SD-1 diode swapping.

bob barcus
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Re: SD-1 diode swapping.

Post by bob barcus » Sat Dec 18, 2021 7:59 pm

I like the GE diodes in my 2001 SD1 But the Best to my ear is the 1984 SD1 with C 6 clipped But I use 100 watt plexi Marshall They got it right back then

holio cornolio
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Re: SD-1 diode swapping.

Post by holio cornolio » Mon Dec 20, 2021 3:38 pm

I've just picked up a vshock super overdrive sd-10. It's supposedly a sd-1 clone and I've yet to trace the board but good god it's a nice overdrive. Notwithstanding the fact that the pots need a good clean, it's about as close to sounding like a long chip od-1 as I've heard. Weirdly, the opamp has has the print scratched off so I don't know what that is, the diodes are 1n4148 but I've yet to trace the rest of the board. The tone section sounds different. It might just be a different sweep to the pot, but it sounds brighter a crisper than even my favourite sd-1. Will report back with pictures if anyone's interested

holio cornolio
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Re: SD-1 diode swapping.

Post by holio cornolio » Mon Dec 20, 2021 3:56 pm

drives2.jpg
drives2.jpg (32.51 KiB) Viewed 4533 times
here it is. notice that the opamp has the print scratched off... I'm not implying that there's any mystery afoot, just seems odd that this would have been done. No idea on date of manufacture or any of that at this point. in the absence of a serial number or a date code on the IC, anyone any ideas? It doesn't show either MIJ or MIT labelling anywhere although it does have a diode and resistor for aca power supply, so pre '97 probably
driveboard2.jpg
driveboard2.jpg (59.91 KiB) Viewed 4533 times
edit - so I have been through the board and can confirm that it's essentially identical to a boss SD-1 with the exception that the tone pot is a B20k rather than W20k. (TBH I didn't check buffer or switching circuits though) I have to say it sounds really quite distinctive though. I guess the component quality and tolerances might be slightly different, and it would be nice to know what the opamp is (although I would guess it's almost certainly a JRC4558DD). Interesting. Must get that volume pot cleaned up though..

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laurie
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Re: SD-1 diode swapping.

Post by laurie » Tue Dec 21, 2021 12:08 am

holio cornolio wrote:
Mon Dec 20, 2021 3:56 pm
in the absence of a serial number or a date code on the IC, anyone any ideas?
Based on the components I'd say early '80s.

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Old_Iron
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Re: SD-1 diode swapping.

Post by Old_Iron » Tue Dec 21, 2021 2:44 pm

During the 80's there was many copy cats of Boss pedals, in this video Josh from JHS pedals shows off a few from his collection:

https://www.youtube.com/watch?v=fK1ISeJiAFg

holio cornolio
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Re: SD-1 diode swapping.

Post by holio cornolio » Wed Dec 22, 2021 6:34 am

bob barcus wrote:
Sat Dec 18, 2021 7:59 pm
I like the GE diodes in my 2001 SD1 But the Best to my ear is the 1984 SD1 with C 6 clipped But I use 100 watt plexi Marshall They got it right back then
Oh the Vshock don't need no c6 clip.

holio cornolio
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Re: SD-1 diode swapping.

Post by holio cornolio » Tue Jan 11, 2022 10:45 am

My sd-1 collection continues to swell. I really don't know why I keep buying them. I'm currently obsessed with black label MIT units, because there seems to be some reasonably significant variation in component suppliers used at that time. I've seen (in my searches), ornage, green and silver caps used, but so far I've only ever seen 4558 opamps and 1n4148 diodes (or at least black stripe diodes which I assumed to be 4148s). I'm just wondering if there are any unicorn spec MIT sd-1s out there with unusual opamps or diodes, or did all that 'variability' stop when production moved to Taiwan? I've given up o. Silver label units, I have enough of them and they are all the same and all sound very similar if not exactly identical (surprise), because they are all more than 12 years old and have all been through a different journey...

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fuzzbuzzfuzz
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Re: SD-1 diode swapping.

Post by fuzzbuzzfuzz » Tue May 24, 2022 7:31 am

I honestly thought the diode differences and small parts variations across the years would make very little difference...until last night when I had to, really had to!, rescue a SD-1 from being sold because it sounded remarkably "up-my-street" tone wise! 

I had:

Amp < July 1983 (my original) < Aug 1985 < Nov 1986

At first I thought, "Ah it's just the placement order, it's the first of three SD-1s I'm chaining together the buffer is dulling the latter ones". Swapped them order wise, nope I can still tell, very surprised!

This one was sweet sounding with sparkly trebly and made me want to play - a very Tube Screamer sound of the vintage variety.

Of the other two, 1983 was the opposite, felt much harder and darker sound wise, with the 1985 SD-1 sitting between the too. After a bit of back-and-forth tone testing (and my my wife entering to say "its a biiiiiiiiiit loud", popped open the backs to examine.

Turns out I'm a fan of the later blue diode one, i.e. those diodes in the actual TS pedals of the time. I have recently restored to spec my rare Maxon ST-9 and had been going through TS style pedals to find "the one" so this figures.

I had played the dark sounding early-diode one for a long time years back in my BCB-6 case and always felt it was a bit blanket-y on the chime factor frequencies and more aggressive than I would have liked, didn't bond so much with it.

Oddly the 1985 also uses the same diodes as the newly found 1986 "The ONE" (as far as I can tell), yet sounds a bit darker, so a few other components may have drifted or be different). 

Also curious as I have the PCB with parts of another SD-1, dark brown PCB and those black striped diodes. 

Anyway, thoroughly schooled now, and goes to show it may take a while to "get a good one"!

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fuzzbuzzfuzz
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Re: SD-1 diode swapping.

Post by fuzzbuzzfuzz » Thu May 26, 2022 6:53 am

...more update, also very much enjoying the "hard punch" of the earlier SD-1 too, I can see why people like it, seems to suit that pushed Marshall boost option ala an OD-1, less fizz or "shush" at the top end, and a focused mid.

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Old_Iron
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Re: SD-1 diode swapping.

Post by Old_Iron » Sat Jul 02, 2022 6:51 pm

I found this page and it is a little bit of information to help who is looking for a certain kind of sound in the most known Boss "drive" pedals, with visual examples (frequency response analysis and some comments about it).

https://guitarpedalsvisualized.wordpress.com/

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