How can I put a compander to the mobius trip looper pedal ( ISD 1000A)

[mathflan]

Hi,

I built the mobius trip looper pedal

http://www.generalguitargadgets.com/index.php?option=content&task=view&id=203&Itemid=228

I thought to put a compander "ne570" or " SA571" to clean the sound of the ISD chip like the PT-80 delay pedal has.

My question is : How can I put a compander to a ISD chip?

thanks

My site ( sorry in french)

[Steve Newton]

Looking at the schems, you would want to put the compression half of the compander just before the "Rec" level control, and the expansion half just before the "Play" level control.

[mathflan]

"Looking at the schems,"

The shems of the PT-8??
I 'll take a look into the PT-80 Shems

Thanks

My site ( sorry in french)

[mathflan]

I looked into the schematic of the PT-80, but I'm wondering if the Compander part can be implant to the ISD chip, It's not the same impedance for SP- and SP+ out of the ISD??
I searched on the Web for an compander but I found only this:

http://www.kolumbus.fi/mikko.esala/expander.pdf ans it's in finnish

so I'd be glad if someone can explain me what schematic of the NE571,570,SA571 can I use for an ISD chip.

[Jaicen_solo]

I'm just wondering, why exactly do you want to add a compander to the mobius??
If I remember correctly, the chip itself has an onboard auto gain control, which is like a limiter to prevent overloading the input. It might be an idea to look into this before going the compander route.
Actually, are you looking at a frequency compander for better sound quality?

[mathflan]

In fact I want to add an compander so as to Clean the noise produce by the ISD chip, like the compander do on the PT-80 to reduce noise cause by the PT2399 chip.
You right on the mobius, you can optimise the Ratio signal-to-noise by a pot,but It can reduce the noise.

[snykanen]

I looked into the schematic of the PT-80, but I'm wondering if the Compander part can be implant to the ISD chip, It's not the same impedance for SP- and SP+ out of the ISD??
I searched on the Web for an compander but I found only this:

http://www.kolumbus.fi/mikko.esala/expander.pdf ans it's in finnish

so I'd be glad if someone can explain me what schematic of the NE571,570,SA571 can I use for an ISD chip.

Mikko Esala   That guy was my teacher... Made my first stompbox with him a few years back, a Big muff. Still works great.
Yay, my first post

[mathflan]

hi, snykanen
If you can understand finnish, can you tell me if There are important informations about this compander schematic..
thanks

[snykanen]

Well there's really no technical information at all about it... While we're at it, here's my question: can the mobius be built with an ISD1416 or should I build the http://humano.ya.com/guruzeta/Guitarra/dirtysam/ with an ISD2560? Those are the two chips available locally. Anyone tried the dirtysam?

[mathflan]

For the mobius, you have to get the obsolete ISD 1000A chip.
ISD 1416 dsoen't have the same pinout.
Smallbearelec sell ISD 1000A on this forum a long time ago.
Try to search on electronic online shop...

I built the dirtysam but It doen't work for me , I 'll try to do a other PCB next time.
the dirtysam is better because it use a more recent ISD chip wich has more quality sound that ISD 1000A,
the dirtysam has effects send and return on it, very useful.
I was so frustrated to not arrive to working my dirtysam that I built the mobius trip..

[Jaicen_solo]

That dirty sam looks pretty cool, but I'm wondering wether the CMOS is actually needed? According to the spec sheet, all the outboard components for record and playback should be passive. Only really need to add a blend circuit.
If you look at page 20 on the pdf below, you'll see an example circuit. You need to add a few components to make it loop, but that's all explained on the ISD website.
http://www.maplin.co.uk/Media/product_pdfs/NM52.pdf

I thought about using the dirtysam too, as it has some interesting features like fx loops and tones, but in the end i'd rather design something myself to suit my needs better. FWIW, the ISD1000A works out cheaper than the newer ISD25xx series.