Super Octaver

[oli]

Hi there,

I have build the following effect , without a major mod (except the bypass switching and output mixing stage).

http://hammer.ampage.org/files/SuperOctaver.ZIP

I have following problem:

The lower octave is only audible for 1 or 2 seconds after I strike the strings, so it seems that the signal ist too low for detecting, when the string starts to fade out.

After these 2 seconds the normal signal is audible, but at much lower volume.

So I raised the amplification rate of the second stage (IC1a) from factor 51 to 230. It is much better now, but now every slight contact to the strings is audible as unwanted noise.

I tried to remove the 2,2µ from the envelope follower. Now the output jumps between octave down and normal sound, but also when the string is nearly silent again.

It is in no way compareable to my DIY OC-2 from Boss which works perfect, at least with single notes.

Have anyone build it with or without the same problems?

Regards,
Oliver Alex

[oli]

Hi,

really nobody has build this box???

Regards,
Oli

[Mark Hammer]

They have.  They have.  Or else the people who said they have were lying (which I doubt).

HEY FOLKS!  Oli asked me a question that I couldn't answer, so I said he should post here because there had been successful builds, and maybe the builders could tell him what it is *supposed* to sound like.

Don't make ME a liar now.

Are all the successful builders of this circuit on vacation at the moment?

[DDD]

I haven't build the device, but IMO there is a bad component or a mistake somewhere there. Check up your device once again with oscilloscope and sine-wave oscillator with various input voltages. Hope you'll fix the problem with ease.

[oli]

Hi,

I have tested the circuit with my scope - but it isn´t easy for my to know, if the picture on the scope is right or wrong, because I don´t know how it should look like when it is right.
On the schematic there is a little wave form with an arrow on the output of the full wave rectifier.
The picture on the scope looks nearly like this, it looks like a normal full wave rectified signal with every 2nd wave looking like the wave in the schematic.
I don´t think I have mistake, because there are several post, that there are more people having same problems - only maneco seems to solved that problem with a mod.
Is maneco still in the forum? I wrote him an PM - but no answer.
Regards,
Oli

[Paul Perry (Frostwave)]

Just looking at the schem, I can't see anything obviously wrong, but it's not one of those circuits where you could get away with subbing parts - eg those Ge diodes, MUST be Ge, I would think!!

[StephenGiles]

I see there is a spare do dah on the 4070 which might just be used for a ring modulator!!

[oli]

Hi,

@ Stephen

Sorry, what is wrong with the 4070? My English is unfortunatelly not the best...

@ Paul

The diodes are AA117 - Germanium. All the parts are exactliy the same - besides the TL062 - I used the quad version TL064. I also tried to use different OP-amps - same result.
Perhaps I have to try different types of the 4013, which seems to be the problematic part of the Super Octaver.

Regards,
Oli

[StephenGiles]

"Sorry, what is wrong with the 4070? My English is unfortunatelly not the best..."

Nothing is wrong - a 4070 is a quad 2 input exclusive OR gate, and I just said that the spare one could be used for a ring modulator.

[oli]

Hi,

ah I see...

But ca anybody tell me which wave forms I have to get, at the Outputs of the OPs (Input is pure sine wave)?

And I need somebody, who has build this thing and works properly.

Regards,
Oli

[oli]

Hi,

I had a look at the Boss FT-2. There is also a rectifier in there but with one major difference:

In the Super Octaver there is a 20k resistor between Pin1 IC1 and Pin6 IC3. Corresponding resistor in the Boss FT-2 is between Pin6 and Pin3 of IC3 (called R41).



Is this the solution of the problem?

I have to try this out

Regards,
Oli

[oli]

Hi again,

still not solved the problem, but I know it is not the rectifier.
I think it is a problem of the schematic (not a construction error of me).

If I feed a pure sine wave to the input (1,14 kHz), will only hear a clean octave down when the input signal is bigger than 2,05 V peak to peak.
And I will get only a "clean" more fuzzy upper octave, when the input signal is between 60 mV and 255 mV peak to peak.

I need help!
Unfortunately Maneco hasn´t answered my mail. He has modified it, so that it works properly.

Regards,
Oli

[Aharon]

I think Maneco buit it.
Aharon

[oli]

Hi,

I think that too, I send him a PM, but he hasn´t answered it - unfortunatelly!

Regards,
Oli