Phase Linear 400 Series II

R

rwagoner

New Around These Parts
#1
Joined
Feb 5, 2024
Messages
2
Location
Southern California
#1
I don't actually have a problem with my 400 II; it had been repaired professionally back in 1988 (6 2SD555; 1 LF351N) and by me in 2007 (6 MJ21196G and all driver/output transistors "re-padded." I bought it used as part of a DJ system and while I've changed the system from turntables to CDs to digital, the amp has been the only amp I ever used with it. Still seems to work fine and sounds really nice to me.

I recently decided to make the system even smaller and lighter, and frankly the reputation of the PL scares me a little, now that it is getting older. So I replaced it in the DJ system. Now I need to decide what to do with it. I am leaning toward selling, as I don't think I'll ever have separates, but am just curious what you think of the amp. I know most here probably upgrade it, which I don't feel I would do. But are they (in factory form) as unreliable as some say? Do they really have an issue frying speakers when the outputs short out (in neither case when it went bad on me did that happen). Or does it only happen they they are pushed hard? Or is it not as common as some seem to say?

Anyway, just curious. I was sent here by AudioKarma.org.

Richard
 
mlucitt

mlucitt

Veteran and General Yakker
#2
Joined
Jun 24, 2011
Messages
3,468
Location
Jacksonville, FL
#2
Welcome to our group. The PL400 Series II is a great amplifier. I have an original PL400 and a fully upgraded PL400 and they both perform well and sound great. There is something to the bad reputation (because of the original design) that we call a "Latch up". When this happens, the full Power Supply voltage (80 Volts DC) is unpredictably sent to the Speaker Binding Posts (usually on the Left channel) which fries the speaker. Phase Linear knew about the issue but they could never solve it.

Today we have the DC Protection Relay/Delay PC Board thanks to Don Imlay (know here as Watts Abundant). This board is easy to install and protects your valuable speakers from the "Blaze Linear" or "Flame Linear" phenomenon. But, the amplifier itself will still have the issue.

Fortunately for us, White Oak Audio has solved the Latch up problem with a new design for the Control PC Board inside the amplifier. The real benefit is the new design uses much better and modern components, has an improved layout, and is a true "Dual Mono" solution. There are more upgrades, but the new Control Board is really a must. Also, new Power Supply Capacitors should be considered. More of a safety and reliability issue, but you do get an improvement in the bass region due to the higher value of the capacitors (15,000uF compared to the original 5,900uF each) in the same size.

Of course, you could sell it as is. The current ebay price for a nice PL400II is about $500.00.
 
R

rwagoner

New Around These Parts
#3
Joined
Feb 5, 2024
Messages
2
Location
Southern California
#3
mlucitt said:
Welcome to our group. The PL400 Series II is a great amplifier. I have an original PL400 and a fully upgraded PL400 and they both perform well and sound great. There is something to the bad reputation (because of the original design) that we call a "Latch up". When this happens, the full Power Supply voltage (80 Volts DC) is unpredictably sent to the Speaker Binding Posts (usually on the Left channel) which fries the speaker. Phase Linear knew about the issue but they could never solve it.

Today we have the DC Protection Relay/Delay PC Board thanks to Don Imlay (know here as Watts Abundant). This board is easy to install and protects your valuable speakers from the "Blaze Linear" or "Flame Linear" phenomenon. But, the amplifier itself will still have the issue.

Fortunately for us, White Oak Audio has solved the Latch up problem with a new design for the Control PC Board inside the amplifier. The real benefit is the new design uses much better and modern components, has an improved layout, and is a true "Dual Mono" solution. There are more upgrades, but the new Control Board is really a must. Also, new Power Supply Capacitors should be considered. More of a safety and reliability issue, but you do get an improvement in the bass region due to the higher value of the capacitors (15,000uF compared to the original 5,900uF each) in the same size.

Of course, you could sell it as is. The current ebay price for a nice PL400II is about $500.00.
Click to expand...
Thank you for the insight! It is much appreciated, and gives a lot to think about!
 
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