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Phase Linear 400

Stereo Power Amplifier

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Phase Linear 400


The Phase Linear 400 is the most advanced amplifier that today's technology can produce.

A new generation of extremely fast, high energy silicon output transistors, and a host of new materials and techniques only dreamed of a short time ago has made possible an amplifier with performance characteristics that extend virtually beyond the limits of measurability.

At 20 cycles per second, damping exceeds one thousand.

Distortion is so low that it must be measured with only the finest laboratory equipment.

Continuous power levels can be delivered into 8 ohms from 20 cycles per second to beyond 20,000 cycles per second.


  • Power output: 210 watts per channel into 8Ω (stereo)

    Frequency response: 20Hz to 20kHz

    Total harmonic distortion: 0.25%

    Damping factor: 1000

    Input sensitivity: 1.7V

    Signal to noise ratio: 100dB

  • Power output: 210 watts per channel into 8Ω (stereo)

    Frequency response: 12Hz to 40kHz

    Total harmonic distortion: 0.09%

    Damping factor: 1000

    Input sensitivity: 1V

    Signal to noise ratio: 110dB

    Speaker load impedance: 4Ω (minimum)

    Dimensions: 483 x 178 x 254mm

    Weight: 16kg



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Reviewed Mar 01st, 2015 by guest

This is a review of the Phase Linear 400 Series 2 amplifier. First this is a great looking amp that has fast LED displays for the wattage output. The amp leverages 16 bi polar transistors in the output stage running quasi complimentary. The amp measures more than 270 per channel into an 8 ohm load. Sonically the amp is fast and punchy with a lot of clarity. While it does not have the finesse of the top tier modern amps it sounds neutral and clean. Highly recommended to the collector of classic gear.

Reviewed Nov 11th, 2014 by GamerAndds

Beautiful sounding amplifier! Looks tough, pounds hard, and is too simple schematic! A true Power amps...



re: 400

Great amps!
Easy to work and they give back in spades!
I've replaced the driver boards with the White Oak universal board kit and it only makes it better and more robust. Simple kit to build and install.
Also for those who are worried about the lack of speaker protection there is a kit from Watts Abundant that installs a relay protection board between the amp and speaker terminals. Also a very well done kit.

re: 400

Hi, fantastic site, i just finished replacing all transistors, caps resisters did a quick test with no current draw, but noticed on D1 and d2 15V Zdiods get VERY hot, there working though, i have seen both manuals R1 and R2 1.8k 5watt but some say 7.5K could i have the wrong resister blocks in there ?
this unit was at some shop for ever a year and said never repaired. Driver board is pl36

any ideas ?

phaes 400 manual

thanks for this been wanting one for years have owned my phase since the 70`s needs work to make it come alive again :)

Wires to VU Meters

I have a Phase Linear 400 that has the front panel removed and all five wires to the VU meters broken off. I want to solder the wires back on, but i cannot tell which wire(s) to connect to which trace(s) on the PL18A board. The schematic shows that the traces on the board are numbered 11, 12, 13, 14, and 15, but it does not show the wire colors. There are two heavier gauge red wires and three lighter gauge wires (red, white, and black) coming from the amp. Can anyone advise me?

Pl 400

I rebuilt mine from the bottom up.

All New Capacitors, Resistors, transistors. It is about Variation, heat transfer and Resistance.

I Cannot Possibly Have knowledge re: your amplifier. (Send Pictures)!

I will Estimate. Easy to Repair. It is A Trouble Shoot.

In My PL. 400 Amplifier existence, there are the Late model boards and then 2 inferior boards.

Early 4000's. Than prior to PL 400 Series 2;

The 'Flame Linears". Low uf PA caps and ETAL.

I have rebuilt many of these.

"Flame Linear Boards?

Narrow your search.

Let me open mine up. ( pictures also ).

I will provide you with pictures. It has Been 2 months and I run it hard.

The "Good News" is there is support for these-PL-l400 Amplifiers.

I can Fix and Rebuild Them.

Time and Material.

In so far as Upgrading!

My pics, will differ only re. light and my modifications.

I converted to LED's. My VU's work fine, just LED lighting. I am not so sure that I like that, but it will last my lifetime!

Been in there to recap and hot rod it. No Longer a "Flame Linear".

northernglenn's picture

re: Pl 400

I had my PL 400 Series 2 since early 80's. I wish I had the service manual! I had to send her in for repairs "TWICE?"
Both times she would only generate a loud oscillation. The did put in new type Transistors. It has been good. Since the repairs, I have worked for Xerox for over 22 years! That manual would have been a great addition
However, I still would need to hunt for the parts.

I do have it now. She continues to punch "Hard," as mentions... into a pair of Bose 901 Series 4!



Thank you for collecting all the info in the service manual and for making it available here. I'll make sure that if I get any more I will send it to you guys for submission!

Thanks again

Laura B

Great service

Great service for audio vintage gear

Best regards
Akla vintage gear

This website is not affiliated with or sponsored by Phase Linear. To purchase 400 spares or accessories, please contact the company via their website or visit an authorised retailer.