CYGN-B

[james]

One situation where you lose half the signal is when you drive a differential output into a single ended input. There's nothing to connect the minus output to, and you get just half the signal via ground. The one place where differential is a true must is on the receiving end of the scanners, even when the drive is single ended.
It also offers a convenient way to flip polarity.

Yes.

That's coming from the person who drew the first schematic of the first prototype of the correction amp.

http://laserboy.org/graphics/huge/laser_h_95.jpg

[lasermaster1977]

That's so hard core! In 1977, perhaps? I assumed that you got started with Laser Images' projectors, like most others from that era.

My "start" was in '76 doing special effects with a .5mW HeNe in a 40' dome planetarium. From there it grew into doing full-blown laser shows at that planetarium in Dec '77, with the official opening the start of Jan '78. I built my own RYGB graphics console and GS115 RYGB projector with RYGB1B2 lumia & diffraction effects.

Yeah, I'm getting lots of requests for a video, but only have a smart phone for a mic and some RPi HQ cams. Don't know how they'll do with frame blanking. Probably need to spend lots of time optimizing all the cycloid frequencies.
Regardless, I'm soon gonna have to put up or shut up.

A smartphone is all I've used with the test videos I've posted recently on PL. No bad artifacts from frame blanking but I normally shoot at 30fps.

Start Here whenever you're ready. I only added 2 more audio shields and duplicated Dave's code, then started mapping MIDI CC's & 'Notes' to the Akai controller.
I'm hoping to have the PCB & code available to share with folks within a few more months. The prototype is currently fully playable. But, I need to add storing/loading image banks to/from uSD, plus sequencing bells & whistles to the code.

I think I've already seen that YT link, thanks. I recently started using KiCAD (very nice freeware) for doing PCB work, still learning, done schematics w/footprint assignments and starting to do two layer PCB layouts, finishing up two DAC boards. A lot of my background and history is in numerous posts on PL so I won't repeat here (which as an ol' fart I'm prone to do (doah!))

Same here. Wife divorced me. An English competitor imported a Laser Media system, playing an animated Ghost Busters sequence, so I saw the writing on the wall. The final straw was when my 'partner' failed to provide a sound system for Pink Floyd's demo, then fogged out my road worn 4 watt Argon road system (that was barely 2 watts). The batteries on my Sony Walkman speakers died, mid demo, seconds after Dave Gilmore's wife asked me to turn up the volume. Didn't even attempt to close the deal on their world tour. There's no excuses or do-overs at that level.

Very cool, dude! My biggest professional embarrassment was while doing a Dallas Symphony Orchestra concert featuring Walter Murphy. My Spectra 5W Argon for beam effects died early in the show, my newly built new generation control console had wiring mistakes that resulted in my graphics accompaniment for Walter's big, popular numbers, how shall I say, go horribly wrong. I was so embarrassed since early that year I did a highly acclaimed Christmas concert with DSO (William Shatner narrating) but learned a valuable lesson from that professional failure.

Do you know of a good supplier of the DT-40's here in the states?

I sure don't, sorry. I only learned of SELEM a few years ago, never been there, and not familiar with Ed. My Apple II development began in late '78, early '79 and evolved thru the IIe with my co-processor Quad DAC boards (also posted in PL posts these recent past years).

I love retirement as well. My ultimate focus and goal is to create my laser "swan song", which I've been working on for the past 18 months in earnest. Well, sort of in earnest, since other things keep popping up. :-).

May I suggest we start a new thread to keep sharing, so we don't keep hijacking Greg's CYGN-B thread?

[TheHermit]

One situation where you lose half the signal is when you drive a differential output into a single ended input. There's nothing to connect the minus output to, and you get just half the signal via ground. The one place where differential is a true must is on the receiving end of the scanners, even when the drive is single ended.
It also offers a convenient way to flip polarity.

Thanks for your input.
Yeah, that was my thinking too, until this thread encouraged me to read this article:
Differential Amplifiers.
Differential inputs on the scan amps MUST have differential signals, right? Not necessarily. Differential signals aren't always + or -, they are both, aka bipolar. One is just the inverse of the other, at the same level with respect to ground. The only difference is induced line noise and/or capacitance from a long cable run.
Haven't tested single bipolar on one scan amp input with the other grounded, yet. @Laserman1977 just mentioned that the signal will be halved. But, I'm not sure whether an offset will be caused by one side being grounded.
@James would know.
Yo, James! Is the higher offset reference voltage on your circuit required to compensate for an offset caused by grounding one side of the scan amp?

[lasermaster1977]

Thanks for your input.
Yeah, that was my thinking too, until this thread encouraged me to read this article:
Differential Amplifiers.
Differential inputs on the scan amps MUST have differential signals, right? But, differential signals aren't + or -, they are both, aka bipolar. One is just the inverse of the other, at the same level with respect to ground. The only difference is induced line noise and/or capacitance from a long cable run.
Haven't tested single bipolar on one scan amp input with the other grounded, yet. @Laserman1977 just mentioned that the signal will be halved. But, I'm not sure whether an offset will be caused by one side being grounded.
@James would know.
Yo, James! Is the higher offset reference voltage on your circuit required to compensate for an offset caused by grounding one side of the scan amp?

No, they do not have to have differential input signals.

Yes, when using a single-ended input into a balanced input, any DC offset present with the single-ended input will also be halved.

[dchammonds]

Haven't tested single bipolar on one scan amp input with the other grounded, yet.

Give it a try and see what happens!

[james]

No. Ground is ground. It is the zero reference. A single ended signal applied to one input with the other grounded can have the same peak to peak as a differential drive. The DC offset is eliminated in the correction amp and the scanner inputs never see it. That's the point. The fact that my amp has a variable offset null is because different sound devices have different DC offsets. Some dac chips work with a +5V supply and others are only +3.3V. So the middle between ground and the supply voltage is the DC offset.

[james]

Something that might be a bit confusing is how an all positive dac signal can end up as audio that swings evenly between negative and positive voltage with respect to ground. This is because of the DC blocking cap in series with the output. This is a high pass filter. It's also a differentiator. That means it gives you the derivative of the dac signal. That is change in voltage over time. It's the slope of the dac output signal. When the dac voltage drops from high to low, that is a negative slope. So the voltage drops below zero.

But this is no good for laser signals because you need absolute voltage over time. A steady voltage above or below ground has no change. That's a slope of zero. So the output after a DC blocking cap will swing to the steady voltage and then drop off to zero at a rate determined by the value of the cap and the input impedance of the amp.

[Greg]

Here is a CYGN-B oscillator. A pair of circuits scale the voltages to 0 -> +5. The clean signal is recorded and played back in sync with a stereo 44.1 .wav file. As well, the two LEDs use two of the remaining 6 tracks, which means pot action to pulse the LEDs during recording plays back in synch with the music also.

The tool I'm writing so far simply does the most obvious thing: leverage the BELA board's resources as a 10 track with 2 tracks being audio.

In the current setup, three push buttons put the engine into one of three modes: idle, play, and record. Next tasks are to write file save / load, and then develop a 351 data import feature.

I'm considering a multi channel system using one BELA per channel that would allow an actual performance in some respectable measure of the original surviving numbers.

I am as interested as can be in any 351 data that still exists. A while back someone offered me a TEAC reel to reel, and another person a load of Laserium mysteries, neither of which were collected unfortunately. Just saying if the opportunity at any point exists again to get more 351 data or anything else interesting, I'll do what ever I can to help it happen.

[dchammonds]

Here is a CYGN-B oscillator. A pair of circuits scale the voltages to 0 -> +5. The clean signal is recorded and played back in sync with a stereo 44.1 .wav file. As well, the two LEDs use two of the remaining 6 tracks, which means pot action to pulse the LEDs during recording plays back in synch with the music also.

The tool I'm writing so far simply does the most obvious thing: leverage the BELA board's resources as a 10 track with 2 tracks being audio.

In the current setup, three push buttons put the engine into one of three modes: idle, play, and record. Next tasks are to write file save / load, and then develop a 351 data import feature.

I'm considering a multi channel system using one BELA per channel that would allow an actual performance in some respectable measure of the original surviving numbers.

I am as interested as can be in any 351 data that still exists. A while back someone offered me a TEAC reel to reel, and another person a load of Laserium mysteries, neither of which were collected unfortunately. Just saying if the opportunity at any point exists again to get more 351 data or anything else interesting, I'll do what ever I can to help it happen.

Good old fashioned hand wired breadboard build- no surface mount stuff here! I was beginning to think nobody does it this way anymore.

Awesome!

[ronhip]

Greg,

I gave all my 1/4" reel to reel tapes back to dsli-jon, who probably forwarded them to Lumalaser. Lumalaser has digitized those tapes and will probably use the files in whatever they have planned for the "Bride of Laserium" return of the shows. However, I do still possess a few beta and ADAT tapes that probably have 352 data on them.

I'd have to take inventory, but I may have these in betamax tape format:

Laserium I

Light Years

Crystal Odyssey

Laser-Rush: Grace Under Pressure

Led Zeppelin: In The Beginning

Grateful Dead

Rainbow Cadenza: Classics

The Police

Laserium Zodiac (Zodiacal Light)

Moonrock

Flashback: '80's (Laseroq: the 80's)

Laserock: Into the '90's

Summer of '69

David Arkenstone: Celestial Dreams

Led Zeppelin: In The Evening

U2

Rock-It '91

Star Trek: The Astral Symphony

The Doors

Hot Led: Zeppelins' Best (Molten Led)

LASER HOLIDAY '92

Laserium Rocks!

the cure: wish

Dream On: The Music of Aerosmith

Inside Laserium

Lollapalaser

Laserium Rocks San Francisco (KGB)

And I only have Metallica in ADAT

As you know already, I have almost every soundtrack (digitized from sometimes questionable tapes) on CD.

Ron

Here is a CYGN-B oscillator. A pair of circuits scale the voltages to 0 -> +5. The clean signal is recorded and played back in sync with a stereo 44.1 .wav file. As well, the two LEDs use two of the remaining 6 tracks, which means pot action to pulse the LEDs during recording plays back in synch with the music also.

The tool I'm writing so far simply does the most obvious thing: leverage the BELA board's resources as a 10 track with 2 tracks being audio.

In the current setup, three push buttons put the engine into one of three modes: idle, play, and record. Next tasks are to write file save / load, and then develop a 351 data import feature.

I'm considering a multi channel system using one BELA per channel that would allow an actual performance in some respectable measure of the original surviving numbers.

I am as interested as can be in any 351 data that still exists. A while back someone offered me a TEAC reel to reel, and another person a load of Laserium mysteries, neither of which were collected unfortunately. Just saying if the opportunity at any point exists again to get more 351 data or anything else interesting, I'll do what ever I can to help it happen.