LOOP BOX

[tubelectron]

Hi All,

I've been busy so much these times... 

I need a LOOP BOX designed to be used in the FX loop of an amp which has no adjsutments, too high and variable level : typically like an old Boogie MKII unusable FX loop...

- max level line signal : 3V RMS, variable along with the master volume fo the amp
- internal manual attenuator (pot, rotary switch) to reach circa the correct level for effects (say 250mV), no matter to the line voltage variation from low signal to 3V RMS
- 9V battery powered
- as simple as possible
- unity gain

Indeed I know how to built it with tubes ! But I am interested with a solidstate/OPamp device, in quite compact box to be put on the amp.
Buffer > Attenuator > Recovery amp, basically.

I'm sure that some of you have built something like that, or have good ideas !!!

Thanks for your input & A+!

[pappasmurfsharem]

I'm still a noob at these things, so I might try and help while also potentially learning something in the process if I am wrong.

Are you saying the send and/or return of the loop is too loud and it does not have a manual adjustment?

If so. Couldn't you just wire an input and output jack with something like a A100K between them to control the send or return level of the effects chain?


Effects send --> enclosure with Audio Pot --> to effects chain --- >  Effects Return.
or
Effects send --> to effects chain --- > enclosure with Audio Pot --> Effects Return.

Or did you mean to high as in frequency?
I would assume the fact that your are posting this with as many posts as you have that you are wanting something that give you more control than just volume attenuation., but you can't blame someone for attempting I suppose

[tubelectron]

Thanks pappasmurfsharem,

Are you saying the send and/or return of the loop is too loud and it does not have a manual adjustment?

Exactly.

If so. Couldn't you just wire an input and output jack with something like a A100K between them to control the send or return level of the effects chain?

Well, it is not enough : a buffer is better for matching impedance and avoid signal losses before the attenuator, and after you need a recovery amp to retrieve the original level.

Here's what I am thinking about as a prototype :



I am probably re-inventing hot water, but... Any comments ?

A+!

[tubelectron]

This is the 2nd version, this time non-inverting.

It's what I will breadboard, first with pots and after with some sections of the calculated attenuator for checking.



The hot water is re-invented, unless someone who might read this post has better to offer...

Over.

[~arph]

+1 for the drawing skills