Hi Folks,
Anyone here tried this Regulated PSU from Gary K.'s website for a preamp?
http://www.the-planet.org/6GV8.html
I'd like to try this but with a 5V4G FW rectifier rather than SS diodes... An exact 250V +B is what I need for a project, and the current draw is around 34mA so this supply suits my needs.
The .pdf file schema linked in the webpage states that C3 should be 100uF, but the parts list indicates 47uF for C3. Should I just go with 100uF?
Anyways, I wanted to do a sim on PSUD2 for the 5V4G with either a small value Cap Input supply or Input R supply. Is getting the ballpark 'pulsating VDC' after C1 to modify the pre-regulated filter network a good start?
I got around 330VDC (C1) after I did a sim on PSUD2 (250VAC-> 1N4007 bridged -> 100uF-> 40mA constant current sink). So I tried to sim 275-0-275-> 5V4G-> 125R-> 100uF-> 40mA load for starters and got the same max VDC. Is this a good start, any suggestions?
BTW, I'll stick to R1 (470R) instead of the optional choke but I might try the OC3/OD3 option in place of the Zeners.
I tried to email Gary about his PSU but I didn't get any reply. Thanks.
fred
Anyone here tried this Regulated PSU from Gary K.'s website for a preamp?
http://www.the-planet.org/6GV8.html
I'd like to try this but with a 5V4G FW rectifier rather than SS diodes... An exact 250V +B is what I need for a project, and the current draw is around 34mA so this supply suits my needs.
The .pdf file schema linked in the webpage states that C3 should be 100uF, but the parts list indicates 47uF for C3. Should I just go with 100uF?
Anyways, I wanted to do a sim on PSUD2 for the 5V4G with either a small value Cap Input supply or Input R supply. Is getting the ballpark 'pulsating VDC' after C1 to modify the pre-regulated filter network a good start?
I got around 330VDC (C1) after I did a sim on PSUD2 (250VAC-> 1N4007 bridged -> 100uF-> 40mA constant current sink). So I tried to sim 275-0-275-> 5V4G-> 125R-> 100uF-> 40mA load for starters and got the same max VDC. Is this a good start, any suggestions?
BTW, I'll stick to R1 (470R) instead of the optional choke but I might try the OC3/OD3 option in place of the Zeners.
I tried to email Gary about his PSU but I didn't get any reply. Thanks.
fred
kevinkr said:
Hi Kevin,
Could you share some pointers on how to get the approx raw VDC from the original ss rectified schema via PSUD2? BTW, what is the purpose of the 470k (R8) bypassing the last 100uF (C2) cap just before the 6GV8 reg comes into play? Thank you.
regards,
fred
PS - it's good to see ur online articles again. It's one of the early webpages I've seen on DHT gear.
looks like from the data sheet, this tube can handle more than the 34ma you require, it handle 5x more. but no one's stopping you from using this.
for an output of 250 volts, you need at least 350 volts at input of regulator, the triode connected pentode series pass tube need some voltage to work on, i am not sure how much exactly, but 350 seems ok. at 350 and 250 volts output, the series pass will be dissipating 3.4watts, just chek that is within the tube's plate dissipation rating.
so if you intend to use this rectifier tube, you need a power traffo of 300-0-300@50mA dc. you are limited to 10uf input cap as per data sheet. you can do a crcrc, with caps increasing as you move away from the rectifier cathode.
the 470k(R8) resistor is a bleeder resistor. provides for minimum current when idling and as safety feature.
it is ok to replace the zeners with gas-ion type vr tubes.
for an output of 250 volts, you need at least 350 volts at input of regulator, the triode connected pentode series pass tube need some voltage to work on, i am not sure how much exactly, but 350 seems ok. at 350 and 250 volts output, the series pass will be dissipating 3.4watts, just chek that is within the tube's plate dissipation rating.
so if you intend to use this rectifier tube, you need a power traffo of 300-0-300@50mA dc. you are limited to 10uf input cap as per data sheet. you can do a crcrc, with caps increasing as you move away from the rectifier cathode.
the 470k(R8) resistor is a bleeder resistor. provides for minimum current when idling and as safety feature.
it is ok to replace the zeners with gas-ion type vr tubes.
hi fedgrove,
your regulator used in4007's in the rectifier section, despite the obvious advantages of using ss rects, and full wave bridge, instead of just full wave rects using tubes, still fred wants to use a tube rectifier, care to elaborate on musicality of ss rects vis-avis tube rects, please?
thanks.
your regulator used in4007's in the rectifier section, despite the obvious advantages of using ss rects, and full wave bridge, instead of just full wave rects using tubes, still fred wants to use a tube rectifier, care to elaborate on musicality of ss rects vis-avis tube rects, please?
thanks.
Hi Tony/joan2,
Thanks for the detailed reply..
I have the tube lying around, so I better use it. 350VDC it is then...
I had a hunch it was a 470k bleeder resistor, but didn't know the real purpose of it in this application w/ a reg. Yes, I used 10uF as input cap for the initial sim, wrong choice power trannie though (275-0-275). I might also try CLCRCRC, since I have a spare Hammond 157J choke. I'll see if I can tame the choke induced resonance (resonant tank).
Thanks again!
fred
Thanks for the detailed reply..
I have the tube lying around, so I better use it. 350VDC it is then...I had a hunch it was a 470k bleeder resistor, but didn't know the real purpose of it in this application w/ a reg. Yes, I used 10uF as input cap for the initial sim, wrong choice power trannie though (275-0-275). I might also try CLCRCRC, since I have a spare Hammond 157J choke. I'll see if I can tame the choke induced resonance (resonant tank).
Thanks again!
fred
Hi,
If it made an audible difference then I would have used a valve rectumfrier but it doesn't.
The AC part of the PS is well filtered as it stands, whatever ripple that's left is shoved under the carpet by copious amounts of NFB, yes that's negative feedback, built into the series regulator and if you'd be able to hear beyond the regulator then there would be something seriously wrong with it.
IOW, valve rectification + regulation = waste of money.
Oh, no need to throw in expensive Schottky diodes en lieu of the humble IN4007s either. Obviously.
Cheers,
If it made an audible difference then I would have used a valve rectumfrier but it doesn't.
The AC part of the PS is well filtered as it stands, whatever ripple that's left is shoved under the carpet by copious amounts of NFB, yes that's negative feedback, built into the series regulator and if you'd be able to hear beyond the regulator then there would be something seriously wrong with it.
IOW, valve rectification + regulation = waste of money.
Oh, no need to throw in expensive Schottky diodes en lieu of the humble IN4007s either. Obviously.
Cheers,
Tony said:
Actually, to a certain extent I do hear a difference too
... A Russian 5U4G sounded gritty IME compared to an American NOS 5U4G in the same amp. Just don't say that a GZ34 sounded better in that same amp coz it was 'superior' even if the amp can 'tolerate' the lesser current etc., that's when I run away...
fred76 said:
Actually, to a certain extent I do hear a difference too
still i run away, tube rolling does not matter to me, i'd rather look at the circuit and find out how it can be improved.
btw, i checked the plate rating of the 6GV8 pentode side, something like 7.5 watts, so all is ok.
I was a total unbeliever and used SS rectification exclusively. Then one project I used a valve rect. for a more "true-tube" asthetic appeal.
I heard a difference.
I switched between a 5Y3, 5R4 and 5U4 - more difference.
Given I was an unbeliever, the psychological factor is out.
There is one way to determine for yourself - try it all ways, regular SS, Schottky and valve.
I'm not saying one is better, they are just different.
I heard a difference.
I switched between a 5Y3, 5R4 and 5U4 - more difference.
Given I was an unbeliever, the psychological factor is out.
There is one way to determine for yourself - try it all ways, regular SS, Schottky and valve.
I'm not saying one is better, they are just different.
Tony said:
still i run away, tube rolling does not matter to me, i'd rather look at the circuit and find out how it can be improved.
btw, i checked the plate rating of the 6GV8 pentode side, something like 7.5 watts, so all is ok.
Tony,
Personally circuit/engineering is high level prioroity - or as Gizmo once said: higher level tweaking... Tube rolling (accounting that the same tube rectifier types are used so as not to alter operating points) is lower level.. And there are those "lower-lower" level still, err.. "cable elevators"?
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