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DIY Delay Line (not Delay/Echo)


stryd_one
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Hey 'boxers,

I have a requirement for a nice sounding (IE, transparent) but hopefully simple/cheap DIY delay line. That means not a delay (echo) but a delay line. The effect is that whatever goes into the input, comes back out X ms later.

I don't even know if it's possible to do this in the analog realm, but I'd prefer to, as doing it digitally probably starts to head into the "cheaper to buy one" realm.

Can anyone help? Thank in advance!

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http://www.canakit.net/

http://www.profusionplc.com/products/RA-FX3C.html

http://www.profusionplc.com/products/RA-FX1V.html

Hi Stryd One

The first link is for a kit using a Bucket Brigade Device similar to the one in the schematic that Nils posted.

The problem with BBD devices is that they are noisy - hence compander cct in Ibanez design, they have poor distortion figures and the bandwidth is limited. To change the delay through the chip the clocking frequency is changed, this in turn changes the bandwidth - basic Nyquist theory.

The other 2 links are for relatively cheap ready made digital delay boards, thinking about getting one myself to play around with.

There are, of course, off the shelf units like Alesis' Picoverb and Behringer's MiniFex which aren't too expensive.

Regards

John

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Nope, those are Delays AKA Echos..... What I need is a Delay Line.

0ms              10ms              20ms              30ms              40ms

Dry: (Input sound)

Sound.................................................................................................

Echo: (sound is repeated)

Sound..................Sound..................Sound..................Sound..................

Delay Line: (sound is delayed, but you only hear it once)

.....................................................................Sound............................

0ms              10ms              20ms              30ms              40ms

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Whoops I missed those last pasts, interesting stuff :) But still not a delay line :(

Thanks anyway guys! Any other hints?

PS: BBD is definitely too lofi... The signal being fed through this will be the last stereo mix of the tune on it's way to mastering processors...

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Long, (In electronic terms being more than 10mS), analog delays are not easy or cheap. You can get old 64uS delay lines with a video bandwidth easily - every analog PAL colour TV has one. You could, in theory, stack them, though I think your budget limit might stack faster.

Realistically, if you want Hi-Fi, you will have to go digital. There are quite a few DSP demo kits out there, which will hold more than enough RAM, and the app isn't exactly a tough write:

.start

Read A->D

Store data

Update input save pointer

Read (output pointer)

Write data to D->A

Update output pointer

check control setting

update output pointer if need be

wait a bit until next sample point

go to start

This will 'only' have a time resolution of one sample interval, but I guess a DSPic might do it, 256K RAM is enough for 1 channel / 1 second at 96KHz 16 bit, and there are quite good validated long term available chip sets from the likes of Crystal. You'll have to polish up your surface mount though, unless you buy a demo board.

Can't you use a dig delay and just dial it to 100% 'wet' output, no feedback?

If you want a DC response, though, then it's definitely out with the soldering iron.

Is it time to tape some padding to your forehead, to avoid keyboard marks, (Sleep.....wassat?).

Best wishes

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Levon you're missing that Mike already said that ;)  heheh

Also, I don't want to kiss one of my good delays goodbye (they're multieffects so I'd be giving away a reverb/chorus/etc etc etc also) if I can DIY it.

Also, it's for lookahead on a compressor so I wanted to build it into the box if possible... It's a fixed installation and doesn't need parameter adjustment (or maybe one or two presets)

Also, it's cheaper to buy a dedicated delay line than a dedicated delay of the same quality...

I think that's it ;)

Thanks Mike... I kinda knew all that but I was hoping someone might have a better solution...

I think I'm gonna have to buy one :(

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Also, it's for lookahead on a compressor so I wanted to build it into the box if possible... It's a fixed installation and doesn't need parameter adjustment (or maybe one or two presets)

Thanks Mike... I kinda knew all that but I was hoping someone might have a better solution...

I thought the lack of sleep had been catching up with you!

If it's for compressor lookahead, what sort of time sre you looking for? There might be a three chip digital solution here, for a short delay. I'm thinking of a codec, a chunk of static RAM and an FPGA making the RAM look like a long shift register, keep the bitstream serial and delay it down a synchronous delay line, tap off as  needed, (in fact it might even work wasting 7 bits of the RAM, it being so cheap and all).

If it could be really easy to install, then a module might be saleable.

Is this why some of the expensive Soundtools plug in compressors work so well? Lookahead is a doddle in the digital domain.

As an experiment, it might be worth looking at the Nyquist language with which you can write plug ins for Audacity. Never tried myself, I'm a bit of a pedestrian when it comes to digital editing, so far. I still like real boxes with real controls myself.

Best wishes

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hmm... what about some mechanical stuff?

you need a music cassette tape, cut it, and make a loop. then take 2 heads, one head for writing and anotherone for reading (e.g. from an old walkman.)

I think you can imagne the rest.

I know it's quite LoFi, that's why I've first posted it when I knew that even the experts (theProf,AC) don't have a solution  ;)

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hmm... what about some mechanical stuff?

you need a music cassette tape, cut it, and make a loop. then take 2 heads, one head for writing and anotherone for reading (e.g. from an old walkman.)

I think you can imagne the rest.

I know it's quite LoFi, that's why I've first posted it when I knew that even the experts (theProf,AC) don't have a solution  ;)

.... and after a few hours you have an AUTO-Set Low-Pass filter included. ;D

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sorry s1, I know it's probably not helpful, but I begin to like tape ;D

Check out this nice thing here => http://www.pixelsumo.com/post/tape

Cheers,

Michael

... nothing against the tape thing, if you use it as an effect. But if you constantly let it run for a look ahead solution, it's will wear down quicker than you like.

Greets, Roger

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