Are the days of cheap 400/700s done.
- Thread starter Oldskoolfan
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- May 4, 2016
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- Northeast Iowa
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- Love great audio, beermaking and pyrotechnics
Just found a local 8 fin 400 II for a pretty good price for a working amp. I was thinking of grabbing it. If the custom faceplates were available with the holes for the power/sensitivity (looks like the 700 II) switch like the one I got from Glen, I would.
That way I would have a pair of matching WOPL 400 II's and they look great with the upgraded face. $200 and a FedEx shipping tag seems reasonable.
Here is what my 400 II WOPL with Glen's face plate looks like. Looks just like my 700 II WOPL. Anybody got one? I pay a finders fee for one.
That way I would have a pair of matching WOPL 400 II's and they look great with the upgraded face. $200 and a FedEx shipping tag seems reasonable.
Here is what my 400 II WOPL with Glen's face plate looks like. Looks just like my 700 II WOPL. Anybody got one? I pay a finders fee for one.
Thought some purchase data might be helpful. I made all eBay purchases primarily on cosmetics. Price was a secondary issue.
2020 Purchases
PHASE LINEAR 700 SERIES TWO / AS IS
US $617.03
2019 Purchases
Phase Linear Model 700, Series Two Power Amplifier, Original Owner, with Manual
US $577.96
Phase Linear Model 700 Series Two Audio Standard Amplifier Amp Read Description
US $464.72
Phase Linear Model 400 Series Two (II) Stereo Amplifier==Nice & Sounds Great!
US $499.99
2017 Purchases
Vintage PHASE LINEAR MODEL 400 SERIES TWO II AMPLIFIER Amp
US $350.00
Phase Linear Model 700 Series Two Power Audio Standard Amplifier
US $453.00
2020 Purchases
PHASE LINEAR 700 SERIES TWO / AS IS
US $617.03
2019 Purchases
Phase Linear Model 700, Series Two Power Amplifier, Original Owner, with Manual
US $577.96
Phase Linear Model 700 Series Two Audio Standard Amplifier Amp Read Description
US $464.72
Phase Linear Model 400 Series Two (II) Stereo Amplifier==Nice & Sounds Great!
US $499.99
2017 Purchases
Vintage PHASE LINEAR MODEL 400 SERIES TWO II AMPLIFIER Amp
US $350.00
Phase Linear Model 700 Series Two Power Audio Standard Amplifier
US $453.00
Managed to snag a cheap 400 on ebay. Exploring ideas on what to do with it. Full comp WOPL is mandatory.
Bridging it for a mono sub driver is my first thought.
Is this doable?
Open to other ideas. This will be my fourth 400 and my third full WOPL when complete.
...hello, my name is Harold and I have an addiction...
Bridging it for a mono sub driver is my first thought.
Is this doable?
Open to other ideas. This will be my fourth 400 and my third full WOPL when complete.
...hello, my name is Harold and I have an addiction...
You can bridge the Phase Linear amplifiers, but you have to do it correctly. The 700B Owner's Manual says to never connect the outputs together!
There was an undated Service Bulletin describing the technique for correctly "Bridging" the 400, 400 II, 700, 700B, and 700 II into 8 Ohms or greater (attached). It mentions the use of a phase shifting Line Input Transformer. With the Left and Right Input Signals 180 degrees out of phase, the output is taken from the Left and Right Positive Speaker Binding Posts. The Output is summed by the two channels to double the wattage. The Line Input Transformer mentioned, TRIAD G-336, is no longer available.
A substitute Line Input Transformer is available here:
https://lightningboyaudio.com/store/p70/UJ20_line_input_transformer.html#/accounts
I have spoken to the technician at Lightning Boy Audio and they do have this in stock at $78.00. I would be curious to hear about your bridging adventures.
There was an undated Service Bulletin describing the technique for correctly "Bridging" the 400, 400 II, 700, 700B, and 700 II into 8 Ohms or greater (attached). It mentions the use of a phase shifting Line Input Transformer. With the Left and Right Input Signals 180 degrees out of phase, the output is taken from the Left and Right Positive Speaker Binding Posts. The Output is summed by the two channels to double the wattage. The Line Input Transformer mentioned, TRIAD G-336, is no longer available.
A substitute Line Input Transformer is available here:
https://lightningboyaudio.com/store/p70/UJ20_line_input_transformer.html#/accounts
I have spoken to the technician at Lightning Boy Audio and they do have this in stock at $78.00. I would be curious to hear about your bridging adventures.
Attachments
The transformer is an option i've explored but to do both channels would require 2 amps and 2 transformers ... I think... 
I was thinking of using a Rolls SX95 to perform the inversion of summed low frequencies from both channels. Inversion of summed signal on 1 output channel only and then fed to the amplifier.
In the schematic P1 sets the signal level applied to U1A and U3A
SW1 performs the combining of left and right signals.
P2 establishes the 12DB per octave cutoff frequency. Infinitely variable from 36 to 200 Hz.
Would this work?
I was thinking of using a Rolls SX95 to perform the inversion of summed low frequencies from both channels. Inversion of summed signal on 1 output channel only and then fed to the amplifier.In the schematic P1 sets the signal level applied to U1A and U3A
SW1 performs the combining of left and right signals.
P2 establishes the 12DB per octave cutoff frequency. Infinitely variable from 36 to 200 Hz.
Would this work?