Got my boards and parts today from the man himself, I'm really wanting to do a single enclosure, what box would work? Heat sinks are 1.5" tall.
I pulled a 25va from another project off the shelf. It’s not going to fit in the 1U. Too tall.
So go with 15va if using the chassis that will be available from modushop. The 15va fits on the PCB that will ship with the kit. Smaller is a different footprint, so it won’t fit on the PCB.
If you build in a different chassis or with a different power supply - pick whatever transformer you like.
So go with 15va if using the chassis that will be available from modushop. The 15va fits on the PCB that will ship with the kit. Smaller is a different footprint, so it won’t fit on the PCB.
If you build in a different chassis or with a different power supply - pick whatever transformer you like.
it's more important which xformer Pearl 3 is liking more
it's more important which xformer Pearl 3 is liking more
With the on PCB 7815 and 7915 the Pearl 3 does not care very much at all.
For those seeking the optimal transformer arrangement for building Pearl 3 -- spend 10 minutes reading and thinking about post #90 of this thread. It was written in right at the midpoint of the UDP3 project.
But your question's tone was borderline trolling... hence why you got all the flak from multiple members.
Anyway, here's a serious answer.
The Pearl 3 boards have LM7815/7915 fixed regulators to make a bipolar +15/GND/-15V DC power supply.
They need at least 2 volts more than their output on the input. 3 is better.
That makes the raw PSU voltage needed somewhere around 18V.
A 15VAC transformer will be enough as when you rectify AC to DC, you gain 40%, but lose two diode drops.
15 x 1.4 = 21v.
21V - 0.7 twice = about 19.6VDC
Good, that's enough. Could you use a transformer with more voltage? Yes. Watch your capacitor voltage rating, and you'll make more heat in the regulators, but the current is pretty low, so that's not all that much of an issue.
Now as for transformer size, which means current, little transformers, to put it politely, suck. They have very poor load regulation, and like to make more voltage than they are supposed to when lightly loaded. They also heat up and make too little voltage when heavily loaded. Could you use 6VA? Again, yes, that's enough current, as the total draw of two boards is about 120mA and the 6VA can supply 200mA, but do you really want that little overhead? It makes everything work harder as the small transformer will vary more with the load than a larger one.
The 15VA is large enough to be loafing, but not so large that it's going to spit buckets of excess magnetic noise where it's not wanted.
It also fits the nifty PCB that's included.
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@6L6
[sigh]
The tone you thought you you perceived was not in any way intended. Trolling is a pretty harsh characterization. I apologize in any event (and try to figure out how you could construe it that way).
I'm just trying to understand what many here probably take for granted. We all start somewhere.
And I was right about the regulation, no?
[sigh]
The tone you thought you you perceived was not in any way intended. Trolling is a pretty harsh characterization. I apologize in any event (and try to figure out how you could construe it that way).
I'm just trying to understand what many here probably take for granted. We all start somewhere.
And I was right about the regulation, no?
Listening test with the OPA2132P in place of the OPA1642:
Same great detail, but perhaps more, because the high frequencies seem to be a little more pronounced than the 1642s, but more balanced. Still very quiet.
I conducted fresh distortion measurements, but this time using REW and Cosmos APU to ADC, and with intervening iRIAA, which definitely flattened the harmonics and frequency response, as far as I can tell.
Tried to save image files of those tests, but the resolution from REW was terrible, so will try again tomorrow.
Same great detail, but perhaps more, because the high frequencies seem to be a little more pronounced than the 1642s, but more balanced. Still very quiet.
I conducted fresh distortion measurements, but this time using REW and Cosmos APU to ADC, and with intervening iRIAA, which definitely flattened the harmonics and frequency response, as far as I can tell.
Tried to save image files of those tests, but the resolution from REW was terrible, so will try again tomorrow.
I think that's what Señor Macho needs so it will stop smoking...
What do you think @Zen Mod ? Do we need one or two of these babies? I can imagine what the Babysitter for this thing must look like...
Are those the tanks for the Plasmatronic speakers?
@Mark Johnson
I remember that post. Good one. It started me thinking of using a pre-regulator on the external PSU to a achieve the voltage the Pearl would like to see to run cool.
Interestingly, when I googled "connect transformers in series" the first explanation investigated connected secondaries together. You're suggesting connecting transformers sequentially, no?
Wayne's suggestion of the isolation transformer from Antek was also helpful.
I remember that post. Good one. It started me thinking of using a pre-regulator on the external PSU to a achieve the voltage the Pearl would like to see to run cool.
Interestingly, when I googled "connect transformers in series" the first explanation investigated connected secondaries together. You're suggesting connecting transformers sequentially, no?
Wayne's suggestion of the isolation transformer from Antek was also helpful.
My prototype is working perfectly, it validates my PCB layout. I have the same volt readings as the original, as posted by 6L6. No DC offset at the output.
I'm using 2SK209GR JFET, and also confirmed that my pcb is compatible with the smd version or TO92 of the ZTX851.
Now time to assemble the UDP3 supply...
I'm using 2SK209GR JFET, and also confirmed that my pcb is compatible with the smd version or TO92 of the ZTX851.
Now time to assemble the UDP3 supply...
Attachments
The pre-regulator idea is being used in a Wyn Palmer designed, DIY phono preamp, still being developed. Supplied by a wall wart, it is combination of series LT317A to parallel 78M15 regs (and complementary negative rail parts). The will all be on the main board, since it uses a wall wart.
