Sample&Hold Add-On Board from the Sharkfin

[Alex]

This is the Sample&Hold part of Madbean Sharkfin.
It was a request.
I think it can be connected to different circuits but I'm not sure how it would work.
You can find a better explanation here:
http://www.madbeanpedals.com/forum/index.php?topic=11120.msg100215#msg100215

[Travis]

This is really cool and surprisingly compact. Nice work Alex, this could be interesting as a standalone on my little guitar synth board paired up with the meatball

[nocentelli]

Nice work. It's not obvious from the layout, but I'm assuming there is a cut under the 47n cap immediately to the left of the 5088 noise transistor (so the base is hanging). I doubt it will work without making that cut.

[Silver Blues]

It looks like there is.

[notnews]

Can someone help me understand? Without an input there must be an oscillator somewhere in here.. the 1044s essentially conditions in 9V input and the 1458 is an amp. Where is the oscillation being generated so that the S/H function can take pictures of voltages at different points during the oscillation's period and hold them? It's not like the circuit is seeing a sine-wave AC voltage... the 1044s kills the AC- part of the input voltage from the wall wart.

Also I'm curious to see a plot of the voltages coming out of that CV output.. knowing that would help in figuring out what types of circuits this S/H add-on could be applied to.

[nocentelli]

Silver Blues wrote

It looks like there is.

Failed to scroll sideways, doh.

[nocentelli]

notnews wrote

Can someone help me understand? Without an input there must be an oscillator somewhere in here.. the 1044s essentially conditions in 9V input and the 1458 is an amp. Where is the oscillation being generated so that the S/H function can take pictures of voltages at different points during the oscillation's period and hold them? It's not like the circuit is seeing a sine-wave AC voltage... the 1044s kills the AC- part of the input voltage from the wall wart.

Also I'm curious to see a plot of the voltages coming out of that CV output.. knowing that would help in figuring out what types of circuits this S/H add-on could be applied to.

The 5088 with the hanging base acts as a reversed zener diode, which simply outputs noise. This is amplified by the lefthand side of the opamp. The righthand opamp is an oscillator with a speed control. The amplified noise is sent to the JFETs, and the oscillator triggers the JFETs to allow the random noise through at regular intervals determined by the rate pot. The resultant CV output is simply a voltage that jumps around randomly, with the rate at which it jumps around set by the speed pot. The "randomness" is dependent on the particular BJT used, some work better than others and give a wider range of random voltage blips.

It would probably be best used with a filter circuit, although some modern digital phaser pedals have a S+H setting. A S+H tremolo would give a random, glitchy sounding effect that might be amusing.

[edo1123]

How could this be used as a tremolo? I was looking for a "glitchy tremolo" so I'm interested in this project.

[notnews]

Thanks, non.. I'm still a little confused. The left- and right- hand sides of the 1458 are symmetrical.. so there is an oscillator in the 1458 op amp? Does that have to do with the inv and non-inv inputs being used in a clever way?

[nocentelli]

Opamps can be configured as amplifiers or LFOs, it just depends on the surrounding components. Check out the maestro schematic, far easier to understand than a layout.