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Phase Linear 700 & 400 series II

There isn’t much not to love about theses amps. Clean accurate linear signal reproduction. Transparent latency output signal. If they do fail they are very easy to repair. We use to joke that it took longer to get off the shelf and take it apart then to get it back working. Usually an output or two a driver and sometimes a pre-driver along with a diode. The units rarely smoked and if they did they still where an easy fix. Biggest repair mistake was substitution of output and driver components then what was original. Can not be mixed up or blow up. Simple series II repair is to stick with Motorola NpN 15024 and PnP 15025 compliments. Use good heat sink compound or good TO-3 wafers. Watch for stressed PCB wires solder joints to the PL-36 driver board. Make those repair by just doing a complete re-solder to all wire connections. Watch for manufacture solder donut holes at capacitors legs. The old wiggle test with a magnified glass worked well. Check for over heated or discolored emitter resistors at on the main heat sink plane. If you have access to a 10 AMP Variac device using an analog meter at the outputs slowly bring up the amp after repairs and watch for excessive fast load draw. The slow power up should be very smooth and minute amp draw on the meter needle. If you have a dummy load rated up to 8Ω @ 400 watts you may bring the amp to the the rated voltage and perform a current sharing test on each bank. Just saying.
ksaldutti
don_c55
1,025 posts
 
Poor sounding amps! Even for the 70's.

High frequencies that are like long needles into the eardrum.

Cold, lifeless everywhere else.

High power for their day, which was what sold them.
dave_72
1,399 posts
 
rivals almost anything made today.

Yeah, right. lol. Also, keep in mind that you said modified and reworked, not stock.
dave_72
1,399 posts
 
Don c55-I can believe that. Also, you had the big McIntosh amps back then which were/are far superior to the Phase Linear, modified or not.
billstevenson
340 posts
 
I replaced two bridged MC2100 amps with a PL 400 in around 1973 or 74. The PL sounded better to me, a lot better, but it all depends on what sound you like. The Macs were warmer, had lush sound, but were not as clear on the highs and had less control of the bass. This is subjective of course, but that Phase 400 is still with me, the Macs are long gone and not much missed. Make no mistake, the Mac amps were built like tanks, the Phase was built cheaply, but again, taken care of, it has stood the test of time. I am going to have the PL400 gone over and modernized just because. All this old stuff is fun to have and to mess with. I have owned a lot of amps over the years including other Macs and Marantz, ARC and Adcoms. They are all good, I have never had a bad one.
dave_72
1,399 posts
 
That's fine. But, you're qualifying the PLs as something great, and the reality is, they're just ok, imo. And the McIntosh model I was referring to was the MC2300. Anyway, we agree to disagree. I'm tired of arguing about this, thanks.
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