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Phase Linear 400

watt

watt

no on
The first series, not the mk II. I'm curious about running one of these with my DQ 10s. I've been using a Hafler 9180 that I like very much, but the extra power of the Phase Linear is very tempting. I've read the horror "Flame Linear" stories out there, and this is the thing that concerns me most. Would the DQ 10's fuse be adequate protection?
 
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Despite the stereotypes, MY original PL 700 behaved very nicely and didn't kill any speakers, cannot say that about other amps I've had...
 
If you want to use that amp, have it checked out/refurbed, if it hasn't already been checked.
 
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watt said:
The first series, not the mk II. I'm curious about running one of these with my DQ 10s. I've been using a Hafler 9180 that I like very much, but the extra power of the Phase Linear is very tempting. I've read the horror "Flame Linear" stories out there, and this is the thing that concerns me most. Would the DQ 10's fuse be adequate protection?
Click to expand...

The guy I bought my DQ-10s from, was running multiple stacked pairs w/ Dahlquist subs and crossovers, driven by PL 400 Series One amps. Wow! What an impressive system that was! Very, very impressive! I never thought much of PL gear, until I heard that system, but it made me a believer! The combination of the PL amps (and preamps) and the Dahlquist DQ-10s is a VERY musical combination that I can highly recommend. :thmbsp:

Be sure to spend some time on the Web saearching for and looking at PL related Web sites. There are lots of PL fans out there and there used to be a guy in the Seattle area that repaired and refuburished PL gear. He claimed to be a former employee and one of the last factory-trained PL technicians still around. In any event spend some time on the Web, there is lots of good info about PL gear there.
 
If a series one shorts an output it will send 84 volts DC to your speakers. Fuses are not adequate protection. I've restored 11 of the 400 1's with no problem, of course they are not running my Model K's.
There is a retrofit protection PCB available through d3imlay, might check with him.
If you are driving irreplaceable speakers with a 400 you might consider this option. That being said the 11 i've done have driven some amp eating speakers, I.E.,
Cerwin- Vega D-9's, Ohm Model F's with no problems.FWIW
 
Works for me!
pict0048yx9.jpg
 
Thanks for the thoughtful replies, everyone. I've heard about the good synergy between the PL 400 and DQ 10s that thunderroad mentions, and this amp's available to me at a good price . . . so it's very tempting. But I also really love the DQ 10s and wouldn't want to risk them. Sounds like a refurb is a must in this situation. I suppose it can't hurt to go out and take a look at it, right?

Thanks again.
 
Here is some contact info on possible sources for restoration:

Dean and Ed's Phase Linear (Lynnwood) Page
http://web.archive.org/web/20071208055327rn_1/hometown.aol.com/PhaseTek/ This is an archive of an old website, but has current contact info. New website is not up yet here http://www.phaselinear.info/

Watts Abundant
http://home.earthlink.net/~dimlay/index.html

Rita's Vintage Audio Repair
http://ritasvintageaudio.net/ Repair for all Bob Carver products

Circle Stereo
http://www.circlestereo.com/info/brands/phase_linear/?content=phase_service_pt1

Sound Idea, Inc.
Charles Alexander has been the service manager for Sound Idea, Inc. in Arlington, Texas for over twenty years. Sound Idea was a Phase Linear dealer from 1972 until the early 1980s and carried all Phase Linear's products. Alexander himself is a degreed electrical engineer, audio designer and service technician. You can call Charles at (817) 277-4061 to learn more.

Hi Tech Audio
http://www.hitechaudioltd.com/repair.htm
 
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I would never use an amplifier that offers zero protection with irreplaceable speakers, and I for sure would look into that retrofit board. That 400 has got some zip and might be a nice amp to run the DQs with, but not without some changes.
 
The DQ 10 speakers are very inefficient and a low impedance load. Not a good thing for a Phase Linear 400 to be happy with long term. An amp with autotransformers or which is happy with a 4 ohm load daily is best. The Phase Linear would be OK if updated and freshly serviced. If it misbehaved, it will pass moderate DC voltages to those speakers which isn't good. A stock Phase Linear 400 has no speaker overload protection on it to speak of.
 
Phase 400.... ..........powerful, meters aren't worth a damn, a little underbiassed in my opinion.

They don't really have the heatsinking to be biased harder without some forced air cooling. You can fuse the speaker outputs. Fuses can provide adequate protection. You just have to choose the right fuse.

If it's got 84 volt rails and the likely failure mode is a shorted output transistor, then consider that type of voltage appearing across your speaker.

Add some guard band and fuse for 60 volts across your speaker. If your speakers DC resistance is 4 ohms, then E/R (60/4) = 15A. Why don't you fuse with 5A Fast-Blo? That's plenty of protection for your DQ's
 
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