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Phase Linear 700B burns speakers
Phase Linear 700B burns speakers
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Old Yesterday, 08:11 AM   #51
H713 is offline H713  United States
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To me what makes them a little special (compared to a lot of other amps from that era) is that they were used as a PA amplifier for a lot of rock concerts. They were one of the first amps that could really make a lot of power.

I wouldn't gut it. Rebuild it and add a DC protection board, and you've got a reasonably cool and useful amp. I honestly never thought they sounded that bad, even if the design is a little primitive.
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Old Yesterday, 12:32 PM   #52
wg_ski is offline wg_ski  United States
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Rock concerts? No, no no…. DISCO made the PL “famous”. Infamous, too - because the name “Flame Linear” was coined when one actually exploded in a club.
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Old Yesterday, 12:58 PM   #53
wg_ski is offline wg_ski  United States
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I suppose a “better” way of producing 350 watts per channel 8 ohms, 550 at 4 ohms with a hunk of iron and copper is the QSC USA1310. Same exact REAL power (not it’s inflated 400 watt EIA rating) as the PL700, but using a bigger trafo for better regulation on lower rails (+/-93V) and 8 output pairs per channel. Perfectly reliable, other than the usual minor QSC aging problems, which are easy to fix and never fatal. I’ve still got two of them - many are still in actual PA service although many are being scrapped because of weight and thus quite cheap. But they just don’t sound as good as a Phase Linear.
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Old Yesterday, 02:23 PM   #54
Bonsai is offline Bonsai  Europe
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Phase Linear 700B burns speakers
There have been a lot of stories about these amps running into problems. Without an output L, and just relying on the speaker cable instead, there are bound to be problems.

A good way forward would be to build a model in LTspice and fix the compensation.

Unfortunately, back in the day when these were designed, there was no LTspice ( or other readily available simulator) so designers had to be very experienced and knowledgeable wrt feedback and compensation - my view is they were generally few and far between.

The slow output devices don’t make it an easy job either.

However, this is a piece of history, so you should try to save it IMV.

(I remember seeing this amp and is companion preamp with a joystick type control at a hi-Fi shop called ‘Sound Specialists’ back in 1970’s and as a 20 yr old lusting for them. My budget didn’t stretch that far!).
Bonsai X-Altra MC/MM preamp http://hifisonix.com/x-altra-phono-eq-preamp/ Ground Loops http://hifisonix.com/ground-loops/
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