Ds-1 Mods?

[Rich_S]

Now that the SD-1 war has reached a stalemate, I'm turning my attention to my DS-1. It presently has an Allums Recto kit in it, which is a big improvement, but could be better. THe Recto mod included replacing the stock diodes with 1N4002's. I'm thinking maybe making it asymetrical with two 4002's on one side and one on the other would make it a bit nastier.

Anybody have any experience making DS-1's asymetrical?

 

[Rich_S]

Re: Ds-1 Mods?

I'll have to check what I've already done with the Recto mod - I suspect that resistor has already been messed with.

I was looking today at the Keeley SEM/Ultra mod. I owned one for a while, and liked "Ultra" better than "SEM". The difference is the clipping circuit - in SEM mode, he has a 3mm red LED in parallel with the stock diode. In Ultra, he adds another LED in series with the stock diode, and that series pair in paralleled with the other LED. So, that got me thinking about the "2 diodes paralleled with 1 diode" thing. It seems I like asymmetrical clipping better (SD-1's rule TS's!)

What's the forward voltage on those LED's you used? Tryin' to figure out where they fall in relation to the other diode types.

 

[Rich_S]

Re: Ds-1 Mods?

Are you talking about R16? It looks like 6.8K (or maybe 5.8K) on my somewhat fuzzy schematic. The IndyGuitarist book says lowering its value will increase lower mids. It's the left-end resistor in a group of three, on the upper-right of the board, near the wire terminations.

And no, my Recto mod package hasn't changed it from stock.

 

[Pierre]

Re: Ds-1 Mods?

2N4002s and a GE diode is what I have in my SD1. I prefer it to any other combinations I tried.

The LEDs in the DS1 really did it give some midrange bite and... bark? Dunno. It had more of a Marshall vibe. I tried it with 2 and 1 LED, both times I prefered something a bit smoother so I didn't keep them in.

 

[ErikH]

Re: Ds-1 Mods?

Hey Rich, dunno if you saw this page on my site yet. I've got a mod that's 6 changes and the DS-1 becomes a fire breathing monster afterwards. Everything else is stock value.

C5 - change to 0.1uf
C11 - change to 0.047uf
C13 - change to 0.1uf
D4 - change to 1N4001
R16 - change to 4.7k

http://www.erikhansen.net/?page_id=28

On the SD-1 vs. TS thing, I like asymmetrical clipping myself too. Last night I was changing C3 in my SD-808 to allow more bass and decided to change D4 and D6 back to the stock diodes. D5 is a 1N4001 still. I'm really glad how that turned out.

 

[Pierre]

Re: Ds-1 Mods?

Erik I have this page as my favorites You can bet I'll try your own set of mods soon, with my own diode complements I didn't get round to it last time but I do think it's time for a new DS1...

 

[ErikH]

Re: Ds-1 Mods?

Cool, Pierre. Try it with just the one diode change first. It sounds huge. Through a clean amp, like the Twin model on my Valvetronix, I get some great Marshally tones with it. And the cut is really good too.

 

[Rich_S]

Re: Ds-1 Mods?

Hey Rich, dunno if you saw this page on my site yet. I've got a mod that's 6 changes and the DS-1 becomes a fire breathing monster afterwards. Everything else is stock value.

C5 - change to 0.1uf
C11 - change to 0.047uf
C13 - change to 0.1uf
D4 - change to 1N4001
R16 - change to 4.7k
R39 - change to 22k

http://www.erikhansen.net/?page_id=28

On the SD-1 vs. TS thing, I like asymmetrical clipping myself too. Last night I was changing C3 in my SD-808 to allow more bass and decided to change D4 and D6 back to the stock diodes. D5 is a 1N4001 still. I'm really glad how that turned out.

I already have most of those with the Recto Mod, but I haven't changed R16 or R39. Also, I presently have a pair of 1N4002's. Maybe I'll change D5 back to the original diode. I suspect that will increase distortion due to its lower clipping voltage, and increase the raunch/complexity factor by making it asymmetrical by about .3 volts. Similar to what Pierre gets with 2 4002's and a GE transisitor, but with a bit more distortion I would think.

Am I barking up the right tree here?

 

[ErikH]

Re: Ds-1 Mods?

You're right on there, Rich. Mine is still symmetrical with the stock diode in D5 and the 1N4001 in D4. I originally had a bunch of mods done to it and then decided to go backwards and that is where I ended it, just those 6 changes. If you ever get another DS-1 (and they're cheap enough), just make those 6 changes and listen to the difference.

I'm don't mean to discredit Montey's mods or any others at all. It's just that many are piggybacks of other mods (which I have done as well) and many changes aren't really necessary (as I discovered in my modding adventures).

 

[Rich_S]

Re: Ds-1 Mods?

What does changing R39 do?

 

[ErikH]

Re: Ds-1 Mods?

What does changing R39 do?

I believe it's a signal limiting resistor. I'm going by memory and the schematic doesn't show it (the one I have anyway which is from 1980). I'll need to look at the board and trace it through to know for sure.

Edit: From what I've found, it goes from Vref (4.5V) to pin 3 of the opamp. Stock value is 4.7k. From that, it sounds like it affects the distortion in some way. I'm going to look in to this more.

 

[ErikH]

Re: Ds-1 Mods?

I've found the same, mods for the sake of modding. Replacing a 120pf ceramic cap with a 120pf silver mica cap. Any difference you'd hear is in component tolerance, you'd hear the same difference with another ceramic cap in there too. I gotta say though, indyguitarist's mods don't do any of those mods for the sake of modding, his mods are really good I've found.

I haven't tried any of his stuff yet. He's been very helpful on Aron's forum though. Really nice guy. I'll admit, when I modded my DS-1, it was somebody else's and I threw a couple of my own ideas in there. Then I went backwards and ended up with what I have.

I'm about to put R39 back to stock value, 4.7k, and listen for any difference.

 

[Rich_S]

Re: Ds-1 Mods?

I'm about to go out to the garage and put the stock D5 back in.

 

[ErikH]

Re: Ds-1 Mods?

Ok, R39 is back to the stock value. I can't hear a bit of difference between it being 22k or 4.7k. It actually is between C5 and pin 3 of the IC (mine has the M5223AL). That is really strange. I don't get that. D8 looks like a new part too. Could be some sort of loop stabilization or something.

With this, I'm taking R39 off the "to change" list.

 

[Rich_S]

Re: Ds-1 Mods?

D5 is back to stock, DS-1 sounds great. Thanks for your help, Erik.

 

[ErikH]

Re: Ds-1 Mods?

Anytime, Rich. Glad it worked out well for you.