Budget XFRMs
I have seen some crafty implementations of power supplies for valves where simply reversing the hook up on a step down XFMR, you end up with a step up. This can obviously avoid the higher cost associated with the application specific metal from Hammond and other suppliers.
It looks like a "cheap" trick and at first it doesn't look very sexy but I see no logical reason such an approach would be wrong or detrimental.
What IS the approx. current draw on Franks 6SN7 circuits? Should I double the capacity on the supply for overhead? Also, I was thinking how low a cost this method is to use and that I could easily afford separate power supplies for each channel for a true dual mono valve pre?
Seems like a win-win situation to me?
Furthermore, calculating current & voltage drop through valve circuits is easy like ohms law? Where can I read about such basic calculations on-line? I’d guess a 6SN7 would draw 100~200mA max?
Moss.
I have seen some crafty implementations of power supplies for valves where simply reversing the hook up on a step down XFMR, you end up with a step up. This can obviously avoid the higher cost associated with the application specific metal from Hammond and other suppliers.
It looks like a "cheap" trick and at first it doesn't look very sexy but I see no logical reason such an approach would be wrong or detrimental.
What IS the approx. current draw on Franks 6SN7 circuits? Should I double the capacity on the supply for overhead? Also, I was thinking how low a cost this method is to use and that I could easily afford separate power supplies for each channel for a true dual mono valve pre?
Seems like a win-win situation to me?
Furthermore, calculating current & voltage drop through valve circuits is easy like ohms law? Where can I read about such basic calculations on-line? I’d guess a 6SN7 would draw 100~200mA max?
Moss.
Attachments
PCB mounting/sockets
Mixing printed circuit boards and tubes could be easy. Watch out for insertion and removal forces. You can mount some sockets to the "top Deck" of your amp to handle the insertion and removal of valves. Then all you need to do is set a few stand-offs on the pcb below and everything will be sturdy and long lasting.
This socket from Tubedepot.com looks like a good contender:
Mixing printed circuit boards and tubes could be easy. Watch out for insertion and removal forces. You can mount some sockets to the "top Deck" of your amp to handle the insertion and removal of valves. Then all you need to do is set a few stand-offs on the pcb below and everything will be sturdy and long lasting.
This socket from Tubedepot.com looks like a good contender:
Attachments
Regarding power supplies
If I use the "Alburquerque" high voltage regulator this will also draw a little more current into waste. Now its getting really hard to figure out the economical XFMR for reverse hook-up to high Vac.
I think small variations in supply line voltage could harm or destroy these circuits after the ratio increase off a reverse hooked up transformer! The need for regulation seems paramount now, with such an implementation.
Hmm...
Moss.
It is true! There is no FREE LUNCH!
If I use the "Alburquerque" high voltage regulator this will also draw a little more current into waste. Now its getting really hard to figure out the economical XFMR for reverse hook-up to high Vac.
I think small variations in supply line voltage could harm or destroy these circuits after the ratio increase off a reverse hooked up transformer! The need for regulation seems paramount now, with such an implementation.
Hmm...
Moss.
It is true! There is no FREE LUNCH!
Antek and Edcor have 200v to 300v power transformers available for right around $50USD. I would go that route before I used two transformers wired like that along with a voltage doubler. You can also still use the ALBQ power supply / regulator circuit, just lose the doubler at the very front.
Cheers
James
Cheers
James
Thanks, yeah I could locally purchase Hammond ala the 269XX family of XFMR's. One per channel or a larger one for both. On the other hand the 10:1 ratio 120Vac-12Vac XFMRs are like $5.00 each. The Hammond's start around $70.00 each with local taxes. Thanks for the references for Antek and Edcor but by the time they reach the door stop they need shipping fees and even worse, sometimes, customs asks for extra $$$$! Furthermore the wacky dollar X-change, which not so long ago was a sweet deal but not now.Not that it is a big deal really. Money well spent gives returns...in the long run. I'm just flexing everything out hereJPeitzman said:
john65b said:
I think your PP tube amp, if not pulled from thin air, may already have a driver stage to make it happy. Jack the thread brother! Good times
Alex Kitic said:
Being that I started out as a SS guy, I don't have this "phobia" concerning SS. Well, I have tried it both ways. One project used a SS power supply and the other a 5U4GB, and the only reason for that was I had a power xfmr with the right current rating, but a too high voltage for SS diodes. I can't tell any difference. If the DC is well filtered, and the rail(s) noise-free, then what does it matter where it came from: hollow state, solid state, or even a bunch of car batteries wired in series?
Only thing that hollow state gets you is glowey bottle coolness points (and I'm sure Hg diodes would sure look pretty). Otherwise, what difference does it really make (except for guitar amps where you want the reduced voltage regulation)?
Miles Prower said:
Wow. I wish i could say the same. I hate vacuum/mercury rectifiers with a passion but nothing made out of sand comes anywhere close. Even flat-earthers/cheapskates like Audio Research eventually figured they couldn't get decent sound without tube rectification. Never mind they have cascaded regulation stages after the rectifiers.
analog_sa said:
All I can do is report what I'm hearing, and I'm not hearing any difference, at least not with PP output stages where the OPT center tap is very close to AC ground. May be it makes a bigger difference with SE designs?
May be the problem is misapplication? A silicon diode can easily source 5 -- 10A or more of Isurge, whereas a VT diode can not. It's easier and cheaper to simply use a huge filter capacitor across the Si diodes than it is to include an LC ripple filter. That's how I designed the SS power supply: with a small enough resevoir capacitor to keep the Isurge below 1.0A and follow up with an effective LC filter. Perhaps there's some sort of core saturation nastiness that's being coupled into other circuits from excessive Isurge? Even if a Si diode won't complain about 10A of Isurge, the power xfmr just might. After all, if NOS, they weren't designed for that. If new, like the Hammond "Classic" series, these weren't designed for big Isurge either.
Regulated PWR supply Solid State
I was looking at a bunch of schematics online and it seems the preamp valve power supply has been done to death with solid sate DC regulation and DC heaters.
I put this schematic and board layout together yesterday. Keeping things simple, I think there is much room for improvement so I put it here for suggestions.
-Diodes can be anything that work 1N4007 or fast schottky type.
-TIP50 can be replaced by any suitable NPN pending voltages...BU522 and others
-78T05 regulator could be 7805 pending current requirments and heatsinking
-Zeners: any combination to deliver the required output voltage
-Capacitors are all 10mm lead spacing
I mention the above to make the layout universal to whom ever uses it. The board I have drawn measures approx. 78mm by 64mm or 3 inches by 2.5 inches.
There is no significant cost to this power supply in terms of components.
I was looking at a bunch of schematics online and it seems the preamp valve power supply has been done to death with solid sate DC regulation and DC heaters.
I put this schematic and board layout together yesterday. Keeping things simple, I think there is much room for improvement so I put it here for suggestions.
-Diodes can be anything that work 1N4007 or fast schottky type.
-TIP50 can be replaced by any suitable NPN pending voltages...BU522 and others
-78T05 regulator could be 7805 pending current requirments and heatsinking
-Zeners: any combination to deliver the required output voltage
-Capacitors are all 10mm lead spacing
I mention the above to make the layout universal to whom ever uses it. The board I have drawn measures approx. 78mm by 64mm or 3 inches by 2.5 inches.
There is no significant cost to this power supply in terms of components.
Attachments
For certain I will layout at least two variations: voltage doubler and a fullwave version. I don't want to talk crazy talk here but I was also thinking about doing a layout for both doubler and full wave with TUBES. I have been made aware the paramount need from many folks to have as little sand as possible. First I need to get the sand off the drawing table.