DOD 440 It works but has a weird distortion (fizz),any suggestions? Video inside

[jimmybjj]

http://www.youtube.com/watch?v=ObrtaeeEGgk

[jimmybjj]

Sorry forgot to include some stuff, here is the schematic I used. The only deviation was R12 I didn't have a 430k so i used 470k.

http://www.generalguitargadgets.com/pdf/ggg_ef440_sc.pdf

using the layout and Jd's pcb

http://www.generalguitargadgets.com/pdf/ggg_ef440_lo.pdf


after some reseach on the net, I tried using 0.1uf caps in place of the .022uf. This seems to have helped, but there is still a pronounced fizz or fuzz on top of the pleasant intended sound.
Does anyone have any suggestions? I don't really know what to do or try. I'm still new to all of the this and I understand how to trouble shoot and use a meter, but all of that doesn't help when the pedal works. It just doesn't work as I think it shoud (observations on youtube). I just don't understand enough of the theory to jump in and start changing components.

Thanks for any help.

[fuzzo]

You're not alone dude. I made one and I had the same trouble without finding out what do to fix that  .

I gave up that circuit even if it's still in my circuit's box.

[jimmybjj]

You're not alone dude. I made one and I had the same trouble without finding out what do to fix that  .

I gave up that circuit even if it's still in my circuit's box.

I am glad i'm not alone. Can anyone help us? This seems to be a reaccuring problem. I see the problem frequently mentioned on the net, but i do not ever see a solution.

[Zzagar]

As I understand, from a lot of forum/google research, the cause of the unwanted fizz/distortion is from using the dual opamp instead of two single opamps. There seems to be cross over distortion between the opamps within the dual opamp (TLO22). There is no real fix other than separating out the amps i.e. two LM741's or two TLO22 wired as single opamps. When you raised the 430k to a 470k you added more gain onto the filter opamp. This will generate a much more overall pronounced 'wah' sound depending upon what value you used on the feedback of the detector opamp (originally a 470k but I have seen this value as high as 2.2m) I hope this helps clarify some. I have spent a lot of time on this circuit and have grown to like the unique sounds you can achieve even with the 'fizz' but am still messing with a modified version with no 'fizz'.

[thedefog]

If you soldered in an IC socket, you could always try different dual opamps and see if it is better or worse. There is probably a better low power dual opamp out there to use for this than the TL022, perhaps the OPA series ICs.

[Zzagar]

I've actually experimented with the following dual opamps in the 440; LF353, LM1458, OPA2134, TLO72, TLO82, TLO22, JRC4558D. By far, the LM1452 and TLO22 had the best 'quack' as well as over all response on the sensitivity knob. To my suprise the worst sounding was the OPA2134! I've kicked around the idea of socketing the dual opamp and run leades or another socket to some perf board with two single opamps but have not gotten around to this.

[thedefog]

I've actually experimented with the following dual opamps in the 440; LF353, LM1458, OPA2134, TLO72, TLO82, TLO22, JRC4558D. By far, the LM1452 and TLO22 had the best 'quack' as well as over all response on the sensitivity knob. To my suprise the worst sounding was the OPA2134! I've kicked around the idea of socketing the dual opamp and run leades or another socket to some perf board with two single opamps but have not gotten around to this.

I'd be curious as to how that sounds. Let me know if you do that for sure, because that was always the drawback of this circuit in my eyes.

I'd breadboard one up to test it out, but I don't have a spare Vactrol handy, and the home-made ones I've done don't always work so well in these kind of circuits.

[jimmybjj]

As I understand, from a lot of forum/google research, the cause of the unwanted fizz/distortion is from using the dual opamp instead of two single opamps. There seems to be cross over distortion between the opamps within the dual opamp (TLO22). There is no real fix other than separating out the amps i.e. two LM741's or two TLO22 wired as single opamps. When you raised the 430k to a 470k you added more gain onto the filter opamp. This will generate a much more overall pronounced 'wah' sound depending upon what value you used on the feedback of the detector opamp (originally a 470k but I have seen this value as high as 2.2m) I hope this helps clarify some. I have spent a lot of time on this circuit and have grown to like the unique sounds you can achieve even with the 'fizz' but am still messing with a modified version with no 'fizz'.

thanks for the input everyone. how is your 440 modified? modified for no fizz? I like this circuit alot but can't stand the extra fizzle on top of he intended sound, so it makes it unusable for me. I did socket the ic and tried what I had on hand (tl022, tl072, jrc4558) but none of the. eliminated the extra fizzle. still looking for a solution.

[fuzzo]

I thought the same thing, the TL072 I , at first, put on the circuit but even in changing it for a TL022 , the "fizz" was still present.

[Zzagar]

So I did a few experiments on my existing stock DOD 440 (GGG Board) I wanted to see what kind the improvement separating the dual opamp into two seperate dual opamps would make. The existing TLO22 was socketed in my 440, so I took some perf board, added three 8 pin DIP sockets. The center DIP had long leads, so I used this socket to jumper over to the the two new dual opamps. Also used the long leads to plug into the existing socket.  There is a very noticable difference between the amount of 'fizz' using a single, dual opamp and using two, dual opamps.  The reason I chose to use two dual opamps instead of two singles, was due to the extra supply of random dual opamps in my shop. The 'fizz' was still present with two opamps but only when the sensitivity is craked fully up. But with the sensitivity at 12 o'clock I had full range on the range knob and achieved a much fuller 'quack' with much less if any 'fizz'. I hope this helps. Z 

[jimmybjj]

So I did a few experiments on my existing stock DOD 440 (GGG Board) I wanted to see what kind the improvement separating the dual opamp into two seperate dual opamps would make. The existing TLO22 was socketed in my 440, so I took some perf board, added three 8 pin DIP sockets. The center DIP had long leads, so I used this socket to jumper over to the the two new dual opamps. Also used the long leads to plug into the existing socket.  There is a very noticable difference between the amount of 'fizz' using a single, dual opamp and using two, dual opamps.  The reason I chose to use two dual opamps instead of two singles, was due to the extra supply of random dual opamps in my shop. The 'fizz' was still present with two opamps but only when the sensitivity is craked fully up. But with the sensitivity at 12 o'clock I had full range on the range knob and achieved a much fuller 'quack' with much less if any 'fizz'. I hope this helps. Z 

Sorry I'm still a new to all of this. Is there any way you could take a picture of what you did? I can't picture it in my mind.

[Zzagar]

Take a look at this page: <a href>http://cimarrontechnology.com/single-to-dualop-ampadapter-dipversionpn021001.aspx</a>
this should give you an idea of what i mean about splitting a Dual Opamp into two Single Opamps.  It takes away quite a bit of the fizz you are talking about. I hope this helps.