Double check that you aren't missing another ground connection.
I'll be nice and not mention Polish vodka.😀
I'll be nice and not mention Polish vodka.😀
I will check. I don't drink neither Polish nor Russian vodka. New Zealand Sauvignon Blanc from Marlborough is better. Zin from SoCal is good as well - you know how to make it.
SY, do you ever sleep? You are always on... Are you in Europe?
Na zdrowie!
SY, do you ever sleep? You are always on... Are you in Europe?
Na zdrowie!
I'm chained to my desk, since writing is 95% of my job. A quick look at the forum is often good for head-clearing.
But my last post to you was at about 5 in the afternoon, Texas time.😀
(can't find an emoticon with a cowboy hat)
But my last post to you was at about 5 in the afternoon, Texas time.😀
(can't find an emoticon with a cowboy hat)
Sy,
I want to build an amp using 6GK5's and 7591 outputs into a pair of Sherwood S5000 OPT. For the 7591 to get 30 watts I need 350 on the screen and plate and -17.5 bias. Would this regulator work?
Kevin
I want to build an amp using 6GK5's and 7591 outputs into a pair of Sherwood S5000 OPT. For the 7591 to get 30 watts I need 350 on the screen and plate and -17.5 bias. Would this regulator work?
Kevin
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You'll want to heatsink the pass transistor pretty well for the 7591 screens, but it should work fine.
Sy,
A stupid question? Is there a web site or article you can recommend that would explain how this type of regulator actually works? I'm clueless when it comes to transistors.
Kevin
A stupid question? Is there a web site or article you can recommend that would explain how this type of regulator actually works? I'm clueless when it comes to transistors.
Kevin
I think I explained it in the RLD article. There's always Michael Maida's application note: http://www.national.com/ms/LB/LB-47.pdf
Thanks Sy,
I found the Syclotron article. By the way. I was thinking of using two separate power supplies for the screens and plates in the amp. You mention this is a bad idea? Can you, in a nutshell, tell me why?
Kevin
I found the Syclotron article. By the way. I was thinking of using two separate power supplies for the screens and plates in the amp. You mention this is a bad idea? Can you, in a nutshell, tell me why?
Kevin
Did I say that? It's been a few years, so I don't remember. 😀
In any case, the principal reason to do that is catastrophe limitation. Let's say the plate supply goes out but the screen supply doesn't. The screens will now cheerfully act as plates, including assuming the plate current. This will impart a lovely red glow during the last few seconds of the output tubes' suddenly shortened life. Since we don't want a simple "wire got disconnected, oops" to result in catastrophic failure of the output tubes (and probably the screen regulators), using the output tubes' raw supply for the screen regulators means that any B+ failure will bring the screens down as well.
You can now resolder that loose wire without having to basically rebuild the output stage.
Sy,
Eli told me that in full pentode mode the screen and bias voltage needed to be rock solid. That the best option was to regulate these voltages. The Maida regulator seems a bit complicated. Mostly because I am unfamiliar with transistors and PCB's.
My idea was to use a simple toroid for the filaments and the plates. The plates using a bridge rectifier and choke input. For the screens and bias supply another toroid. Using its 6.3 windings in series to then put 12.6 into a Greinacher to supply the bias voltage. While it's high voltage winding would supply the screens. This winding would have a current capability 2-3 times the 40ma necessary to supply the 7591A screens.
In this way the plate draw could vary while the screens and bias would not be affected. The idea came to me while looking at Jim McShane's modification to the HK Citation power supply.
The idea was to build the amp without any regulation.
Kevin
Eli told me that in full pentode mode the screen and bias voltage needed to be rock solid. That the best option was to regulate these voltages. The Maida regulator seems a bit complicated. Mostly because I am unfamiliar with transistors and PCB's.
My idea was to use a simple toroid for the filaments and the plates. The plates using a bridge rectifier and choke input. For the screens and bias supply another toroid. Using its 6.3 windings in series to then put 12.6 into a Greinacher to supply the bias voltage. While it's high voltage winding would supply the screens. This winding would have a current capability 2-3 times the 40ma necessary to supply the 7591A screens.
In this way the plate draw could vary while the screens and bias would not be affected. The idea came to me while looking at Jim McShane's modification to the HK Citation power supply.
The idea was to build the amp without any regulation.
Kevin
That arrangement won't work with an RLD because you'll lose the adjustability of the output stage current. The Maida is really quite simple and if/when you screw something up, the parts are cheap. Buy 10 of all of the semiconductors as spares for getting the amp running in the first place, you'll be out $30 or so (less, if you're a good shopper). Once it's working and set up, you'll never have to touch the regs again except to adjust output stage idle current from time to time (or when changing tubes).
Keeping the driver stage transformer separate is more potentially advantageous.
Keeping the driver stage transformer separate is more potentially advantageous.
you could use a simple linear regulator (An NPN with a few Zeners). Then you'd only be out 10 bucks. You could also search many places for a Maida PCB (SY shows one on his website!) so the entire regulator would just be high voltage legos
Hey all,
Is that the Syclotron website? I didn't see the PCB there.
And Sy, my next amp will be a stereo amp using Sherwood S5000 transformers and 7591A outputs. I was planning to use the Dynaco 120 front end from the Dynaco transformer catalog. Using 6GK5's instead of the 12AX7. And the output section from the S5000 using 7591A's instead of the 7868s. The transformers are capable of 32 watts.
I have some 6P15P's coming from Russia. The RLD will come then.
Kevin
P.S. Do you have Maida regulator PCB's?
Is that the Syclotron website? I didn't see the PCB there.
And Sy, my next amp will be a stereo amp using Sherwood S5000 transformers and 7591A outputs. I was planning to use the Dynaco 120 front end from the Dynaco transformer catalog. Using 6GK5's instead of the 12AX7. And the output section from the S5000 using 7591A's instead of the 7868s. The transformers are capable of 32 watts.
I have some 6P15P's coming from Russia. The RLD will come then.
Kevin
P.S. Do you have Maida regulator PCB's?
I showed the layout for a Maida pcb, but I have never sold any boards. You're free to use my layout (actually, it was pinkmouse who did it) to make boards of your own, either through a board house or etching them yourself (easy- it's one layer, not tight spacing). Jack Walton (jackinnj here on diyAudio) has been threatening to do some boards- you might drop him a line and see if he's made any or is planning to.
It would be real handy if Jack's boards fit your FPE layout ...
And, I suppose (while I'm dreaming) if they had the quality of John Broskie's boards.
And, I suppose (while I'm dreaming) if they had the quality of John Broskie's boards.
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If not, I may also still have them. I'm back home on Wednesday night and if you haven't found them, I'll take a look.
