Building a LTC1799 oscillator on stripboard - simple tutorial

Circuitbenders · January 04, 2011, 07:42:41 PM

As i'm going to be offering LTC1799's mounted on a 6 pin DIL adapter from the circuitbenders site very soon, i've just put together a very simple tutorial on building an LTC1799 oscillator on stripboard that can add pitch control to any number of machines.

You can find it here: http://www.circuitbenders.co.uk/forsale/LTC/LTCguide1.html

Is it 'building A LTC1799' or 'building AN LTC1799'. You'd say AN, but is A grammatically correct? $:-\$

Nixot · January 04, 2011, 10:11:59 PM

Only if you're one of those people who'd say "lutcer" instead of LTC.

That's an awesome guide you have there - maybe it's time to add one into my little sa-2!
Thanks for writing it!

Circuitbenders · January 04, 2011, 11:22:27 PM

Anyone who says 'lutcer' probably deserves a savage beating don't they?

Gordonjcp · January 04, 2011, 11:23:09 PM

lutefisk controlled oscillator

noiseybeast · January 05, 2011, 05:36:32 AM

I love this tutorial, but I offer a few ideas.

I use a resistor substitution box instead of measuring the resistance of the pot. I like doing that because it's really quick to know a usable range for a pitch mod.

BTW, I like your stripboard technique QUITE a bit better than my usual point to point for these.

The "other guy" has custom PCBs with the capacitor already in place, but the DIV is permanently set. I think I like your trade off.

I'd be up for buying a package that has the stripboard+capacitor as well.

Circuitbenders · January 05, 2011, 12:09:53 PM

Quote from: noiseybeast on January 05, 2011, 05:36:32 AM
I use a resistor substitution box instead of measuring the resistance of the pot. I like doing that because it's really quick to know a usable range for a pitch mod.

To be honest so do i a lot of the time but in that this is a pretty basic guide, i'm guessing that a resistance substitution box isn't something most people who need to follow it will actually own. I'd imagine that far more people will own a basic multimeter of some sort.

As far as i can tell the cap isn't actually strictly necessary if you have a decently smooth and regulated 5v supply. Its mainly there to keep the LTC stable when the 5v supply is a bit wobbly or dirty.

I wasn't really plannng on offering stripboard kits as such, as i don't really want to be stepping on Getlofi's toes too much, but if theres some demand i'll look into it. The main reason i decided to look into selling the LTC's mounted on adapters in the first place was because theres been a fair few occassions i've wanted to use an LTC, but perhaps not in the exact format of a Getlofi module and there didn't seem to be a whole lot of alternatives, especially not if you are using any kind of design that isn't surface mount.

noiseybeast · January 05, 2011, 07:25:38 PM

Quote from: Circuitbenders on January 05, 2011, 12:09:53 PM

I wasn't really plannng on offering stripboard kits as such, as i don't really want to be stepping on Getlofi's toes too much, but if theres some demand i'll look into it. The main reason i decided to look into selling the LTC's mounted on adapters in the first place was because theres been a fair few occassions i've wanted to use an LTC, but perhaps not in the exact format of a Getlofi module and there didn't seem to be a whole lot of alternatives, especially not if you are using any kind of design that isn't surface mount.

I've noticed the LTC1799 isn't as stable without the capacitor for the few that I bought on ebay.

STEP ON THEIR TOES!!! They charge an AWFUL lot compared to what you're talking about. $15 for the chip and a pot? I love them but a bit of friendly competition is always good.

It's a bitch for me to find stripboard, so if you included a bit of it for a little more, I'd definitely take it.

Circuitbenders · January 08, 2011, 02:45:16 PM

LTC1799's are now available here http://www.circuitbenders.co.uk/forsale/LTC/LTC.html

alienized · June 18, 2011, 06:14:28 PM

Hi everyone,

I'm having a hard time with LTC1799...
I built modules using GetLoFi and Sailormouth schematics but I can't make them work with my PT-88 and SA-5 keyboards. Those use crystals with 3 legs.
What I did :
Connected pin 2 to Ground
Connected pin 1 to a stable +5v (+6.4v on the PT-88 lowered to +4.8v using a resistor)
I have a 100nf cap ("104") between pins 1 and 2
I have a 500k pot between pins 1 and 3, with a 10k resistor to avoid possible crash
Pin 5 is connected to a switch to switch between ground and +5v

I tried to connect pin to all three legs of the crystal, with or without the leg still on the board.
I tried with two LTC modules to be shure I did not damage the first chip as I mixed up pins 1 and 3 on my first attempt (not that I thing this is a real issue) : none of them work.

So : how do I make it work ?...

Thanks in advance for your help as I spent a very frustrating afternoon...
(Hopefully I'm going to see Lee Ranaldo at a gig tonight so this will save the day

)

EDIT : pin 4 is for pin 5 and vice versa... I did it right on my layout.

Circuitbenders · June 18, 2011, 08:04:14 PM

pin 5 is the output, pin 4 is the range selector that you should wire your switch too, although i'm guessing connecting it to +5v is going to produce an output thats too low frequency to run anything.

alienized · June 18, 2011, 11:07:49 PM

I just mixed up pins 4 and 5 in my post but I did it right on the board... Sorry. Any clue ? What should I connect pin 4 to ?

Circuitbenders · June 19, 2011, 12:41:25 AM

i'd wire pin 4 to ground for this. You might be able to hear the squarewave at pin 5 if its set below 20khz and wired to an mixer or amp.

This is where an oscilloscope really comes in handy, so you at least see if its actually outputting anything.

The three pin crystal/ceramic resonator is usually the same as a two pin one, but with the pair of small caps you'll always find near a two pin one actually built into the component. I take it that the moddle pin is connected to ground?

alienized · June 19, 2011, 02:01:02 PM

Hi,
I tried the LTC1799 module on my bent SK-1 following GetLoFi 's guide and it works great ! So my circuitry is correct... I'm going to try it again, maybe I did something wrong...

alienized · June 19, 2011, 02:29:02 PM

Well I think I spoke a little to quickly...
My SK-1 is now dead.
I made better solder points and when I turned the power back on it produced no sound at all.
Now the power stays on even with switched to "off" when power cord or batteries in place.
I unsoldered the LTC module and made a bridge to reconnect crystal as it was initially but nothing worked.
It's a bit hard to look at a dead SK1, especially when there has been a 2 days work on it...

EDIT : I think I have a killer LTC module : it just broke my PT-88... No sound, or a big ugly noise if volume up. No way to get anything straight.

Here is a picture of my LTC module in case there is something obvious...
There is a 100nf cap (ref. 104, rather big one) between pins 1 and 2.

Thanks in advance for ANY help

Bogus Noise · June 19, 2011, 06:44:15 PM

For the SA, I think the pot is too high a value. This flummoxed me for *ages* while trying to get it to work with an SA over here! Best value I've found is a 22k, hardly any "dead spots" with that. That also translates to 5% of the range of a 500k pot, so you'd only get the keyboard to start up in that tiny little window!

I was going to do a Casio SA LTC tutorial Christmas last year but haven't had time yet

Sucks about the SK btw, hope you can get that one going again soon!