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 Forum index » DIY Hardware and Software » Thomas Henry designs
The Sound One
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Thomas_Henry



Joined: Jul 24, 2009
Posts: 140
Location: N. Mankato, MN

PostPosted: Fri Mar 28, 2014 1:49 pm    Post subject: The Sound One
Subject description: A One-Chip Cigar Box Synth
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Hello gang,

This project is just for fun, but it gave me a chance to try an idea which really worked out nicely. And, I'll also pass along a few thoughts concerning the SN76477.

The new idea is this: the VCO, LFO, noise clock, noise filter, attack, release and one-shot all require a timing resistor. But it occurred to me that each of those resistors could be replaced with a one-transistor current sink if desired. This has several advantages. First, it gives voltage control for each of these parameters. But most important is the greatly expanded range.

For example, using the circuit of the TI data sheet, the VCO range is a measly 10:1. With the current sink, this becomes a staggering 50000:1!

If you look at the TI data sheet, you'll see that the designers there make extensive use of range switching. There are gigantic multi-position rotary switches to kick in a half-dozen capacitors all over the place. But with this current sink idea, they all get jettisoned. One pot covers the entire range.

For the purposes of this project, though, I decided to restrict things a bit, just to make the PWM effect more pronounced.

Anyway, attached is the schem. Here are the features:

-- VCO
-- LFO
-- sweepable noise
-- FM
-- mixer
-- AR type envelope generator
-- battery operated, 10mA draw
-- one-chip design
-- no range switching, hence a super-low parts count
-- internal Zener is used to create the +5V supply
-- internal preamp outputs a line-level signal

A couple other thoughts: the internal one-shot business in the data sheet to generate the envelope stinks. It's completely awkward. So this design uses the external logic affair that Scott Stites stumbled upon. I simply redesigned everything to use a single transistor to generate the needed gate and trigger.

I also used Scott's idea for the PWM. You might want to compare this with the SN-Voice that he and I designed several years back. You'll find it on his Web site.

Note, too, how I do the noise sweep with a single transistor. You can't get any simpler than this for a very wide range noise source.

Be sure to pay strict attention to the power supply. There are two 9V batteries. The positive one feeds the Zener input at pin 14; this is its only connection. But the output of the Zener, at pin 15, creates the +5V supply throughout. Total current drain on the +5V supply is about 1mA, well under the 10mA limit imposed by the data sheet.

On the other hand, the negative battery creates the pot voltages required by the current sinks.

Speaking of which, with the values shown, the sinks sink 200uA max, as specified by the data sheet.

While this particular circuit may not be what you are looking for, some of the ideas in it might prove useful elsewhere.

As usual, please don't republish this schematic anywhere, but instead link back to electro-music. And be sure to ask first if you intend to do a circuit board or anything commercial with it. Other than that, have fun with it and be sure to post any results here.

Thomas Henry


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elmegil



Joined: Mar 20, 2012
Posts: 1582
Location: Chicago
Audio files: 14

PostPosted: Fri Mar 28, 2014 6:34 pm    Post subject: Reply with quote  Mark this post and the followings unread

That looks really cool.

I think it might be interesting (though obviously it adds complexity) to add a simple VCF with a similar set up to control it like the noise sweep, EG/LFO/Manual....
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Thomas_Henry



Joined: Jul 24, 2009
Posts: 140
Location: N. Mankato, MN

PostPosted: Fri Mar 28, 2014 10:09 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hi,

Yes, a person could do that but...the filter is only a one-pole affair, and hence quite weak.

On the other hand, the noise clock sweep sounds for all the world like a potent bandpass filter with heavy resonance. So my suspicion is that sweeping the lowpass filter wouldn't add very much to that. But don't let me stop you from experimenting!

By the way, I first hit upon this noise clock sweep = bandpass filter effect back in 1981. It's perhaps the best thing in the world about the SN chip. I don't recall hearing anything else like it.

Thomas Henry
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bijlevel



Joined: Sep 20, 2014
Posts: 23
Location: Delfgauw, The Netherlands

PostPosted: Wed Sep 24, 2014 7:24 am    Post subject: The Sound One
Subject description: schematic
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Hi,
I'm a relative newbie on building devices like this Sound One, using a provided schematic, as in this case. Before I start I want to be sure if I'm reading the schematic correctly, especially the capacitors. It is clear that you mean electrolytic capacitors when there is a plus sign, so I figure the other capacitors in the schematic are just "plain" capacitors. Am I right? Also you mention in your description "sinks". Do you mean heat sinks and do I need them or do you mean something totally different? Thanks in advance!

Regards,
Sjoerd Bijleveld
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Wobuse



Joined: Dec 07, 2011
Posts: 33
Location: Lyons,il

PostPosted: Thu Sep 25, 2014 3:26 am    Post subject: Re: The Sound One
Subject description: schematic
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bijlevel wrote:
Hi,
I'm a relative newbie on building devices like this Sound One, using a provided schematic, as in this case. Before I start I want to be sure if I'm reading the schematic correctly, especially the capacitors. It is clear that you mean electrolytic capacitors when there is a plus sign, so I figure the other capacitors in the schematic are just "plain" capacitors. Am I right?


Yes , that is correct...
Quote:

Also you mention in your description "sinks". Do you mean heat sinks and do I need them or do you mean something totally different? Thanks in advance!

Regards,
Sjoerd Bijleveld

No ,,no heat sinks required.. Current sink, is an electrical concept , and part of this curcuit .

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bijlevel



Joined: Sep 20, 2014
Posts: 23
Location: Delfgauw, The Netherlands

PostPosted: Thu Sep 25, 2014 5:06 am    Post subject: The Sound One
Subject description: schematic
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Thanks a lot for the quick reply! Your answers make me feel less insecure Smile .
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bijlevel



Joined: Sep 20, 2014
Posts: 23
Location: Delfgauw, The Netherlands

PostPosted: Wed Oct 01, 2014 11:31 am    Post subject: Reply with quote  Mark this post and the followings unread

Did someone design a PCB for this Sound One?
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bijlevel



Joined: Sep 20, 2014
Posts: 23
Location: Delfgauw, The Netherlands

PostPosted: Sun Oct 19, 2014 11:06 am    Post subject: Sound One
Subject description: what kind of switches to use
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I posted this also one level up (Thomas Henry Designs, sorry)
I'm in the process of designing a PCB from the provided schematic with EAGLE. It is not clear to me what physical kind of switch, or set of switches, to use for VCO FM, Mixer ABC and Env Sel 1,2. Also Thomas Henry provided the table for the various combinations of the mixer en de Envelope Select, but what happens if the switch VCO FM is switched to "on", or is this an independent switch? Hope someone can answer my (newbie) questions.
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elmegil



Joined: Mar 20, 2012
Posts: 1582
Location: Chicago
Audio files: 14

PostPosted: Sun Oct 19, 2014 12:25 pm    Post subject: Reply with quote  Mark this post and the followings unread

VCO FM is a simple SPST (you could use an SPDT and only connect one side).

If you didn't want to just have a bank of switches for mixer select and envelope select, there are binary/hex encoded switches out there. The one I'm most familiar with is the Grayhill 25LB22-H which has 16 positions, a bit of overkill, but definitely for the mix select it would be pretty straightforward to use the 25LB45-H which has 8 positions. It's a rotary hex-encoded switch, so it would let you generate the switch patterns necessary to select which mix you want.

There are another type of grayhill encoder that could work, but they're very expensive ($20 and up), but they are also 4 bit encoded, and would allow you to adjust the number of positions down to 4. http://www.mouser.com/Electromechanical/Encoders/_/N-39xfc?Keyword=BCD+switch&FS=True&Ns=Pricing|0

This one might work: http://www.mouser.com/ProductDetail/Apem/PT65312/?qs=sGAEpiMZZMsfGXvUAbE5P77o%252bw6vaF%2fJOcvenQozs0o%3d

but it's not clear how big it is (haven't dug through all the data sheet yet). Could just be like a trimmer.
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bijlevel



Joined: Sep 20, 2014
Posts: 23
Location: Delfgauw, The Netherlands

PostPosted: Mon Oct 20, 2014 10:58 am    Post subject: Sound One
Subject description: what kind of switches to use
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Thanks for the help and information! I will definitely look into those hex-encoded switches, but for my first prototype I will stick to SPST-switches (I have a couple of them laying around).
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bijlevel



Joined: Sep 20, 2014
Posts: 23
Location: Delfgauw, The Netherlands

PostPosted: Mon Oct 20, 2014 11:02 am    Post subject: Re: The Sound One
Subject description: A One-Chip Cigar Box Synth
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Thomas_Henry wrote:

And be sure to ask first if you intend to do a circuit board or anything commercial with it.

Thomas Henry

I'm working on a PCB design for your schematic, which should eventually lead to a prototype PCB for personal use. Do I need to ask your permission or isn't that what you mean?
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bijlevel



Joined: Sep 20, 2014
Posts: 23
Location: Delfgauw, The Netherlands

PostPosted: Wed Dec 17, 2014 8:22 am    Post subject: regulated supply for Sound One Reply with quote  Mark this post and the followings unread

I intend to use/build a regulated supply for the Sound One, but how much power does this circuit draw? I need to know this to be able to choose the right transformator.
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bijlevel



Joined: Sep 20, 2014
Posts: 23
Location: Delfgauw, The Netherlands

PostPosted: Wed Dec 17, 2014 8:26 am    Post subject: power supply for Sound One Reply with quote  Mark this post and the followings unread

Oops, I just read it draws 10 mA. Is this right, because it seems very modest?
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bijlevel



Joined: Sep 20, 2014
Posts: 23
Location: Delfgauw, The Netherlands

PostPosted: Sun Jan 11, 2015 7:12 am    Post subject: Sound One
Subject description: build it, now experimenting with the millions different settings...
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Finally finished designing an making a PCB for this device, soldered all the components and hallelujah, it worked! I'm special exited because this is my first electronic project since 35 years! All the different settings seem to work, but I find especial the various combinations of the multiswitches NoiseSweep and PWM Select confusing. If I'm right they seem to interact. Sometimes a combination produces a sound, but most of the time nothing happens. At the moment I just have a prototype with the various potmeters and switches illogical mounted on a inconvenient panel. As soon as have put this prototype in a nice box I will report my further findings and upload some sounds.
As I still have a MidiTron laying around, the next step will be trying to interface the Sound One with MidiTron, so I can control things with MIDI.
I also still have two SN76477's, so I will build two more Sound Ones and combine all three devices.
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roglok



Joined: Aug 28, 2010
Posts: 180
Location: uptown

PostPosted: Sun Jan 11, 2015 1:01 pm    Post subject: Re: Sound One
Subject description: build it, now experimenting with the millions different settings...
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bijlevel wrote:
All the different settings seem to work, but I find especial the various combinations of the multiswitches NoiseSweep and PWM Select confusing.


Yes, the switches are indeed a bit confusing. The reason is that this chip was conceived as a multi-purpose device, which can be reconfigured using various combinations of binary logic at its inputs. Thomas Henry included a couple of truth tables on the schematics which should help you decode these settings: http://electro-music.com/forum/phpbb-files/sound_one_514.pdf

also see the original datasheet:
http://amigan.yatho.com/sn76477d.pdf
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bijlevel



Joined: Sep 20, 2014
Posts: 23
Location: Delfgauw, The Netherlands

PostPosted: Sun Jan 11, 2015 1:10 pm    Post subject: Reply with quote  Mark this post and the followings unread

Thanks for the reply. Yes I am aware of these truth tables and they do work, but when looking at the schematic I think NoiseSweep and PWM select switches are in a way interactive, but I have trouble finding out the logic if these, because as I wrote most of the time setting these switches has no audible result. So maybe you could provide me with an example of setting NoiseSweep and PWM select to a setting which should have a certain kind of audio effect. This way I might be able to check if my there is something wrong with my Sound One e.g. a broken component or bad functioning potentio meter. Thanks in advance!
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roglok



Joined: Aug 28, 2010
Posts: 180
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PostPosted: Sun Jan 11, 2015 1:20 pm    Post subject: Reply with quote  Mark this post and the followings unread

bijlevel wrote:
So maybe you could provide me with an example of setting NoiseSweep and PWM select to a setting which should have a certain kind of audio effect. This way I might be able to check if my there is something wrong with my Sound One e.g. a broken component or bad functioning potentio meter. Thanks in advance!


OK, sorry, I misread your question. Those switches have nothing to do with the tables. If they have no effect, I suspect a wiring error on your end. What type of switches did you use? I'd recommend rotary switches, such as these...
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roglok



Joined: Aug 28, 2010
Posts: 180
Location: uptown

PostPosted: Sun Jan 11, 2015 1:30 pm    Post subject: Reply with quote  Mark this post and the followings unread

PWM influences the pulse width of the output pulse wave. If IC pin 19 is connected to ground, the pulse width is 20%. Connected to +5V, the resulting wave should be a symmetrical square wave. Pin 21 is the LFO signal - connecting this to pin 19 via the 4.7M resistor results in a modulation of the pulse width at the rate set by R6/R7. Noise frequency modulation works in a similar vein.

If you are unsure about how your switches work, use a multimeter and test for continuity between the pins. If you want to use all the functions, you need at least a single pole quad throw switch (SP4T) for SW1 and a SP3T for SW8. The switches I linked to above have 12 positions but can be modified to have fewer throws using a lock ring...
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bijlevel



Joined: Sep 20, 2014
Posts: 23
Location: Delfgauw, The Netherlands

PostPosted: Mon Jan 12, 2015 8:16 am    Post subject: Sound One
Subject description: rotary switches
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Thanks for your input! I do use exactly those switches, restricted to 4 positions. Setting the PWM select to 20% or to 50% does not have an audible effect, in fact none of the settings of this switch do have any effect. I wonder if setting 3 and 4 of the PWM Select are depending on the setting of the on/off switches of the Mixer select.

Also setting the NoiseSweep switch to 'Manual' does not have an audible effect. Sometimes a certain combination of both switches does have an effect but always hardly noticeable. I will check the wiring again.
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roglok



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PostPosted: Mon Jan 12, 2015 8:37 am    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
Setting the PWM select to 20% or to 50% does not have an audible effect, in fact none of the settings of this switch do have any effect.


while i haven't built a Sound-One, I have a fully functional SN-Voice (http://www.birthofasynth.com/Thomas_Henry/Pages/SN-Voice_schematics.html). The PWM configuration is exactly the same so it should work, really. The difference between 20% and 50% should definitely yield an audible timbral change. 20% should sound "thinner", more "reedy" than the full, hollow square wave.

Quote:
I wonder if setting 3 and 4 of the PWM Select are depending on the setting of the on/off switches of the Mixer select.


no, they shouldn't. if i recall correctly, the mixer only influences the main output.

Quote:

Also setting the NoiseSweep switch to 'Manual' does not have an audible effect. Sometimes a certain combination of both switches does have an effect but always hardly noticeable. I will check the wiring again.


yes, please check your wiring again. the center pole of your switches should connect to the dot the arrow is pointing away from on the schematics. maybe try disconnecting the switches altogether and connecting to the different points with crocodile clips to for testing.
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bijlevel



Joined: Sep 20, 2014
Posts: 23
Location: Delfgauw, The Netherlands

PostPosted: Mon Jan 12, 2015 8:46 am    Post subject: Sound One
Subject description: rotary switches
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Thanks! I certainly will check the wiring. I will let you know my findings.

BTW thanks for the link to Mouser Electronics. They seem really cheap. For instance I paid locally 7 euro for a variable resistor while at Mouser one can have them for about 0,80 Euro. Hopefully they ship to The Netherlands!
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Thomas_Henry



Joined: Jul 24, 2009
Posts: 140
Location: N. Mankato, MN

PostPosted: Mon Jan 12, 2015 5:23 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hi,

The difference between 20% and 50% is very noticeable. So, if you're not hearing any change, the most likely candidate is the voltage divider (R16/R17) on pin 16. If this pin is simply grounded, the VCO still works, but the pulse width business doesn't. So check that pin 16 isn't just 0V due to a short or bad connection.

By the way, that's reason for the kluge in the SN-Exerciser; I left the bias of this pin out, and the 20%/50% failed to work. That's something I knew at one time but forgot when designing the PCB.

Thomas Henry
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bijlevel



Joined: Sep 20, 2014
Posts: 23
Location: Delfgauw, The Netherlands

PostPosted: Tue Jan 13, 2015 7:34 am    Post subject: Reply with quote  Mark this post and the followings unread

After very careful inspecting all the wiring and soldering I could not detect anything wrong. But after experimenting more with the settings I found that when I have switched on the VCO FM switch, THEN there is a noticeable change of Pulse Width and the other two rotary switch settings (EG and LFO) also have audible effect. So I guess I still have some learning to do.
The manual setting of the NoiseSweep still is a bit strange. The noise rapidly changes into a very low frequency noise (when just turning the potmeter a little bit), into a regular ticking sound. Maybe this has to do with the quality of my potmeter(s).
So far I'm still pleased with the overall result, lots of weird, funny and interesting sounds! When everything is nicely fit into an enclosure I will upload some sounds.
I wonder if anybody is interested in my PCB layout. I have to say it is a PCB layout of a beginner, designed with DipTrace. Because I wanted to etch the board myself I was restricted to one layer. The result was a lot of jumper wires and a not so compact layout. But my intention was to build a prototype to experiment with. Maybe I find time to optimize the layout, but first I want to interface it with the MidiTron. (And Thomas Henry got me also interested in the SN-Excerciser...)
Speaking of MIDI, I also ordered a Gakken SX-150 MARK II Analog Synthesizer because it also makes use of the SN76477N chip and mods for interfacing this device with MIDI can be found on the internet. So maybe I can learn something from that. And it was only $ 35 including shipping all the way from Japan!
BTW what does "kluge" mean?
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Thomas_Henry



Joined: Jul 24, 2009
Posts: 140
Location: N. Mankato, MN

PostPosted: Wed Jan 14, 2015 2:18 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi again,

Here's something else you can try. Replace the 100k pullup resistor on the VCO FM switch with a 10k one instead. This will ensure that the FM pin goes more strongly to ground. This gave me some trouble on the SN-Exerciser until I sorted it out.

"Kludge" means to change something after the fact with some cutting or pasting of external components.

Thomas Henry
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bijlevel



Joined: Sep 20, 2014
Posts: 23
Location: Delfgauw, The Netherlands

PostPosted: Wed Jan 14, 2015 2:38 am    Post subject: Reply with quote  Mark this post and the followings unread

Thanks for the advice! I will try it, though it seems that de PWM-effect is now present since switching VCO FM to "on". I have more a "problem" with the noise sweep, but that is probably mainly because I don't know what the audible effect in it "purest" form should be.
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