No more 60 Hz hum in a PL2000 preamp.

stetter

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This is the snubbing. I believe it's correct. At least it looks perfect on the scope using the Quasimodo. Now going to install some soft recovery diodes and just listen to it. I'll dig around local and see if I can't find a good spectrum analyzer. View attachment 54494
enjoying your thread and your efforts, I have a PL2000 that I plan on upgrading so your pictures and info you have brought up has been a great read.
 

George S.

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I agree. Going to do some more reading about the noise issue with the PC based analyzer. Sitting here now listening to a FLAC digital file, and to me it's never sounded better. Just wish I could quantify the changes. Oh well.
 

George S.

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Be nice if I had better test equipment, but have to make due with what I have now and learn as I go. Pretty sure it's good as it is. No noise in the system prior to snubbing and swapping in soft recovery rectifiers. So I've got 2 to build. One for the main system and another for the "computer/electronics" room. Both of these other 2 PL2000s are all original and appear to have been sitting a long time. I'll keep the old one as it is for a test mule. I started on the first one today. Decided to take a week off work.
 

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Gepetto

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Be nice if I had better test equipment, but have to make due with what I have now and learn as I go. Pretty sure it's good as it is. No noise in the system prior to snubbing and swapping in soft recovery rectifiers. So I've got 2 to build. One for the main system and another for the "computer/electronics" room. Both of these other 2 PL2000s are all original and appear to have been sitting a long time. I'll keep the old one as it is for a test mule. I started on the first one today. Decided to take a week off work.
Good quality, low noise floor spectrum analyzers are quite pricey George.
 

George S.

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Good quality, low noise floor spectrum analyzers are quite pricey George.
Yes indeed! Been looking, will find one eventually. Sitting here listening to "Eat a Peach", a album I'm very familiar with. Hearing it as I know it and hearing some extra details that are different. I'm very satisfied with the preamp as it is. I think it was well worth upgrading it to match the WOPLs, they deserve a matching preamp. Someday I'll have the equipment to benchmark it.
 

George S.

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Making progress. Short a pair of resistors for the phono section on this one and short several items for the next. Put in a Mouser order, they appear to be having supply issues like everyone else.
 

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Gepetto

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Making progress. Short a pair of resistors for the phono section on this one and short several items for the next. Put in a Mouser order, they appear to be having supply issues like everyone else.
Yes they are George. Shortages everywhere.
 

VSAT88

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Mark, here's a photo of my modded unit with the probes connected to the pcb trace where the secondaries are soldered. Same as yours. Been thinking about what Joe said. Have considered using a regulated power supply add-on board, but don't really want to. Having too much fun learning about this! As far as I'm concerned the unit works perfect as is, just want to see if I can get the inaudible 60hz lower.
And, best of of all, I don't see the Browndogs misbehaving, the main reason I pursued getting the spectrum analyzer up and running.
Sitting here listening to Black Sabbath "Snow Blind" on a old Akai integrated amp and Pioneer CS-99 speakers. Damn this old gear sounds good!

Sabbath.JPG
 

VSAT88

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Interesting thread. I have finally read all the way thru. reminds me of the Kenwood C1/C2 builds a bit with the over volt op amps and how we cured that. I have no problem with no accessory outlets either but if I ever sold a unit I have no idea what another person might like or dislike about that. Some want these vintage units like stock. It also reminds me of some who have taken the Hafler DH-101 and removed the phono section from the pre amp altogether I suppose mounting it in a separate box outside of the preamp to lessen noise. The units like Jim were refering to like the Aragon 24K with the external power supply's are cool. My Sumo Diana was like that. The Aragon 28k I have now is not. To be honest I cannot tell any difference between the preamps I have used like the Diana as opposed to the 28K sound wise. However my recollecter is old and tired. I can however tell one hell of a difference between the MOD Squad line drive and the others. That only makes sense though. Its about a pure as it gets. Once again great thread.
 

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Got the IEC power socket and feet installed on #1. I'm going to put on some Black Sabbath and start on #2. This one was originally wired 240 and rigged for 120. It's turn on thump trips the WOPLs DC protect relays.
That thump may improve with OPA2134s installed.

You may want to install a 4.7M or something close to that across C47/49 and C48/50 to ensure they bleed off properly when powered down.
 

George S.

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Nah, not concerned about turn on thump. I hit 1 switch on a power strip and the whole system is on noise free. I'll be leaving all accessory power wiring out on these.
Was listening to a digital file of Emerson Lake and Palmer "Lucky Man" this morning, cranked, the windows were vibrating. This is one of the clearest most dynamic recordings I know of, and the system just handled it effortlessly. The preamp as is just blows me away. Joe, thanks for your help.
Now back to stripping down #2, it's a oily mess, prior owner way over lubed the pots. Whatever he used didn't evaporate
 
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George S.

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Well Denny did a great soldering job back in 78 or 79. Every trace is intact and tight.
I have yet to find a broken joint or plastic jack on all three PL2000s.
These Hakko vacuum desoldering stations make this easy.
Now the hard part, getting the old flux off. Wife was nice and got me a new bottle of 99% Isopropyl. Making sure everything is turned off before I use it!
 

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VSAT88

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That ELP Lucky man is bad ass on a set of SDA Polk speakers. Kind of amazed at how well it was recorded too. The image quality of your pictures is great. Nice camera. What you are doing is way over my head. I would probably never get that preamp back together if I took everything off that board like that. Pictures or not.
 

laatsch55

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That ELP Lucky man is bad ass on a set of SDA Polk speakers. Kind of amazed at how well it was recorded too. The image quality of your pictures is great. Nice camera. What you are doing is way over my head. I would probably never get that preamp back together if I took everything off that board like that. Pictures or not.

Supertramp was some Excellently recorded and engineered stuff...
 
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