Phase Linear 700 ??

[midlife]

Can a Phase Linear 700 power amp comfortably operate at a four ohm load? Haven't seen much mentioned about these amps, are they desireable and good performers? Are they compatible with different preamps?

[SEAWOLF97]

Can a Phase Linear 700 power amp comfortably operate at a four ohm load? Haven't seen much mentioned about these amps, are they desireable and good performers? Are they compatible with different preamps?

Commonly referred as "Flame Linear" or "Fuse Linear" for their ability to catch fire while driving a low ohm load ..

My "other good vintage" speakers are 3 ohm OHMs. When I emailed tech support , the company president answered....He SPECIFICALLY told me NOT to use PL amps with his product as they have been the base for many failures in the past.

http://www.audiokarma.org/forums/sho...d.php?t=123724

Phase Linear 700 series amps have some significant technicall differences depending on what exact model and when manufactured.

Last I knew there was a factory trained tech or engineer in the Washington State area that services and reconditions these.

These amps can sound very good and have a lot of current.

They CANNOT be abused or allowed to run hot.

The entire PL line from this era has earned a reputation for being tempramental and unreliable (with good reason).

The rudimentary protection circuits are faulty by design and they DO NOT WORK. In the event the amp fails and goes DC there is enough power and current to form a significant FIRE HAZARD.

Because of this, these amps earned nicknames such as 'Flame Linear' and 'Blaze Linear'

I understand that this amp was the brainchild of engineer Bob Carver and one of his first commercial successes.

I used to use 3 of these in commercial applications along with a couple of 400s all through the 80's and finally retired them in the 1998.

Careful as I am , I had a 400 go up in smoke on me just sitting there idling one day in a monitor application. These are delicate and fragfile amps despite their tough looks.

I think $500 is high unless it was recently reconditioned by a qualified tech experienced with the speicific issues these units had.

It is your choice - if you buy it you will probably become a fan.

whatever you decide, enjoy!

http://www.talkbass.com/forum/archiv.../t-515095.html

There are a multitude of amps that are smaller, lighter, better sounding and more reliable than the old Flame Linears. I had 3 400's years ago and all passed DC voltage at one time or another. I have a couple of Crest 7001s that are killer amps. YMMV, of course.

That made me lol!

Actually years ago I had a Phase Linear amp I was using with Roland pre and it DID flame out!

In the middle of a song all of a sudden there was no bass. When I turned around there were flames coming from in between the amp and pre. It went out when I yanked the plug from the wall though.!
62bass
02-09-2009, 02:38 AM

I too have had experience with a new Phase Linear amp going D.C. and destroying several JBL speakers.

hrgiger
02-09-2009, 07:49 AM

Okay this doesn't sound good, flaming linears and all, could you guys who had this problem mention whether you had your amps bridged at all or not? I read a reference to the amps being bridged but I'm not even sure if that's possible (w/ or w/out modification.) Also do you recall what ohm cabs you were running? I read about fuses blowing with 4 ohm loads with bench test signals...

xbassmanx
02-09-2009, 09:00 AM

Okay this doesn't sound good, flaming linears and all, could you guys who had this problem mention whether you had your amps bridged at all or not? I read a reference to the amps being bridged but I'm not even sure if that's possible (w/ or w/out modification.) Also do you recall what ohm cabs you were running? I read about fuses blowing with 4 ohm loads with bench test signals...

I was running one side @ 4 ohms when mine flamed out.

and from one of our members:
http://www.audioheritage.org/vbullet...98&postcount=7

Couldn't help it, sorry! All of the Fail Liners seemed to reach a point of un-stability sooner or later...700's and 700B's could take out twice as many speakers as a 400. Maybe the home stereo models like you are looking for had enough protection circuits added to make them safer. When we used to use them, they'd be an amplifier one day, smoke show the next. Those 700B's did sound really good, and made plenty of horsepower! Tim

[midlife]

[quote=SEAWOLF97;254620]Commonly referred as "Flame Linear" or "Fuse Linear" for their ability to catch fire while driving a low ohm load ..

Yikes

[robertbartsch]

Amp technology has come a long way so I make a habit of avoiding old electronics - it is just not worth it for me.

[jcrobso]

That was about 15 years ago, 700B ran without problems into 4 ohms, both channels driven. I met Bob Carver shortly after that amp come out, very interesting guy.
Yes, when working good it is a great amp. However today I would use QSC or Crown.

[jerry_rig]

I think we used to call them Fuzz Linear.

I bought the top line PL preamp in the mid '70s and returned it immediately. It was unlistenable. I settled for a Harmon Kardon Citation 11 instead.

[Ian Mackenzie]

Can a Phase Linear 700 power amp comfortably operate at a four ohm load? Haven't seen much mentioned about these amps, are they desireable and good performers? Are they compatible with different preamps?

With a fan Yes: per the original owners manual (install 8 amp fuses)

The thing about this amp was its threshold of clipping into 8 ohms was around 450 watts into 8 ohms and 700 into 4 ohms. That was the whole point of the design and high damping factor like 1000 : 1 to drive the ART LST and other relatively low sensitivity loudspeakes. The advent of high voltage transisters used in TV HT power supplies made the 700B a reality.
http://images.google.com.au/images?h...title&resnum=4


Obviously efficiency goes to hell into 4 ohms in a linear amplifier (with such high supply rails) . The problem with 4 ohms is the losses with such high currents and high power levels and the heat. Most of the class leading super amps can now approach 6 fold those numbers into 8 ohms and down to 2 ohms with switchmode PS. The point is a dyanmic range from an amp that can put out such large voltage swings.

http://www.labgruppen.com/downloads/...LM14000_V3.pdf

The Crown amps of that era could not do that and only then in bridge mode.

[Woofer]

It must be remembered that we're talking about amps that are 40+ years old don't forget.
These were the first of the 'Super-Amps' and were at the forefront of technology for the times.
It was a HUGE transition going from reasonably low powered Valve/Tube amps to these Solid State high powered devices.
I think the Crown DC300 came just before the Phase Linear 700, (correct me if I'm wrong), and there wasn't much more about except for maybe the BGW's which came a little later.
(... feel free to add to that list, IF you're old enough!)
Some have said that they don't remember seeing these in 'action' but there were companies about during the 70's and 80's, eg Clair Bros, USA, that must have had a thousand PL's for their huge Concert Touring Rigs.
You may not have seen them, but you certainly heard them.
.... but then again, this only applies to those from THAT era that were out and about at the time.
Some companies used PL's, and some used Crowns.
Same as recording studios.
It was always one or the other, but the one thing most had in common were JBL monitors. A match made in heaven regardless of which amp you used.
We have so much to be grateful for to these two Audio Co's as we wouldn't have some of the most exotic stuff today without their, (PL & C's), pioneering R&D and productivity.
I mentioned before I have a heap of PL's. I'm now starting up a similar Crown set-up. Again from 'found' broken bits.
I don't necessarily prefer one over the other. I love both.
They both have their problems, but there's so many solutions available on the 'net these days, that not having a perfectly working unit is no excuse really.
Anyway, whichever you have, enjoy it/them.

Cheers all.

[Ian Mackenzie]

Agreed,


Has anyone heard of SAE.

I repaired a 50/50 watt SAE power amp about 18 months ago and it was really nice. I replaced most of the transisters including the drivers with original types (darlington outputs) and used more modern low noise true equivalents for the Dual input Diff pairs and matched the HFE. Some capacitors were also past their used by date.

That made a hugh difference from being just another amp to the dizzy heights of a Levinson. Its surprising how different a transister can sound with the same spec. When match with the optimum HFE it can be night and day in terms of resolution and tonal balance. In this amp the previous repairer put in odd types (probably from another repair) so it was a sick puppy for a long time. Now I get a free beer whenever I see the owner!

I think SAE man has a big stash of those.

The point of this post is that if you buy an old Phase Linear it probably wont sound as good as new and even less likely to be working properly if it had been blown up.

[Woofer]

Agreed,


Has anyone heard of SAE.

I repaired a 50/50 watt SAE power amp about 18 months ago and it was really nice. I replaced most of the transisters including the drivers with original types (darlington outputs) and used more modern low noise true equivalents for the Dual input Diff pairs and matched the HFE. Some capacitors were also past their used by date.

That made a hugh difference from being just another amp to the dizzy heights of a Levinson. Its surprising how different a transister can sound with the same spec. When match with the optimum HFE it can be night and day in terms of resolution and tonal balance. In this amp the previous repairer put in odd types (probably from another repair) so it was a sick puppy for a long time. Now I get a free beer whenever I see the owner!

I think SAE man has a big stash of those.

The point of this post is that if you buy an old Phase Linear it probably wont sound as good as new and even less likely to be working properly if it had been blown up.

Absolutely spot on Ian....
I think anyone reading this can apply what you said to just about any of the BIG amps of the time.

So the best advice for possible future purchasers of any VINTAGE amp, go over it first before you power it up.
... and as Ian already mentioned, replace a few of the essential bits, eg, make sure all the transistors are matching and working, and chuck out any capacitors in the signal path and replace with the better stuff available today, and be prepared to have the biggest grin on your dial for a good length of time.

SAE stuff was good too I thought. On par with the big ALTEC amps.

I think I'll go and have a nap now....

[Dual-500]

Can a Phase Linear 700 power amp comfortably operate at a four ohm load? Haven't seen much mentioned about these amps, are they desireable and good performers? Are they compatible with different preamps?

This question always draws out the naysayers. Gotta laugh. Yes it's true, if you load up a Phase Linear model 700 with a stout 4 ohm load and pour the coals to it - it will indeed go China Syndrome and in relatively short order. I guarantee it.

Now, is it the amp or the user? Not to bash here. It's already been posted the owners manual mentions cooling fans being necessary for high power applications. They are.

Lots of air and air exchange - cool air. I always use 200+ CFM of fans (2 x 100 cfm) on the 700's in commercial use. And ensure the air in the rack circulates properly.

Companies like Audio Analysts, Heil Sound, and Clair Brothers Audio used Phase Linear amps back in the day for many years. That fact speaks volumes about the amps and how robust they are/were.

I used 400's, 700's and 300's in pro sound, disco's and my home system for many years. 3 clubs running 700's through the 80's open 7 nights a week and I had 2 amp failures from the 700's and 1 failure with a 300. Also had 2 portable systems running - one for DJ and one for club bands.

Tore up a few JBL E-120 12" 16 ohm low mids and a few E-155 8 ohm 18's with the 700's until I learned to correctly calobrate the gain structure in the systems with the old Ashly limiters and crossovers.

What I'm saying is they are flamethrower amps and about as reliable as any if properly setup.

For home use, 12v 120mm whisper fans work pretty well - depending upon how hard the amp is pushed at 4 ohms and for how long.

About the only thing one can grip about for these amps is the fan noise needed to push enough air across them to prevent amp failure.

[mikeharris]

Sorry for the late reply...but one of our clients used 700's exclusively many (30+)years ago. They had BiPolar 140v power supplies and could swing some current...but no protection.
Not to say DC300's didnt have issues..but most were due to crappy equalisers or poor stage habits. A Soundcraftsman EQ would put out DC on turn on...or when the cord was plugged back into the wall (after being kicked out). Not the Crowns fault but it would smoke the drivers every time.

[Progneta]

I once came across some McIntosh amplifiers because the guy liked the phase linears better. I was happy, got some Mc's

He fired the PL on some altec A7's and it did sound good man...

[tinevalen]

the first amplifier i recall as being 100wpc and over, or (then) "super-amp" material was the Mattes SSP200, a 100 wpc pwer amplifier. i believe within a year of it's release Mattes produced the SSA 200 which was an integrated amplifier. I owned an SSA200 and ran a pair of Altec-Lansing Flamenco's (see Bogator's avatar). It was a very good-looking piece of equipment, with a very coplex control panel. I haven't been able to find a picture of any Mattes components online, and even mention of it is hard to come by. there is some discussion at this link.
http://www.audiokarma.org/forums/arc...p/t-25298.html

and roger russel of mcintosh fame also has a review of one for sale at
http://www.roger-russell.com/magrevhf.htm

[jcrobso]

the first amplifier i recall as being 100wpc and over, or (then) "super-amp" material was the Mattes SSP200, a 100 wpc pwer amplifier. i believe within a year of it's release Mattes produced the SSA 200 which was an integrated amplifier. I owned an SSA200 and ran a pair of Altec-Lansing Flamenco's (see Bogator's avatar). It was a very good-looking piece of equipment, with a very coplex control panel. I haven't been able to find a picture of any Mattes components online, and even mention of it is hard to come by. there is some discussion at this link.
http://www.audiokarma.org/forums/arc...p/t-25298.html

and roger russel of mcintosh fame also has a review of one for sale at
http://www.roger-russell.com/magrevhf.htm

The factory was not to far from school. One I stopped over and talked to the owner and designer of the Mattes amp. I was a very interesting, the amp operated class A up to 15 w then switched over to class AB. HK used this concept in HK Ciation 16.