Dod 440 issue and mods

[fuzzo]

Few time ago, I made a Dod 440 clone, I really like it but there's a strange issue. At the treble side with the range pot there's a strange buzz that remplaces the sound with the auto-wah. I don't know where that comes from . I use a TL072 (I don't manage to find a TL022 in my electronic store). What is it ? I thought puting a little cap to break a little bit the highs frequencies but I don't think that will solve the probleme.

Also , The  controles aren't really "progressive", I used linear pot instead of Log.

Do you know some cool mod to improve this little box , and increase the possibilities ?

What will happen if I increase R12 ? I saw a post where someone wired a 100K + 390K to have a "Q" control .

[davent]

Hi Fuzzo,

I was directed back to this thread  by a poster on youtube when i asked what he had done to mod his 440. http://www.diystompboxes.com/smfforum/index.php?topic=66678.0

This was the video that made me want to build a 440, (which i haven't done yet.)  http://www.youtube.com/watch?v=2W4dKSmPkL0&feature=related

And i believe the TL022 is a very low current device at least when compared to a TL072.

dave

[fuzzo]

Yeah, I saw a lot of people recomends to use the TL022, but I don't manage to find one (I must order one via Banzai). You think the strange distortioned tone at the treble side comes from the TL072 ?

http://www.youtube.com/watch?v=2W4dKSmPkL0&feature=related

He gave you more informations abouth this additionnal pots ?

Yes I read the tread yesterday, but I don't know if it's an useful control (but Krinor and johngreene seems to be happy with it)

[davent]

Yeah, I saw a lot of people recomends to use the TL022, but I don't manage to find one (I must order one via Banzai). You think the strange distortioned tone at the treble side comes from the TL072 ?

http://www.youtube.com/watch?v=2W4dKSmPkL0&feature=related

He gave you more informations abouth this additionnal pots ?

Yes I read the tread yesterday, but I don't know if it's an useful control (but Krinor and johngreene seems to be happy with it)

Hello,

The youtube video is i believe Krinor's. (His signature here is the same as the name used by the person that posted the video.) He just told me was everything i needed to know was in that thread and didn't elaborate on the specifics of the extra pots.  He did say that if i had further questions to PM him. Since i haven't done any work on it other then designing a PCB, i haven't been in further contact with him.  (Our brief conversation is posted in the comments to the video.)

dave

[fuzzo]

Hi,

Ok I'll try to send him a MP on youtube.

Altough I spent many time to find out mods and I found nothing about this pedal.

Otherwise ,the kind of smashed drive  tone produced by the pedal with the range pot at treble side is only caused by the TL072 ?  Why only the TL022 seems to work properly  in the circuit?

[davent]

Hello,

This is way over my head i may  have read someplace of others having problems with subbing the tl072 for the lower power consuming tl022. Power consumption for the tl072 is listed as 2.8-5mA and for the tl022 only 130-250µA.  As to why this might make a difference... i have no idea.

Found these but again doesn't really shed any light on why?

http://www.diystompboxes.com/smfforum/index.php?topic=56200.0
http://www.diystompboxes.com/smfforum/index.php?topic=68192.0

dave

[fuzzo]

I'll order one or two TL022 with my next components order and I'll see that. Exept the wrong IC I see nothing else.

For the mods, I'm still looking for....

[mr_doyle]

I'm curious as well: i got an original 440 (orange version) that has similar distortion issues since a "tech" replaced the opamp... so bad as it's my favourite pedal ever!

Thanks,
D.

[fuzzo]

Remplaced by what ? TL072 also ?

When the pedal works for the first time, I used a JRC022 from my GE7 Boss (maybe damaged) and the effect didn't work very good, a lot of distortion and any auto-wah sound. I put a TL072, the sound was really better but with this smashed dirstoned tone at the treble side.

But, actually, even in the middle position there's that noise but little bit hidden by the auto-wah movement.

[mr_doyle]

yep, 99% sure it was a TL072

D.

[fuzzo]

It's not hte TL072. I' ve just put a new TL022 and the smashed tone is still here. I start to desesperate (beside I've a big ploc everytime I kick the switch)

Any suggestion ? a crappy cap ? (I used metal film, the little yellow cap)

[jrc4558]

I think a pull-down resistor is missing on the output, at least on the schematic... just add a 10M resistor from the switch side of the 47n capacitor to ground. As for ripple and noise on the treble side of things - I have it too and no swap of an op-amp has healed that yet...

[fuzzo]

I can't believe there're any solutions to fix that @#$%in' bad noise

It's a really cool pedal withtout that smashed distortion tone at treble side.

[fuzzo]

Do you think the quality of cap can play a role in that noise ? (I don't think so but I'm not an expert)

help would be really apprecied .

That pedal is really cool and muscial but that problem makes I can't really play with it.

thanks.

[mwynwood]

Did anyone ever work out how to get rid of the little distortion noise in this pedal?