[sdiy] Analog matrix chip in Boss ES-8 pedal switcher

[rsdio at audiobanshee.com]

It's very likely that the ES-8 does not handle all switching in a single chip.

First of all, IN 1 and IN 2 cannot both be active at the same time. The diagram shows a simple 2-to-1 switch that is independent of the matrix.

The AD8113 has a 60 MHz bandwidth - it's probably way too expensive and overqualified for guitar pedal switching, although the $700 ES-8 might be able to get away with it. Internally, it's implemented as 16 separate 16-to-1 multiplexor switches, and it would probably be cheaper to just use 16 separate chips if you don't need the 60 MHz bandwidth.

The ES-8 also has 2 mono mixer units that can alternately be used as 1 stereo mixer unit. These mixer inputs and outputs must also be part of the matrix.

They probably dedicate a cheaper, audio bandwidth (not video bandwidth), 12-to-1 analog mux for each output (9 sends, 2 mixer inputs, out 1 left & out 1 right). I count only 11 inputs for each destination. Standard 16-to-1 mux chips cost less than two 8-to1 mux chips, so they might even waste inputs.

Don't forget that the switching could be handled by reed switches or individual FET parts instead of an analog multiplexor chip.

Brian


On Jan 24, 2016, at 3:49 PM, Tom Wiltshire <tom at electricdruid.net> wrote:
> Ok, so that rules out a load of the smaller ones instead then. AD don't seem to make a 12x12 matrix, so it'd have to be a 16x16, something like AD8113. But that seems unlikely because I can't see a commercial product paying for more switch than they need. Perhaps a different manufacturer? Who makes a 12x12?
> 
> On 24 Jan 2016, at 22:40, Mikko Helin <maohelin at gmail.com> wrote:
> 
>> ES-8 has two inputs (and outputs), seven mono sends (and returns), one
>> stereo send (and return) plus single mono (volume) mono send and
>> return. For that you need at least 12x12 matrix.
>> 
>> On Mon, Jan 25, 2016 at 12:08 AM, Tom Wiltshire <tom at electricdruid.net> wrote:
>>> 
>>> There's a lot of possibilities…maybe one of these?:
>>> 
>>> http://www.analog.com/en/products/switches-multiplexers.html
>>> 
>>> It's only 8 loops, so that probably rules out the biggest 16x16 chips.
>>> 
>>> On 24 Jan 2016, at 19:31, "cheater00 ." <cheater00 at gmail.com> wrote:
>>> 
>>>> Hey guys,
>>>> anyone know what chip they might be using here?
>>>> 
>>>> http://www.bossus.com/products/es-8/
>>>> 
>>>> What's your guess on the crosstalk between two adjacent channels? -40 dB?
>