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Conference napalm::commusic_v1

Title:* * Computer Music, MIDI, and Related Topics * *
Notice:Conference has been write-locked. Use new version.
Moderator:DYPSS1::SCHAFER
Created:Thu Feb 20 1986
Last Modified:Mon Aug 29 1994
Last Successful Update:Fri Jun 06 1997
Number of topics:2852
Total number of notes:33157

66.0. "PAIA circuits box" by PIPA::JANZEN () Mon Feb 18 1985 20:23

Hello.  This is not computer music but you might be interested.
I finished building the PAIA circuit box using 4700 series modules
(except one which is 2700 I think the noise source).

I have a 
VCO (really only to drive the balanced modulator)
	Works pretty well. My 'scope (which is fuzzy -needs a new tube)
	shows a pointy sine.  I will try to adjust the oscillator
	some more; maybe it can be curvier.  (I originally adjusted
	without a scope because the 'scope was broken.)
	It works for me.  It is all discrete treansistors.
	Must have some external control voltage in to go,
	but has a knob to adjust over part of the range.
	Uses UJT relaxation osc. design; comparator to make
	adjustalbe pulse.  has sine and triangle.
VCF 
	This uses three different kinds of op amps - Norton,	
	Operational Transconductance, and 748? or similar.
	It is impressive to me.  Works pretty well.  Must
	have a control voltage in to go, but has  a knob
	to adjust over part of the range.  Adjustable Q is
	sharp.
road box
	I have no experience; seems OK to me.  Only got one.
power supply
	I have blown it out twice because it is unfused.  I will	
	fuse it.  It is the +-9 adjustable with two control outputs.
	Quick and dirty design.  Also has an unregulated 18V
	supply righty off the rectifier with 1000uF cap, which made
	some circuits hum.  P.U.  Uses 7805 and 7905 in an
	adjustable voltage circuit topology.
balanced modulator (replaces OLD diode ring modulators)
	I had built this last year, but the movers lost it.
	I have never been able to adjust away the inputs completely,
	but they are very quiet, almost unnoticeable.
Mixer
	El Cheapo (what did I expect?)
	One little op amp for each channel.  Four Inputs, each
	with pan and volume, and each of the two 
	output channel has  a volume.  it will do the job for me,
	except mic preamping, which I need.
control osc /noise source
	The noise is full of snaps and cracks, based on a 
	base-emitter junction noise source.  I don't like it.
	It is also hummy.  It uses the unregulated 18V supply.
	All Discrete semiconductors, I recall.
reverb 	
	Will be hummy if you use unshielded cables (surprise, surprise).
	Seems to work a little differently from the one the movers
	lost, but maybe not.  I still have to check my assembly.
TOm
still no vocoder from the Wells-Fargo Wagon
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66.1PIPA::JANZENMon Feb 18 1985 20:299
I also got the enveople follower.  Works fine, but the level is sort of low.
Just put in a high level.

The movers lost home-brew oscillator (8038) and envelope follower 
I had PAIA reverb and modulator
(National Semiconductor Linear Databook examples of precision rectifiers 
and low pass filters - the same thing PAiA did.)

TOm
66.2BARNUM::JWALTONTue Feb 19 1985 12:0223
	TOm,

	I've got some PAIA stuff that I don't use anymore;
	27 series (2)VCO's, (1)ENV FOL, (1)CVO/noise, (1) 
	BAL MOD, and (1)VCA. 47 series (2)ENV FOL, (1)VCO,
	(1)MULTI MODE FILTER, (1)SEQUENCER, oh ya and the
	reverb. If you would like them, FOR FREE you are
	welcome to them. BUT I must warn you these are the 
	modules that I 'practiced' soldering on. I almost
	wouldn't offer them because I'm embarassed about 
	the workmanship. oh ya and one of those 4chan mixers.
	Again you may have them If you like, but some are
	I should say all are in various states of disrepair
	raped, unfinished. They may be more trouble than they 
	are worth. But there are a LOT of them. Oh ya there's
	the keyboard module and the gilde retrofit.
	I may have left something out. Or added something I 
	don't have, but It has been a long time.

	I used to get some real mean dogbarks out of it.
	

	John
66.3PIPA::JANZENTue Feb 19 1985 12:387
I called PAiA last night; the vocoder hasn't shipped to anybody yet.
It was supposed to ship last november.  It will probably ship 2-25.
There were last minute parts changes.

Sound familiar?

Tom
66.4DCVAX::SBROWNWed Mar 27 1985 00:198
I've got some mods to that little cheapo mixer for ya. Replace the 741's
with TL081's, and it'll be noticeably less hissy. As for the hum, careful
routing of signal wires and the AC power, as well as good grounding will
help. The TL081's better cmrr may help, too. That little mixer will run
for hours on nicads. I'm still thinking of what to do with the rest of my
PAiA stuff. Never could get my old analog keyboard to stay in tune. 

-seymour-
66.5PIPA::JANZENMon May 13 1985 14:5313
I just found out that I had put in the 2N2712 transistors backwards in
the VCO.  The drawing showing installation is a little tricky.
Now the sine tone is sinier, but still not as pure as the 8038 chip puts out.
the sine tone is now loud enough to use as a level.

I fused the power supply, mounting a mini fuse in one of the special holes
for capacitively coupled connections, since I don't need that.

The noise source and the reverb still hum, so I will investigate that next.
I wish the envelope follower had a bigger amplitude; maybe I made an error
there too.

Thomas
66.6PIPA::JANZENTue May 14 1985 11:353
I fixed the reverb.  I had the 5K pot and the 500k pot reversed.  It works
better, still hums somewhat.
Thomas
66.7PIPA::JANZENThu May 30 1985 22:208
Preliminary indications are that my home-brew LM317-based
18 volt power suply all but eliminated the hum on the PAiA circuits that
required 18V, including I recall perhaps imperfectly, the modulator
and the noise source.  I got a new 25.2V Xformer and screwd it in there
in what little space is left.

The LM317 is adjustable.
Tom
66.8PIPA::JANZENMon Jun 03 1985 15:104
but there is still hum in the reverb.  the spring is next to two transformers.
It could be mechanical (shaking) or magnetic (probable) or electro-magnetic.
Got to get some mu-metal.
Thomas