Simplfiying Deep blue delay. Can original input buffer / Mixer be replaced?

[nguitar12]

I am going to Simplfiying Deep blue delay to keep the part count as low as possible.
Just wonder if the original opamp input buffer / Mixer be replaced by a buff'n blend circuit?

[mth5044]

Post a schematic please!

[nguitar12]

Post a schematic please!

I haven't draw the schematic yet but I'll try and reported back 

[MrStab]

Going by schematics found on Google, i have to say this doesn't seem worth it. the part count is low already. but if you want a challenge...

input buffer? you really shouldn't get rid of that. i was gonna suggest that maybe you could use the free opamp in the PT2399, but that seems to already be in use for the output in the Deep Blue Delay.

mixer? maybe, but it would mean a not-so-great output impedance, and your signal would be inverted (because it was inverted in the 1st op-amp and twice in the PT2399, at least i think). Maybe this would work:



Put a 1k resistor where the 22k used to be, as the output impedance from the PT2399 seems to be 1k. but i could be wrong.
You may notice that the text around the Mix pot is backwards. this is because the signal is inverted.

One of my first circuits was a passive blender - i found 50k linear to work quite well, so you could probably use the original pot.
The actual mixing may be less useful or intuitive than with the mixer, but who knows - it might suit your needs.

[MrStab]

It didn't occur to me that you probably wanted to get rid of the whole dual opamp. oops. lol

As i understand it, the buffer in the Buff n' Blend is non-inverting. You need something more like this if you wanna use it in the Deep Blue Delay: http://upload.wikimedia.org/wikipedia/commons/thumb/4/4f/N-channel_JFET_common_source.svg/2000px-N-channel_JFET_common_source.svg.png

That's "common source" configuration, if you wanna look it up.

[midwayfair]

You can use the PT2399 as the only active element, but it will not sound that good and you won't have a true mix control. The filtering for the delay repeats -- which is necessary -- will also filter your dry signal. Madbean's Cave Dweller delay is literally the simplest possible thing you can build with the Pt2399, so just use that project if you really MUST get rid of the input and output stages.