MKIIA-LATOR

[tubelectron]

Hello All DIYers,

OK, this is not really a stompbox by itself... And moreover now you can find similar commercial products at affordable prices 

It is an adaptator which allow connecting guitar-level (-10dBV = 0.32VRMS) stompboxes to the FX loop jacks of an amp that works at higher levels, typically a passive loop where the signal is several VRMS.

I designed it to be used with my Boogie MKIIA - hence the name : MKIIA-LATOR - where the signal voltage is 3.20VRMS at max. power onset of clipping (400Hz sinus) in the PWR AMP IN / PREAMP OUT jack. It works as expected, no issue.

This device could be useful for those who have a Boogie MKIIA or B - or any similar FX loop system-fitted amp - and want to DIY...

Schematic :



VERO layout - copper side :



VERO layout - component side :



Pictures of the finished device :









A+!

[robthequiet]

Great idea! I have a MKII-b and have always wanted to put a wah and flanger in the loop to get the preamp first. On my ever-growing build list.

[tubelectron]

Great idea! I have a MKII-b and have always wanted to put a wah and flanger in the loop to get the preamp first. On my ever-growing build list.

Thanks robthequiet !

The difference with the cheap commercial models that you can find for that purpose is that the FX SEND is buffered lo-Z (< 10K) instead of a simple pad pot, allowing preservation of the high frequencies. The admissible signal level on the AMP side of the device before clipping is 5.2VRMS under 2x9V batteries and 7.0VRMS under 24V ext. psu. Once you have adjusted the SEND and RECOVERY trimpots once for all, the MKIIA-LATOR is nearly a plug-and-play unit...

A+!