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PT2395 Delay

2004-04-04 by Ryan

hi all,

I built the pt2395 delay on a breadboard last night. After a few hours I
got it to work, but it seems like I've got something wrong still.

I'm using a vco from a 4046 PLL as the clock so I could get voltage
control but, it seems to change the pitch of anything that has already
went into the delay if I change the clock speed before it's echoed back
out. Is this to be expected? If so, then I don't see why voltage control
would be all that useful?

also, the output seems to be a lowpass filtered version of the input
with a fairly low cutoff frequency. I'm loosing all the higher
frequencies. The input and output sound exact if I filter the input and
put my oakley multiladder cutoff at about 1/4 of it's range. Sorry, I
don't know what frequency that would be. Is this what it does, or did I
do something wrong?

has anyone else built this module? I'd like to hear what other people
are doing.

-Ryan Williams

Re: PT2395 Delay

2004-04-04 by sasami@hotkey.net.au

>I'm using a vco from a 4046 PLL as the clock so I could get voltage
>control but, it seems to change the pitch of anything that has already
>went into the delay if I change the clock speed before it's echoed back
>out. Is this to be expected? If so, then I don't see why voltage control
>would be all that useful?

It is the correct behavior. This sort of thing is used to do flanging and
chorus effects, though admittedly the delay time is a bit too long for that
here. That is why there is provision to cut a couple of the address lines -
to shorten the delay.

In this case VC of the delay would probably be most useful for remote
setting of the delay, for example by a computer, so that the delay could be
saved along with other settings in some setups.

When running shorter delays, it is also useful for changing the "resonant
frequency" of the echo loop, when a lot of feedback is used.

>also, the output seems to be a lowpass filtered version of the input
>with a fairly low cutoff frequency. I'm loosing all the higher
>frequencies. The input and output sound exact if I filter the input and
>put my oakley multiladder cutoff at about 1/4 of it's range. Sorry, I
>don't know what frequency that would be. Is this what it does, or did I
>do something wrong?

You may have a wrong capacitor value - I had a similar problem at the start.
Another thing - when run in the meduim and long modes, a second filter kicks
in to remove the lower clock frequency. Keep it running in the short mode
for the best bandwidth.

Ken
_______________________________________________________________________
Ken Stone sasami@... or ken@...
Modular Synth PCBs for sale <http://www.blaze.net.au/~sasami/synth/>
Australian Miniature Horses & Ponies <http://www.blaze.net.au/~sasami/>

Re: PT2395 Delay

2004-04-06 by Ryan Williams

ok, I've played with it for a day now and the short mode does seem to
work best. I think that it's the input and output filters that are doing
filtering I described. I guess I was expecting the output to sound
exactly the same as the input. but It seems that the cutoff on the input
and output filters is pretty low (am I right?). Would it hurt anything
to increase the cutoff on these filters? Most of the info I've found on
delays talk about BBD circuits with a really low clock frequency
compared to this. I'd think this chip would handle higher frequencies
better because of the high sample rate. Is this the case or am I missing
something? (I've got a feeling I am)

so far, it sounds pretty nice. A bit noisy, but I haven't added the
compander yet, and I actually dont' have the digital/analog grounds
seperated for now.\

thanks,
Ryan

sasami@... wrote:

Show quoted textHide quoted text

>>also, the output seems to be a lowpass filtered version of the input
>>with a fairly low cutoff frequency. I'm loosing all the higher
>>frequencies. The input and output sound exact if I filter the input and
>>put my oakley multiladder cutoff at about 1/4 of it's range. Sorry, I
>>don't know what frequency that would be. Is this what it does, or did I
>>do something wrong?
>
>
> You may have a wrong capacitor value - I had a similar problem at the start.
> Another thing - when run in the meduim and long modes, a second filter kicks
> in to remove the lower clock frequency. Keep it running in the short mode
> for the best bandwidth.

Re: PT2395 Delay

2004-04-06 by sasami@hotkey.net.au

The best advice I can give re the filters is to try it. This is a
development board after all. The schematic is taken from their app-note. If
we can improve the response, then excellent. Share what you find out. I
simply haven't had time to do anything more with my one of late.

Ken

Show quoted textHide quoted text

>ok, I've played with it for a day now and the short mode does seem to
>work best. I think that it's the input and output filters that are doing
>filtering I described. I guess I was expecting the output to sound
>exactly the same as the input. but It seems that the cutoff on the input
>and output filters is pretty low (am I right?). Would it hurt anything
>to increase the cutoff on these filters? Most of the info I've found on
>delays talk about BBD circuits with a really low clock frequency
>compared to this. I'd think this chip would handle higher frequencies
>better because of the high sample rate. Is this the case or am I missing
>something? (I've got a feeling I am)
>
>so far, it sounds pretty nice. A bit noisy, but I haven't added the
>compander yet, and I actually dont' have the digital/analog grounds
>seperated for now.\
>
>thanks,
>Ryan

_______________________________________________________________________
Ken Stone sasami@... or ken@...
Modular Synth PCBs for sale <http://www.blaze.net.au/~sasami/synth/>
Australian Miniature Horses & Ponies <http://www.blaze.net.au/~sasami/>

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PT2395 Delay

PT2395 Delay

Re: PT2395 Delay

Re: PT2395 Delay

Re: PT2395 Delay

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