Topic: Howto: simple Differential Amp + TTL ?

[James]

(it's how I do it)

Nuff said. 

Now if I could get you to say that about C/C++ ! 

James. 

PS. Dean does everything left-handed, backwards, inside-out and upside-down. Fortunately, by the laws of math and physics, this works out just fine.

[meandean]

PS. Dean does everything left-handed, backwards, inside-out and upside-down. Fortunately, by the laws of math and physics, this works out just fine.

 That's some high praise- thanks (I think).

[James]

PS. Dean does everything left-handed, backwards, inside-out and upside-down. Fortunately, by the laws of math and physics, this works out just fine.

 That's some high praise- thanks (I think).

Soit-en-lee, nyuck nyuck nyuck !

Every time this guy, Dean, comes over, he totaly wrecks my whole concept of reality.

And by that I mean he puts my mouse on the left side of my keyboard.........

AND LEAVES IT THERE!!!!

James. 

PS. My revenge is LaserBoy! 

[James]

My scanner amps are old early Cambridge prototypes. The amps themselves are single ended input only. So, I could not use a differential DAC output, even if I wanted to.

I run the system the way it was wired in the first place, by the person who made it. My ILDA input connector takes X & Y single ended wires and GND and puts them into a standard XLR jack. I use a 10 meter microphone cable from there to my projector. The color mod lines terminate into a DB9 connector that plugs right into the back of the NEOS PCAOM signal generator and from there it runs to the crystal as an RF signal on RF coax with BNC connectors at both ends.

ILDA SCHM-ILDA!

It works exactly the way it was designed to work!

And I am ultimately responsible for knowing how NOT to damage my own or other people's equipment.

James.  

[meandean]

Every time this guy, Dean, comes over, he totaly wrecks my whole concept of reality.

And by that I mean he puts my mouse on the left side of my keyboard.........

AND LEAVES IT THERE!!!!

  And that's why so many people experience computer problems- they put the mouse on the wrong side!

  BTW, I've seen many people gripe in posts about not getting enough scan angle with audio DAC's and a correction
amp- early on, I assumed that all scanners operate in the +/- 5V range, but some require +/- 10V including Cambridge.

[James]

They all operate within whatever range you specify with the input gain trim pot on the scanner amp!

James. 

[James]

Yes. We have identified your problem, sir.

We are going to file this one under section ID 10T.

The error is in the BKAC region of your system; between keyboard and chair.

James. 

[meandean]

They all operate within whatever range you specify with the input gain trim pot on the scanner amp!

 Yeah, I'm still trying to find that pot in the series 658XX Cambridge doc that I have... There is a pot that allows
about a 10% range of gain adjustment and if you mess with it, you have to retune...

[James]

No. YOU have to come over and yell and scream at and with me and flail your arms around like Kermit The Frog, while WE attempt to retune.

Damn! We should make an instructional video! 

I'll bust out the Wendy O.

James. 

[James]

Believe it or not.....

There is one more good reason to go with the simple, single ended design.

All the channels are exactly identical!

That means that there is no difference between the X,Y and the R,G,B.

Since you have 6 channels in the amp, could lose one and use any other as a replacement.

It also means that you could just as easily use the 6 channels to control two mono laser projectors.

X1, Y1, I1 + X2, Y2, I2.

All of these signals could be put together into a single 6 channel wave and played just like any other LaserBoy wave.

The max peak-to-peak voltage is just a matter of which DC/DC converter you get.

I made all of my LaserBoy DACs with plug-in wire leads. All you have to do is take off the cover and plug it in a different way.

http://akrobiz.com/laserboy/forum/index.php/topic,8.0.html
http://akrobiz.com/laserboy/forum/index.php/topic,333.0.html
http://akrobiz.com/laserboy/forum/index.php/topic,378.msg4672.html

It won't take you very long to discover there are two rules to the art of laser projection:

Rule #1. It doesn't work. 

James. 

[Xer0]

Ok, neither of your Circuits work

Dean's last one is perfekt in simulation, but dont works in real. i managed to get something usable with weartronic's original one, but it has the Zeropoint at 1.25V in and not 2.25V like it should. So it swings to -1 @ 0.7V input and 5V at 3.8V...

[meandean]

Dean's last one is perfekt in simulation, but dont works in real.

 I would need a little more info to be helpful... First, is your offset reference circuit actually adjustable from at least -3 to +3v? 

[James]

Get an LM337, a few 10uF Tantalum caps, a 120 ohm resister and a 200 to 500 ohm 25 turn trim pot and you will have a regulated voltage reference from about -1.25 to -5 VDC.

James. 

[Xer0]

I have a LM336-2.5 which is adjustable from something like 2-3V, currently a bit less because im using the two-diode circuit from the datasheet for extra good temperature stability. then an inverting 1xgain opamp is inverting it to exact -2.55V.

of course i could adjust the gain of the opa and thus make the -3 to +3V reference, but why? i thought the CM106 has this value as offset...

[James]

It does.

I want my correction amp design to be able to work with almost any kind of computer sound device, internal, external, whatever. So I tried to make it as versatile and accurate as possible.

James.