A typical bi-polar supply only has one bridge feeding pairs of caps etc.
The Pearl has two according to the schematic.
No?
The Pearl has two according to the schematic.
No?
Ah, I see what you’re saying. I know that specific PSU was meant to accommodate Class A power amps and it’s typically ran with the two bridges - one for each side of board/polarity.
Thank you for the circuit knowledge Mark. I‘ll get those caps soldered in ASAP.
6L6, I have an Antek AS-0522, 22V, 50VA transformer.
As for the PSU board itself, I will end up with an unregulated bi-polar supply similar to what is shown on post #1 of the thread, correct? Let me know if I am missing something.
6L6, I have an Antek AS-0522, 22V, 50VA transformer.
As for the PSU board itself, I will end up with an unregulated bi-polar supply similar to what is shown on post #1 of the thread, correct? Let me know if I am missing something.
Sure. Take a look at page 1 of this thread (click on "First" in the navigation bar).
6L6 drew out a version but if you scroll down there is a circuit from the original article (with a slight correction)
Hope that helps.
Let us know how it goes.
6L6 drew out a version but if you scroll down there is a circuit from the original article (with a slight correction)
Hope that helps.
Let us know how it goes.
Jwjarch - The PSU will work fine. Stuff the capacitors, use one 0.47 (or a little bigger) per side for the filter resistors, and tie the grounds together. Bleeder resistors, LEDs, and input snubber are optional, but a good idea.
Mhenschel - Dual bridges have the advantage of keeping the transformer from making excess mechanical noise when the PSU draws on the phases unsymmetrically. This is a bigger issue in power amps, but being a phonostage and reduction in noise is a good idea, and you could of course use one bridge if you wanted.
Mhenschel - Dual bridges have the advantage of keeping the transformer from making excess mechanical noise when the PSU draws on the phases unsymmetrically. This is a bigger issue in power amps, but being a phonostage and reduction in noise is a good idea, and you could of course use one bridge if you wanted.
@6L6
I read the Pearl 2 article. I wasn't arguing to have one bridge or two or why Wayne chose two. From the photo, that decision was already made in the build.
My question was the connections between the two boards. What I saw looked like two bridges creating two bi-polar (+/-). I misunderstood the board. My mistake. Sorry.
On the other hand, for a transformer rated at 22VAC output I would have expected a higher measured voltage -- more on the order of 28-30 volts -- no? I did a test with a "28V" secondary transformer and a bridge connected as in the photo. The voltage at the secondary was 36.2VAC and at the output of the bridge 32.6VDC.
I read the Pearl 2 article. I wasn't arguing to have one bridge or two or why Wayne chose two. From the photo, that decision was already made in the build.
My question was the connections between the two boards. What I saw looked like two bridges creating two bi-polar (+/-). I misunderstood the board. My mistake. Sorry.
On the other hand, for a transformer rated at 22VAC output I would have expected a higher measured voltage -- more on the order of 28-30 volts -- no? I did a test with a "28V" secondary transformer and a bridge connected as in the photo. The voltage at the secondary was 36.2VAC and at the output of the bridge 32.6VDC.
Mine was done without a cap too -- just the transformer and the bridge.
Wouldn't one expect that with typical regulation specs the actual measured voltage would be higher, no?
Wouldn't one expect that with typical regulation specs the actual measured voltage would be higher, no?
That depends on how your meter measures things. It's DC in that the voltage
is positive, but it is far from steady (basically just a bunch of 120Hz bumps
swinging from 0 to the peak value)
is positive, but it is far from steady (basically just a bunch of 120Hz bumps
swinging from 0 to the peak value)
I just used the "DC" setting on my Fluke 77.
I did another test with a different transformer (24-0-24) output both with and without the cap.
The voltage at the output of the transformer -input of the bridge was ~32VAC with and without the cap.
The voltage at the output of the bridge was 28VDC without the cap and 39.8VDC with the cap.
Again, I'm talking about the lowish voltages reported. Maybe the Antek is much better regulated than my Triads?
I did another test with a different transformer (24-0-24) output both with and without the cap.
The voltage at the output of the transformer -input of the bridge was ~32VAC with and without the cap.
The voltage at the output of the bridge was 28VDC without the cap and 39.8VDC with the cap.
Again, I'm talking about the lowish voltages reported. Maybe the Antek is much better regulated than my Triads?
Ah...
Yes, the Anteks are funny that way and the voltage in the model sometimes isn't what you can expect
under a full load condition (which seems to be how many other manufacturers quote
things). So one really need to check their datasheets.
For example:
https://www.antekinc.com/content/AS-0522.pdf
The secondaries, unloaded are 23VAC, but fully loaded that drops to about 20VAC.
(So if you want 22VAC under load, the '24V' transformer is probably the one to get.)
Yes, the Anteks are funny that way and the voltage in the model sometimes isn't what you can expect
under a full load condition (which seems to be how many other manufacturers quote
things). So one really need to check their datasheets.
For example:
https://www.antekinc.com/content/AS-0522.pdf
The secondaries, unloaded are 23VAC, but fully loaded that drops to about 20VAC.
(So if you want 22VAC under load, the '24V' transformer is probably the one to get.)
Ahhh...
So this is where the discussion started.
The measurements look "funny" because the Anteks are "funny".
I looked at that data sheet but bypassed the "Under Load" figures because I was looking for "No Load" info or percent regulation. That'll learn me.
I've never bought an Antek but if I do consider this make, I now know how to compare 'em to units with standard specs and choose correctly. Thanks.
On that... I wonder how the 22-0-22 transformer Wayne spec'd compares to the 22-0-22 Antek... and whether or not that matters?
So this is where the discussion started.
The measurements look "funny" because the Anteks are "funny".
I looked at that data sheet but bypassed the "Under Load" figures because I was looking for "No Load" info or percent regulation. That'll learn me.
I've never bought an Antek but if I do consider this make, I now know how to compare 'em to units with standard specs and choose correctly. Thanks.
On that... I wonder how the 22-0-22 transformer Wayne spec'd compares to the 22-0-22 Antek... and whether or not that matters?
I don't know if Wayne had spec'ed a particular transformer but Anteks
are generally fine and many members have used them successfully.
The load in this case is fairly light so I don't expect any issue of lower
voltage under full load and the transformer should have no trouble
giving a good (min) +/-28V to feed the +/-24V regulators.
are generally fine and many members have used them successfully.
The load in this case is fairly light so I don't expect any issue of lower
voltage under full load and the transformer should have no trouble
giving a good (min) +/-28V to feed the +/-24V regulators.
Another Pearl2 is born... have it hooked up and playing nice music.
I optimized my layout for minimal input wiring and small footprint.
Capacitance loading is adjustable with caps on pin headers.
Resistance options are 100,470 and 47K with DPDT per channel.
Chassis by Landfall systems which came out perfect.
2 final notes regarding some questions asked by myself or others recently:
1) I built the PSU exactly per Wayne's schematic with the Antek AS-0522. Connected to both boards, the unregulated supply is 29.2-29.4V.
2) I was slightly concerned with the high gain since I'm using a 4.0mV MM cart. It turned out just fine since overall I don't have high gain in my system. Preamp based on AMB alpha24 line stage with 5x (15dB) gain, and power amp is a Benchmark AHB2 with low gain setting (9.8Vrms input sensitivity)
I optimized my layout for minimal input wiring and small footprint.
Capacitance loading is adjustable with caps on pin headers.
Resistance options are 100,470 and 47K with DPDT per channel.
Chassis by Landfall systems which came out perfect.
2 final notes regarding some questions asked by myself or others recently:
1) I built the PSU exactly per Wayne's schematic with the Antek AS-0522. Connected to both boards, the unregulated supply is 29.2-29.4V.
2) I was slightly concerned with the high gain since I'm using a 4.0mV MM cart. It turned out just fine since overall I don't have high gain in my system. Preamp based on AMB alpha24 line stage with 5x (15dB) gain, and power amp is a Benchmark AHB2 with low gain setting (9.8Vrms input sensitivity)
Attachments
Hey, that's a really smart and nicely-done build. A model for others.
What's the power inlet you used?
And those long-handled switches?
What's the power inlet you used?
And those long-handled switches?
Thanks alot!!
The power inlet is just a standard XLR. They are rated for 50V, 16A so no issues there.
I typically prefer the Switchcraft Con-X connectors for DC power, but I had a few XLR spares that would go to waste otherwise.
The switches are TOCOS, which are really beautiful switches. They are out of production but Michael Percy has some DPDT and 4PDT left. Otherwise, I use NKK from Mouser/Digikey which are very good as well
The power inlet is just a standard XLR. They are rated for 50V, 16A so no issues there.
I typically prefer the Switchcraft Con-X connectors for DC power, but I had a few XLR spares that would go to waste otherwise.
The switches are TOCOS, which are really beautiful switches. They are out of production but Michael Percy has some DPDT and 4PDT left. Otherwise, I use NKK from Mouser/Digikey which are very good as well
re the XLR
I like the way it fits neatly into a round hole. Round holes are "thumbs-friendly" to achieve.
Make and model? Or is that too much to ask?
I like the way it fits neatly into a round hole. Round holes are "thumbs-friendly" to achieve.
Make and model? Or is that too much to ask?
Its a Neutrik DLX series which are pretty standard
Black/Gold - NC3MD-LX-B
Nickel/Silver - NC3MD-LX
Black/Gold - NC3MD-LX-B
Nickel/Silver - NC3MD-LX