Video Delay Lines

So I picked up this video delay line box off Ebay:

My expectation was that it would provide a very tiny amount of, you know, delay to a signal. But maybe I misunderstand what these things do, because I see absolutely no effect whatsoever.

First was just testing with video feedback but that wasn’t quite a controlled enough situation for me to tell if anything was happening (esp. since there is a slightly loss of signal whenever a knob is turned).

Now running the output of a synced horizontal square wave oscillator (i.e. B&W vertical bars) through a distribution amp and then one copy directly into a mixer and another thru the delay line box and then into the mixer. Even at its highest setting, do not see any difference between the two signals when switching back and forth.

So, yeah, anybody have any experience with these things? Did I just buy something that doesn’t do what I thought it did? Or is this thing not working?

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1,100ns is 1.1us, or about 0.91MHz. That’s enough that you should just be able to see an effect, but it will only be a fairly thin vertical line. Try running the original signal into one colour input of an encoder and the delayed signal into another, and see if the colours separate.

Also, can you open it up and post a photo of the insides? Is it powered or passive?

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Been tinkering with small delay lines in Discret11 (and soon to be released CBV002 :slight_smile:) of about 700-1000ns, which result in small horizontal displacement, as long as hue shift in NTSC (less spectacular in PAL unfortunately). https://www.instagram.com/p/CFjO4_BKhEW/

Though, as @VisibleSignals pointed out, you need to keep the original, non delayed signal during the sync/blanking interval, as it will be the reference, and then delay only during active part of the video. Else, the delay delays the whole signal, sync included, so delay isn’t noticeable, the monitor only picks up the picture a tiny bit later.

If you have LZX Cadet I, II and III, you can try the following:

  • composite video to Cadet I, so the system is synced to the non-delayed signal
  • then send the signal from Cadet I to the delay
  • then from the delay to Cadet III to extract Luma
  • finally Luma to Cadet II for RGB encoding, and since it uses the non-delayed signal sync, you should be able to see the delay in effect, no hue shift since it’s pre-encoder, though it should move from left to right.

Also interested to see the inside :slight_smile:

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Ah, yes, of course. Did not think about how it is the relationship between the image and sync that needs to be delayed — and that my mixer was just syncing both signals and thus removing the delay.

I don’t have Cadets, but do have a Cortex and a Vidiot. Ran the same camera signal into both: directly into Cortex; thru the delay first and then into Vidiot. Synced each to their respective feed, not each other. Put each luma out into a different channel in Cortex. Encoded signal from Cortex was synced to the non-delayed feed.

Et voilà!

Also tried just running an oscillator straight from the Vidiot (not encoded to composite) through the delay line and overlaying with the original. Produced an effect, but more like a filter or waveshaper than a delay.

Wonder if I had @VisibleSignals’ new 1IF module to convert the signal, if this might’ve worked better?

I can put the short videos from which I grabbed these stills online, if people would be interested in seeing them.

Tried to open the box up but the screws seem locked up pretty tight. Don’t have a drill at home at the moment and my hands are apparently too weak to make it happen. But will give it another try…

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One more test, with camera into Cortex and output into delay line and then Vidiot. Vidiot luma processor output back into right side of Cortex, multiplying (or adding, I forget) with original camera luma on left side.

Basically a feedback loop. But with wider feedback than a loop without the delay.

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Well that’s more like it!
PLEASE POST VIDEOS
:slight_smile:

I have this thing I’ve been meaning to play with but haven’t managed to find time for yet:

Good idea about the 1IF - that sort of thing is exactly the sort of experimentation it’s intended for!

Is there a power cable on the Delay Line you have, or is passive? My one above is passive, a bunch of coils of varying length with the switches controlling how many are in circuit.

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Yes, mine is passive too.

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@VisibleSignals
now I’m interested … put it in series and sequence the sections…

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Okay, here’s a video of some quick testing:

Four parts:

  1. Camera delay
  2. Unencoded oscillator delay
  3. Camera feedback
  4. Monitor re-scan feedback
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this is a fantastic resource! thank you so much for putting this together
I’ve always wondered about those little boxes.

Very interesting indeed - I agree with Martijn, having CV and animation over the length of the delay would be pretty cool. My favourite part is definitely the colour smear in the first section.

Just spotted a relevant new product on Modular Grid from Syntonie, doesn’t appear to be available for purchase yet though.

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If you can open it in a non-destructive way that’s fine, else no worries :wink:
Being passive, I suppose it’s switching between delay lines made of inductors/capacitors. Sometime the inductors/capcacitors are housed in big plastic enclosure, such as in this composite to YC converter (green block in the center).

Integrated circuits such as TDA4565 used in CBV002 often use gyrator cells delay, which are also LC filters, but the inductor is replaced by a so-called gyrator circuit, which mimics an inductor, and can be made variable more easily than a passive LC network.

TDA4565 Datasheet.pdf (81.6 KB)

Then there is also fixed-delay time/fixed frequency delays, which have probably less “art potential” as they’re made for really specific use cases, though it uses a different but interesting technology (quartz crystal shaped to delay a specific frequency + piezo transducers) more information about this here


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