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Phase Linear 400 II Pops when turns off

N

nicosalto

New Member
Hi,
I recently bought a phase Linear 400 II in good condition and i use it to drive my JBL 4319 Studio Monitor Bookshelf Speakers. It sounds great but i have an issue, when i turn the amp off i always get a Pop into my speakers, which annoys me, and iam afraid it will slowly damage them.
This is a vintage amp, and it basically only have 2 knobs for the left / right ways, no power off button. Even when i put the volume knobs to 0, it still pops. It doesn't pop right away after i turn the plug off only after about 30 seconds.
Please let me know if you had any similar issues with vintages amps and how to avoid this ?
 
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That amp has no speaker relays, so you are hearing the "power down" cycle of the amp. It is very common, and in some cases you will hear an audible "squeal" as the capacitors discharge. Volume makes no difference, since the issue occurs mainly downstream of the volume controls. As mentioned, there are aftermarket relay boards readily available for this amp, and will solve your issue.
 
Agree with savitage1973. I have a 700B (does have a power switch) and on power down there was a "thump" and mentioned in PL literature. I say was because the installation of a Watts Abundant speaker protect relay board eliminated it.
 
The "thump" can be remedied be replacing the front end op amp chips. I know this because I spent some time on the phone a few years back with a guy named Dave Nissin who used to be a tech at Phase Linear back in the 70's. He explained that the op amp was one used with poor specs and he said to replace them with new one's. Can't recall off hand what the new one's were as I got rid of my 400 series two a long time ago.

EDIT: Dean Nissen not Dave Nissen.
 
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Thanks guys!
I googled "Watts Abundant speaker protect relay board" as you metionned Vauxhall and Savatage and i found those links:
http://home.earthlink.net/~dimlay/id24.html
http://home.earthlink.net/~dimlay/sitebuildercontent/sitebuilderfiles/400_Installation_Procedure.pdf
iam guessing i should go for something like this, do you have any other board in mind i should look into ?
. I dont feel like installing this myself so i will probably try to find some help...

Cademan, yes i also rode somewhere online that the transistor in the power supply are not adapted for the amplifier. I wonder how easy it would be to fix them.
 
You may wish to investigate White Oak Audio - products for Phase Linear. There's a website and Google searching should turn up some informative threads/posts from this and other forums.
 
Changing opamp won't change the turn off thump. Any amplifier without an output relay will provide some type of noise at shutdown.

This noise will not hurt your speakers.

If you decide to add it, go with Watts Abundant (our own D3imlay). It will attach directly to your speaker posts and be the easiest to add to your amp - it was designed for it!

There are other good reasons to add the relay, most important would be to protect your speakers in the chance your amplifier goes South.

White Oak audio also has other goodies that can turn your PL 400 II into an amp that is very hard to best for SQ and power combination. If you like the way your amp sounds now, you would be in for quite a treat should you decide to explore the improvements that have been engineered for your particular amplifier.
 
White Oak all the way!!!

If you just want the relay you can't go wrong with Dimlay's. I have one in my 400 that has been White Oaked (WOPL'ed). It now puts out around 260 watts!!

Awesome thing about these kits is the ability to do everything in steps so it doesn't break the bank.
 
Gibsonian said:
Changing opamp won't change the turn off thump. Any amplifier without an output relay will provide some type of noise at shutdown.
Click to expand...

Um, when talking directly to a Phase Linear tech, he said that this particular problem is in the op amps used. It might not make a bit of difference with other brands and amplifiers, but it was one of the problems that caused thump at turn off in the 400 series two amplifiers.

I would also do the relay thing.
 
A simple speaker switch, Niles,etc., will solve the issue easily. Turn the speakers off at the switcher and them turn off the amp. A simple easy fix.
 
cademan said:
Um, when talking directly to a Phase Linear tech, he said that this particular problem is in the op amps used. It might not make a bit of difference with other brands and amplifiers, but it was one of the problems that caused thump at turn off in the 400 series two amplifiers.

I would also do the relay thing.
Click to expand...

We will see if Ed or Dean knows him. They are our go to PL Tech's as they really are ex employees of Phase Linear. Don's board is the ticket
 
Thank you! I couldn't remember his first name. It was Dean Nissen that I had talked with but wow, that was like the year 2001 or 2002 or somewhere around there! I remember When I first talked with him, I made the mistake of pronouncing his last name as the car Nissan. He very abruptly scolded me and said, "I am not a car" and then he told me how it was pronounced.:rolleyes:
 
Thanks a lot for all the answers! ;)
I did a bit of research in Singapore about relays. And I found a very good shop in simlim where an old guy have been repearing and updating amplifiers for decades. He told me the relay will cause no issues. He offered me 2 types of relay.
https://pasteboard.co/11Am0NJEQ.jpg
Lirrd or omron, did you ever eard about those brands?
I think I will also order the capacitor upgrades from White oak and upgrade them at the same time. :)
 
If you are looking to just get the capacitor upgrade and plan to ship all the way to Singapore, you could just look into getting comparable capacitors locally. There really isn't anything specifically special about the upgrade kit. The real magic is in the new driver and backplane boards.

Also I know Omron is a well known brand. I would really suggest getting the relay board from Watts Abundant. I really think it is worth the price and shipping.
 
mjstriker5 said:
If you are looking to just get the capacitor upgrade and plan to ship all the way to Singapore, you could just look into getting comparable capacitors locally. There really isn't anything specifically special about the upgrade kit. The real magic is in the new driver and backplane boards.

Also I know Omron is a well known brand. I would really suggest getting the relay board from Watts Abundant. I really think it is worth the price and shipping.
Click to expand...

And it's friggin' easy to install. Order the new speaker binding posts at the same time. That's what anchors the protect board and outputs to the speakers The original posts likely have their wires soldered onto them so the threads will be kind of messed up.
 
dimlay's DC protect relay will eliminate it. Also, if you install Joe's WO control board, that eliminates turn/off thump by itself also

Head over to the Phoenix Audio Forum board and you will have your answers in a day or less (and someone to fix the issue if you don't want to mess with it. I recommend Perry, Lee or Ed (Dean's friend)
 
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