Alesis ADAT Question

[illuzion]

I have a question, does anyone have floating around on their hard drive, (or in their head) how to modify the original Alesis ADAT (blackface) to work with ILDA/LFI format tapes (make the unit DC passive, and able to drive -10/+10v on its analog outputs)?? I know pangolin sells a manual for this, but before I ordered it from them, I figured someone had this info.
Thanks

[Pangolin]

Hi Illuzion,

We produced a manual of how to do that. We used to charge $25 for the manual, but now it is available for free in PDF form.

If you contact Hayden in our office, he will send it to you by email. He can be reached using our contact form at:
http://www.pangolin.com/contact

Best regards,

William Benner

[illuzion]

I already spoke to Hayden about this he was very helpful. I have another question though. Assuming you had a "ILDA standard" show recorded on an ADAT, is it possible to play it back using no outputs on the back of the ADAT except the ELCO connector? Here is the reason I ask, normally the ELCO connector supplies -10 to +10v differential signals or 10v single ended signals, the Phono jacks provide -2.5 to +2.5v differential, or 2.5v single ended (according to your manual). Now most scanner amps (CTI) accept the +/-10v differential input, but color modulation is a different animal. The standard for color modulation seems to be 0-5v where 0 is blanked, and 5v is max output. Sure you could use the phono differential outputs and ignore the ground, but that doesn't answer the question. My main preference is to use only the ELCO connector between the ADAT and the projector (mainly for durability reasons and to prevent accidental misconnections/reversals of the RGB outputs). How do you output the color data from the ADAT? Now the "easy" answer is to use the ELCO and record the signals at a lower level, but that would be cheating, as it is no longer ILDA standard. I suppose an op-amp on the output to divide by 2 the ELCO signal is the difficult answer, I am looking for a simpler solution, any ideas, or how do you handle it?

[Pangolin]

Hi Illuzion,

I am afraid it has been so long since we played around with old black-faced ADATs, that my memory is foggy regarding the details. BUT, as far as I know, the phono jacks on that unit are NOT differential. On more recent ADAT devices, they are, but on the old black face, they were not (if memory serves).

Let me see if I can remember this. FOR THE INPUTS, I think we recommended that you use a 0-to-5V signal (for color) or -5V to +5V signal (for X and Y) coming from the signal source (usually a computer). Then, you put this into the single-ended input of the ADAT, using an impedance-matching / divider series resistor, which reduced these signals to a 0-to-2.5V (for color) or -2.5V to +2.5V signal (for X and Y) which is compatible with the needs of the ADAT.

FOR THE OUTPUTS, I think we recommended that you use the ELCO connector. For color, we probably recommended that you NOT! use "differential" per se, but rather, we probably recommended that you use the ground pin of the ELCO, and only the "positive" (non-inverting) signal for the colors. That will give you 0-to-+5V for color control devices such as PCAOM. For the X and Y signals, I think we recommended that you use both the "negative" (inverting) and "positive" (non-inverting) signals which would give you -10V to +10V differential voltage, required for the X and Y scan amps.

I think if you do that, all of the signals will be of the correct voltage level.

Best regards,

William Benner

[illuzion]

If you look at the ILDA standard recorded material, it is channel 1 and 2 is X/Y deflection where 0 level on the ADAT is one end of the screen and 100% is the other end, and the same holds true for colors on channels 3,4,5 where 0% is blanked and 100% is full on, now if you look at levels, if you use your method of the single ended elco output, your color signals would be 0-10v (too high). the X/Y would be correct and -10/+10 (20v total end to end on the servos). As far as I know black faced adats support differential, but not 100% sure, you may be right about the phonos being single ended.

[Pangolin]

Hi Illuzion,

I think it is a matter that our ADAT Manual is incorrect. The LED meters will show "zero" in the case that there is zero volts. For X, Y, R, G and B, this will happen when there is no signal. (Actually, those LEDs may show a slight signal -- it is not uncommon for one or two little LEDs to be lit on the black faced ADATs even when there is no signal applied.).

The LED meter will show 100% signal in the case of X or Y, if you have either -10V or +10V applied. The meters show the "absolute value" of the signal.

Basically, my advice is to just do what the manual says, and then see how it works out. Don't try to second-guess the manual before you have actually built the cables and used it as we suggest...

Best regards,

William Benner

[illuzion]

I built the output cable from the ELCO connector, it works fine for driving the scanners (CTI), your guide seemed to be written around using the same device to record and playback the signals, so if you wanted to record certain channels (like color) at a reduced level (to be within 0-5v), or output it at a reduced level from the computer, you could do so. I am looking at this strictly as a playback device, so I must assume prerecorded content conforms to ilda standards for adat, so 100% signal for full on, would yield a rail voltage on the output (+10v or 20v differentially) from the elco, clearly outside the range of the modulation device input (0-5v).

[Pangolin]

Again, all I can say is, if you follow our recommendations, it will probably work as required.

Yes, our manual assumes that it will be used for both recording and playback. BUT, our manual is "the standard"... So if you have tapes from other people who recorded it to "the standard", the it should play back fine.

Even more recent systems from Pangolin, such as the CADA-MOD for newer ADATs (including the HD24) are compatible with what we have said in that manual.

Compatibility is very important to us. Frames and shows that were made with our very earliest software will still playback on our newest LD2000 software... Surprisingly, compatibility isn't that big of a priority to other companies, both inside this industry and outside (for example, Microsoft, who amazes me with the changes they made in VS:2005 with no "compatibility modes" for software made with previous versions, thus breaking software that ran fine for years prior. And lets not even talk about KB891781...)

It sounds to me like you are trying to overanalyze this. Just do what we say in the manual and everything will be fine when you wake up in the morning. Like the old QM32 color effect used to say in it's commentary -- "Don't try to understand how this works, just use it!".

Best regards,

William Benner