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Re: digital reverb

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12/5/2000 6:12 PM

Re: digital reverb

Good reverb simulations require the calculation of many different early and later reflections of sound, so what you want is something that requires not only *hardware*, but also *software*, perhaps burned into a PIC or other microcontroller. To my knowledge, there are no available chips that have the software routine burned into a single chip along with memory for the delays, a/d and d/a conversion, etc. Indeed, much of what separates desired digital reverbs from less desired ones IS their patented software algorithms for calculating more realistic or interesting reflections.

However, maybe what you want is simply a digital delay where you can use additional controls to make an echo *sound* like reverb. If so, then the Holtek and Mitsubishi corporations both make inexpensive digital delay chips, providing anywhere between 200 and 800msec of delay. They have datasheets with a typical design at their web-sites.

To produce a more "reverb-like" sound out of a standard delay, whether digital or analog, there should be some lowpass filtering on the recirculated signal, so that the echo gets more dull over each repeat. When mixed in with the straight signal, the treble should also be trimmed a bit more from the delay portion, so that the bandwidth of the straight signal is much wider than the delay signal. Most designs do not provide this ability, so you would have to add it yourself, although in some cases you can simply increase the value of relevant capacitors in the existing design to roll off more treble. If you look at the datasheets from H or M above, and look at some of the schematics posted for delay devices on the net, you can start to see some places where it may be possible to modify the device for reverb-appropriate bandwidth.

12/7/2000 9:38 PM

Thx for the explanation.

If you have anything that sounds like reverb

and doesn't include tubes or springs please

send it to me or let me know where to

find it.

About the buying part.

My friend was looking for it and he couldn't

find it.So he asked me to try and find the

schematic for it.And in Croatia it's cheaper

to build effect than to by one, because the

parts are a lot cheaper then the effect

in a shop.

12/8/2000 4:15 PM

If you can find ANY sort of analog delay, even if it is a cheap karaoke machine that somebody threw out because the tape didn't work (a VERY good place to look for chips because karaoke machines are major consumers of delay chips), there are two very simple things you can do to make it sound a little more like a reverb.

1) Find the MIX or BALANCE control that combines the delayed signal with the straight signal, and connect a small value capacitor between the two outside lugs of the potentiometer (input and ground). A good value is probably something between 10n and 47n. This will take the treble out of the delayed portion, so that it sounds more like a hallway or parking garage. You can always install a toggle switch to lift this connection if you find a reason to want full bandwidth.

2) Find the REPEAT or REGENERATION control that feeds back part of the delayed signal back to the input of the delay chip. Run a similar value cap between the centre lug (output) and ground. This will take off a little bit more treble every time the signal is recirculated, so that by the 3rd or 4th time through it is very dull-sounding...just like the real world!! By connecting the cap to the output of that pot, instead of the input, the amount of treble cut will depend a bit on where you set the control. If you set it for "runaway" repeats, it will have little or no effect (no treble cut). If you set the control halfway, it will have more treble cut.

I did both of these to an old delay unit, and was very pleased by how much it sounded like a room, instead of an electronic device.

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