# Octagon



## Mike52 (Dec 8, 2021)

So I'm getting ready to build an Octagon MultiFX pedal and wanted to do some pre-planning. I have never built a Reverb pedal before and never worked with FV-1 tech so, as usual, I'm out of my depth here. But I'd like to build it stock and still leave the option open to easily mod it here and there to tweak some of the tones. Can anyone give recommendations for where it would make sense to solder in sockets during the initial build? 






Like I said, I've never built a Reverb pedal before so not really aware of the possible mods. I just like to tinker.


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## eh là bas ma (Dec 8, 2021)

I am not sure FV-1 circuits can easily be modified : It is built around  an algorythm if I am not mistaking. You could write your own algorythm and reprogram the octagon chip...other than that i don't see what you can do.


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## JamieJ (Dec 9, 2021)

A simple mod is to attach pin 13 of the FV1 to ground on a switch to be able to access the FV1 internal patches which I think sound good. http://www.spinsemi.com/Products/datasheets/spn1001/FV-1.pdf

Some people have used rotary controls to put the different pots on an effects pedal. Some people have modded them to have two EEPROMs. Both those mods are a lot more complex.


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## eh là bas ma (Dec 9, 2021)

JamieJ said:


> Some people have modded them to have two EEPROMs. Both those mods are a lot more complex.



2 EEPROM ? why, what does it do to the circuit ?



> A simple mod is to attach pin 13 of the FV1 to ground on a switch to be able to access the FV1 internal patches which I think sound good.



Wait, there is two sets of effects on every EEPROM from pedalpcb ?! Pedalpcb patch and an FV-1 internal/factory patch ? Can this mod work on any FV-1 circuit, like the Unison for exemple ?


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## JamieJ (Dec 9, 2021)

The FV-1 has internal patches in it so you can use it without an EEPROM. Pin 13 to ground accesses these patches. 

If you have two EEPROM you can choose from more patches - you can still only use one patch at a time.






						Dual EEPROM Arachnid
					

Massive thanks to @phi1 for his original schematic (https://forum.pedalpcb.com/threads/arachnid-dual-eeprom.1818/) and to @Moltenmetalburn for designing the PCB from this thread.  This was probably my hardest build to date. The off board wiring was the trickiest bit with the mods that I wanted...




					forum.pedalpcb.com


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## Mike52 (Dec 22, 2021)

JamieJ said:


> A simple mod is to attach pin 13 of the FV1 to ground on a switch to be able to access the FV1 internal patches which I think sound good. http://www.spinsemi.com/Products/datasheets/spn1001/FV-1.pdf
> 
> Some people have used rotary controls to put the different pots on an effects pedal. Some people have modded them to have two EEPROMs. Both those mods are a lot more complex.


Someone just sent me a Dual IC to Single Conversion Board and I had no idea what I'd do with it. I'm probably a month away from starting my build on an Octagon. Hmm, this might be a good application for that.


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## JamieJ (Dec 22, 2021)

Mike52 said:


> Someone just sent me a Dual IC to Single Conversion Board and I had no idea what I'd do with it. I'm probably a month away from starting my build on an Octagon. Hmm, this might be a good application for that.


The dual EEPROM PCB I am talking about is based on the mod in this build.






						Arachnid - Dual Eeprom
					

This is my 2nd Arachnid build, my first was the old version with the potentiometer to select patches.  This new version with the 8-way switch is much nicer.  Since PedalPCB hasn't released a dual eeprom board yet, I had to cobble together my own on perfboard.  If @PedalPCB does release a dual...




					forum.pedalpcb.com
				




 If you have what I think you have, I assume you are talking about a board that allows you to use say a dual op amp as a single opamp. I.e. TL072 to a TL071. That won’t work in this application. Have a look at the drawings in the build report. Hopefully that makes sense.


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## Mike52 (Dec 22, 2021)

JamieJ said:


> The dual EEPROM PCB I am talking about is based on the mod in this build.
> 
> 
> 
> ...


Yeah, I'm at work and don't recall precisely what I have. It's two 8-pin pads on top and they would go to a single 8-pin pad underneath. It looks like the Arachnid dual op amp mod requires you tie resistors between the EEPROMs. That may be asking too much of this board.




PS: Looking back at my email with the source, it appears I have what you are describing. Darn.


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