DS-1 Keely Mod

[PedalSouldier]

Hi. I am new to modding and building pedals and am looking forward to using this forum to help me learn how to improve my skills.

Here is my problem. I bought a used DS-1 stock and it sounded ok. I likes the sound of the Keely mod so I bought the kit and modded it according to the directions that came with the mod. After I put it back together the SEM works and the pedal works but I have to turn up the distortion pot all the way to get the crunch sound, the pedal is no better than a boost pedal when at 12 o'clock. Well when I was looking at it I realized in a moment of horror that my bench power supply I was using to power the pedal was set to 18v!.. this might not be the culprit. the pedal still works just not as it should.. if anybody could point me in the right direction that would be nice.

[GibsonGM]

Welcome to the forum!  Love to help....We'd need some more info first, Pedal.

What exactly were the mods you did (post a link to a page showing them...and a schematic, please).   What is your background in electronics?

Can you see if any electrolytic caps on the PCB are rated for <18V?  That is one place to start. 

All things being equal, if the pedal is different now than before, either the mod does this or you messed up something while doing it     

We'll need voltages of each pin of the opamp with 9V applied to the ckt, also.  Not sure which OA it is, but some don't like 18V...

[PedalSouldier]

I did the Keely Ultra Mod and the Seeing Eye Mod on this Pedal. I followed word instructions on how to do it but here is a schematic of the mod. (other one is the seeing eye mod.)

I have been soldering and working on bigger electronic things all my life but not an awful lot with PCBs. I have done a ton of research and want to get into pedal building. and modding.

I have to go and look at the caps to see what they are rated at. Is it possible that the OA being introduced to too much voltage would cause it to weaken but not fry completely?

How would I test the op amp correctly?

Ultra Mod

https://www.google.com/search?q=keeley+mod+ds-1&biw=1600&bih=839&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjXr7SribfOAhUCKyYKHXbFC6sQ_AUICCgD#imgrc=c7vbavrgazs4CM%3A

Seeing Eye Mod

https://www.google.com/search?q=keeley+mod+ds-1&biw=1600&bih=839&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjXr7SribfOAhUCKyYKHXbFC6sQ_AUICCgD#imgrc=JVkFyPn3mFlAPM%3A

[anotherjim]

Check the extra switch wiring - it could be you don't have all the clipping diodes/leds connecting via that switch.

[PedalSouldier]

When I strum the guitar though they both light up. If I had a Diode backwards they would not am I correct?

I heard that R9 resistor controls the gain. Maybe that needs to be changed again.

[Renegadrian]

r13 controls the gain, you can change it to 2.2k or even 1k if you're after some more gain, as wampler suggested. when put as clipping diodes, leds are back to back and one is reversed, but they both light up.

[GibsonGM]

I love LEDs. They are more 'crunch' than 914's, to my ear, and louder.  When hit right, they should give you all the distortion you need.   If you just hit the thing with double supply voltage, I wouldn't wonder about increasing gain - I'd wonder if I fried something, LOL!

To measure the voltage on your IC, attach your negative probe (black) to a ground...batter "-" will do, or a grounded jack sleeve.   Carefully use the red probe on each IC leg to get the DC voltage, and write it down.  There is a notch on the IC....the left pin by that notch is #1, proceeds down 1 2 3 4 then to lower R leg 5 up to 6 7 8.   

I'm just wondering if the over-voltage damaged anything.   9V on the trannies were 18V, and the bias was 9V! 

[PedalSouldier]

Thank you all for the input I will do some testing and Will post the "fix" if I can find it.

[anotherjim]

My experience (well, I've only modded one) is that just one LED instead of a diode makes it LOUD. Anything over 9 o'clock on the level knob can overdrive whatevers next.
If the LED's do glow, that bit may well be working, so maybe the bypass switching isn't working properly?

[GibsonGM]

My experience (well, I've only modded one) is that just one LED instead of a diode makes it LOUD. Anything over 9 o'clock on the level knob can overdrive whatevers next.
If the LED's do glow, that bit may well be working, so maybe the bypass switching isn't working properly?

My experience, too....WAY louder.  I second the switching...

[PedalSouldier]

The switching meaning the bypass it has stock or the seeing eye mod switching? I read that replacing the Diodes with LEDs cuts gain. After all It is a distortion pedal I really would like more gain at this point.

I suppose ill mess with that and the R13 resistor on a breadboard to see what I can get.

Thank you all for input

[GibsonGM]

The switching meaning the bypass it has stock or the seeing eye mod switching? I read that replacing the Diodes with LEDs cuts gain. After all It is a distortion pedal I really would like more gain at this point.

I suppose ill mess with that and the R13 resistor on a breadboard to see what I can get.

Thank you all for input

Classic conversation there, Souldier...what do you mean by gain?  Gain is loosely defined as an increase in signal level from input to output (yes, it can be negative too, but not today ok).   The GAIN of an amplifier.   Since regular Ge diodes clip somewhere near .3V, and LEDs can vary - let's say 2V for our purposes here -   you WOULD have more gain with LEDs than regular Ge (or Si) diodes.

Do you mean more DISTORTION?  Well, that's generated by running a signal thru a non-linear process, which diodes certainly meet.  So, at .3V or thereabouts, more of your signal is clipping with Ge diodes, and therefore you perceive more distortion.

LEDs will both raise your signal level (louder...more output...to a tube amp, more signal to overdrive it...), AND generate distortion when you exceed their clipping threshold.  They sound more "Crunchy" than Ge to many, as they're not totally hard-clipping and compressed due to this process.

So, it's a matter of semantics and how you are defining "Gain"...see?   I think you mean "distortion".

[PedalSouldier]

There is a reason I have "Im learning.. " as my signature.

You are very right. I meant distortion. I will note what you said for future reference when building and fixing pedals.

As stated before I have lost a fair amount of Distortion after modifying my pedal. Then I was only following directions then but now I really need to learn what actually causes the distortion sound.

and what on this particular pedal to test to see where I can achieve more of it.

[GibsonGM]

No worries, Souldier, I know that you're learning.   Just wanted to point out that very common accidental use of gain for distortion, most of us have done that 

This might help get you going on "what the heck is going on in there?":  http://www.electrosmash.com/boss-ds1-analysis

The DS-1 does what it does, pretty well.  If you want to mod it to get more distortion from it, I would suggest replacing D4 and D5 with germanium diodes, like 1N34A's.  That would make the unit clip EARLIER (more distortion) than when you got it, but it would make the output a bit lower, too...(trade offs...).    To make the output louder if you added germanium diodes would be difficult with the existing board...if you could ADD a small board, you could change the transistor output buffer to a gain stage (I suppose you COULD do that if you wired it point to point on top of the board, but might be unstable).


Get the LEDs out of there, they are raising the clipping threshold above where you are saying you want to hear it (they are not clipping the signal early enough, so you get more boost/clean type sound).  Seems to me that that IS the mod....

With the original 4148 diodes, well, you know how those sound since that is how the DS came.     It would be easy to make a nasty high-gain dist. from scratch, rather than mod this on any more.....hint hint, lol...

[PedalSouldier]

I will do as you say and put the new diodes in.

Well when I heard the stock vs mod video they were getting really good tones from the modded one at like 12 oclock position when I have to turn mine up to max. But perhaps you are right. God only knows they might have done theirs differently. I guess "Keely" mod is not set in stone, you could put anything in there.

Thank you for you time.

[GibsonGM]

Yeah, you COULD mess around with some of the gain components - but once the signal is cut, it's cut....so you'd really need to make it louder on the OUTPUT side, and that's a buffer there...you would have to reconfigure that transistor, which is not impossible, but might stink trying to do on a PCB not meant for it...

You're certainly welcome, hope the diodes work out!

[lukeferg]

I'm a bit late to the party here. The DS-1 Keeley Mod was my first foray into pedal building.
I blindly followed these instructions (with pics!) and it worked first time.
http://www.instructables.com/id/Modify-Your-Boss-DS-1/

You should definitely not have any loss of distortion. The two modes of the DS-1 sound awesome now.

On the diode swapping, I have run across bad diodes, particularly in cheap Chinese pedals. But your Boss ones should be right.

[PedalSouldier]

Well I certainly Have lost distortion. I will have to analyze the components and see if they differ from the mod listed online.

[lukeferg]

I was just reading some previous posts. Did you end up checking the direction of your LED's?
If one is backwards it still will light. An LED lights when voltage is present in the direction it's going. If you've got two LEDs pointing in the same direction then they will both light up.
If an LED is facing the wrong way then I'm guessing you will get much less distortion from it because the signal isn't being clipped on half of the wavelength. Not sure on this point though.

[PedalSouldier]

Very Good point.. I will look into that. I was not sure if they would light in both directions so I guess I assumed it was the correct direction.

Thank you