SD-1 diode swapping.

holio cornolio
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SD-1 diode swapping.

Post by holio cornolio » Thu Dec 02, 2021 4:05 pm

Hi all. I'm new to the forum. Been a Boss fan for decades but not in any sense hardcore, but recently been obsessing over some smaller details of my all time favourite pedal. I realised recently that I have 4 SD-1 now, 2 silver label MIT versions and 2 Japanese. I'm not really sure why I have so many, I like how they sound (obviously) and I like to have a backup, and I was gifted one of the MIJ ones and the other I saw for sale for £30 and couldn't pass it up. The silver labels are (or rather were) both identical component wise and sounded all but identical. The Japanese are not identical, one has a 5812 chip and 1n1588 diodes the other is the nec4558, but.... they also sound all but identical to my ears. There's really not much to put between the MIT and MIJ ones either. You can hear verrrryyyy subtle differences, but not different enough to be able to say what recipe of chip and diodes are in there. I've always believed that any tonal differences between pedals have more to do with component tolerances than any specific recipe or combination of components. Anyhow I took the soldering iron to one of the silver labels recently, just out of curiosity. I made some capacitor changes to thicken it up a bit and the result is ... Different. I can't say I prefer it to the standard pedal, but it's changed the character so I would now use it more as an always on effect rather than a boost or for lead stuff. Anyhow now that it's already something of a mule I thought I would test my precious theory and swap out the 1n4148 diodes for some NOS 1n1588 diodes that I've found. I'm betting I will struggle to tell any difference, but will try and record some sounds before and after. FWIW the cap mods that I did were C1,2,3,6, 8,9 &12. TBH I think just changing c2 and 3 would have been plenty. I'm not a fan of clipping c6 but I did put a smaller value (0.0047) in there than, which is fine.

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Pepe
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Re: SD-1 diode swapping.

Post by Pepe » Thu Dec 02, 2021 4:11 pm

Welcome to the forum! :)

Some of us have their BOSS favourites. Overdrive-wise my favourite pedal is the OD-2R. Interesting stuff what you write about the SD-1. Some other members might give you further advice for modifications.
Pepe at YouTube and Instagram

holio cornolio
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Re: SD-1 diode swapping.

Post by holio cornolio » Thu Dec 02, 2021 4:43 pm

Thanks for the welcome :-D Ive never tried the od2r. I have an od-1 clone (homemade) which is about my favourite overdrive ever, and I hear good things about the od-2 and od-2r. Maybe that will be next on the GAS list 🙂

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Old_Iron
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Re: SD-1 diode swapping.

Post by Old_Iron » Thu Dec 02, 2021 5:09 pm

Hello holio cornolio,

Welcome!

When you say 1S1588, what band/stripe color has the diode? Black or blue?

I have almost all MIJ SD-1 chip and diode combinations, and as you have said, the difference is very subtle.

The diodes are the ones that can make some difference, they shape the clipping in the sound wave, therefore they give some "personality" to the overdrive.

The yellow band 1S2473 is a bit more "trebly" and aggressive, the blue band 1S1588 is a bit more "mellow", round and smooth, and the black one, that some people say it is the same as the blue (I don't think so) is somewhat in between the yellow and the blue.

In my experience, there are 3 "distinct" (again, very subtle) voices among the MIJ SD-1, the ones with the NEC c4558c chip with the yellow diodes are the most aggressive, good for lead and solos, the ones with the JRC4558D chip and yellow band diodes, has a very smooth and "dense" overdrive, like a foam with tiny bubbles :P , reminds me a tube screamer, and the ones from the second half of the 80's with the JRC4558DD chip with blue band diodes, mellow and good for rhythm.

All the other combinations are more or less in between those 3.

So as you can see, the yellow diode is the opposite of the blue one, sound wise.

The Mitsubishi 5218 chip that you have is not considered a sought-after variant by musicians, but it is by collectors due to it's rarity.

The NEC c4558c is a good chip, and with the yellow diodes it is very sought-after by guitar players.

All opinions above are my experience, but some people may see it differently.

P.S.: If you want to experiment swapping diodes, I would suggest you to try these: the ones Boss used during the 80's, Rohms 1S2473 and Toshiba 1S1588 (blue), LEDs as diodes (they are diodes), the very sought-after Panasonic MA150 (used in the TS-808) and some germanium diodes, like 1N60.

holio cornolio
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Re: SD-1 diode swapping.

Post by holio cornolio » Thu Dec 02, 2021 6:49 pm

Thanks for the welcome old iron and for the info. The 1n1588 I have are blue stripes. I have 5 of them and they're supposedly Toshiba but I have no way to verify that. I've been on the lookout for some 1s2473, because I'd like to try those out too, but although they seem plentiful on eBay, I suspect those that are available are not legit, and are likely just 1n4148 with a yellow stripe. maybe I will take a chance..

Edit: I've been doing a bit of another skim of the interwebz and I wonder if the parts I'm seeing being sold as 1s2473 are actually 1ss133. I might give them a whirl after all. Hadn't thought about the ma150 either. Another option for the pot.

I'd heard similar descriptions to the tonal properties of chips and diodes to those you mentioned but I profess to still being sceptical. I think part tolerance is more responsible for the variations in tone, But I'd love to get a dozen jrc4558x 1n1588 and a dozen nec4558 X 1s2473 in a room and blind test them all 😁.
Anyhow I'm doing this diode swap experiment to challenge my theory although I suspect my personal bias may skew the results 😁
Last edited by holio cornolio on Thu Dec 02, 2021 7:12 pm, edited 1 time in total.

holio cornolio
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Re: SD-1 diode swapping.

Post by holio cornolio » Thu Dec 02, 2021 6:51 pm

Oh I have tried ge diodes in the past but I didn't like them and the volume drop was a bit dramatic. Never bothered with LEDs before in an OD.

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Old_Iron
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Re: SD-1 diode swapping.

Post by Old_Iron » Thu Dec 02, 2021 7:51 pm

I agree that parts tolerance, or parts value drifting over time, is a considerable factor when you compare different pedals, but it is more pronounced when you compare new pedals with vintage ones. Like in a made in Japan vs made in Taiwan comparison.

When you compare a vintage MIJ with another vintage MIJ, same model, that is less important.

Believe me, when you play with those 3 different variants that I mentioned, you can hear the (subtle) difference.

P.S.: Another relevant detail, I have also MIJ OD-1s and DS-1s with those diode combinations, and when compared that same result comes up.

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Old_Iron
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Re: SD-1 diode swapping.

Post by Old_Iron » Thu Dec 02, 2021 10:49 pm

holio cornolio, since you are looking for an improved SD-1, here is a suggestion to spice up a MIT SD-1.

It doesn't change radically the sound of a SD-1, but gives it more volume, less overdrive, more headroom and a much more "tight" sound.

Years ago, when I didn't have any MIJ SD-1, I decided to improve my MIT, changing most capacitors to a "better" ones (xircon and panasonic) without changing original values, put some sockets to experiment with chips and diodes and, most important, put a voltage doubler inside it to raise the juice up to ~17V. when a 9V. power supply is connected.

You must take care and change any capacitor (electrolytic) that have the working range bellow 25V., and change the zener diode D1 to something equal or above 18V.

Here are some pics and the layout of the voltage doubler, it is very simple and easy to build:

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laurie
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Re: SD-1 diode swapping.

Post by laurie » Thu Dec 02, 2021 11:21 pm

Not about an SD-1 but an OD-1...

Many years ago I built a quad-opamp OD-1 with all new components. A new JRC3403 opamp, and 1N4148 diodes. I laid out my own circuit board, with no reference to the vintage Boss layout or lead-dress.

The clip comparing it to a vintage pedal is here:
https://www.youtube.com/watch?v=upFJytwqTCo

The objective was to see if the tone came from the design/schematic, or from the vintage components, or both. You can maybe hear a subtle difference. But it isn't much.

My conclusion is that the majority of the tone comes from the schematic.

holio cornolio
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Re: SD-1 diode swapping.

Post by holio cornolio » Fri Dec 03, 2021 6:18 am

Old_Iron wrote:
Thu Dec 02, 2021 7:51 pm
I agree that parts tolerance, or parts value drifting over time, is a considerable factor when you compare different pedals, but it is more pronounced when you compare new pedals with vintage ones. Like in a made in Japan vs made in Taiwan comparison.

When you compare a vintage MIJ with another vintage MIJ, same model, that is less important.

Believe me, when you play with those 3 different variants that I mentioned, you can hear the (subtle) difference.

P.S.: Another relevant detail, I have also MIJ OD-1s and DS-1s with those diode combinations, and when compared that same result comes up.
Fair enough. I won't argue with your experience, bit my aim with my experiment is to challenge my own preconceived idea. It won't be scientific because I'm modifying one pedal with 1 set of diodes - so hardly a data set. I'm also prepared to accept that I just don't have good enough ears to appreciate the subtleties 😁. I'm looking forward to doing the swap some time soon.

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