Weird Decay in DS-1 mod, please help!

[nicholasim]

Hi everyone,

This is my first post on the forum. I have read up a bit on modding of pedals and stuff. I am not very familiar with electronic terms though.

I have tried modding my DS-1 which i had lying around. It sounds really nice, however, i am facing a problem. The decay of the pedal sounds really weird. It sounds like something shorting out or shutting down. I am not sure how to describe the decay. But just before the decay dies out, there is this "squeal". I have replaced the opamp inside to NE5532, 2 of them. This "Squal decay" only occurs when i have BOTH chips in there. When i removed one, the problem went away. But i much prefer the sound with both chips inside.

Here is the mod i did to the DS-1:
Changed resistors:
2.4k resistor in R13
20k resistor in R39
1.5k resistor in R14

Changed opamp to:
2x NE5532

D5: white led
D4: Orange LED

47uf across d4 & d5

Any idea what could be the problem??

Thanks in advance!

[dwmorrin]

Hm, well I guess I am first and foremost confused about the opamp situation.
Doesn't the DS-1 usually have just 1 dual opamp chip?  How are you fitting 2 NE5532s in there, and what are the other 2 op amps doing?  Is this an actual Boss pedal, or a DIY version?  Have I missed some new version of the DS-1?

Secondly, I'm guessing you mean 47pF across D4 and D5, not 47µF... as the 47pF cap seems to be the common mod choice, while 47µF seems like it would be a little odd.

[nicholasim]

Hm, well I guess I am first and foremost confused about the opamp situation.
Doesn't the DS-1 usually have just 1 dual opamp chip?  How are you fitting 2 NE5532s in there, and what are the other 2 op amps doing?  Is this an actual Boss pedal, or a DIY version?  Have I missed some new version of the DS-1?

Secondly, I'm guessing you mean 47pF across D4 and D5, not 47µF... as the 47pF cap seems to be the common mod choice, while 47µF seems like it would be a little odd.

Hi, yes its a 47pf, sorry for the typo.

About the opamp, the initial one in there was a single 8pin. I replaced it with a dual stack using something like this:
http://www.monteallums.com/images/DS_Adapter_Web.jpg

[dwmorrin]

About the opamp, the initial one in there was a single 8pin. I replaced it with a dual stack using something like this:
http://www.monteallums.com/images/DS_Adapter_Web.jpg

Is it "something like that" or actually that?
If it's that, you've got the 2 opamps "stacked" or running in parallel with each other.

I'm kind of curious to hear the weird decay.

I don't know about the original op amp, but the 5532 is known to be current hungry, and the input pins draw more current than typical op amps.  That could be a clue to your problem.

[nicholasim]

About the opamp, the initial one in there was a single 8pin. I replaced it with a dual stack using something like this:
http://www.monteallums.com/images/DS_Adapter_Web.jpg

Is it "something like that" or actually that?
If it's that, you've got the 2 opamps "stacked" or running in parallel with each other.

I'm kind of curious to hear the weird decay.

I don't know about the original op amp, but the 5532 is known to be current hungry, and the input pins draw more current than typical op amps.  That could be a clue to your problem.

I have the same 5532s in my bd-2 blues driver without the "decay problem". Not sure if the circuitry allows for difference in current?

I will try to get a recording of it up later on

[nicholasim]

Finally got a short recording done.

You can hear the weird decay at the later part when i turn up the gain.

https://soundcloud.com/nicholasim/ds-1-decay-test

[dwmorrin]

Sounds cool! I'd probably keep it as a weird effect if it was my pedal. 
Don't know what you've got there.  Maybe someone else here can figure out what's really going on in there.

[nicholasim]

haha no can do for me! Too out of this world 

Bump! Anyone has any idea whats going on?

[dwmorrin]

I have the same 5532s in my bd-2 blues driver without the "decay problem".

http://www.freeinfosociety.com/electronics/schematics/audio/pictures/bossbd2.gif
The BD-2's opamps have very different functions that the DS-1.
One side of the BD-2 is just buffering the +4V reference voltage, and the other side is a fixed gain amp... looks like either make-up gain for the tone control, or maybe some active filter as well.
On the other hand, the DS-1's opamps are arranged in series: buffer into high gain amp.

Point is, I don't think you can make comparisons between stacking op amps in the BD-2 and the DS-1.  You're making two completely different mods.

I've never messed around with stacking, as I only know of it as a low noise technique, and I'm usually not pursing low noise in my distortion pedals.  Maybe it's just not a great idea to stack a high gain stage, or maybe you need to pick your resistors and caps around the opamp carefully to avoid weird noises.

Is this mod (change resistors + stacking in a DS-1) a verified, commonly done mod, as far as you know?  Or are you pioneering new territory here?

[nicholasim]

I have the same 5532s in my bd-2 blues driver without the "decay problem".

http://www.freeinfosociety.com/electronics/schematics/audio/pictures/bossbd2.gif
The BD-2's opamps have very different functions that the DS-1.
One side of the BD-2 is just buffering the +4V reference voltage, and the other side is a fixed gain amp... looks like either make-up gain for the tone control, or maybe some active filter as well.
On the other hand, the DS-1's opamps are arranged in series: buffer into high gain amp.

Point is, I don't think you can make comparisons between stacking op amps in the BD-2 and the DS-1.  You're making two completely different mods.

I've never messed around with stacking, as I only know of it as a low noise technique, and I'm usually not pursing low noise in my distortion pedals.  Maybe it's just not a great idea to stack a high gain stage, or maybe you need to pick your resistors and caps around the opamp carefully to avoid weird noises.

Is this mod (change resistors + stacking in a DS-1) a verified, commonly done mod, as far as you know?  Or are you pioneering new territory here?

Wow! Thanks so much for the information and taking the time to get it. Very interesting indeed!

As for the mod, yes i am trying out something new haha. BUT i can tell you all that this mod (with BOTH opamps stack) sounds really really amazing, other than the decay problem. Thats why i am hoping that there is a "cure" to this haha. You guys should give it a try for fun. It really sounds killer! With only 1 opamp, not so much..

[pinkjimiphoton]

the biasing is way off, for all intents the chips being "starved"... i've gotten similar sounds stacking stuff. if you don't like it, but like the sound you get, try different opamps.
as long as they're both duals, you should be able to stack 'em up and find something that will sound close enough with a better decay.

i did something like this with a digitech grunge, i forget which oa's i used, but stacking a second one right on top of the first sounded great.

try a 4558 or tl082 or something.

[nicholasim]

the biasing is way off, for all intents the chips being "starved"... i've gotten similar sounds stacking stuff. if you don't like it, but like the sound you get, try different opamps.
as long as they're both duals, you should be able to stack 'em up and find something that will sound close enough with a better decay.

i did something like this with a digitech grunge, i forget which oa's i used, but stacking a second one right on top of the first sounded great.

try a 4558 or tl082 or something. ;)l

Ah, i see. Alright i'll try fitting in other opamps. Quite impossible to get them from where im staying, gotta get them shipped from the US.

Any idea if the burr brown opamps will work? I would really want to try them haha.

[pinkjimiphoton]

i dunno, i always buy crummy cheap ones from tayda... 72's 82's  4558's  and crap like that. a bud gave me several bags full of ne5532's and 4's and i generally don't bother with expensive op amps
when my initial determination is to molest the damn circuit til something blows up.

where do you live?

i'd imagine anything with a similar pinout would probably work, but the higher the current required by the chip, the more weirdness you'll get.


i kinda liked the clip.