Dual-500 king of the Castle

grapplesaw

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#1
I will take some time over the next while to bring the Phase Liear to the forefront of the line up. I have the privilege to own a few. One is the second of the line. I have taken the time to fully understand these beasts and tweaked them to what I feel is now the best of the best. I am not finished my quest as I have plane to improve them further.

There seams to be mistery and misnomers abound when ever people talk about this amp

I am not surprised by that it’s partially due to it being a rare bird. Not may were made, less than two thousand units, over about two years of production. It was only sold in a quassi complimentary state. Ev has said one may have been made as full Complimentary.

so to start up here is a post I found on the internet:

Reviewed Feb 19th, 2019 by Andy Liddiard

Awesome beast amps. I used to fix the heavily-modified D500's as used for the Pink Floyd Wall shows; racked and flightcased, two to a rack, power transformers relocated to the bottom of the rack and hooked in by 8-pin plugs to the amps, retapped to give + / - 128v instead of 120v on the rails.

These would produce 1kW/chan into 2 ohms nominal. The output stages had to be biased bang on for maximum sweetness, but this could (and often did) cause a couple of blown output transistors - if the biasing had been set when cold and it drifted up when hot, pop. Apart from the usual misuse from the engineer du jour.

Magic sound, though. Power, dynamics, clarity and an output damping factor that had the loudspeakers by the balls, I never heard anything back then that could remotely come close. MOSFETS sound horrible to me to this day (well, once they've got hot and pinchy), BJT just owns them and the Dual 500 does it in spades. They were my babies for a couple of years and I still cherish the memories.
net to start us off
 

grapplesaw

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#2
I will not rewrite the overview of the Dual-500

this is from a good reference site
http://www.phaselinearhistory.stereomanuals.com/d500amp.htm




The D-500 was Phase Linear's most powerful and expensive amplifier. Its designation came from its rated output of 505 watts per channel. It was introduced in 1978 as the Dual 500 Series Two, even though there had been no "Series One", in order to coincide with the other Series Two components in the Phase Linear line.
Bob Carver had not completed the design of this amp when he left Phase Linear in 1977 to launch Carver Corporation. The design was finalized by Phase Linear staff engineers in the closing months of 1977.The design differed considerably from the 400 and 700. The front panel layout was nearly identical to the 700 Series Two, but the comparison ends there.



The transformers (one for power and one for the AC relay) were mounted inside the metal enclosure. The heat sinks were laid out horizontally, with speaker and other connections above the heat sink. A cooling fan was used to draw heat away from the heat sinks. Unless the amp was driven hard, the fan usually did not have to run. List price was $1395.95 and tipped the scales at 70 pounds.
Later designated the D-500 due to a name dispute with the turntable manufacturer Dual, Phase Linear discontinued this amp after the 1980 model year when the list price reached a breath-taking $1600. It was magnificent excess, and marked the zenith of Phase Linear amplifier design.
Left and right channel input could be varied with the input selector knob. The antiquated VU: meters were not carried over to the Series Two amplifiers. In their place were new variable LED meters to more accurately reflect the amplifier's output. as hown in this closeup. The Series Two amps were certainly more attractive than the first generation and the quality of the design is evident. The Series Two amps do not look dated even today.

.​
This closeup of the front panel shows this to be one of the earlier models because it still has the Dual 500 designation. After the name dispute with Dual turntables, the designation on the front would simply read D-500.
 

grapplesaw

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#4
So the good and bad of the dual -500 which I refer as 500 going forward

some really good things
The front meter board has added features. There is embedded on the single board (seen in photo)
DCP control
-High frequency feedback led indicators (part of the -High frequency safety control of feed back cancellation circuit embedded on the factory control board) more on this one later
-High temp relay control and Led indicator
-High - Low rail voltage control.
-On- off relay switch and controls


These replays are located in the bowls of the unit and are high current capacity relays for (seen attached photos)
-Power on off
-High low rail
-Speaker output (DCP and timed output startup like Don’s board) A7BA898F-7858-4DF7-AD41-CE65042512D7.jpeg
 

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grapplesaw

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#5
And now the Bad

as with anything there are some things not useful to all of us.

-high Low rail switching will auto protect the amp from over load due to low ohm settings and excessive output ( I have on occasion removed this feature) This feature repeat prevented the MJ15024 outputs from failing. As the amp ran at high rail voltage it was easy to overload/ overheat the outputs. I saw at a Lead Zeppelin show some 500’s which had attached to the back of the Amps a wood box-chute which was loaded with dry ice. Obviously they bypassed the feature as well. More on these outputs in modifying the amp
-high frequency attenuated the volume to prevent common mode conductance of the outputs (Clipping guys)
 
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grapplesaw

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#8
So to bring life back to this thread I have a new build started this weekend. Got to work on it right after I tore apart my gas leaf blower to see what I f,?@#d on it. total right off

I hope to entice a few good people to want one of these units. I have owned one for about 30 years it’s still in its original format waiting for its day to be upgraded. As you may know I got a couple more from Perry a few years back. One of which I added a WO control board in a full complimentary setup. I have used it everyday that I am home since it was finished. The other was serial 1002 which I rebuilt using the original control board with complete rework.

the one on the bench came from eBay. It has a story but that’s for an other day.
 
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grapplesaw

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#9
The thing I like about these things is the sear might in all aspect..

as you see it’s a whole different construction than the 700’s. It’s also got a very busy inside.

on this unit I will attempt to further declutter the beast. so Here we go


the back plain is started with all new components

it got to be clean to sound good right?

D16BCB8D-38E8-4598-97DC-EB4417EF2170.jpeg 172B38CF-D304-4E65-AAEE-5998180DBFA6.jpeg 04A7FCA0-95B0-4933-82C7-22EF55B9AECE.jpeg
 

grapplesaw

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#10
I got some heaven TO-3 bases for this build. They take a #6-32 screw so useable to Allen cap screws. I put 1/8” long nylon bushings in the bolt holes as extra safety against a screw shifting and causing a ground.

i have started the neg rail layout. I am using some 5 watt Panasonic emitter resistors. Added 1 ohm subber resistors on the base connection to each output.

04A2A754-640A-425E-BC2F-9FEFB206FB81.jpeg 86FBEABE-6792-4AFD-98AA-3D0A06E39ED4.jpeg 25BB450C-A98D-4930-8E54-7BF6091FA9A0.jpeg
 

grapplesaw

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#13
Got a terminal strip setup in the middle for added some fuse holds for the control board supply. I have decided to got with the G control board. The E board is a better fit but do to the 700 series II I just did having such low noise floor thought i had to at least one with the G

you will notice there are two high heat switches with one at either end with a #20 wire attaching one to the other. This setup operates a relay and dose not pass any main ac power over the back plain. There is also fan on switch located in the middle under the new term setup

50990245-B2CC-4CCB-BD89-18534C35E4E9.jpeg
 

WOPL Sniffer

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#20
You said
“They are rather rare so getting some guys to move to a 500 is nearly impossible”
I said “watch me “ referring to the fact I will get people to move to 500’s
then I said something childish

If we can't find 500's, how can we switch??? You only have 1 (or 2)
 
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