Maestro Filter Sample/Hold

Here’s something a little different. It’s a synthesizer Voltage Controlled Filter module (envelope filter) and a Sample & Hold module all in a stompox suitable for guitar (and other instruments). This is listed as Maestro Filter Sample/Hold, but it is exactly the same circuit as the Oberheim Voltage Controlled Filter. The envelope filter on this unit is excellent for guitar and bass. Of course the main attraction is the sample & hold, which is rare to find in a stompbox for guitar (or bass). A big Thanks to Rick Lawerence, R.G. Keen and Aron Nelson for helping make this project happen!  Any trademarks mention on this page belong to their rightful owners and not to General Guitar Gadgets. 

A note about the Noise Transistor (Q4) selection:

The Schematic lists it as a 2N3904. While testing transistors in boosters we noticed that we had a batch of BC182L transistors that had a lot of background hiss. As expected, these transistors work well as “noise” transistors, so the kit uses one of these BC182L transistors for Q4 and it is the best transistor we have found for Q4.  A bad transistor is hard to find these days!


Here are a couple of other schematics for reference. One is the schematic of the original unit. The other schematic includes some modifications highlighted in pink. Some of the mods can be added to the existing board with no changes to the board. The “Reverse Direction” mod, that reverses the sweep, requires an extra IC and associated parts that can be built on a small board and wired into the main board.

Buy a Maestro Filter Sample and Hold Replcia™ Complete Kit. Includes all the parts and materials you need to build one, all for about the price you would pay for a PCB and parts.

Would you like a Ready to Solder Circuit Board for this project? Note: If you buy the kit, the Ready-to-Solder Printed Circuit Board (RTS PCB) is included in the kit.  You do not need to purchase this Ready to Solder Circuit Printed Board if you buy the kit.

FSH Demo Video