MOSFET Op Amps for Distortion?

[kylecavanaugh]

Hey guys, I came acrossed a dual op-amp called the CA3260 (http://www.intersil.com/data/fn/fn1266.pdf) which happens to be composed mostly of MOSFETS.  I also noticed in the schematic that the first gain stages on the inverting and non-inverting amplifiers have what could possibly act as clipping diodes.  It looks to be a drop in replacement for a JRC4558 or similar.  Has anyone tried these chips in an overdrive or distortion pedal?  They go for $2.40 over at www.mouser.com, a standard dual op-amp goes for 30 to 80 cents from there.

[Dragonfly]

I *think* the Ibanez Mostortion uses that one...

AC

[WGTP]

Yes they are mentioned around here as peoples favorites from time to time.  In the stuff I have tried they, seem to have a pretty "BIG" sound.  Whether you like them more than the std. TL072, 4558, 4559, 5532, 2262, 275, etc. depends on your taste and the circuit they are in.  Never heard reference to the diodes.  IIRC there was an ?? Ibanez MOSTORTION that used it.  Probably would work good with this:  http://aronnelson.com/gallery/WGTP/Moster?full=1

Might do a search there should be several Posts.  Welcome to the forum  

[Steben]

Looks like zener configuration (series).

Anyway, other MOS opamps like TLC2262 act perfectly as clippers ont their own (SansAmp).

[majormono]

I have CA3140, CA3240 (bipolar out while CA3260 has CMOS) and TLC2262 as MOS-OPAMPS in my tryout-box and while the TLC offers a nice mellowed OD characteristic the CA come out mostly too dark for my taste... maybe good for some bluesy tone - up 'til now they did find no permanent home in anything I built.

[MartyMart]

http://www.diystompboxes.com/smfforum/index.php?topic=52388.0

Went there a few months ago with quite decent results, ended up with
a kind of Mostortion/808 hybrid with a great sound to it.

MM.

[Johan]

the diods are probably for protection..the input Z is 1.5TerraOhm  ...so it is probably easy to zap with a bit of static electricity..
j

[kylecavanaugh]

Oh yeah, and does anyone know of any inline MOSFET based dual Op Amps?  I'm curious how one would sound in a Boss DS-1...   

[Steben]

Oh yeah, and does anyone know of any inline MOSFET based dual Op Amps?  I'm curious how one would sound in a Boss DS-1...   

Wiring to a veroboard...?

[Meanderthal]

 Naaa, the Ds-1 has in-line opamps stock for some reason... It's why there's no "4558" mojo associated with it, well, that and for some reason a lotta folks don't like the DS-1 to begin with(personally I think it's the hideous orange paint).

[MR COFFEE]

Mouser has JRC 4558 op amps in the sip package... 072's too

[jakenold]

the diods are probably for protection..the input Z is 1.5TerraOhm  ...so it is probably easy to zap with a bit of static electricity..
j

Wouldn't that make for a great buffer? Or aren't they linear enough?

[Meanderthal]

 

Mouser has JRC 4558 op amps in the sip package... 072's too

Ahh, but they're not shaped like the ones SRV used in his 808... where's the mojo?  That just leaves... parts...

But, the inline mosfet in a DS-1 idea intreagues me...

[Steben]

The insertion of a Fetzerinstead of the bipolar in front of the DS1's opamp is a far more interesting idea. I had nice results with it. A bit cleaner and glimmering clean when distortion on zero.

[Mark Hammer]

The Mostortion is supposed to be a decent pedal.  One should bear in mind, however, that there are enough design aspects that are different about it that it's hard to separate the contribution of the chip from the rest of the circuit.

It is certainly a different enough chip from a number of other contenders that it is worth trying out.  On the other hand, at a certain point one has to acknowledge just how many different types of dual op-amps there are out there, put on blinders, and restrict yourself to the "usual suspects".

[Sir H C]

That looks like a pretty cruddy op-amp to me unless the schematic is just a rough draft missing a lot of the internals.  The last stage is just using an inverter as the gain stage, that will give huge current variations as can be seen in the supply current of up to 15.5mA with no load.  I think this is a mutant op-amp from the early CMOS days, when it was really a bipolar process that they shoved MOS devices onto (as seen by the use of some bipolars).  Could sound really good, might sound really bad, but it is a current hog.

And those diodes are for protection, it is mentioned in the second paragraph on the first page.

[WGTP]

It appears from my trials, that the Rail to Rail op amps drive the clipping diodes harder than a 4558, etc.