741 as a booster / octabe.

[newfish]

I have a little stash of 741 op-amps.

My plan is to use one as a clean boost to drive a transformer / diode octave section (to give a clean octave up).

Does anyone know of a suitable schematic?

I've built Bobtavias and such before, but I'd like a clean octave as my 'Fuzz of Choice' is already there (Fuzz Face with Mayer mods).

Cheers guys!

[frequencycentral]

http://www.diystompboxes.com/smfforum/index.php?topic=67197.msg535030#msg535030

[newfish]

Cheers for that.

I think that whatever I build will look a little bit like the OD250, or thereabouts.

Dug my breadboard out last night and started playing - and have come up with a circuit that will do what I'm after.

I'll put a couple of options on there (switchable octave on / off and some sort of blend) to make it a little more versatile.
That way, once I've finished drawing a layout, if anyone else is interested, you're more than welcome to use it.

The projetc is based around a single op-amp with silicon diodes - so any 'mojo' will have to be imagined (tongue firmly in cheek)...

[ocelot]

dont use 741 very noisey

[drewl]

For distortion or Octave?
I swapped out the 741 for some  low noise opamps we had a bunch of at work, but it just didn't have the dame oommphh as the 741.
I think I tried 5534's, OP27, B1350.

[Dragonfly]

dont use 741 very noisey

Some people like the sound of a 741, regardless of the fact that it's noisier than some other op amps.

Noise shouldn't be the only determining factor when selecting an op amp

[newfish]

To be honest, my op-amp selection procedure goes something like this...

1) Do I have any?
2) Can I find a pin-out?
3) Does it work?

Other than that, I'm happy jumping in with both feet to see what happens.

If someone told me last year how engrossing it could be to monkey around with components and such - and how much you can learn - I'd have thought they were having a laugh.

If a 741 is so noisy, why are they used in OD250 and the like?
Maybe the noise is part of their charm - or (dare I say it...) 'Mojo'? 

[petemoore]

1) Do I have any?
2) Can I find a pin-out?
3) Does it work?
  Mighty Picky !!
  You'd pick the beans out of bean soup !!
 
  If a 741 is so noisy, why are they used in OD250 and the like?
  I lump the 741 in the 'low noise category' of components, with all the other opamps...maybe I'm not doing it right, it seems ever so barely discernably noise produceing compared to [any other opamp] ...with ear 'in speaker.

[newfish]

Picky?  Maybe... 

I was given a shed load (literally) of components, so I'm trying to work through them and figure out what they all do.

I figured I'd start with the simpler op-amps and such - hence the 'Do I have any?'.

Either way, I'm learning - which is never a bad thing.

Have a good weekend all...

[Dragonfly]

Picky?  Maybe... 

I was given a shed load (literally) of components, so I'm trying to work through them and figure out what they all do.

I figured I'd start with the simpler op-amps and such - hence the 'Do I have any?'.

Either way, I'm learning - which is never a bad thing.

Have a good weekend all...

VERY good way to go about things my friend.

[newfish]

So - I built an octaver - and it works!

http://www.iansnape.co.uk/images/Octaver_Layout_100508.png

No sound clips as yet, but I'm typing this at almost midnight.
Will try tomorrow.

Simple Op-Amp job (I think) - relation between the 1M resistor and the 47K pot governs gain - switch the Diodes in or out for the octave, and blend the result with your original guitar signal.

I realise the layout could be made smaller - but then it might be a little harder to read.

With the gain turned down and a little octave blended in, it gives a clean octave (which is what I was aiming for) - obviously turning the gain up will do exactly what it says on the tin...



Cheers!

Ian.