MudFlap - a bass booster.

[anotherjim]

I've been messing with these ISD1820 voice memo chips and had an idea that they were cheap enough to ignore the recorder part and just use the AGC front end in something.

What I got is a clean path through both halves of the TL072 with a send-return through the memo chip which is fixed in "Feed Through" mode to disable the recorder.
There not much you can do to control the AGC in the memo chip, it has no silence detection so ends up boosting all the noise and hiss it can find when the input signal decays. The datasheet AGC control cap value of 4.7uF seems to be about right for most things.
Rather than give up on it, I figured out I can use it well enough just for the bass end of the spectrum and hide the hiss by filtering.
C7 low-passes the built-in mic preamp by sending high frequencies to both + and - preamp inputs. R5 sets the chips internal filter low to cut the worst of the hiss the chip adds in itself.
What comes out is a smooth and level bass tone that is mixed in with the clean signal according to the Mud control. This lends guitar or bass a full-bodied undertone without harming the attack and dynamics. It's similar to the parallel compression recording studio trick.

It's a one-knob effect!

Only had it on breadboard so far, so in a screened box it may be possible to raise the upper-frequency limit through the AGC with less noise getting in.

[Fancy Lime]

*Love* the name for a bass booster! We can haz sound samples, pleaz?

Andy

[anotherjim]

*Love* the name for a bass booster! We can haz sound samples, pleaz?

Andy

Not 'till I've boxed one up Andy - and I've got lots of things on the go. Wouldn't take you long to breadboard it. There's not a lot in if you discount the protection and supply filter bits - the drawing shows every chip with 100n power caps and so forth.

[FUZZZZzzzz]

*Love* the name for a bass booster! We can haz sound samples, pleaz?

Andy

I second this !!