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 Red/black vs brown/black jacks - which is original 2700? 
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Joined: Wed Sep 25, 2013 10:31 pm
Posts: 56
Post Red/black vs brown/black jacks - which is original 2700?
I have received another Paia 27xx type synth and I have noticed something very interesting - while it contains two 4700 type modules, which have red and black CV jacks, the others seem to be the original 2700 ones, but they have brown and black jacks, not the red and black ones that my other 2720 has. Also the power supply, and many of the other modules (except the 47xx) have those old silver barrel type capacitors that look like something from the 60's. I can't help but think that this one started out as a first gen 2700 that was later retro fitted with a real keyboard and the 47xx modules. Is my theory correct?


Thu Nov 07, 2013 4:55 pm
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Joined: Sun Nov 09, 2008 2:49 pm
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Post Re: Red/black vs brown/black jacks - which is original 2700?
It wasn't unusual to see combinations of 2720 and 4700 series modules, especially since the 4700 series had a larger wing cabinet.

As builders expanded their systems, they'd often opt to include some of their older 2720 series modules in a cabinet along with their newer 4700 series ones and the more powerful supply and keyboard controllers, sequencer, etc. introduced with the series.

I don't recall seeing brown connectors -- maybe they're aged red ones???

The vintage looking capacitors could well be from the sixties.

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Scott Lee
scott@paia.com


Fri Nov 08, 2013 4:08 pm
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Joined: Wed Sep 25, 2013 10:31 pm
Posts: 56
Post Re: Red/black vs brown/black jacks - which is original 2700?
No, it's not an aged red color. Those Jacks are dark brown as in Chocolate brown, front and body. That and the old style components (silver caps, dark brown resistors) lead me to believe that those modules might be first generation 2700 modules, not the 2720 modules with red jacks. Just trying to make sense of what I see. When I saw the ebay pictures, I thought there might have been something off with the seller's camera, but apparently that wasn't the case.

PS: I just came across this old post on Matrixsynth. This seems to confirm my theory.

http://www.matrixsynth.com/2012/05/paia-modular-synth-2700-4700-with.html

Here's the actual synth that I won:
http://i.ebayimg.com/t/Vintage-modular-synth-needs-work-paia-2720-rare-keyboard-diy-/00/s/MTIwMFgxNjAw/z/okkAAOxyg7xSaHcf/$T2eC16Z,!)IFIeZSuPrVBS,Hcdndig~~60_57.JPG

Note that there's no oscillator present, but it looks like the wires at the rigt end of the case were meant to hook up a box of extra modules. The slider hanging out next to the power module appears to be what was the tuning knob inthe back (modified to some kind of pitch bender?)
It's in pieces now because the case was so shabbily put together, it was nearly falling apart when I took it out of the box. I'll have to custom cut me some of the wood pieces at home depot, and give the whole thing a new paint job. I plan to spray paint it yellow and put a giant blue Paia logo on the back :D


Sat Nov 09, 2013 1:14 pm
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Joined: Thu Mar 07, 2013 1:15 am
Posts: 36
Post Re: Red/black vs brown/black jacks - which is original 2700?
Congrats on your purchase. One of the fun things about PAIA equipment is customizing it, but you may want to give pause to the idea of painting that orange case, especially since yours looks in good condition. That orange case is part of what makes those vintage synths a PAIA. Something to give thought to is that spraying it a different color may reduce it's desirableness for resale value, if that's a consideration. I would recommend starting with the electronics rehabbing first.

If you haven't already seen it, another user has a site with some handy tips for those older synths: http://obsolete-synthesis.blogspot.com/


Sat Nov 09, 2013 6:04 pm
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Joined: Wed Sep 25, 2013 10:31 pm
Posts: 56
Post Re: Red/black vs brown/black jacks - which is original 2700?
Interesting. I was actually thinking about saving the metal cover and perhaps put together one made of clear/colored plexiglass/plastic, and put some lights in it. I intend to extend the rackspace anyhow so it holds two rows of modules. Actually I could do that with my other Paia, I was gonna replace the Keyboard anyhow. Hope it'll work out. I'm thinking about adding status and blinky lights for the power and other modules as well..

Another idea just popped in my head - how about a "baby 2720"? That would involve unscrewing the faceplates from the pcbs and fasten them horizontally above the pcbs, and arrange them, so I end up with something similar to a Minimoog or Buchla music Easel or something. That would make it highly portable. The tricky part would be to include the 4780 sequencer as well.. Those 25 turn pots are a problem.

PS: About the metal cover - would it be a problem if I put just the paia logo on it, without painting the whole thing yellow?


Sat Nov 09, 2013 10:16 pm
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Joined: Thu Mar 07, 2013 1:15 am
Posts: 36
Post Re: Red/black vs brown/black jacks - which is original 2700?
Any sticker you create and attach in a non-destructive manner should work. You can try clear adhesive film, paper, label stock, etc.

Waterslide decals are one way to attach a non-destructive logo or artwork. Print your image on inkjet decal or laserjet decal paper (the two are not interchangeable), soak in water to release the backing, and transfer the artwork to your synth. It can be tricky to do as the decals are delicate and want to fold and bunch up. Usually you protect the decal by spraying it with a clear fixative spray, but this is not mandatory, though the decal can scratch without it. Decal paper can be found on auction sites.

PAIA provides some logos which you can use as a starting point. Look for "logos" under "sitemap." The logos are small and seem intended for websites, but you could scale one up to a larger size.

You have so many ideas, I think the hardest part for you will be deciding where to start!


Mon Nov 11, 2013 8:21 pm
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Joined: Wed Sep 25, 2013 10:31 pm
Posts: 56
Post Re: Red/black vs brown/black jacks - which is original 2700?
Yeah, that's my problem, I have so many ideas flying around in my head, and they collide with each other and I'm like "Oh, screw this!". Well I don't have the time and money to do a complete redesign of a Paia case/modules at this point in time plus they (the modules) are more valuable in original condition, but I was thinking about ditching the original power reels for a strip of mini Molex plugs, and fit the modules with connectors. Makes for easier moving/replaceing of modules. By the way I undid most of the mods that were done on my other Paia, mainly because they didn't work or were impractical. I was hoping that undoing the mods would fix the issue with the PWM, but it didn't. It still sounds weird and fuzz like, and has a very short range. Same thing with the Sine/PWM module. Did they all really sound that way? Compared to a Demo video I found on Youtube it sounds very distorted doesn't seem to track with the oscillator (as in it changes and phases out, the higher the notes I play) I'll see if I can put up a quick demo so you see what I mean.


Thu Nov 14, 2013 2:12 pm
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Joined: Thu Mar 07, 2013 1:15 am
Posts: 36
Post Re: Red/black vs brown/black jacks - which is original 2700?
Pulse wave output problems? Here's something to try on the 2720-2A VCO with a non-existent pulse wave audio output and/or a pulse width modulation that is narrow in range: Replace R8 with a 10k trim pot, and lower the resistance until the pulse returns. Then try the pulse width modulation control. If the range is still too narrow, continue to dial down the resistance till you get a full range. That's the resistance you want. You can measure that and use a resistor, or just keep the trimpot installed. I used a 25-turn cermet pot, and just left it in the circuit, as cermet pots are designed for "set it and forget it" applications. If you don't have a trimpot handy, just try a resistor that is lower in resistance than the one installed in the circuit. Perhaps there are other solutions, but this approach worked for me.

While the value of R8 should be matched to the circuit in the original kit, it is possible that components were replaced by a previous owner, and that the R8 resistance value is no longer suitable.


Thu Nov 14, 2013 4:40 pm
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Joined: Wed Sep 25, 2013 10:31 pm
Posts: 56
Post Re: Red/black vs brown/black jacks - which is original 2700?
I don't think that anything was changed/modified in the circuit, other than some internal patching between some of the modules. When I routed for example the VCO's triangle or pulse output to the Sine/PWM module, and controlled it from one of the bias dials, it had the same effect - distorted and fuzzy sounding, and phasing out the higher notes I played.
Here is the Youtube demo I was talking about. Note how it sounds when he turns the PWM knob? This is NOT how it sounds on my Paia, even when using said Sine/PWM module. It does sound badass on my synth, but that's not how it's supposed to be.


Fri Nov 15, 2013 12:34 am
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Joined: Wed Sep 25, 2013 10:31 pm
Posts: 56
Post Re: Red/black vs brown/black jacks - which is original 2700?
Ok, here ara some quick clips demonstrating how the PWM on my first Paia behaves:

1. PWM from the 2720-2a VCO - note how it doesn't seem to track right with the keyboard scale, and how intense and distorted it sounds? (I know, the keys need some serious tuning)
https://app.box.com/s/8yov8xuo3wiseblfmeg3

2. PWM with square wave routed through the 2720-14 Sine/PWM converter - it doesn't sound as intense and fuzzy and distorted as from the VCO itself, but still doesn't sound right to me.
https://app.box.com/s/t921se34pk7v7mjfom3y

3. Same as #2 but with keyboard CV control, which didn't help at all.
https://app.box.com/s/qghkotf6r0td022henz9

Is this normal or what's up with that?


Sat Nov 16, 2013 7:03 pm
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