My twin SN-Voice

para · Joined: Oct 16, 2006 Posts: 276

i read on the XR VCO page that you shouldn't sub out the LF442 for anything else without ill effects so maybe the same thing applies here

"The LF442 is recommended as the opamp to use for IC2. We tried a few different op amps, LM1458, LF442, TL072 and TL052, with the LF442 giving the best performance. In fact, the TL072 worked abysmally and should not be considered a candidate. The TL052 fared a bit better than the TL072, but tended to act quite squirrely at certain frequencies (heavy oscillation of the VCO output) and should not be considered as well. The LM1458 works 'OK', but does not possess the superior specifications of the LF442 and will not be nearly as accurate. Other op amps other than those mentioned may or may not work - we just never tried them. "

http://mypeoplepc.com/members/scottnoanh/birthofasynth/id20.html

andrewF · Posted: Thu Feb 08, 2007 4:04 am Post subject:

Hi
I used TL074s (2nd hand ones even)
no problems at all, so I'm sure 084s would be ok

fonik · Posted: Thu Feb 08, 2007 5:29 am Post subject:

thanks for that info. so it's time to troubleshoot... (business as usual)

Scott Stites · Posted: Thu Feb 08, 2007 7:34 am Post subject:

fonik · Posted: Thu Feb 08, 2007 7:53 am Post subject:

State Machine · Posted: Thu Feb 08, 2007 12:58 pm Post subject:

fonik · Posted: Thu Feb 08, 2007 3:18 pm Post subject:

State Machine · Posted: Thu Feb 08, 2007 5:45 pm Post subject:

fonik · Posted: Mon Feb 12, 2007 2:08 am Post subject:

hi all,
what should the output of the SN voice actually be?
i measured about 2.8ppV for the pulse before the buffer (0.25 after the buffer - must something wrong with it!).

BTW here is a picture of my SN voice module for my modular (eurorack)

State Machine · Posted: Mon Feb 12, 2007 7:36 pm Post subject:

fonik · Posted: Mon Feb 12, 2007 11:38 pm Post subject:

State Machine · Posted: Tue Feb 13, 2007 7:57 am Post subject:

fonik · Posted: Tue Feb 13, 2007 3:46 pm Post subject:

mosc · Posted: Tue Feb 13, 2007 3:49 pm Post subject:

State Machine · Posted: Tue Feb 13, 2007 4:35 pm Post subject:

State Machine · Posted: Fri Feb 16, 2007 4:27 pm Post subject:

Fonik,

I had taken some scope images of various signals on on the SN Voice. YOU can use these as a reference as you troubleshoot.

NOTE: The images are partially out pf order so. Image "x" where "x" is the file name.

Image "0" is of U4-10. It is the audio output of the SN76477.

Image "1" is of U4-8, pulse/noise output.

Image "5" is U1-12, feedback.

Image "2" is U4-7, triangle output.

Image "3" is U4-5, VCO CAPACITOR

Also, SYSYTEM INHIBIT, U1-9 should be 0V. AMPLITUDE CONTROL RESISTOR should be a 220K unit.

I hope some of these images help you in your search.

Bill

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State Machine · Posted: Fri Feb 16, 2007 7:20 pm Post subject:

One other thing I wanted to add to the above post is that in all the oscilloscope screen shots, the ground reference is center display indicated by the channel number "1" and right arrow.

As you already know I am sure, an inexpensive dual trace 30 mhz oscilloscope is the best choice when trying to troubleshoot problems concerning waveform shape, amplitude, frequency, etc .... Sometimes you can find very good second hand scopes on Ebay for very good prices.

Bill

State Machine · Posted: Fri Feb 16, 2007 7:34 pm Post subject:

synthmonger · Posted: Tue Feb 20, 2007 7:54 pm Post subject:

Oh yep! I ordered MOFS single buss PCB's and used that hehe Very Happy

2 pics for ya

Posted Image, might have been reduced in size. Click Image to view fullscreen.

Also I posted some vids of my Bleep Machine on my youtube account. One of which is being CV'd by the EG of the SN-Voice.

http://www.youtube.com/profile?user=synthmonger

I still have one PCB left that I'm going to use with a 4-5 octave keyboard and extra typical synthie goodies. I won't have time to start it until the summer though when my band "Bananarchy" is in full effect. Very Happy

toybox · Posted: Tue Feb 20, 2007 9:32 pm Post subject:

bad ass good job thumb up

bambam · Joined: Feb 20, 2007 Posts: 60 Location: australia

Hi All

I've just about finished my two snvoice pcbs but wanted to confirm a few things before i finish them up before the weekend.

I found i dont have 470pf poly caps at home and i went to a few local places today and they only seem to ahve the value in ceramics and not in polys Sad

'apparently' its a pretty small value for a poly and thats why they dont have it as its not that common.
Of course i can order a few and wait but theres a chance they wont get here before the weekend and i really would like to have them up and running by then!
Does anyone know if the 470pf poly at C5 can be raplaced with maybe just a ceramic without any negative results?
I know ceramic can be swapped for poly in some situations but im not sure here.

Apart from that the only other thing thats holding me up is the pot wiring etc
I was looking at the wiring diagram for the pots and it seems to indicate the resistor etc to wire to and not the pin on the connectors labelled J1 to J3 Do I need to follow the schematic to figure out what wires into where? Also the parts list has J1-10 listed as being for the 1\4” jacks but I cant find them anywhere.
Am I missing a bit of doco that covers this or is it a case of following the schems to figure out wiring pots and jacks?
I have asked bil but our mail is playing up and anyway id prefer not to hassle him direct Wink

cheers
Brett

cheers
Brett

andrewF · Posted: Wed Feb 21, 2007 12:38 am Post subject:

Hi Brett
C5 is the timing cap for the VCO in the 4046, if I didn't have anything else I'd use a ceramic. it won't hurt to use a ceramic temporarily but replace it when you can.

Bill sent out a page with all the pots and jack connections to the connector pins, it sounds like you are missing it.
i can scan it and post it if you like?
or if Bills around, I'm sure he already has a digital version...Bill?

CJ Miller · Joined: Jan 07, 2007 Posts: 368 Location: 127.0.0.1

Bambam, I'm in the same boat here with 470pF caps. This is a rare value for polypropylene in my experience, but not uncommon for polystyrene. I too will likely sub a ceramic for the short term.

My boards are 95% done! I am just trying to be patient while waiting for the last few parts to arrive.

bambam · Joined: Feb 20, 2007 Posts: 60 Location: australia

Thanks for the replies guys.

Bill got back to me overnight and forwarded the doc with the wiring and now it all makes sense Wink

I was pulling my hair out trying to figure where the hell J1-10 were for the jacks!

I think i may use a ceramic for C5 for now but if its just a temp thing i may be patient and wait till an online order for the polys arrive.

Huge thanks to bill for answering all my questions along the way and for forwarding the doco last night despite being sick with the flu!

B