Phase Linear/White Oak driver boards

laatsch55 said:
Here's how well Joe understands this. This post was in answer to why the P{L's would latch up to a rail....


Description of latch up tendency in Phase Linear Amplifiers
......
Click to expand...

Does the diode fix mentioned apply to the stock boards, or only Joe's boards? I get the shutdown thumps out of this 700-II. Just thinking if this is something simple I can do before it goes back home, I'll do it. Its not mine, but I really don't want to see it again and I don't want my friend to have problems with it.
 
gadget73 said:
Does the diode fix mentioned apply to the stock boards, or only Joe's boards? I get the shutdown thumps out of this 700-II. Just thinking if this is something simple I can do before it goes back home, I'll do it. Its not mine, but I really don't want to see it again and I don't want my friend to have problems with it.
Click to expand...

The back to back diodes will fix the initial power up latching issue but it won't fix the turn off thump. This modification applies to the original controller board and IIRC was used for the White Oak controller boards too. There are multiple versions of controller boards that Phase Linear used - so Lee or someone else would need to verify if the mod would work for the board in question. If you want to fix the turn off thump and improve the sonic characteristics a controller board replacement from White Oak would be in your future.

There are a number of modifications / improvements that will make one of these amps sing - I've had a PL 400 that I bought new in '75 and I've done a couple of improvements that have made a significant improvement in the most important area - how it sounds.
 
Joe cured the turn off/on thump by treating how Q5 discharges the current of the PS caps to ground. The stock boards can not be modded to do that. IF you do the diode fix, put a 470uf/50 volt cap in place of the 100uf. The low frequency response is greatly enhanced...
 
You can minimize the thump to something very hard to hear by closely matching Q1,Q2 with TIS 97 Fairchilds, that is usually 90% of the problem..
 
There is nothing like a Full Comp WOPL. A lot of people end up selling their other amps after hearing one. Just because an amp is 40+ years old does not mean it can't be made better and Joe did that in spades. Eye wince? Try a snare shot at half volume. You will blink like your face is right next to the snare live, my wife has been startled numerous time by the transient impacts. She has asked several times "how are you not hurting those speakers"

They need to be heard to be appreciated. Regarding rebuilding the old boards... why bother? They sound nothing like the new FC WOPL's and in a head to head test between a freshly built to stock spec PL vs a WOPL will disappoint you and leave you shaking your head why you just did not bite the bullet and do the upgrades

I sold a Mark Levinson 333, sold all my old McIntosh tube and SS gear and happily will never look back. Dynamics, transparency, wide soundstage, clean power with tons of headroom and reliability, it's all there just waiting for you. Because a WOPL is so quiet, you need a damn good preamp to match it
 
Most of my reason for fooling with the old boards is because its not mine. My friend's budget won't go for upgrades, and his speakers and preamp would never make use of it anyway. He's using crappy PA speakers that are rated to handle lots of power and a PL 4000 preamp. As far as he's concerned, it has to be loud and not emit smoke. If it will do that, it passes. If tacking in $0.25 worth of diodes might prevent the speakers from going nova, I'm all for that.

I'll look into adding the diodes to prevent the startup latch problem. I muchly appreciate the info.
 
gadget73 said:
Most of my reason for fooling with the old boards is because its not mine. My friend's budget won't go for upgrades, and his speakers and preamp would never make use of it anyway. He's using crappy PA speakers that are rated to handle lots of power and a PL 4000 preamp. As far as he's concerned, it has to be loud and not emit smoke. If it will do that, it passes. If tacking in $0.25 worth of diodes might prevent the speakers from going nova, I'm all for that.

I'll look into adding the diodes to prevent the startup latch problem. I muchly appreciate the info.
Click to expand...

While you're in there adding diodes I would replace the 100uF cap with a 470uF cap as Lee suggested. This simple modification will improve the lower end.
 
Northwinds said:
There is nothing like a Full Comp WOPL. A lot of people end up selling their other amps after hearing one. Just because an amp is 40+ years old does not mean it can't be made better and Joe did that in spades. Eye wince? Try a snare shot at half volume. You will blink like your face is right next to the snare live, my wife has been startled numerous time by the transient impacts. She has asked several times "how are you not hurting those speakers"

They need to be heard to be appreciated. Regarding rebuilding the old boards... why bother? They sound nothing like the new FC WOPL's and in a head to head test between a freshly built to stock spec PL vs a WOPL will disappoint you and leave you shaking your head why you just did not bite the bullet and do the upgrades

I sold a Mark Levinson 333, sold all my old McIntosh tube and SS gear and happily will never look back. Dynamics, transparency, wide soundstage, clean power with tons of headroom and reliability, it's all there just waiting for you. Because a WOPL is so quiet, you need a damn good preamp to match it
Click to expand...

Thank you. Sounds like my kind of amp. I think I'm sold. :yes:
 
laatsch55 said:
Joe cured the turn off/on thump by treating how Q5 discharges the current of the PS caps to ground. The stock boards can not be modded to do that. IF you do the diode fix, put a 470uf/50 volt cap in place of the 100uf. The low frequency response is greatly enhanced...
Click to expand...

Looks like my parts numbering is very different. The driver board in this one is a PL36. Also, looking around the White Oak site, I don't see the PL36 board offered, only the PL14 board that I guess the older models used. Does the diode fix apply on the PL36 too? This is a Series II that I'm fooling with.
 
No, rhe latch-up tendency was on the 14 and 020 board. The White Oak board can and does replace the PL36 board. The early op-amps on that board do not do the platform justice...
 
laatsch55 said:
No, rhe latch-up tendency was on the 14 and 020 board. The White Oak board can and does replace the PL36 board. The early op-amps on that board do not do the platform justice...
Click to expand...

well, if its not inclined to latch up and blow the speakers, I'll leave it for now.
 
If doing loud PA work , it can and will blow XPL-909 outputs. DC protect boards are a good idea. Good way to get rid of crappy PA speakers though....couple seconds....
 
laatsch55 said:
If doing loud PA work , it can and will blow XPL-909 outputs. DC protect boards are a good idea. Good way to get rid of crappy PA speakers though....couple seconds....
Click to expand...

It already popped one of the XPL909's, though that was more from the wires coming out of the speaker an shorting than the speaker itself. Its got the On-Semi MJ-whatever outputs now. Thats why its here in the first place. Its not doing loud PA work so much as driving the people in the house nuts from really loud music in the garage.
 
I wouldn't trade my WOPL 1000(white oak upgraded 700b fc) for nothin. Lee did a amazing job on the restore and it's pushing 513wpc into 8ohm. The cleanest amp I've ever heard. The bass response is crazy good. And headroom all day .. It sounds great using my fully restored p3600 pre and a peachtree dacit-x and a technics sp-15. I've heard all version since stock. And the fc is the way to go. It beats out the 7k Cary and 5k modwright amps I have heard . Best upgrade I've ever had done ... And lee and joe and nav are the shit... You guys rock
 
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