Is it possible
- Thread starter jaymanaa
- Start date
jaymanaa
RIP 1961-2018
Yeh, I was wanting to use one TX to go into the rectifiers but have two DC supplies coming out. Basically a dual mono supply after rectification. Each tube is one diode, so I assume with four diodes I can get two full wave lines out. Or would I be better off doing a full bridge with the tubes, then splitting it off to each channel? I still have a hard time understanding how the filament voltage rides on the high voltage. I was wanting to run the filaments in series at 10v, instead of having 4) 2.5v, 5 amp TXs. I already have a 10 volt that will handle the current no sweat.
jaymanaa
RIP 1961-2018
This is cool, I like fig. 2. http://n4trb.com/AmateurRadio/RCA_Ham_Tips/issues/rcahamtips0401.pdf
Last edited:
jaymanaa
RIP 1961-2018
That's them, you think 4 of those will give me enough current for 20w total music power?
Trio
Super Member
When I rebuilt a vintage "Battery eliminator", I needed different voltages, and I wound up using half wave rectification with one half of the "BH" gas rectifier for the high B+ and low B+ used the other half- using the original center tapped transformer.
If you were to use your original drawing as a reference for your heaters, you could use a pair of them to rectify one center tapped transformer each. Otherwise as drawn, you have a voltage divider.
But be aware that mercury rectifiers do generate a lot of RF, so they may not be the best choice for audio. It is worth experimenting with, but do not be surprised if you need to shield them. The BH used helium. The gas tubes also throw off a great deal of UV light, so use them with care.
If you were to use your original drawing as a reference for your heaters, you could use a pair of them to rectify one center tapped transformer each. Otherwise as drawn, you have a voltage divider.
But be aware that mercury rectifiers do generate a lot of RF, so they may not be the best choice for audio. It is worth experimenting with, but do not be surprised if you need to shield them. The BH used helium. The gas tubes also throw off a great deal of UV light, so use them with care.
jaymanaa
RIP 1961-2018
The thing I don't have a good handle on is using one transformer with or without a center tap for all 4 tube's filaments. That would allow me to use a 10v fil. TX and smaller wire. This power supply will be on a separate chassis from the mono amps it will power.
Trio
Super Member
Okay, I have attached a simple power supply schematic. It is a bit fuzzy as it was the only thing handy that was quite clear for an explanation.
All that is happening with the rectifiers is you are using two (or 4)tubes where one would normallly be used. The problem is the current flow of the B voltage circuit. While you could get away with 4 half wave supplies as long as the circuits are completely isolated electrically, where a nontapped B voltage source would attach to a pin of the heater of the rectifier. However when you have 4 in series like that, you are giving alternate paths through the filament transformer or the filaments themselves for the other B voltages, and some B voltage does pass through the filament as you can see in the simple supply image.
Put another way- if you have a circuit through the grounding circuit of each amp that is electrically common to all amps, you will have alternate paths for B voltage than just from plate to cathode of one rectifier. So having multiple B transformers is not workable with a series filament string. You would be limited to a single B transformer as shown in the modified original image. You would double the plate current by having the rectifiers in parallel, but you would need a potentially beefy B transformer to make it worthwhile. If you were to isolate the ground circuits completely between the two amps, and also avoid capacitive paths, you could experimentally have a second B voltage tap at the point in the filament string between tube 2 and 3, but you would have a potential undesired alternate B path between the amps if the twain meet.
My eyes are crossing after that. But using the simple supply image as a guide, it will hopefully be clear enough that what you want to try is not going to work very well. But you could use a bunch of power resistors to experiment with the circuit more to develop a more thorough understanding. Just keep the weenies and marshmallows close because those kinds of current and disipated power will cook a wiener in seconds. A brat will handle more power and last longer, and you can cook the marshmallows over the resistors as well.
Anyone for 5 killowatt Brats?
All that is happening with the rectifiers is you are using two (or 4)tubes where one would normallly be used. The problem is the current flow of the B voltage circuit. While you could get away with 4 half wave supplies as long as the circuits are completely isolated electrically, where a nontapped B voltage source would attach to a pin of the heater of the rectifier. However when you have 4 in series like that, you are giving alternate paths through the filament transformer or the filaments themselves for the other B voltages, and some B voltage does pass through the filament as you can see in the simple supply image.
Put another way- if you have a circuit through the grounding circuit of each amp that is electrically common to all amps, you will have alternate paths for B voltage than just from plate to cathode of one rectifier. So having multiple B transformers is not workable with a series filament string. You would be limited to a single B transformer as shown in the modified original image. You would double the plate current by having the rectifiers in parallel, but you would need a potentially beefy B transformer to make it worthwhile. If you were to isolate the ground circuits completely between the two amps, and also avoid capacitive paths, you could experimentally have a second B voltage tap at the point in the filament string between tube 2 and 3, but you would have a potential undesired alternate B path between the amps if the twain meet.
My eyes are crossing after that. But using the simple supply image as a guide, it will hopefully be clear enough that what you want to try is not going to work very well. But you could use a bunch of power resistors to experiment with the circuit more to develop a more thorough understanding. Just keep the weenies and marshmallows close because those kinds of current and disipated power will cook a wiener in seconds. A brat will handle more power and last longer, and you can cook the marshmallows over the resistors as well.
Anyone for 5 killowatt Brats?
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jaymanaa
RIP 1961-2018
OK, I think we got this. I've decided to go true dual mono full wave. Here's what I want to do, the only remaining question is; is it better to get a CT secondary on the filament TX and pull B+ from there, or is it the same as just pulling of of one side of the filament. The fil. TXs I have do have CTs, so if that's the best way, that's what I'll do. This is one channel only. Heck, this still leaves me needing a CT on the secondary of the power TX for a circuit ground.
