PL14_20 Revision D Control Board Assembly now available

Gepetto

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#1
After some extensive beta testing (thanks Lee) on this new board version, we are pleased to say that it is now generally available. It continues to build on the White Oak Audio commitment to continuous quality improvement in the design and components used on the board assembly. Below are the release notes that go along with this board assembly. Pricing will be slightly higher than the predecessor board due to increases in costs associated with the new components specified in the improvement areas.

Release notes for PL14_PL20 RevD PCB

  1. Move silkscreen legend for R23R that was clashing with Q10R silkscreen.
  2. Eliminate unused option resistors and diodes to free up space for additional changes. Components removed from RevC are: R70L,R70R, R71L, R71R, R72L, R72R, R78L, R78R, R79L, R79R, D3L, D14L, D14R (note some of these reference designators are reused in different applications on the RevD PCB, R70L, R70R, R71L, R71R)
  3. Change lead spacing for C1L, C1R, C7L, C7R, C10L, C10R to more appropriately match the 0.234†spacing on mica CM05/CD15 type capacitors.
  4. Enlarge pads on all mica and film caps to improve board durability.
  5. Move components farther away from Q6 bias transistor connections to allow installation of the Phoenix Contact connector on the back side without hitting other pads.
  6. Change Q3L and Q3R to MPSA92 and make circuit symmetrical with Q4L and Q4R for better behavior during turn on and off as well as bandwidth improvement. Provision for original 2N5087 circuit is retained with a resistor population option on the board. Added new heatsink requirement for Q3 same as the one used on Q4 in previous versions
  7. Provide connection from Q3L/R collector through R78L/R to the B- rail to improve the symmetric current drain on the B+/B- rails. This improves power supply load symmetry and ensures that both supplies power on and decay at very similar rates, improving turn on and off control.
  8. Increase the value of C8L/R and C9L/R to improve stability of the bias voltage during active operation.
  9. Increase the value of C20L/R to better offset the ESR of C6 and provide more consistent and flat response at higher frequencies.
  10. Change vertical mounting hole spacing from 4.0625†to 4.00†to match actual PL chassis mounting hole spacing.
  11. Add new lower edge I/O pad to allow use of the RevD board to replace the original PL36 board version in the fully complementary versions of the PL400/PL700 Series 2 amplifier (the last PL36 board artwork added these extra pins). Resistor options and wiring options now enable the RevD board to be used in this application.
  12. Increased space around C23L and C23R to allow the use of the same capacitor as C3L and C3R in all locations.
  13. Added C21L and C21R as lead network across R15L and R15R in the global feedback path.
  14. Added C22L and C22R as Miller capacitors across the collector-base junction of Q5 to tailor/optimize the gain bandwidth and slew rate of Q5.
  15. Added R78L, 79L, R78R and R79R in series with the collector of Q7L and Q7R respectively to provision for RevD board use in the complementary configuration.
  16. Create new library pad stack for R20L and R20R to properly show the action of the trimmer with respect to CW rotation. The symbol showed CCW rotation on prior revisions.
  17. Move connection pads 16L, 17L, 16R and 17R out from underneath C11L, C11R, R77L and R77R respectively to allow simultaneous access to both the static and dynamic bootstrap boost features.
  18. Move lower edge connection pad silkscreen numbering upward to increase visibility when Phoenix Contact connectors are installed.
  19. Overall, improved upon the already high quality of the RevC board in the creation of the RevD artwork by making small moves of components to improve assembly clearances, shorten and widen traces, increase trace clearances and improve signal integrity to maximize audio quality.

Release Notes
Revision F White Oak Audio Design Proprietary Information
 

laatsch55

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Some pics of the board assembly, I didn't do this one in my normal 3 hours. This one took 5 hours, mainly I triple checked every component before and after soldering. Beta matched everything I could, and in general didn't wannt any problems on the rollout version...
 

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laatsch55

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My personal preference for this version was MPSA18 for Q1,2-- MPSA93 FOR q3,4. nICNICON mUSE FOR C6,C11,C15,C16 and Elna Silmic II's for C3, and C23.

It started out being in a hanger queen and that decision cost us a few days, as there were some chassis problems sooooo.................ENTER THE PIG!!!!!!
Yep the Pig volunteered, should have heard im, just pitiful. So the pig got the new board, and Joe fired up the Spice program and started calling down component changes and swaps. I kept up though by God, the worlds greatest solder sucker and the soldering station were wound up, the AP was going non-stop. At the end of that night Joe counted 54 e-mails of back and forth chat.
There was some last minute flurry of chassis component changes and I didn't have enough stuff on hand to do both channels and when I get my Mouser order I will finish the optimization and post the test results.
Listening to the Pig now, mighty fine even in Quiasi mode, Gentlemen you are in for a treat !!!!!
 

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NavLinear

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This is real exciting guys - nice job on the board assembly Lee.

I'm going to go out on a limb here and guess that the design changes will have a sonic impact - can't wait to hear what you think about the delta between RevC and RevD.
 

laatsch55

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After a week with it Dennis.......... not much until that last minute flurry of chassis changes. I put on a CD I am VERY familiar with---"Tales of the Inexpressible" and there are things I haven't heard before. The bass seems even TIGHTER, the mids are damn sure cleaner and I'll be damned if there doesnt appear to be a better soundstage. I'm thinkin it'll get better when I have the new chassis components for the other side.
Guess we should detail those changes--WARNING----these changes have not been through the "Laatsch" amp test yet. It involves kicking the bias to .510 VOLTS-yep 510MV, and at the same time changing R38, R39 to 15 ohms, NOT TEN, FIFTEEN, make those a 1% MO in a 1 watt package. We are also in the middle of reworking the zoebel values but are waiting on a Mouser order on those. AND as soon as that gets proved up we'll post those results.

The temperatures, both idling and running are only 3-5% greater in this configuration near as I can measure. The effects of long term hi wattage Mach 8 are not known YET. If you make these changes, be cool for awhile till I shake it down proper, or you can shake it down , or Sutton can shake it down or.....
 

NavLinear

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Damn Joe and Lee - it seems you guys are taking some tremendous strides here with more improvements to the Phase Linear amplifers. So when do you expect your Mouser order? Can't wait!!!

The Zoebel Network has been an issue and getting it dialed in will help to get the most out of these amps. I've always wondered how the load interaction influnces the filter component selection. Too many variables - but I'm glad you guys are taking this on!
 

Gepetto

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We will try to keep it coming guys. News breaks on this forum before anywhere else. :)

(maybe that will draw in the 250th member)
 

NavLinear

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We will try to keep it coming guys. News breaks on this forum before anywhere else. :)

(maybe that will draw in the 250th member)
I was kicking around the idea of registering again as Pinocchio. :laughing9:
 
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