Phase Linear 2000 PREAMPLIFIER SUPER UPGRADE AND REPAIR

[GeorgeP]

Well... I purchased one off E-BAY. The guy said it was in perfect working order for the $300 bucks. NOT! No Big deal... very clean and not butchered at all!
So... Rear Channels don't work, Ambiance control not working, Volume pot very scratchy and worn out, all switches noisy / intermittent.
I Initially see the ambience circuit op amps not working at all. I temporarily installed a dual LM1458 just get life into it. Easy... 3 pins match, then added the additional connections. Pic attached. Then I find the Ambiance pot totally open, not 5K Ohms. I temporarily wired in a 5K SMT pot and the circuit works. General purpose op-amp, but response is flat to over 20KHz.
OK. Now ordered the Chip adaptors for all the chips (quad RC4136 and dual RC4739), to use the superior OP1602 op-amp. Data sheet attached below. NO DISTORTION AND SUPER SPECS.
I ORDERED THE ADAPTORS WITH THE OP AMPS SOLDERED ON. This may be a drop in, but I will stabilize them if needed. 35MHz Bandwidth types!
I will post pictures and test results when I'm finished with it. Should be a dream clean sounding beast!
Open the pics for all the info for the upgrade in process. Stay tuned,

 

[George S.]

George, you should be able to open the original reverb pot and clean and grease it, and hopefully reuse it.
I have two I use constantly, and parts to build another. They have higher noise than a Acurus line level preamp, but I prefer the PL2000 due to it matching the amps, and I think it sounds excellent.
Couple months back I switched from a large toroid transformer to a smaller toroid with a cover. Lowered my noise levels some. Granted these are dB levels I see on a Real Time Analyzer and are far below the threshold of hearing, but improvements are what it's all about.
I'll post some photos here when I get home and have time.
Strange that you have the old style rounded top plastic RCA jacks in that 2000. All of mine had or have the square top jacks.
Good to see others with a interest in that pre. My favorite.

 

[GeorgeP]

I just installed the Ambience level pot and volume pot. No noise and very close tracking...0.3 dB across the full range. The Ambience POT was destroyed...some of the resistance material fell out of it! The volume pot, very intermittent at the center point....wore out.
The newer 35 MHz super low distortion chip set to replace the quad 4136 is PHENOMINAL! NO DISTORTION AT ALL, and now flat to 30Khz! No instability at all.
Ill be replacing the other two dual chips with the newer op-amps next bench work.
I just need to add a 120vac relay for power, as the small SPST switch on the POT is to light. I want to change out the AC cord for a very heavy one, have the relay be good for 20 amps for two Phase linear 400s to be switched on. I'll add an RF interference rejection filter, since the New Op-Amp chips are good to 35 MHz ++. Don't want any HAM radio, Police fire department, or switching power supplies signals coming through the AC input!!
I think this preamp will be a hoot!! I attached a few pics...have a look.

 

[GeorgeP]

I added the Two New Chips for the Phono and Ambiance circuits. Perfectly clean, no instabilities ringing or anything! Also added the high-power relay for the switched AC Sockets,
Should be good for two PL400s Amps. I'll change out the original line cord next, maybe a heavy 3-Prong with Ground type.
I'd bet this is the best sounding preamp out there... totally transparent. All Tone controls function the same way... just no roll-off to 30 KHz...Better, but not really necessary of course.

 

[mr_rye89]

I need to get back into my Carver C1. I may socket a few of the RC4136s and do a little op amp rolling. I thought about getting one of Mondial’s offerings but I like how the tone controls work on the c1 and the fact you can defeat them, because I don’t use the all the time but sometimes need em. Also the appearance of Aragon pre’s are not my cup of tea (don’t tell J!m) and they don’t rack mount

 

[J!m]

Have you seen what my Perreaux preamp looks like?!? I don’t care about appearance (unless I make it).

 

[mr_rye89]

I got the opposite problem.....

 

[Gepetto]

I got the opposite problem.....

I opine that Aragon would have had a much larger following had they hired a different industrial design team...

 

[J!m]

I still have my 47k and D2A…

probably should move the 47k on.

 

[laatsch55]

They can pry the Coherence out of my cold, dead hands...

 

[Gepetto]

They can pry the Coherence out of my cold, dead hands...

That is a keeper Lee...on performance and appearance

 

[laatsch55]

Indeed sir Joe!!

 

[grapplesaw]

I need to get back into my Carver C1. I may socket a few of the RC4136s and do a little op amp rolling. I thought about getting one of Mondial’s offerings but I like how the tone controls work on the c1 and the fact you can defeat them, because I don’t use the all the time but sometimes need em. Also the appearance of Aragon pre’s are not my cup of tea (don’t tell J!m) and they don’t rack mount

Having done this experiment several times on Carvers using brown dog adapters and opa2134 chips I have gone back to installing new RC4136’s In the phono and main drive circuits only No measurable sound difference or in noise floor measuring on the AP. I’ll be interested in your results

 

[GeorgeP]

THE ONLY MEASURABLE DIFFERENCE WAS THE FLAT OUT GAIN IMPROVENT TO 30KHz. SOUNDS GREAT, SO I'LL KEEP THEM IN.

 

[mr_rye89]

Having done this experiment several times on Carvers using brown dog adapters and opa2134 chips I have gone back to installing new RC4136’s In the phono and main drive circuits only No measurable sound difference or in noise floor measuring on the AP. I’ll be interested in your results

good to know. I did a full recap and replaced all the 4136s, but I at least need to add that voltage regulator board. I also plan on a remote for the volume pot

 

[George S.]

Everything I've done to my PL2000 other than the transformer has improved the mid range and treble.
The transformer upgrade really helped reinforce the bass. Not entirely happy with the toroid transformers. They don't quite have the authority that the Hammond 166J33. 33 VCT at 1 Amp transformer has. I've seen Hammond makes a shielded version that could be hung outside the preamp like PL did the amps. I plan on getting one of those eventually. The bass with the Hammond was rather amazing, but still good with the toroids. I've finally come to grips that the transformer should probably be outside the chassis, but I still need to test this to be sure. The QA403 shows quite a bit of 60 Hz inside the cabinet from the transformer I believe. I'll find out for sure eventually. And yes, it's totally quiet with the volume cranked, just bothers me it's got higher noise than the Acurus L10.
Oh well, no free time and much planned to eventually do.

 

[J!m]

Oh, yeah. Get the transformer out of the box. Mount it remote and send low voltage DC up to the main box. No AC.

 

[George S.]

Then a "Power One" external supply that Joe has recommended in the past would be the way to go. I've looked at them several times a good while back.
Working six long, long days a week now. I'll get back to this eventually.

 

[GeorgeP]

I'll be moving the ac transformer out of the box sometime soon. The Low level hum, a bit annoying. I'll move the recently added high power AC relay out also for the switched outlets. There is a :shield there over the AC primary lines. It does reduce the hum level... found out by leaving it out once, by accident, then put it back and noticed it was better.

 

[GeorgeP]

So...I look more carefully on the scope...and I see low level fuzz...yeap...its an instability at 16,750 Hz!
Simple fix! Add 100 ohm resistor in each channels output, in series. Isolates the capacitive loading at the output Two cuts under side, add 100 ohm 1/4 watt resistors where shown. Cleeen signals!