Delay Circuit with the flattest response

[michael_krell]

Does anyone have any advice for me on the a delay circuit with the flattest response?

[Auke Haarsma]

check out the datasheet for the pt2399 and/or the rebote 2.0

[michael_krell]

I am familiar with the pt2399. I have used it a few times. Do you think the delay circuit could provide enough of a flat response that it could be used in a recording setting? like before a microphone just to delay the mic signal by a set amount?

[Mark Hammer]

Flat, but flat out to where?  I think you're confusing a few things.  I don't know any delay lines, analog or digital that introduce resonant peaks or dips between the upper and lower bounds of their bandwidth.  However, they will almost all have steep lowpass filtering to eliminate noise and clock artifacts, and where that rolloff begins will depend on the particulars of the circuit, such as what the clock frequency is, whether companding is used, etc..  My sense is that you are essentially seeking a delay signal with enough bandwidth at the top end that the wet signal sounds very close to the dry signal.

[Processaurus]

Hi, is this, rather than an effect, something to time align different sources in a recording environment?  If so, the PT chip wouldn't be good to use, because it can't delay shorter than ~40ms.  An analog bucket brigade chip might be a better choice for short times, if you clock it at a high speed you can get hi fidelity out of it.  They are used like that in surround sound systems to delay the back speakers, to surroundify a regular stereo signal.

[michael_krell]

Hi, is this, rather than an effect, something to time align different sources in a recording environment?  If so, the PT chip wouldn't be good to use, because it can't delay shorter than ~40ms.  An analog bucket brigade chip might be a better choice for short times, if you clock it at a high speed you can get hi fidelity out of it.  They are used like that in surround sound systems to delay the back speakers, to surroundify a regular stereo signal.

Hi, is this, rather than an effect, something to time align different sources in a recording environment?  If so, the PT chip wouldn't be good to use, because it can't delay shorter than ~40ms.  An analog bucket brigade chip might be a better choice for short times, if you clock it at a high speed you can get hi fidelity out of it.  They are used like that in surround sound systems to delay the back speakers, to surroundify a regular stereo signal.

That is EXACTLY the information I am looking for. Are Bucket Brigade Chips even still available?

[oskar]

That is EXACTLY the information I am looking for. Are Bucket Brigade Chips even still available?

Ho, ho, ho!!!

[michael_krell]

What do you know about this Holtek chip?

Can anyone recommend a good IC for the application i am looking for?

[michael_krell]

I am really looking for a chip that will provide a delay range between 10 and 70 ms.

[sleepybrighteyez]

To time align mics, you may even want something with less than 10ms of delay time. I've messed with it in the past, but I just used a plugin delay. I think most of my settings were under 10ms, but at the same time I was recording in relatively small rooms.

[cloudscapes]

to be honest, when I think of bucket brigade chips, that's the farthest away from flattest that I can think of

[Mark Hammer]

1) The delay time achieved by any delay chip, whether analog or digital, is a function of clocking, that steps the chip through a series of actions.  The faster the clocking, the less delay time is achieved.

2) Since more delay time can be achieved by either cascading more delay chips OR by clocking slower, the choice often made by manufacturers is to clock slower, since it's the cheaper option and has a smaller footprint.  The lack of flat response out to some upper limit which faithfully recreates the original signal is often a byproduct of the filtering used to keep the clock signal and associated artifacts out of the final signal.  The faster the clock frequency, the greater the likelihood that filter cutoff will be way up there in a zone well above what your speakers can reproduce.

3) The delay times you aim for are well within the capability of most available BBD chips.  Although the PT2399 can also nail those delay times, the essentially infinite resolution of the BBD starts to become attractive when the clock range in use is high enough to permit a HF rolloff that one might consider "full range".  So, for instance, Scott Swartz' AD-3208 project (at GGG) is an excellent candidate for the goal you set.  The timing cap of 100pf shown might be on the high side; something in the 47-68pf zone will bring you closer to what you want.  As well, the capacitor values shown for the lowpass filter sections (the 3 associated with the transistor just before the first BBD and the 5 associated with the two transistors after the 2nd BBD) could be made smaller to rais the HF cutoff point.

[michael_krell]

Can always rely on Mark Hammer for a detailed response.

Maybe i will try and build that AD3208 and see if it has the response that I am looking for. This is in fact for friend of mine that is trying to find a tool for time aligning mics, and for the audio purist I know him to be I would imagine he maybe not like the response. But who knows.