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Old 17th October 2002, 07:41 AM   #1
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Join Date: Oct 2002
Location: SC, USA
Default DIY delay

Do any of you guys have a schematic for an adjustable (up to about 0.5 seconds) analog delay? High-end response isn't necessary since I can't hear above about 5K, but fidelity below that range would be nice for speech intelligibility. I guess I could chain bucket brigades, but that would require 10 of, for example, the NTE1641's.

The problem: the sound on ESPN from my local cable company is about 0.5 seconds ahead of the video. This makes watching football almost unbearable. You hear, for example, "he's down at the five" when the guy is still at the twenty or "it's not good" just as a kick leaves the foot of the kicker. Charter said the problem probably won't be fixed for a couple of years until they upgrade their equipment. I'm asking for help, because I'd like to get something working before the end of football season. If you DIY'ers are anything like me, finishing projects on a schedule isn't my forte, so this is a lot of pressure.z
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Old 19th October 2002, 01:53 AM   #2
remp is offline remp  New Zealand
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Join Date: Nov 2001
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Older style reel to reel tape deck with separate record and play heads. Preferably one with slow speed.

If there is not enough delay you can make the tape travel a longer loop between record and play head with extra tape guides/rollers. (with slight difficulty) or separate distance between record and playback heads.

Might even be able to control capstan drive motor speed to get delay adjustable. Maybe smaller motor pulley.

Possibly spring reverberation unit that some musicians use to get echo.

Sit 0.5 miles away from TV. Should be close to 0.5 seconds delay.
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Old 19th October 2002, 03:22 AM   #3
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Join Date: Feb 2001
Location: Columbia, SC
Sounds like the kind of thing that should be brought to the attention of the regulatory agencies. There's no need for you to have to build a piece of equipment just because some <i>non compos mentis</i> can't be bothered to get the signal right.

... inflamatory content moderated ...

If you're a paying customer, then you should expect a certain minimum amount of service.

Grey
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Old 20th October 2002, 10:06 PM   #4
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Location: SC, USA
I don't understand what a rant about South Carolina has to do with a company founded by a group mainly from Seattle with Microsoft money and many former Microsoft employees. It's even based in St Louis. Are you actually claiming it's people from South Carolina that have worked their way up the corporate ladder at Paul Allen's company that are sabotaging it from within because they're stupid? That's a little ridiculous. It's a Fortune 500 company. What does your opinion of people in this state have to do with the actions of a large out-of-state company?

I tried the tape delay with an old Sony real-to-real. I couldn't find an endless loop tape, so I tried it with an old tape I had. The TV is actually at work, and we power the entire floor with an online UPS. The tape drive just didn't work well with the "modified" (probably a synonym for almost square) sine wave. Even if I was able to fix the power supply noise, I don't have a comfortable feeling that running the same length of tape across the heads would be reliable. It might be ok for something on the order of 10 hours, but for a TV that's used several hours per week?

I opened-up an audio delay box a local studio, where my great-nephew works, that they use to sync video and sound. It uses four Panasonic MN3011's. I couldn't find a datasheet for it, so I called DigiKey. They have a datasheet, and it's $3.50. The part is $25.17 each in qty's of 10! They also only have ten in stock, and don't know if they're ever going to be able to get more. I've got the datasheet on order, but if it only delays 50 milliseconds, like I think it does, there's no way I could justify spending $250 for ten of them just so we can make watching TV at work more pleasant.

Any other suggestions? Doesn't Dolby surround sound use a 20 millisecond delay on the rear channels? Chaining 20 of those together might be enough of a delay.z
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Old 21st October 2002, 12:29 AM   #5
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Join Date: Feb 2001
Location: Columbia, SC
You're going to have trouble calibrating the audio to the visual. An estimated .5 seconds may or may not turn out to be the right interval. Human hearing turns out to be sensitive down into the millisecond range. If you continue with the bucket brigade idea, you'll probably want to provide for some sort of switching to choose different settings. How fine those divisions might need to be is up to you. Given that you're talking about ESPN as opposed to, say, VH-1 or something that would require tighter matching, you might be able to get away with larger divisions between settings.
You might consider cruising pawn shops looking for used stage delays. Take a musician with you to advise. Getting a used delay might be cheaper in the long run than building one, especially if you view it as only a temporary fix.
As for matters South Carolinian...is the equipment to be upgraded (referring to your original post) in Seattle, St. Louis, or here in SC? No matter where the hardware is, if the delay is their fault, they should fix it. You shouldn't have to spend the time and money to unravel their blunder.
If you just feel like building a delay, that's one thing. But to be forced into it by someone else's goof...it ain't fair. If the company won't fix it, then call the regulatory folks.
Save your money for projects you really want to do.

Grey

P.S.: Microsoft? <i>Waaay</i> too easy a target. I'll let someone else rant about them.
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Old 21st October 2002, 06:48 PM   #6
HDTVman is offline HDTVman  United States
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Join Date: Aug 2001
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Hi Zoom, Is the ESPN feed your looking at a DIGITAL feed? If so the problem you are having "Lipsync error" is generally the fault of the Digital receiver/cable box. A software upgrade will take care of it. I don't think you can blame the cable guy's for encoding errors as they only pass on the digital stream in almost all cases.

On the other hand if you are digitally processing the video signal some way then this falls back in your lap. No matter how fast a computer is it takes time to change analog into digital. Most mpeg encoders I've seen will take about .5 to 1.5 seconds to pass the video signal. The audio must then be inserted, as data, and timed to the video data. The decoding takes time too, so there are plenty of places for video delay to get in. Unless both the video and the audio go through the same digital path the "Lipsync" will be random and a delay line will be a fun and different way to confuse your friends but not fix the problem.


Good luck
Later
Bruce
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Old 23rd October 2002, 12:48 AM   #7
Ken L is offline Ken L  United States
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Default I think Bruce is probably got this about right!

I had given this thought off and on since you posted.

I did not come up with any good solution. I remember some of the delay tape loop configurations decades ago - they required variable geometry on the the head position and were pretty complex - would be difficult to synch - and unreliable for full time use.

Looks like Bruce is on the money on this one.


Later

Ken L
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Old 23rd October 2002, 02:30 AM   #8
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Location: SC, USA
Thanks for the replies.

Quote:
Given that you're talking about ESPN...
That was exactly my thought! Since you only rarely see the announcer's mouth, I thought it would easy to get the audio close enough.

Quote:
You might consider cruising pawn shops looking for used stage delays.
Good idea. I've stopped by about a dozen in the past two days looking for a 1/2" hammer drill. Other than guitar-related, I didn't see any pro-sound equipment. I went to a nice pro-sound shop and asked about a delay. I got dumb looks as I tried to explain that I didn't want reverb, chorus, etc.. I didn't see anything I thought would work, but then again, I didn't know exactly what to ask for.

The cable is analog, and the area just got it a few months ago. Yes, we're in the middle of downtown and just now got cable. There isn't a set top box, so that can't be the issue. I had one of our board members, who is a football fan and a member of the city council, call Charter. We finally got through to someone who sounded like they knew what they were talking about. He claimed the extra delay for the sound was that for some channels they pick-up the audio from a feed that has two satellite hops whereas the video only has one. That explains the magnitude of the delay. He said they had no plans to fix the problem, because they're planning to go all digital and add HDTV support in the area within five years therefore they can't justify the purchase of new equipment.

The current solution I'm attempting is to use a computer to do the delay. I've got a nice Sound Blaster AWE Gold (about $250 new!) card that claims to be able to record and play at the same time. About 8 years ago, I wrote a program for Linux that would output a FFT of the input (text form, never got around to adding graphics) and play sine waves using the original SB I bought about 12 years ago. I used that same program (yes, it still worked!) as a starting point for this one. I've got it recording, but when I try to play while recording, it simply doesn't play. I know many of the sound cards that claim to do that simply don't. If I can find the fix for that problem, I'll have a solution. I didn't want to waste an entire computer on this, but my boss suggested adding a second sound card to use as the message on-hold for our phone system. Currently, we're swapping CD's three or four times a day, so converting them to MP3 and playing them from harddrive would definitely be much less hassle for the receptionist.

Thursday night, we'll have a full room to watch Clemson play. It's on ESPN so most of my coworkers can't get it at home. I hope I get it working before then.

I still can't believe there isn't an easier way to build an analog delay...z
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Old 23rd October 2002, 06:21 AM   #9
remp is offline remp  New Zealand
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Tape is still the easiest way. Its just a deck with a record and play head and if the delay is insufficient, move the play head. Not at all difficult. I dont know why you are concerned about reliability. Lots of older style reel to reel tape decks were built like battleships with oversize motors and good bearings etc. Worked for years with little or no maintenance except for an occasional head clean and a drop of oil down the capstan bearing.

You deck could have worked oK except for the UPS. Thats not the fault of the tape deck. It was designed for sineway power input.

Years ago I worked for Philips Electrical Industries installing sound reinforcement systems in many locations including Churches and schools. Many churches are built long and narrow so those at the back had trouble hearing the minister. Originally we installed speaker columns at the front but these had to be too loud for those at the back to hear clearly. Lots of echo's as well. We put smaller speakers along each side wall. These worked but we found the ones at the back did not sound correct for a church. So we put in a Philips tape delay unit.

This was an industrial grade reel to reel tape deck with 6 playback heads spaced 1 inch apart and 6 line outputs running at 1 & 7/8ths inches per second speed.. We installed a small amplifier and it worked very well. Those at the back heard the sound with a small delay just as they expected. Same in the centre of the church but with a smaller delay. Its still there as far as I know. Saint Paul's Cathederal Wellington New Zealand.

This unit proved very reliable and we probably used over 20 at different locations. One or two bands bought them to make a bigger on stage sound. We even experimented with two decks running the tape from one across to the other with several yards between decks.

You might be able to find one from sound system installers.
Revox turned out a good reel to reel tape deck.

That type of unit would suit your problem but you will have to solve the UPS problem. Possibly a 1:1 transformer would make the waveform more sinewave. I am not sure about that.
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Old 23rd October 2002, 06:33 AM   #10
haldor is offline haldor  United States
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One of the functions in the Behringer DSP-110 is a digital delay and it sells for around $70 (plus shipping).

Here is one place I found it at.

http://www.zzounds.com/love.music?p=p.BEHDSP110&f=5572

I keep one of these in my PA rack for use as an emergency problem solver. It is not the very highest audio quality, but should be plenty good enough for watching TV and it's just about impossible to beat the price.

Phil
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