Play Your Guitar Through Your Sound Lab

[Uncle Krunkus]

No,
A - is Log
B - is Linear
C - is Antilog

[Gonecat]

Ok, I guess my question is this: if we know the KB is linear, what is the one marked just "k"? Seems wierd they'd have two different names and symbols for the same thing - right next to each other.

I'm just trying to get the right parts and haven't found anyone online that's actually built this thing.

I am going to do a tutorial if i ever get it working, given the lack of info on it!!

[Uncle Krunkus]

If it just says something like "50K", I'd assume it was linear.
You can check it with a multimeter. Say, for example, it does say 50K. turn the shaft to roughly the mid position and check the resistance between the wiper (centre tag) and one side. If both sides from the wiper read about 25K then it's linear. If one is about 22K and the other side about 3K then it's a log pot.

[marmora]

I've been planning a WP-20 build and was hoping I could use the guitar trigger with it.
I understand the connection to the external gate would remain the same. Where would the connection that normally goes to PIN 3 of IC4 on the Sound Lab, connect on the WP-20?
I understand it connects to the voltage controlled filter, I'm just trying to figure out where the correct place would be.
WP-20 VCF schem:
http://www.musicfromouterspace.com/analogsynth/WP20/WP20_PG16.html

[Uncle Krunkus]

At the junction of R27, R26 and Pin 6 of IC2b, connect a copy of the R46, C20, R26 input from the oscillator. So you have three inputs all meeting at pin 6 of IC2b.

[Tronato]

Hello!

Happy New Year to all you fine gentlemen!

Hey Ray!

What happened to the link on the very first post?

Not apparently available anymore...

Best wishes to y'all!

TRON

[spippoli]

Ray updated the site some time ago.

anyway you can find the guitar trigger page here:
http://musicfromouterspace.com/analogsynth/OLD_SOUNDLABMINISYNTH/guitar_trigger.html

[Tronato]

Hello!

Thank you Spippoli!

Cheers!

TRON

[inlifeindeath]

hey guys, i thought some people might like a PCB of the guitar trigger, so here's the one i put together. Hasn't been hooked up to the soundlab yet, so give it a run through against the schem, but i checked it a few times and it looks good to me. Hope this helps someone!

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[inlifeindeath]

this layout is verified FYI

[minimofo]

Hi all,
Completed an MFOS Mini-Synth recently, and what do you know? It actually worked

Am primarily a guitar/bass player and thus planning to build this interface next.

Am used, with guitar pedals I've built, to just bunging a 9v battery in there and dealing with red "go juice" and black "earth" wires... was difficult to get my head around using two 9 volt batteries and the concept of +9, -9 and earth I must admit.

I came across this useful looking charge pump converter circuit and wondered if I could use it here to save using a second 9 volt battery?


And, if so, would I use pin three of the MAX1044 chip for the earth/ 0v connection on the stripboard layout?


Thanks for any help.

[inlifeindeath]

yeah the downward arrow is your ground reference. are you going to use the charge pump just for the guitar interface or for the whole soundlab?
i ask because IIRC that chip can only provide a limited amount of current, and the SL might pull too much.

[mosc]

minimofo to electro-music.com

I would agree with the previous post. These kinds of charge pump circuits can also produce noise on the power leads when the load increases. I'd avoid them if at all possible.

[minimofo]

Thanks fellas for your thoughts

I've already completed the soundlab and used the stock double 9v battery method. So pleased with it and am still astounded it worked first time. I've built many simple circuits and then wasted multiple hours de-bugging the little blighters but, for some reason, the solder Gods were with me on this one.

I'll give the charge pump a go as it's such a simple circuit but I hear you regarding the noise Mosc. Bit of a shame that little side effect. There's a connection you can make between pins that'll send the signal (supposedly) out of audible range, we'll see whether I can get away with it.

[minimofo]

Like to hear a really stupid question?

What does the guitar trigger actually do?!

Building it at the mo'. Labelled the box up as "audio to cv synth" but, that's not quite accurate, it isn't putting out control voltages is it?

[slacker]

It does two things, it boosts the level of your guitar up to a level that will work with the sound lab's VCF and VCA, so you can play your guitar through them.

The gate part of it generates a signal that does the same thing as pressing the manual gate/trigger button for the attack release generator. So your guitar will automatically control this.

[minimofo]

Superb explanation slacker, much appreciated. I've already labelled and lacquered up the enclosure calling it an "audio to cv synth interface" and then, reading this thread again realised it isn't quite working as universally as that makes it sound. It's a bit anal, but I like to build things imagining other people are going to use them, I think I get a better finish that way!
I'll add an extra label on the back based on your explanation, cheers.

[minimofo]

Hi all, can I just check something before soldering things together;



The cathode of C4 is installed in row 3 and (via the jumper) is going to 0v. The anode of C4 is installed to row 1 and going to +9v?
And, for C3, anode is installed in row 2 and going to 0v and the cathode in row 4 and (via jumper) going to -9v?

[minimofo]

^^ Scratch the above- realised I'd got the answers I needed via the other side illustration of your stripboard layout Uncle Krunkus

Well, finished it off this afternoon and I couldn't be happier. Have only had 20 minutes with it due to a sore (soldering) back but it's tremendous fun. I've yet to add the input to my Mini Synth in order to hear the guitar, but checked it amplifies correctly and whatnot. The gate feature is great on it's own- not sure why d1cking about on the fretboard is so much more satisfying than the little button on the synth itself, but it is, so there you go!







Built a stripboard version of the Charge Pump in the end (in the top/left corner) and used a little socket and leads to enable me to connect and disconnect the high frequency option on the chip. Will see, when I've got the synth modded, whether the oscillation is audible.

Ran R5 out to a 10k pot with a 3.7k resistor in series (right hand pot) to give a gain adjustment of 3.7-13.7k and also ran R13 out (left hand pot) to the same arrangement in order to provide gate sensitivity adjustment.

For the overdriven/clean leads, they're going out to a switch selecting between the standard 1M resister for the former and an adjustable preset for the latter. Used a 470k preset and 370k resistor in series to adjust the clean signal level from 370-800ish k.

Well worth a build, thanks everyone for your layout, your help and thanks to Ray for sharing the idea in the first place.

[mosc]

minimofo: Beautiful work. It looks great.

[slacker]

Nice, clever use of the trim pot, very neat.

[Alfredo]

Hello mates, please one question : it is posible to do same with the noise toaster?
Thanks a lot.

[hububalli]

Thanks for the PCB inlifeindeath. I had one question though. Where do you take the gate for the soundlab from? I am sure I am just being a noob but I can only see the +9, -9, Ground. The clean/dist points that go to a switch and on to pin 3 of IC4 of the soundlab, and the input.

Any advice would be most appreciated

[inlifeindeath]

oops looks like i forgot to include a pad for that.
you can add a pad or solder to the junction of D2 and R12.

[hububalli]

Thanks for clearing that up. I wasn't holding out much hope for a reply considering how old the original post was!