Phase Linear D-500 DC Protect (and other questions)

[jshupe]

I have two Phase Linear D-500 amps that have been sitting in storage for the last decade or so. I'm going to be pulling them out, cleaning them up, recapping them, and hopefully putting them back into service.

I've read online about the "flame linear" issue with 400 and 700 amps since they don't have DC protect and can inadvertently send 70+V DC directly to the speakers. I can't find any information about this on the D-500s, except for one post where someone mentions that they do have DC protection on the outputs.

Should I be looking at adding DC protect to this AMP? Even if it has it, does it work adequately enough to trust? I bought a few UPC1237 ICs to experiment with but realize now that I may not need them.

I'm going to be using one amp to drive my mains (2x Pi 4 w/ B&C DE250 and JBL 2226H) and the other to drive my subs (2x Pi 3 w/ Eminence LAB12). I have two PL-4000 II preamps, but don't plan on using them. Instead, I plan to use a Yamaha RX-A830 w/ pre-outs because this is going to double as a home theater.

A couple other questions:

• Any suggestions for caps since I'm recapping?
• I know a lot of people where recommend White Oak, but they don't seem to have anything for the D-500s. Does anyone know if the PL14_20 is used in the D-500? If so, is it worth replacing?

 

[laatsch55]

I believe the D-500's had the PL-36 driver board. They had DC protect. Pop the hood and post some pics, I believe the WO board could drive the d-500 but I'll leave that question for Joe.

 

[Northwinds]

Welcome aboard! I'd love to stumble across a D-500!

 

[jshupe]

I believe the D-500's had the PL-36 driver board. They had DC protect. Pop the hood and post some pics

I will as soon as I get them! They're at my dad's house still - about five hours away. I might make the trek this week to get them. He's the original owner from when he bought them in 1982, I believe.

 

[laatsch55]

And welcome to Phoenix, you've come to the right place. We've been waiting for someone with a D-500 to see what could be done with them...

 

[jshupe]

And welcome to Phoenix, you've come to the right place. We've been waiting for someone with a D-500 to see what could be done with them...

I've read they're quite rare.

If they do have the PL-36 driver boards in them, it seems like the White Oak RevD will work according to http://forums.phxaudiotape.com/show...vision-D-Control-Board-Assembly-now-available

So was the issue on the 400/700's that they didn't have DC protect, or that it was faulty?

 

[laatsch55]

Some 700 Ser II's with the PL36 dtiver board have been converted with excellent results. like I said , there were none around to play with. The D-500 is not rare, but darn sure not as many of those were built as say like the 700B.

 

[jshupe]

Welcome aboard! I'd love to stumble across a D-500!

Thanks! My dad was generous enough to give me two of them, along with two PL-4000 II preamps (one non-working) and a Sansui XR-Q7 TT. I just have to make a ten hour round trip to pick them up.

 

[laatsch55]

That's a ten hour trip I would gladly make, save a few hours to visit the old man too, I bet he misses his son....

 

[laatsch55]

As you can see jshupe we pull no punches around here, hope you can deal with that, we're a pretty real bunch, but loyal and fair as hell..

 

[jshupe]

That's a ten hour trip I would gladly make, save a few hours to visit the old man too, I bet he misses his son....

My wife and I are talking about driving up and spending a few days there this week. We head up there at least 3-4 times a year and stay a few nights each time.

 

[NavLinear]

Welcome JS to Phoenix. Those D-500s will be cool to see. Does anyone know approximately how many were made?

The 400s and 700s did not have DC protection on the outputs - the recommendation was to fuse the positive output but speaker coils would generally go before the fuse.

 

[laatsch55]

Your a good son.......

 

[jshupe]

Going to be heading home with these guys tomorrow.

 

[laatsch55]

That's a boat load of power there lad...

 

[laatsch55]

What neck of woods are you in?

 

[jshupe]

What neck of woods are you in?

I live in Austin, Texas. Visiting my parents in the NE TX today.

 

[laatsch55]

I was born in Harlingen, yep a fella can drive all day and not get outta Texas...

 

[jshupe]

I believe the D-500's had the PL-36 driver board. They had DC protect. Pop the hood and post some pics, I believe the WO board could drive the d-500 but I'll leave that question for Joe.

I emailed WOA this morning asking about it, but haven't heard back yet. If anybody has any information about this, please let me know. We ended up staying another day so I haven't been able to test the amps or pull any parts for better photos yet.

From what I've read about WOA, they significantly reduce noise and improve response. A few people have commented on increased power output, but I don't see how the WOA would accomplish this. Can you explain if that is true?

I plan on replacing the power caps on each amp with higher capacity units, installing WOA boards, and potentially replacing -all- output transistors if any of them have issues. Are there any other things that I should consider doing assuming that the amps work fine from the start?

Edit: Also, I have two PL-4000 II pre-amps I'm not going to use. I may be putting them on Ebay or something to recoup some of the D-500 rebuild costs. Any idea if there is even demand for them?

 

[laatsch55]

How are your tech skills? You feel comfortable inside that monster? If you do , Joe with White Oak Audio posts here as Gepetto. He's seen your thread. He does not post immediately, probably because he's evaluating your question of converting the D-500's to a White Oak driver board.

On the subject of White Oak conversions of 400's and 700's I can say unequivicolly that a White Oaked amp is better in every regard than the factory version, quieter, better crosstalk, signal to noise ratio, better response(way better), better distortion specs, and yes more power--due to the slight gain in Joe's design, and better output transistors than used back in the day. I've had some 700's test in the 500-525 watt per channel range but that was mainly due to a hot transformer design. And you are correct in questioning that as power is usually a result of rail voltage , but a more subltle factor is how you use that power. When a PL is White Oaked (here we call em WOPL"s for White Oaked Phase Linears) it will stand toe to toe with almost anything made today or ever for pure, clean audio power. I've done it, heard it and have heard the testaments of others in the before and after catagories. I guess the proof is in the fact that after all the conversions I've done I've NEVER had someone say BS and that they wanted their amp UNCONVERTED. Joe's choice of components is the best he can get and the board design and manufacture takes a back seat to nothing, in Joe's day job he is a very well respected world class electrical engineer, and thermal, and power, and mechanical.... he does not do anything halfway nor does he rest on his laurels, he's always striving for better. And yes I sing Joe's praises because you won't hear it from him, he's just that kinda guy. I feel extremely lucky that Joe's hobby is audio and all that expertise is at our disposal...
The 4000Ser II's should fare better that the Ser I's for damn sure. The earlier model is not known for reliability..