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 Forum index » DIY Hardware and Software
GM Voice for the 21st Century
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Dan Lavin



Joined: Nov 09, 2006
Posts: 649
Location: Spring Lake, Mi, USA
Audio files: 21

PostPosted: Sat Mar 08, 2014 12:54 pm    Post subject: GM Voice for the 21st Century
Subject description: An update to the GM Voice found in the Thomas Henry subforum
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Hello group. It's been a while since my last project, but I finally have a new one to present. Since work on the original GM Voice, ( http://electro-music.com/forum/topic-21634.html ),I've been on constant outlook for other boards and chips to use for upgrades to the project. Let's face it, the GM Voice is currently dependent on boards made in the 90's shipping from a couple guys in China. There's no telling how long these will be available. Lately, there have been a couple of newer GM synth chips out there intended for use in mobile phones. I found the SAM2195 chip which looks like a really good update candidate. It has 64 voices and built in effects. On the downside, they aren't DIY friendly. Besides being SMD, they are extremely tiny. It would be difficult for most DIYers to use as is.

Fortunately, there is a company called Modern Devices which makes a product called the Fluxamasynth. Yeah, not a great name, but who cares if it works? The original intent of the Fluxamasynth is to act as an Arduino shield, however with a simple circuit addition, it's possible to create a new updated GM Voice to use as a standalone midi product.

Here's the Bill Of Materials:
Qty 1 5volt power supply
Qty 1 Fluxamasynth board ( http://moderndevice.com/product/fluxamasynth-shield/ )
Qty 1 Midi connector
Qty 1 8 pin DIN socket
Qty 1 1N914 small signal diode
Qty 1 220 ohm 1/4W resistor
Qty 2 390 ohm ΒΌ W resistor
Qty 1 LED (your choice of color)
Qty 1 perfboard (or you can make a pcb)
Your choice of panel or case and mounting hardware
A few wire scraps
Optional stereo audio taper 10-100K pot for manual output volume adjustments

That's it! It's embarrassingly short and simple. This barely qualifies as DIY in my book. You'll probably spend more time on the case/mounting panel than the electronics.

Sound-wise, it's quite good, in my opinion. I think I still like my db50xg boards a little better but that may be just a personal choice.


GMVoicepcbs_compressed.jpg
 Description:
if you look carefully you'll see I accidentally wired the +5V power supply to the +5V Flux pin instead of the Vin pin!
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GMVoicepcbs_compressed.jpg



GMVoiceStack_compressed.jpg
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here's what the 2 boards look like together
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GMVoiceStack_compressed.jpg



DSCN4055 (2).jpg
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updated front panel (still not perfect, but much better than previous pic!)
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DSCN4055 (2).jpg



GMVoice21Cschematic.pdf
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 Filename:  GMVoice21Cschematic.pdf
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Last edited by Dan Lavin on Tue Apr 29, 2014 4:39 pm; edited 1 time in total
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Dan Lavin



Joined: Nov 09, 2006
Posts: 649
Location: Spring Lake, Mi, USA
Audio files: 21

PostPosted: Sat Mar 22, 2014 1:44 pm    Post subject: Reply with quote  Mark this post and the followings unread

I just submitted an updated schematic. I have added a fourth resistor to the interface circuit. Pin 7 really needs a pull down resistor to keep from getting stuck notes on dense midi file playback. In this case, I used a 10K ohm.
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Dan Lavin



Joined: Nov 09, 2006
Posts: 649
Location: Spring Lake, Mi, USA
Audio files: 21

PostPosted: Wed Mar 26, 2014 5:02 pm    Post subject: Reply with quote  Mark this post and the followings unread

Here's a sound sample of its capabilities in a rock context.


LosEndos.mp3
 Description:
Genesis' LosEndos...pretty faithful to the original recording. This is a standard midi file found online. Sorry forgot the address. Watch out...has a couple false endings!

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richardc64



Joined: Jun 01, 2006
Posts: 679
Location: NYC
Audio files: 26

PostPosted: Thu Mar 27, 2014 7:43 am    Post subject: Reply with quote  Mark this post and the followings unread

Niiiice. That's a lotta sound from a project that "... barely qualifies as DIY."
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Dan Lavin



Joined: Nov 09, 2006
Posts: 649
Location: Spring Lake, Mi, USA
Audio files: 21

PostPosted: Tue Apr 29, 2014 4:40 pm    Post subject: Reply with quote  Mark this post and the followings unread

updated the front panel photo. Not sure why this one has been so hard to get a good photo of!?
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fonik



Joined: Jun 07, 2006
Posts: 3950
Location: Germany
Audio files: 23

PostPosted: Wed Apr 30, 2014 2:29 am    Post subject: Reply with quote  Mark this post and the followings unread

i just ordered the board. will make a small eurorack module from it. this way i could justify to bring a smaller portable modular case to the bands rehearsals Very Happy

thank you, dan!

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Dan Lavin



Joined: Nov 09, 2006
Posts: 649
Location: Spring Lake, Mi, USA
Audio files: 21

PostPosted: Wed Apr 30, 2014 6:17 pm    Post subject: Reply with quote  Mark this post and the followings unread

Thanks and you're welcome Matthias! I had the same issue with the original GM Voice, but I moved it to a smaller 6U rack case for that same reason. Wink
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Dan Lavin



Joined: Nov 09, 2006
Posts: 649
Location: Spring Lake, Mi, USA
Audio files: 21

PostPosted: Tue Jul 01, 2014 11:23 am    Post subject: Reply with quote  Mark this post and the followings unread

I just posted in the Arduino sub-forum a way to make the GM Voice respond to a single midi channel instead of all midi channels. Should be easier to work with other midi modules:

http://electro-music.com/forum/post-401253.html#401253

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fonik



Joined: Jun 07, 2006
Posts: 3950
Location: Germany
Audio files: 23

PostPosted: Tue Jul 01, 2014 3:18 pm    Post subject: Reply with quote  Mark this post and the followings unread

the synthboard is on, alas, i have had no time yet to build anything... so i will definetely have a llok ath the midifilter.
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Dan Lavin



Joined: Nov 09, 2006
Posts: 649
Location: Spring Lake, Mi, USA
Audio files: 21

PostPosted: Tue Jul 01, 2014 3:41 pm    Post subject: Reply with quote  Mark this post and the followings unread

Yeah Matthias, I wish I hadn't built my panel so fast. I would've had the channel filter built in. OTOH, I have a Yamaha db50XG version of the GM voice which can use the standalone Channel Filter.

Another thought if you build with the Channel Filter: use a switch to select from the raw midi in or the Channel Filter out. That way it can function as a single channel voice or a 16 channel synth for midi file playback.

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yogi



Joined: Jun 26, 2008
Posts: 29
Location: Maryland

PostPosted: Tue Aug 05, 2014 12:31 am    Post subject: Reply with quote  Mark this post and the followings unread

This is very cool, have wanted to build a DB synth for a long time but finding a card has put me off, and it looks like the China source has dried up now. Thanks for finding a good alternative Smile
Just finished reading through the original GM Midi Mod thread (s) which I think I looked over awhile back. A real fan of XG midi and even though the SAM chip isn't quite the same as a DB60 it looks like it's the closest I'll get without spending a bundle.
Kind of got interested again in this project because of a thread over at MidiBox.org that pointed to this thread (very circular ). Anyway, the board that was mentioned is the DREAMBLASTER SYNTH S1 by the Belgium company SERDA SHOP.
http://www.serdashop.com/waveblaster
It is based on the SAM 2195 also but has a Waveblaster connector so one could use it on a soundcard also. It might be a good alternative for European builders shipping wise.
Got an order in for a Fluxamasynth and looking forward to playing with it Smile Thinking it would make a great tone generator for a Atari ST!
yogi
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