PM1000 question (probably the first of many)

R-Diggital · Post by **R-Diggital** » Fri Apr 10, 2015 6:10 pm

Hey all, first time poster here.... hi!

I ordered ordered a couple PM1000 modules to try my hand at racking a them up. I didn't notice when I bought em, but these strips don't have buss selector switches, but rather a knob dedicated to each buss. Did some searching, but can't find anything on this. Not that this will affect my racking project, but was just curious to see if this was a diff version or what? Other than that, the guts look identical to the other pics I've seen.

Here's a pic

http://imgur.com/49DLcjd

Thanks! This is the biggest thing I've taken on and am definitely taking my time. But I have to spend some time staring at th e modulenas well as the schematic.

Thanks!
Randy

The Scum · Post by **The Scum** » Fri Apr 10, 2015 10:10 pm

Regarding the knobs - You've got one that was modified to be a monitor console.

The panpot was also lost in the process.

Really, the biggest thing lost is that the winkeye switches are kinda nifty...and none of it matters if you're just tapping off the fader buffer amp.

R-Diggital · Post by **R-Diggital** » Fri Apr 10, 2015 11:03 pm

OK, that makes total sense! Those buss switches are cool, and I would love to use them for something else but oh well. For this project I'm gonna keep it simple and keep all the switches where they are, etc. I figure I will be doing well just to get the jacks wired up correctly as well as the power supply.

You mentioned tapping off of the fader buffer amp- I have the pot that is connected to the fader itself, does that go straight to said buffer amp? Would I go from there to the output transformer to get a balanced output?

Yes- total noob. Thanks for the reply!

The Scum · Post by **The Scum** » Sat Apr 11, 2015 12:21 am

Tap the signal from the "-" leg of C37.

You want to include the amplifier stage that follows the fader before you hit a transformer.

R-Diggital · Post by **R-Diggital** » Sun Apr 12, 2015 12:06 pm

Fantastic! I really do appreciate that. Here's another question: I am looking at the caps and resistors and stuff that I will be replacing. I noticed that the microcenter down the street has tons ofncaps, reisistors, etc. Is there any specific attribute I need to watch for as far as material used to make them, or anything like that which might make not want to use them from there? I figured if not, I'd just make a list of the different values I need and go there for everything.

Thanks again. This is exciting stuff.

digitaldrummer · Post by **digitaldrummer** » Thu Apr 16, 2015 8:00 pm

I had a few strips like that and pretty much all of that stuff just gets cut off anyway when you rack it...

as far as components, I like to get some caps that are good for audio. The Nichicon Muse are nice, (or Panasonic FC I think - although there may be a new model now) and the Wima polypropylene or some polystyrene for bypass.

but Mouser.com is 1 ground shipping day away for me, so...

Mike

honkyjonk · Post by **honkyjonk** » Thu Apr 23, 2015 9:08 am

A long time ago I did what I thought was as close an A/B listening test as I could muster, comparing channels (in my 16 channel PM1000) with a couple different kinds of Nichicons and a couple different Panasonic types, and I came away liking the Nichicon PW series. FWIW. . . . .

Jim Williams · Post by **Jim Williams** » Sat May 09, 2015 6:26 pm

Make C37 bigger if you use that to feed an transformer or line out. I think it was 33 uf, 330 uf or so ought to feed a 1/1 600 ohm line transformer without rolling off the low end.

digitaldrummer · Post by **digitaldrummer** » Sat May 16, 2015 10:52 am

C37 was usually a 33uF on the channels and a 100uF on other boards (i.e. the output of the line amp). I always replace with a 220 or 330.

Jim Williams · Post by **Jim Williams** » Sat May 16, 2015 11:20 am

Driving a 600 ohm primary with that design may also up the THD and lower available output voltage. Replacing the output transistors with MJE 172 PNP or 182 NPN will allow for more current, less THD.

The old 2SC1000 NPN transistors are also noisy, I replace those with 2SC3329 BL and that hiss goes down. Use 2SA1084's for the PNP's.

R-Diggital · Post by **R-Diggital** » Sun Jul 12, 2015 12:33 pm

thank you all very much for the assistance! I've learned quite a bit, and am very happy that one of my channels is working great. I fried a resistor on the second one, but posted a separate thread on it.

honkyjonk · Post by **honkyjonk** » Sun Aug 02, 2015 2:57 pm

Jim, speaking of those output transistors, we're talking about Q12 and Q13 in this pic right? http://i26.tinypic.com/2vtwpvo.jpg (This is actually a pic of the master output I believe, but they're the same circuit as the input strip and this would be the spot before C37. In the input strip, these transistors are Q4 an Q9) Just verifying.

This is an interesting thread as well about the ability to drive a 600 ohm transformer: http://groupdiy.com/index.php?topic=14588.0

So, changing the output transistors to one of Jim's recommendations might improve it. I've read elsewhere on groupdiy though where that dude called 'PRR' (who is really smart,) saying it can drive a 600 ohm transformer fine.

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PM1000 question (probably the first of many)

PM1000 question (probably the first of many)

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