Meet "Val" PL 400 series 1, SN 171xx

[Oldskoolfan]

This is Val. She's a little worn and tired, but worthy of restoration and improvement. My hope is to chronicle my first ever rebuild of this amplifier.
Yes it's ambitious, but I'm retiring toward the end of this year and I want a hobby that will put 27 years of avionics skills to work.
I hope to do the following modifications;

1. Power capacitor, busbar replacement, and snubber kit install.
2. Isolation of power transformer.
3. Install a WOA full comp backplane including new output and driver transistors.
4. Install a WOA control board.
5. Install Watts Abundant DCP board.
6. Install LED light mod and mount a sensitivity selector switch.
7. Install some form of input attenuation control.
8. Complete replacement of existing wiring.

I'm sure I'll be asking A LOT of questions, but I'm sur if I read a bit ya'll will have already answered them at least once already.

 

[Oldskoolfan]

...And a few more pics. Ever see such a mix of outputs?

 

[laatsch55]

Oh yeah...you wouldnt believe what I've seen..
I think you'll find this project very rewarding. .

 

[wattsabundant]

Keep the RCA drivers until you convert it to full comp. The driver board hasn't been on fire which is good. the TO92's with corroded black leads are a failure waiting to happen.

 

[Oldskoolfan]

Got the knobs for the meter range and input gain controls Val is getting. Curious which arrangement ya'll might like best.
I'm kinda partial to the black top silver lower.

 

[mr_rye89]

Where’d you get the knobs? I like em.

 

[Oldskoolfan]

Where’d you get the knobs? I like em.

Amazon. Search for guitar knobs.

 

[George S.]

Build it like you want it. But recommend you read post 25 of the link and think about it before drilling the face plate and adding attenuators.
https://forums.phxaudiotape.com/threads/pl-700-ii-replacement-main-volume-pots.10726/page-2
I removed the attenuators from my Series 2's and replaced them with LED's. Very happy results.
https://forums.phxaudiotape.com/threads/leds-in-place-of-attenuators.10756/

 

[Oldskoolfan]

Build it like you want it. But recommend you read post 25 of the link and think about it before drilling the face plate and adding attenuators.
https://forums.phxaudiotape.com/threads/pl-700-ii-replacement-main-volume-pots.10726/page-2
I removed the attenuators from my Series 2's and replaced them with LED's. Very happy results.
https://forums.phxaudiotape.com/threads/leds-in-place-of-attenuators.10756/

Thanks for this George. I took the time to read the whole thread...and reread it...and again...lots to digest. I'm left with the question of how then to control the output of my pl400. My problem is I have the pre out of an Sa 9800 to control 3 power amps. 2 pl400's and the amp stage of the 9800. I have 4 pair of speakers with varying levels of power handling and sensitivity.
How would I then vary the outputs to achieve a balance?
I would rarely fire up all of the amps and I really can't turn it up much over 20 watts. At 5 watts the infinity's are a lot louder than the JBL's. I have these amps because of the clarity and headroom they provide. This probably should be a thread all by itself.

 

[Mohawk]

Thanks for this George. I took the time to read the whole thread...and reread it...and again...lots to digest. I'm left with the question of how then to control the output of my pl400. My problem is I have the pre out of an Sa 9800 to control 3 power amps. 2 pl400's and the amp stage of the 9800. I have 4 pair of speakers with varying levels of power handling and sensitivity.
How would I then vary the outputs to achieve a balance?
I would rarely fire up all of the amps and I really can't turn it up much over 20 watts. At 5 watts the infinity's are a lot louder than the JBL's. I have these amps because of the clarity and headroom they provide. This probably should be a thread all by itself.

DSP

 

[Oldskoolfan]

DSP

DSP? I don't know what that is.
Please refer to username...

 

[Mohawk]

If you need control of multiple amps your going to want a DSP !

https://www.minidsp.com/products/minidsp-in-a-box/minidsp-flex-eight

 

[George S.]

Yup, absolutely, DSP.
If Gene browses by, maybe he'll describe his system. Think he's running four 400's.
I'm running two, a 700 and a 400. Eventually will add two more 400's. Other projects to do first.

 

[gene french]

Yup, absolutely, DSP.
If Gene browses by, maybe he'll describe his system. Think he's running four 400's.
I'm running two, a 700 and a 400. Eventually will add two more 400's. Other projects to do first.

actually 5....i have a 400 driving 15" woofers, a 400 driving 10" mid bass speakers...a 400 driving 6" midrange speakers...and a pioneer sx1080 driving the 1" soft dome titanium tweeters....they are controlled by a dayton 408 dsp....handles the parametric eq....mixing....and active crossover....
i have another 400 driving a set of voigts controlled by another dayton 408 dsp...
the active crossover made the biggest difference for me....so clean...you will never regret the dsp....
and the amps run cool...especially the mids and tweeters....as they use so little power....
the woofer amp is a wopl....the voigt amp is a wopl....both were old 4 fins i had collected....the rest are stock 8 fins with ps cap upgrades, dc protect boards....led lighting up grade...and one wopl has digital vu meters as one of my 8 fins had bad meters....a previous owner evidently took them apart...
i have another 8 fin redone and ready for duty....as a spare or maybe will replace the axr100 in the bedroom....which has my 3rd dsp....
i just today found another 8 fin....on the bay.....will refurbish it too....
will be here in a couple of weeks....
quite addicting....
great bunch of guys here....lots of smarts...lots of very nice systems....

 

[gene french]

Thanks for this George. I took the time to read the whole thread...and reread it...and again...lots to digest. I'm left with the question of how then to control the output of my pl400. My problem is I have the pre out of an Sa 9800 to control 3 power amps. 2 pl400's and the amp stage of the 9800. I have 4 pair of speakers with varying levels of power handling and sensitivity.
How would I then vary the outputs to achieve a balance?
I would rarely fire up all of the amps and I really can't turn it up much over 20 watts. At 5 watts the infinity's are a lot louder than the JBL's. I have these amps because of the clarity and headroom they provide. This probably should be a thread all by itself.

you just described the versitility of a dsp....you have total control....mixer...parametric eq...active crossovers....total input output control....fantastic...
when i fire mine up....blinks the lights on that breaker....

 

[gene french]

actually 5....i have a 400 driving 15" woofers, a 400 driving 10" mid bass speakers...a 400 driving 6" midrange speakers...and a pioneer sx1080 driving the 1" soft dome titanium tweeters....they are controlled by a dayton 408 dsp....handles the parametric eq....mixing....and active crossover....
i have another 400 driving a set of voigts controlled by another dayton 408 dsp...
the active crossover made the biggest difference for me....so clean...you will never regret the dsp....
and the amps run cool...especially the mids and tweeters....as they use so little power....
the woofer amp is a wopl....the voigt amp is a wopl....both were old 4 fins i had collected....the rest are stock 8 fins with ps cap upgrades, dc protect boards....led lighting up grade...and one wopl has digital vu meters as one of my 8 fins had bad meters....a previous owner evidently took them apart...
i have another 8 fin redone and ready for duty....as a spare or maybe will replace the axr100 in the bedroom....which has my 3rd dsp....
i just today found another 8 fin....on the bay.....will refurbish it too....
will be here in a couple of weeks....
quite addicting....
great bunch of guys here....lots of smarts...lots of very nice systems....

i forgot to mention i have a schiit dac pushing a schiit preamp....which i use a y cable on the output of the preamp to drive the inputs of the dsp....which directs the correct signals to the correct output....my dsp has 4 inputs and 8 outputs...(2 stereo inputs...4 stereo outputs)....

 

[Oldskoolfan]

you just described the versitility of a dsp....you have total control....mixer...parametric eq...active crossovers....total input output control....fantastic...
when i fire mine up....blinks the lights on that breaker....

Looks like that Dayton 408 is the way to go. Don't know what I'm gonna do with those purty knobs and pots now though...

 

[gene french]

Looks like that Dayton 408 is the way to go. Don't know what I'm gonna do with those purty knobs and pots now though...

lots of bang for the buck....
minidsp is fantastic as well...
i read a lot of reviews before i pulled the trigger..
your mileage may vary!!!

 

[Oldskoolfan]

I always wanted to try bi=amping, but never bought a stand alone active crossover or a pair of speakers that could be bi-amped. A small mod to these SM-155's will resolve that issue then I can check it out once I have Val resto modded and tested.

 

[gene french]

Looks like that Dayton 408 is the way to go. Don't know what I'm gonna do with those purty knobs and pots now though...

goes between preamp and amps ....
still keep those knobs....i got bluetooth dongle for mine to configure and experiment....
and you will need to bypass the passive crossovers to take full advantage ....when i built my speakers ... i put xovers outside the enclosures....so i could experiment...glad i did ..easy to remove ..