You can do the same for the driver tube.
Before I established the operating point for the 300B I would draw the load lines to determine an operating point that gives the wattage you need at a low distortion.
The simulation assumes that all the tubes conduct immediately and so the surge in current is not real. That's why PSDUII gives you the option of a "stepped load." Use the stepped load function to start the 300Bs at a small current, say 10mA and then after a .5 second or so apply the full load. You can do the same for the driver tube.
Before I established the operating point for the 300B I would draw the load lines to determine an operating point that gives the wattage you need at a low distortion.
aha... makes sense about the stepped load.
time to look back on my possible 300b operating points.
350v or 400v across the 300b? hmm..
I will do more research.
time to look back on my possible 300b operating points.
350v or 400v across the 300b? hmm..
I will do more research.
Why not choose any "conservative" operating point?
Rule of thumb of long life power tubes: not more, than 80% of maximum plate dissipation!
Try any simulator, for example Triode / Pentode Loadline Simulator v.1.0 (20161216 www.trioda.com).
Rule of thumb of long life power tubes: not more, than 80% of maximum plate dissipation!
Try any simulator, for example Triode / Pentode Loadline Simulator v.1.0 (20161216 www.trioda.com).
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I am not making quite that voltage, but current is comparable, and I have yet to see a PIV/over current warning. I have a simple LC filter with a tuned up resistive load.
I guess the question I'd put to you is: did you try the 6CJ3?
A similar supply( critical L, and about a mF ), makes 866's flash quite nicely when the 115NO45 closes on the plate iron primary.
cheers,
Douglas
I guess the question I'd put to you is: did you try the 6CJ3?
A similar supply( critical L, and about a mF ), makes 866's flash quite nicely when the 115NO45 closes on the plate iron primary.
cheers,
Douglas
yes i have used that loadline calculator and also the WE documentation.
So now i think 350v, 80ma, 2.5K or 3K, -70v cathode bias.
I think a pretty standard operating point.
So now i think 350v, 80ma, 2.5K or 3K, -70v cathode bias.
I think a pretty standard operating point.
Sounds better - 28w dissipation. I've always preferred the sound of higher primary values, like 5K. Sounds cleaner to me.