I am building a simple E810F => IT => 300B amp with seperate PSU for driver and 300B.
I have to use a 650 volt (no center tap) transformer for the powersection. I want to use a GZ37 as rectifier and two silicon diodes before this tube.
I guess I have to use some resistors in the PSU to arrive at the precribed 425 B+ for the 300B.
Duncans simulation program tells me to use about 1000 ohm (or 2x 470 ohm). Where to place to resistors is the question ?
Is it also possible and advisable to use a small resistor before the rectifier ? Or is it possible to use a higher B+ and raise the cathode resistor of the 300 B ?
What would be the best strategy ?
Thanks,
Jaap
I have to use a 650 volt (no center tap) transformer for the powersection. I want to use a GZ37 as rectifier and two silicon diodes before this tube.
I guess I have to use some resistors in the PSU to arrive at the precribed 425 B+ for the 300B.
Duncans simulation program tells me to use about 1000 ohm (or 2x 470 ohm). Where to place to resistors is the question ?
Is it also possible and advisable to use a small resistor before the rectifier ? Or is it possible to use a higher B+ and raise the cathode resistor of the 300 B ?
What would be the best strategy ?
Thanks,
Jaap
You might use a choke-input filter for your PS instead of the more conventional capacitor-input type. This will give you lower B+, though I don't think will bring it down to 425V.
Why not try some sort of direct coupled/Monkey/Free Lunch/DRD/Loftin-White style of amp? If you have to waste power in a hot resistor, it might as well be a hot cathode resistor as you will be able to get rid of the interstage transformer, or maybe use it as the anode load of the driver valve (as in the Monkey/Free Lunch topology).
Jason
Why not try some sort of direct coupled/Monkey/Free Lunch/DRD/Loftin-White style of amp? If you have to waste power in a hot resistor, it might as well be a hot cathode resistor as you will be able to get rid of the interstage transformer, or maybe use it as the anode load of the driver valve (as in the Monkey/Free Lunch topology).
Jason
Jaap:
How big (VA-rating) is that 650V transformer?
I happen to need something like 650VAC 300VA for a big tube amp project, maybe you are interested in trading it for a 385-0-385V transformer with 5V and 6,3V filament windings that I have somewhere?
Just a thought...
Cheers
/Daniel
How big (VA-rating) is that 650V transformer?
I happen to need something like 650VAC 300VA for a big tube amp project, maybe you are interested in trading it for a 385-0-385V transformer with 5V and 6,3V filament windings that I have somewhere?
Just a thought...
Cheers
/Daniel
thanks, to the suggestions.
I will certainly use a choke-input supply, forgot to mention that. By the way I have chosen to build two monoblocks.
It is simpler for me to keep the powertransformers; I suppose sending them to Sweden will cost you as much as new ones because they are rather heavy. And I have chosen to keep the filaments on a separate transformer.
I would like to stick to the IT, because it is a high quality one (amorf core from Tribute). So any more suggestions for the PSU are more than welcome. Particular the question about resistors before the rectifier.
regards,
Jaap
I will certainly use a choke-input supply, forgot to mention that. By the way I have chosen to build two monoblocks.
It is simpler for me to keep the powertransformers; I suppose sending them to Sweden will cost you as much as new ones because they are rather heavy. And I have chosen to keep the filaments on a separate transformer.
I would like to stick to the IT, because it is a high quality one (amorf core from Tribute). So any more suggestions for the PSU are more than welcome. Particular the question about resistors before the rectifier.
regards,
Jaap
Why use resistors? Hot and wasteful.
You could do several things:
If you're fearless, you can unwind some turns from the secondary.
If you're not limited by funds and really want a hot-rod, you could regulate the B+.
If you're neither of the above, you can use a filament transformer to buck some of the AC voltage on the primary.
You could do several things:
If you're fearless, you can unwind some turns from the secondary.
If you're not limited by funds and really want a hot-rod, you could regulate the B+.
If you're neither of the above, you can use a filament transformer to buck some of the AC voltage on the primary.
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