Phase linear upgrades

Jackson1960

New Around These Parts
Joined
Jun 19, 2025
Messages
3
#1
Hello,
New on this forum but love vintage audio gear and at 65 yrs old I still love the same music as I did when I was 15 and went to my first concert to see Bob Seger open for Queen.
I recently acquired 9 different Phase Linear amps and pre amps with most needing cleaned and some repairs . I purchased them from a guy i met a year ago when I bought 3 reel to reel tape decks from him on Facebook. He had these phase linear pcs and I had never heard of them but ask him if he wanted to sell them and he told me they were his father's and his father had health problems and wanted to keep them for now . So I gave him my number and ask him to call me if he changed his mind. He called me a few weeks back and said his father had passed and wanted to know if I was still interested in the amps and I purchased all 9 of them plus a dynaco400 for 1500 dollars. The amps are a Dual500 2 - 700b a 700 and a 400
I now have the dual 500 and both 700b units working but no new components and they sound amazing to me . I have a sansui 9700 and a Toshiba 7150 and the phase linears even in their poor state put them to shame.
My question is which amp would be the best to do all the white oak mods to and would have the most benefit and biggest difference in sound quality although I dont see how any of them can sound any better than they already do. But money is a factor so I want to pick one for now and hopefully can do them all at some point. I just don't know which one to do first. I am planning on the circut board upgrades the back plane, the light kits , new capacitors etc...
Thanks ,
Jack
 

mr_rye89

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Aug 12, 2015
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Land of Entrapment
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Lost in the Ozone Again
#2
I'd probably keep and convert a few of them (probably the 700s) sell the rest as "cores" for WOPL conversions. Some of us here bi and tri amp our speakers so 2-3 amps is good.

Dual 500s can be WOPL'd but you have to do the back planes/output transistor wiring yourself.
 

Jackson1960

New Around These Parts
Joined
Jun 19, 2025
Messages
3
#3
Seems like the 700b might be the one to do first but I will probly keep all of them for now , I have the first series 700 torn apart and plan on getting new output transisters and new run capacitors this week , I have the dual 500 and both 700b amps working and am hoping to get the 400 and the 700 both up and running at the least . I know there are many other things to check first before trying to fire them up so I will take it slow . I am surprised at the amount of info that is out there for these amps . From most of the posts I have read people seem to either love them or hate them .
 

mlucitt

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Jun 24, 2011
Messages
3,512
Location
Jacksonville, FL
#6
If I was you... I would upgrade the PL400 first. It is a much simpler amplifier and the upgrade is less costly. You will learn so much and this learning will assist you if you decide to upgrade the PL700 amplifier. The sound of those upgraded PL400 amplifiers is magical. You will not regret every penny and hour spent on the full upgrade. Many folks here on the Forum can assist you, so don't be intimidated at first.
 
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