New DS-1 Schematic

[phillip]

Here's a new schematic of the DS-1 that I just finished tracing from a new unit.  Boss has started using a different IC since the other schematic was drawn, so there are some differences in the area around the IC.  They're now using the Mitsubishi M5223AL, which has a different pinout from the TA7136AP, but it's also an inline IC.  

There was also an error in the other schematic in the JFET switching section with the way Q7 attaches to Q6 and Q8.  It also appears that there's a missing 1M resistor that needs to go between +4.5V to the drains of Q7 and Q8.  (The drains of these two JFETs are connected.)

The resistor and diode on the negative connection of the AC-adapter jack have been removed in these new units, which increases power being delivered to the pedal, like they're now also doing with the SD-1.  The negative connection of the adapter jack now goes directly to the sleeve connection of the input jack for power switching.

My new schematic has the part numbers, which correspond with the part numbers on the circuit board to make modifications easier when they're all that you're given.

http://axiseffects.home.att.net/misc/DS1.gif

If anyone's interested, I can also add the circuit board part numbers to my SD-1 schematic.

Have fun

Phillip

[Marcos - Munky]

Thanks, Phillip.

[AL]

Thanks for the work Phillip.  I would be interested in the part #'s on the SD-1 Schematic.

AL

[phillip]

Thanks guys.  I'll get the SD-1 schematic numbered ASAP.

Phillip

[ian87]

thanks phillip!

do you know how recently Boss changed to this new layout and IC?

-ian

[phillip]

I'm not real sure when they changed the IC...I would say within the last year or two.

It looks like they did a redo in the circuit board by changing around the area around the IC, but left everything else the same.  Notice that there is no C6...it was probably one of the ones that was removed from the previous IC configuration.

Phillip

[phillip]

I've updated the schematic of the DS-1.  I had R13 (the 4K7 connected to the 3rd lug of the distortion pot) labeled as R11.  Nothing major, but it bugged me

http://axiseffects.home.att.net/misc/DS1.gif

I've also added the schematics of the DS-1 "Seeing Eye" mod and the DS-1 "Ultra" mod.

http://axiseffects.home.att.net/misc/DS1_Seeingeye.gif

http://axiseffects.home.att.net/misc/DS1_Ultra.gif

Phillip

[Arn C.]

thanks Philip
I think this will clear a lot of things up for my DS1 mod!
Arn C.

[phillip]

The one strange thing about his DS-1 mods is that C12 is already a 0.1uF capacitor.  All the capacitors that he uses in his mods are the Panasonic V-Series stacked metal film, so I guess he replaces that 0.1uF with the Panasonic just for the improved sound quality.  

I think I'm going to get ahold of a DS-1 and try the Ultra mod, minus the switched diode...mainly because I don't want to hack a hole in a new Boss pedal in case I don't like the way it sounds

Phillip

[analogguru]

Film capacitors sound better in the signal path cause of a different tan *delta*.

analogguru

[ian87]

i'm halfway done w/ my SEM mod -- ran out of the right cap & rez values --  but so far it sounds great. thanks, phillip!!  

[phillip]

As an additional mod, you might try changing the value of R2 (470K) to 620K, which will increase the input impedance of the input buffer.  This mod is performed in his 5-star Germanium SD-1 mod, and the DS-1 would also share the same benefits of the mod

Phillip

[Gripp]

Hi Phillip, thanks for some nicely drawn schematics!

I was just wondering, are you sure that in the ultra mod another 1n4148 is switched in? I got the impression from Keely's site that it was another led in series with the original 1n4148 (D4).

And, speaking as a person who tried to figure out exactly what caps he uses by knowing only that they come from digi-key and their relative sizes(see http://www.robertkeeley.com/audio6l6/dstech.html ), how did you come to the conclusion that it is the Panasonic V-series (never seen one myself but know their sizes)? Obviously, I didn't come very far in my detective career... :wink:

I just want to use the right caps and that for the same reasons I guess Keely's using them. Good sound and resonable dimensions. Haven't found a suitable cap myself...all too big....

To finish this embarrasing long post :oops:
Isn't it supposed to be a 47pF cap across the clipping diodes and not a 470pF?

Going to mod my DS-1 soon, holiday is coming to Sweden too! I just want to be sure about the details first.

Best! Pelle Garpebring

[Joep]

Hi Gripp,

I think you are right on both the subject. The 470pF should be a 47pF and the 1N4148 that can be switched in should be a Led.

Bye,

Joep

[Gripp]

Ok. Thanks Joep!

/Pelle Garpebring

[ian87]

As an additional mod, you might try changing the value of R2 (470K) to 620K, which will increase the input impedance of the input buffer.  This mod is performed in his 5-star Germanium SD-1 mod, and the DS-1 would also share the same benefits of the mod

Phillip

hey phillip -- any chance you (or any other knowledgable party) could break this down in terms a noob could understand? i.e., what's the benefit of higher input impedance?

thx,
ian

[phillip]

Whoops, you're right about the cap and LED...I'll get those corrected ASAP.  

As for the mod caps, he gave the part numbers of the ones that he uses in the SD-1 mods, and they turn out to the the V-Series from Digikey, which are nice small stacked metal film caps.  The 1uF are pretty expensive though...$6.00 for a pack of 10 (10 is the minimum order quantity).  I've also seen pictures of a Keeley modified SD-1 circuit board and they're also the same small brownish red capacitors.  

The larger resistor creates a higher input impedance in the input buffer and helps prevent signal loading, which could have a negative impact on the tone when bypassed

Phillip

[ian87]

The larger resistor creates a higher input impedance in the input buffer and helps prevent signal loading, which could have a negative impact on the tone when bypassed

thank you, sir!

[phillip]

The corrected DS-1 mod schematics are posted!

http://axiseffects.home.att.net/misc/DS1_Seeingeye.gif

http://axiseffects.home.att.net/misc/DS1_Ultra.gif

Phillip

[Alex C]

Hey Philip, I am in the midst of a Seeing Eye Mod, which was made very simple by your excellent schematics.  I just wanted to say thanks, and well done!

Alex