Looking for a good delay 0-60ms

[stonerbox]

Looking for a high quality delay chip that can pass full frequency spectrum (at least 60Hz — 10kHz). Fairly good headroom would be great too . Would a PT2399 suffice?
I'm planing to draw a multidistortion/overdrive circuit with one signal path that generates a low to high mid heavy distortion, which hits the speaker first. Then let another fuller frequency ranged overdrive/distortion hit somewhere around 20-50 ms after the focused, tight and mid pronounced one. It could end up feeling focused and snappy and at the same time full and thick.

I'm very tired but hopefully I'm making some sort of sense to you guys.

/Regards
Ben

[dschwartz]

I see what you're up to..
But i think a delay is not the way to go..
Maybe an envelope controlled filter tuned to boost the mids on attack will get you there easier.
Using a delay, combining two different circuits may yoeld to phase issues

[stonerbox]

An envelope controlled filter will sound completely different from what I am aiming for but thank your for the suggestion and input. Also I do not worry about the possible phase issues, a little bad phase is expected.

[stonerbox]

Remove

[anotherjim]

PT2399 delay can't get anywhere near the 0 in your 0-60ms spec. Maybe 25ms is the fastest. But, we humans don't really notice fixed delays below 20ms, so I think the chip has the delay time needed.

I don't know how dynamic you expect the delayed sound to be. Full range distortion usual implies a fairly compressed/limited range, so headroom may really be a non-issue.

Besides all that, the PT2399 is probably the easiest/cheapest choice by far, so it seems it ought to be worth giving it a chance?

[stonerbox]

Thanks Jim! I'll start with a PT2399 and see how it preforms. I'll probably set it to around 30-40ms so it should work.

[ElectricDruid]

Yeah, another vote for PT2399 from me. At the sort of delays that you're talking about the quality will be perfectly adequate. It gets pretty gritty as you get out further, but that's not an issue for the doubling effect you're wanting.
Beware of the filter frequencies on the PT2399 if you want a 10KHz top end. Depending on the circuit, they're probably set lower to allow for longer delays. The usual filter with the on-chip op-amps is a 12dB/oct multiple feedback filter, and the Okawa-Denshi filter tool is the best for designing those:

http://sim.okawa-denshi.jp/en/OPtazyuLowkeisan.htm

HTH,
Tom

[stonerbox]

Great! A drop off at 9-10kHz will not be a problem. I would in fact filter out those frequecys anyway.

[Mark Hammer]

Forum member Thomeeque posted a daughter-board schematic (and layout) for a very short delay (0.5-9ms) to adapt "normal" flangers to through-zero flangers.  If your goal is to be able to slightly stagger several distortions so that it sounds like more than one amplifier, then I doubt you'd want more delay than that, and certainly the short delays for slightly staggering things would not be achievable via a PT2399.  If one wants more delay time, change C11 to a slightly larger value, like 82pf or 100pf.  The high clock frequency will be well out of audible range, requiring less lowpass filtering.

Having said that, what Thomeeque came up with is not as cheap as using a PT2399.

[ElectricDruid]

Is the hefty 4049 buffering really necessary just to drive a MN3207?

It would be if we had thousands of stages and a high clock pin capacitance,  but that shouldn't really be the case here. I suppose the clock is running very fast, so it would tend to get rounded even with fairly small capacitance. But that said, the Morley Sapphire flanger manages ok driving the BBD directly from a 4047, so it can be done. I'd drop the 4049 and simplify it a bit more.

[Mark Hammer]

The 4049 was there, I gather, to push the humble 3207 past its usual limit of 1msec delay.  But  since the present application would probably not make use of delay times quite that short, I concur with your judgment.  Simplify.

[stonerbox]

Thanks for the recommendation Mark and the suggested simplification of it Tom!

I've never built a delay so I'll need to study that schem for a little bit before understanding what it really does.

[Mark Hammer]

Not much to it, really.  The 4047 provides a high-frequency clock that is fed to delay-chip pins CP1 and CP2 as complementary "tick" and "tock" pulses.  The two internal paths of the delay chip are stitched together like a zipper at output pins 7 and 8, to form one continuous signal.

CP1 and CP2 have what is referred to as an input capacitance.  Think of this as a lowpass filter, but really high up.  As long as the clock frequency is low enough, that input capacitance has no impact on the quality of the clock pulses.  When the clock goes much higher than 100khz (according to the datasheet), that input capacitance starts to have an impact and the clock pulses are less "crisp", making the handoff between tick and tock less precise and continuous.  The 4049 is intended to provide some buffering and also pump up the current of the clock pulses so that they survive the input capacitance better.  It is not all that different than the way that a buffer/line-driver helps an audio signal travel greater distances and overcome cable capacitance to preserve treble.

The networks labelled LPF in/out are intended to both minimize clock noise and aliasing.  Because the clock frequency will be rather high, any aliasing or clock noise will be largely inaudible, in contrast to those circuits where a similar chip may be clocked as low as 20khz or even less.

RT1 provides a bias voltage that the audio input needs to ride on.  It can be optimally set for lowest distortion with a scope, but can be set reasonably accurately by ear.  At trimmer settings much higher or lower than optimal, you won't hear any audio output.  As the bias voltage gets closer to optimal, you'll hear a distorted output, gradually getting cleaner (and louder) until you hit the optimal bias voltage.

Naturally, since the labelling is for the adaptor board, making sense of "Pad 3" without the board layout can be a little confusing.  I can send you the layout graphics, or perhaps someone can post a link to them, since they were initially provided on this site.  I'm better at explaining than using the "search" function.   

[stonerbox]

Mark, you are solid gold. I've been looking for the layout to post here but have not yet found it.

[patrick398]

Interested to see how you get on with this. I was playing around with a dod dfx9 i found the other day and enjoyed the thickening of the sound at the quickest delay times. No idea how quick it can go but i suspect not as short as the times you're looking at