Pearl 3 Burning Amp 2023

[6L6]

Mark sent him that. They are both residents of the Bay Area.

I’m very interested in Mark’s UDP3, I’ll try it once the initial testing in the various chassis is completed.

 

[pfarrell]

I have PCBs for Marks PSU as well, PM—shipping and pack cost only—Shipping from northish east US.

 

[Mark Johnson]

The timeline will help you decide: which happened first, the Burning Amp Festival or the UDP3 circuit boards?

_

 

[cubicincher]

Good evening PEARL 3-builders,

today I started my boards the first time. It was a crazy day...

First, I adjusted the outputvoltages of my PSU to +-15 V DC - no problem.

Put two OPA2134 into the boards.

Switched on - no LED lighting - reversed. Repaired...

Switched on again - uuuh, LED on.

Some measurements (over the resistors):

voltages over pcb 1 pcb 2

R4 (10Ohm) 0,048V 0,048V
R5 0,048V 0,048V
R6 0,048V 0,048V
R7 0,048V 0,049V so, all JFets are running at 4.8 to 4.9 mA (ONSEMI 2SK2394)

R27 (220Ohm) 2,36V 2,37V circa 10 mA out of the J112- pretty high. Wayne suggests 2-5mA. I think I have to increasee R27

offset at output below 1mV 1mV was slightly fluctuating, but in both channels below 1mV!

R23 (22 Ohm) 0,34 V 0,338V
R24 (22 Ohm) 0,34 V 0,338V so, bias of the output BJTs is anywhere around 15,36 to 15,45 mA.

Enough for today. I am done.
Good night!
Dirk 😴

 

[cubicincher]

This was the highest DC-offset at the output: -0,78 mV!

 

[6L6]

Amazing work! Well done!

 

[jackinnj]

Yes for the 220uF electrolytics, 50V is okay. I wish the ESR wasn't so big and I wish the ripple current wasn't so small, those details will reduce its effectiveness a little bit. But the unit will work correctly and provide clean power to the umbilical cable, while you wait for the low ESR and high ripple current parts to arrive. Then when you swap in the correct parts the unit will work (a little) better and the cable will get (a little) cleaner power. Like when you switch your high performance sports car from 89 octane petrol to 93 octane.

I put aviation gas into the generator and my leaf blower.

For the noise test I illustrated a few days ago I used the Silmic 220uF 50V (perhaps I should have noted that.)

 

[6L6]

I put aviation gas into the generator and my leaf blower.

AvGas is wonderfully stable. Can sit for years with little or no degradation. Modern auto fuel? Starts to go old in about 3 months. Particularly with how much Ethanol is blended into it here in the US…

 

[jackinnj]

Here's an ESR chart -- I don't have Wurth to include. Silmic 50V looks good

 

[Mark Johnson]

Panasonic FR and FM are among the very best electrolytic capacitor possibilities for the Perl 3 umbilical cable driver, if you can find them and afford them. FC not so much. Nichicon UHW are also top tier, but the UHW product line doesn't include a 220uF / 35V model.

 

[pfarrell]

Game time...

 

[Mark Johnson]

That black PCB with black heatsinks looks badazsszz . Great job!

 

[Abx74]

Hi everybody,
how can we calculate gain with different value of R9 and R22 ?

Damien

 

[rhthatcher]

This is from a draft of a build guide doc.

Jumper Out: Gain = 20 X Log (R9/10) +24 dB
Jumper In: Gain = 20 X Log ((R9 || R22)/10) +24 dB

 

[Abx74]

Great !
Thanks !👍

 

[Mark Johnson]

If you're interested in calculating gain to the balanced output ("CN1"), Wayne put a note on his schematic explaining how. Draw a line on the schematic between C9 and C16; that line intersects the explanation.

 

[rhthatcher]

Getting back to it. Little more wiring and solder to go

 

[rhthatcher]

Wiring done. Test time. Then music time

 

[rhthatcher]

Build is done!

 

[mhenschel]

Too bad these are destined to be apart (by 6 feet)
They look nice together!
(Those are tight twists)