I gotta ask... in the power supplies that I'm seeing in this thread and others... Why the use of multiple big chokes. Back in the days of tube rectifiers you had to have them to get ripple down to manageable levels because you could not use a very large filter cap right after the rec tube. But today we have good SS rectifiers... and we can put a huge cap right after it. Then maybe a small choke to smooth things out a little bit more... but with a simple SSREC+C+RC filter the b+ is pretty clean with a decent sized first Cap.
I'm a tube snob for the most part but not so much when it comes to power supplies...
Just seems like a waste of iron to end up with a semi saggy power supply when you can have a rigid, fast power supply for much less effort. (Saggy power supplies are good bluesy guitar amps... but I'd think not so much with Hi-Fi gear... Gut reaction tells me that I'd not want my Power supply to be a variable in the sound of my amp... Make it clean and solid and let my amp sound like it is supposed to without the added variable of the Power Supply.
Note that I come from Guitar amp land... But we go to great lengths sometimes to keep power supply noise out of these things. And depending on what we are going for we use the power supply to tailor the tone of the amps.
Maybe I'm missing something... But over engineering is not always a good thing.
I'm a tube snob for the most part but not so much when it comes to power supplies...
Just seems like a waste of iron to end up with a semi saggy power supply when you can have a rigid, fast power supply for much less effort. (Saggy power supplies are good bluesy guitar amps... but I'd think not so much with Hi-Fi gear... Gut reaction tells me that I'd not want my Power supply to be a variable in the sound of my amp... Make it clean and solid and let my amp sound like it is supposed to without the added variable of the Power Supply.
Note that I come from Guitar amp land... But we go to great lengths sometimes to keep power supply noise out of these things. And depending on what we are going for we use the power supply to tailor the tone of the amps.
Maybe I'm missing something... But over engineering is not always a good thing.
Overbuild PSUs
In general I agree with this. However, with respect to power supplies, I am of the opinion that they cannot be too good for an amp, particularly a phono preamp where any noise will kill you (figuratively speaking). The PSU that I described was rather simple from my standards. Previously, I've also incorporated shunting voltage regulators in conjunction with CCS's. I acquired this perspective after reading Allen Wright's Tube Preamp Cookbook (fantastic btw) as well as paying a lot of attention to what Gary Pimm has been up to in the CCS domain.
Different strokes I guess.
BTW - my 1626-based Darling clone has a dirty simple PSU (similar to what you describe) and it sounds great.
In general I agree with this. However, with respect to power supplies, I am of the opinion that they cannot be too good for an amp, particularly a phono preamp where any noise will kill you (figuratively speaking). The PSU that I described was rather simple from my standards. Previously, I've also incorporated shunting voltage regulators in conjunction with CCS's. I acquired this perspective after reading Allen Wright's Tube Preamp Cookbook (fantastic btw) as well as paying a lot of attention to what Gary Pimm has been up to in the CCS domain.
Different strokes I guess.
BTW - my 1626-based Darling clone has a dirty simple PSU (similar to what you describe) and it sounds great.
OK, I like what I am getting for replies. I feel a lot more comfortable with what I should be looking for in a PSU.
The PSU from DrExotica looks very good, but so does the cheap one from RenegadeAmps.
I have priced both:
around $200 for the DrExotica
around $50 for the one by Renegade Amps
My orignal rationale for doing a DIY preamp was to get a tube design with relatively low gain, and to try to do it cheaply. For my first attempt, I am going to go for the RenegadeAmp PSU, as it'll allow me to concentrate on the preamp itself. As long as I keep tha casework reasonable, I can upgrade to to Tube rectified PSU later.
So, RenegadeAmps
1. How did you spec the 269 transformer (ie. V and ohms used in PSUDII)?
2. What kind of caps should I get, and where can I get 94uF from? My guess is that 100uF will work just as well as 94uF.
3. Bridge rectifier to get 6V DC?
DrExotica, please let me know how the PSU works out, I will certainly want to try it, once I get a basic Aikido up-and-running.
Charlie
The PSU from DrExotica looks very good, but so does the cheap one from RenegadeAmps.
I have priced both:
around $200 for the DrExotica
around $50 for the one by Renegade Amps
My orignal rationale for doing a DIY preamp was to get a tube design with relatively low gain, and to try to do it cheaply. For my first attempt, I am going to go for the RenegadeAmp PSU, as it'll allow me to concentrate on the preamp itself. As long as I keep tha casework reasonable, I can upgrade to to Tube rectified PSU later.
So, RenegadeAmps
1. How did you spec the 269 transformer (ie. V and ohms used in PSUDII)?
2. What kind of caps should I get, and where can I get 94uF from? My guess is that 100uF will work just as well as 94uF.
3. Bridge rectifier to get 6V DC?
DrExotica, please let me know how the PSU works out, I will certainly want to try it, once I get a basic Aikido up-and-running.
Charlie
This is probably going to go over as well as farting in church, but have you considered a basic raw supply followed by simple active regulator? A Maida regulator will knock down ripple and noise to a millivolt or two, worst-case; with the intrinsic PSR of the circuit, the contribution of the supply to output noise will be buried. And the Maida will cost perhaps 5% of the price of a good choke.
cbutterworth said:
1. I've used the 269 transformers in small SE amps and stand alone Preamps in the past... A 269EX is a good for about 250-260Vdc and A 269JX is good for about 310-315Vdc after rectification. And I know that either has no problem supporting 4 typical preamp triodes.
2. 94uF = two 47uF in parallel... (I've always got a stash of them laying around so that's what my brain thinks... (so yes 100uF is fine, or bigger is good too if that's what you have)
3. A Full wave bridge connected to the 6.3v taps to get the 6v or so for a DC filament supply. (for quiet operation)
My power supply for my Aikido (just finished wiring the PSU):
Lundahl LL1683 250V mains
Hybrid bridge w/ 5AR4 rectifier
3.3uF poly cap
Lundahl LL1673 15H choke
20uF ASC motor run
...splits to...
Lundahl LL1673 15H choke (one per side)
20uF ASC motor run (one per side)
PSUD gives me 300V theoretically, at 30mA draw (15mA per side).
In order to test the PSU circuit, without wiring in the audio circuit, should I just connect 20k resistors across the B+s to ground? 20K R should give me a 15mA drop at 300V...
Lundahl LL1683 250V mains
Hybrid bridge w/ 5AR4 rectifier
3.3uF poly cap
Lundahl LL1673 15H choke
20uF ASC motor run
...splits to...
Lundahl LL1673 15H choke (one per side)
20uF ASC motor run (one per side)
PSUD gives me 300V theoretically, at 30mA draw (15mA per side).
In order to test the PSU circuit, without wiring in the audio circuit, should I just connect 20k resistors across the B+s to ground? 20K R should give me a 15mA drop at 300V...
Yeah, I admit I splurged on the PSU components, but I wanted to avoid electrolytic caps, and the only way to do that is with some heavy iron chokes.
And, Lundahl has such a good reputation for high-quality trannys at a not-too-outrageous price...I couldn't resist...
I figure I am still coming in a heck of a lot cheaper than buying a retail preamp, that's for sure.
And, Lundahl has such a good reputation for high-quality trannys at a not-too-outrageous price...I couldn't resist...
I figure I am still coming in a heck of a lot cheaper than buying a retail preamp, that's for sure.
RenegadeAmp,
You mention paralleling 47uF caps to get 94uF, although 100uF works fine.
Now, what kind of caps work best here? For example, I could buy Can caps from TubeDepot - 47uF / 385V; 100uF/500V; 50uF/500V
What about electrolytic caps? Or are the cans electrolytics. I looked for polypropylene of the same specs, but couldn't find any.
Charlie
You mention paralleling 47uF caps to get 94uF, although 100uF works fine.
Now, what kind of caps work best here? For example, I could buy Can caps from TubeDepot - 47uF / 385V; 100uF/500V; 50uF/500V
What about electrolytic caps? Or are the cans electrolytics. I looked for polypropylene of the same specs, but couldn't find any.
Charlie
Oil caps
You may want to consider ASC oil-filled polypropelene caps - they are cheap and work very well; certainly a lot nicer that electrolytics. You can find them here (me - I'm a very satisfied customer):
ASC Caps
I recently bought some of their 50uF/440V jobs (pretty big - 2.5" diameter, 5" tall).
You may want to consider ASC oil-filled polypropelene caps - they are cheap and work very well; certainly a lot nicer that electrolytics. You can find them here (me - I'm a very satisfied customer):
ASC Caps
I recently bought some of their 50uF/440V jobs (pretty big - 2.5" diameter, 5" tall).
cbutterworth said:
Me... I'd go with Sprague Atom Electrolytic... as a good comprimise between qulity and size, but that's just me... evidently a lot of guys here don't likek electrolytics any where near their amps... Especially in the siganal path. And of course the power supply does always carry signal...
my last preamp I used a simple LCLC filter using a GZ30, Hammond power transformer, Hammond chokes and Solen caps. Then that was fed right into a 6BM8 regulator (from an old Sound Practices issue) which is pretty cheap to do.
http://img135.imageshack.us/img135/5392/6bm8regnk7.jpg
Another alternate is the inexpensive ECL85.
http://www.the-planet.org/6GV8.html
You can also go the solid-state way with a TIP50/etc.
http://img135.imageshack.us/img135/5392/6bm8regnk7.jpg
Another alternate is the inexpensive ECL85.
http://www.the-planet.org/6GV8.html
You can also go the solid-state way with a TIP50/etc.
I had a brainwave this morning!!!! I do not get them very often. In my DNA lab, I have a spare Heath Zenith SP-2717A regulated high-voltage power supply. I have two units, one which I use, and the other is spare. I was given them by an old employer, so they do actually belong to me.
It produces from 0 to 400V with up to 100mA continuous. Regulation is less than 1%. Ripple, jitter, and noise is spec'd at less than 10mV RMS. Output impedance is less than 10 ohm from DC to 1MHz.
The unit also filament connections of 6.3V at 4 amps, and 12V at 2 amps. It uses a single 6AU6, control amplifier; 2 6L6GC series regulators; 9 silicon diodes; and 10 Zenner diode voltage regulators.
So, my guess is that this would work, wouldn't it? It would allow me time to cobble together parts for a good PSU, while also testing different voltages and tubes.
Now another completely different question:
If I use the Broskie Octal Stereo board, could I use sockets for the resistors and caps? This would allow the interchange of parts.
Regards,
Charlie
It produces from 0 to 400V with up to 100mA continuous. Regulation is less than 1%. Ripple, jitter, and noise is spec'd at less than 10mV RMS. Output impedance is less than 10 ohm from DC to 1MHz.
The unit also filament connections of 6.3V at 4 amps, and 12V at 2 amps. It uses a single 6AU6, control amplifier; 2 6L6GC series regulators; 9 silicon diodes; and 10 Zenner diode voltage regulators.
So, my guess is that this would work, wouldn't it? It would allow me time to cobble together parts for a good PSU, while also testing different voltages and tubes.
Now another completely different question:
If I use the Broskie Octal Stereo board, could I use sockets for the resistors and caps? This would allow the interchange of parts.
Regards,
Charlie
Might work well. Couple of things about electrophoresis power supplies: Some offer a constant current, or constant power mode. One that old may offer only constant voltage, but that's what you want anyway. In electrophoresis applications, one doesn't worry about higher frequency stuff. That doesn't mean that it will produce any noise, it probably won't, as the design principles are pretty standard. Just check for that in the unlikely event you run into any weirdness.
Sheldon
Sheldon
Sheldon,
Yes, but the Heath PSU was designed for audio or HAM radio equipment. In fact, the manual shows how to connect it to an audio amplifier.
For the amplifier, it shows:
B+ connected to the amplifier chassis
the COM (common) connected to the -ve lead of the amplifier
Jumper connect from PSU B+ binding post to PSU GND to bring the chassis of the PSU and the amp to the same potential.
Looking at the description of the circuit, the manual describes how changes in load effects the voltage feedback amplifier, which in turn has an effect on the regulator tubes to restore the volatge to that set by the B+ voltage control.
It appears that it is more than capable of regulating B+ voltage under a varying load.
The manual is copyright 1982, so the PSU itself is probably of a similar vintage.
Charlie
Yes, but the Heath PSU was designed for audio or HAM radio equipment. In fact, the manual shows how to connect it to an audio amplifier.
For the amplifier, it shows:
B+ connected to the amplifier chassis
the COM (common) connected to the -ve lead of the amplifier
Jumper connect from PSU B+ binding post to PSU GND to bring the chassis of the PSU and the amp to the same potential.
Looking at the description of the circuit, the manual describes how changes in load effects the voltage feedback amplifier, which in turn has an effect on the regulator tubes to restore the volatge to that set by the B+ voltage control.
It appears that it is more than capable of regulating B+ voltage under a varying load.
The manual is copyright 1982, so the PSU itself is probably of a similar vintage.
Charlie
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