Larry's Phase Linear 700B

mlucitt

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Lee, I always pull that switch and the .47 mfd caps that go along with it in the PL 700. Joe's board design is robust enough that DC should not damage it. Many amps claim no caps in the audio path anyway. Plus, most preamps these days have DC limiting caps on the outputs, that is where you want to catch the DC.
 

fitz43

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I'm having trouble visualizing it. Can you post a picture of it. What was the reason the original location couldn't be used? Larger diameter power cord? Moving the AC away from that side?
 

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The cable would exit the chassis about 1-1/2 inch above the point of the screwdriver. It would not be visible from the front as the overhang of the faceplat would concveal it. We move the cord to improve the signal to noise ratio. At the same time that is being movd the whole wiring gets rebundled to keep hi and lo level signals away from each other and AC and DC separated also.
 

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Mark, the only reason I did not do that to this one was the Larrt liked the sound enough I was trying to impact it as little as possible.
 

laatsch55

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This is more like it. Right channel, Loaded, 8 ohms, 6 watt output, THD & N..... And this is the noisy channel....
 

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Where did that user name come from?? Gotta admit it's unique enough to deserve an explanation. Are the speakers you have listed all you have owned previously??
 

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Doug, dropped off the face of the world for a couple days(the Wyoming oilfield) but I'm back at it. While doing a max output test we were at 525 a channel when something on the left channel went south. This is not a rare occurance Doug and sometimes requires the owner of an amp I'm working on to have mountains of patience. BUT--it will perform as stated for my lifetime or send it back. And in your case I will make this offer, if and when you get tired of waiting I will refund your 750 back in a moments notice. I have promised a done date 3 times now and feel I have to make that offer in all good conscience.
 

laatsch55

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To the other PL nuts out there, while doing a max output test the left channel dropped output by half. The input is where I'm losing gain. With 500mv input from the AP I'm getting 250 mv input just past the RCA in jacks, in fact with the probes on the input jack pin of the RCA from the AP while it is plugged in it's 250mv. Unplug the AP and measure it then it is 500. So something is pulling the input down as soon as it is plugged in. Any ideas?
 

laatsch55

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Also, when you go ahead and turn on the other channel input the left channel goes to full input.......
 

NavLinear

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To the other PL nuts out there, while doing a max output test the left channel dropped output by half. The input is where I'm losing gain. With 500mv input from the AP I'm getting 250 mv input just past the RCA in jacks, in fact with the probes on the input jack pin of the RCA from the AP while it is plugged in it's 250mv. Unplug the AP and measure it then it is 500. So something is pulling the input down as soon as it is plugged in. Any ideas?
I haven't seen a 700 but looking at a schematic of a 700B it shows the input passing through the volume pot into the base of a transistor on the controller board. I'd begin with the pot and see if it is damaged. You might want to pull the wire from the output of the pot to the board and see what happens to your signal.
 

Oktyabr

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Where did that user name come from?? Gotta admit it's unique enough to deserve an explanation. Are the speakers you have listed all you have owned previously??
HI! :wave:

I'm one of your refugees from the Sound Thinking forums!

The name? It's Russian for "October". I got "October" from a calender years ago when I was trying to think up yet-another-user-name for a forum that I didn't think I would visit more than that one time. I hung out there (part of delphi.com) for a couple of years and the handle just sort of stuck. More recently others have had the same idea, believe it or not, and it's become more and more difficult to find "October" not already reserved by someone else. A few years ago I adopted the Russian spelling (even though I'm not Russian!) just because...

Yes, those are some of the speakers I remember owning. :laughing6:

I've owned a lot of amps, a few pre amps, turntables, etc. too over the years but ultimately I think I am pretty much a "speaker guy". It is, after all, the only component in a stereo directly responsible for reproducing your music. Living in the Seattle area in the age of craigslist made it easy to acquire different gear on what turned into a seasonal hunt for the *ultimate speaker*. I think it's really the journey that has counted and I don't think I'll ever reach it as a destination... but yeah, I've owned lots and lots of speakers. Loving my home made ones now, which I sold the Martin Logans to help finance.

This is a photo of some of the collection I owned a couple of years ago... see how many you can name?

(clickable thumnail, then click the larger image to see full size):


 

jbeckva

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This is a photo of some of the collection I owned a couple of years ago... see how many you can name?
I see a pair I recognize, yessir... (look at me siggie):hello1:

Gotta have them beeeg woofs! I bypassed a lot of the "schtuff" like the CB's and lpads. I think I could do more with recapping, but just haven't quite got the 'round tuit for it yet.
 

jbeckva

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To the other PL nuts out there, while doing a max output test the left channel dropped output by half. The input is where I'm losing gain. With 500mv input from the AP I'm getting 250 mv input just past the RCA in jacks, in fact with the probes on the input jack pin of the RCA from the AP while it is plugged in it's 250mv. Unplug the AP and measure it then it is 500. So something is pulling the input down as soon as it is plugged in. Any ideas?
First off, what's your DC resistance on the suspect channel versus the other? But then... with just the RCA plugged in (without the sig gen on the other end), does it drop? Might could be the RCA jack itself?

But also - Is it right across the input where (if I recall) those two clamping diodes were placed ala across the big cap at the top (going by what I remember on a rev "a" WO board)?
 

laatsch55

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Nav, the pot was suspect and something I hadn't isolated yet.
Jer, input impedence or DC offset??
 
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