analogman ds-1 mod

[brianq]

I have a 90's version ds-1 & I can't give the damn thing away! It's so thin & unpleasant maybe worth a modding before I throw it away music-go-round won't even take it

[Fancy Lime]

Hi gmaslin,

no, I didn't mean you have to trace everything. Just find the schematic that has the same component numbering as your unit. I'm fairly certain it is out there. The you just have to jot down what type each component is a check if it's the correct value. Shouldn't take more than 5 minutes 

Andy

[gmaslin]

Fancy Lime
Maybe you can jot that fast, I can't

brianq
If you think your DS-1 is nasty, you should hear mine. Have a look at the link I posted on the prior page, spot on assessment there.

[ElectricDruid]

Sorry, I'm not understanding you.

I'm suggesting using a pot as an easy way to test several fixed resistor values. Once you've decided what value you like, measure it, and then solder in a fixed resistor of that value (or the closest available). At no point should the pot response have anything to do with this, since you're not supposed to be wiggling the knob. The "old school" approach would be a resistance decade box, but I don't supposed anyone uses such things much these days - but it's the same idea.

What did you mean?

Tom

[gmaslin]

Tom
I understood you completely. Yes, the pot will dial in the right resistance value but it won't mimic the resistor parasitics. This is what I meant when I said it might not sound the same when I select the resistor with the same pot value. I much prefer getting in the ballpark first (680R will do that) and tweaking the Diodes to raise the clipping floor to taste. If that is still unsatisfactory, we start looking at C10/C11. The tone banks are the last resort. Oh, the replacement resistor will be 1/4 watt. It should fit. The decade box has become esoterica, just like the Wheatstone bridge

[thermionix]

I admit to being a relative dummy when compared to some of the electronic wizards here.  I'm no EE, very far from it, just a broke guitar player who likes to build stuff.  And as such, I had to google "resistor parasitics" and came up with this article:

https://www.edn.com/design/components-and-packaging/4423492/Resistors-aren-t-resistors

Seems the issues they're talking about come into play at very high frequencies, in their words "hundreds of megahertz," so I'm left wondering how this applies to guitar or other AF circuits, especially a piece of trash (IMO) like the DS-1.

[gmaslin]

thermionix
Yes, but parasitic effects increase as the current decreases. When you get into the megahertz/milliamp range, even resistor endcaps can become an issue. Note the operating frequency of the 5223 and the transistors on this board. Perhaps it's a bit overcautious but it's a real issue even in the low megahertz range.

[Hatredman]

thermionix
Yes, but parasitic effects increase as the current decreases. When you get into the megahertz/milliamp range, even resistor endcaps can become an issue. Note the operating frequency of the 5223 and the transistors on this board. Perhaps it's a bit overcautious but it's a real issue even in the low megahertz range.

Yes, but you are not in the megahertz range, in fact 6kHz is already high for you. Those parasitics may not (will not)  have any effect at this frequency and below.

.

[ElectricDruid]

+1 Agree. Resistor parasitics is not something I've ever had to worry about, or been bitten by. And a portion of my work is with processors, so I'm not always dealing just with audio frequencies.

Tom

[gmaslin]

Hatredman
What makes you believe the components on this circuit are operating <6kHz?

Electric Druid
I concede that I might be overcautious. Anyway it's in and we're definitely going in the right direction. Its clipping still goes into caricature mode but it's definitely more pleasing with the distortion knob at 9:00 o'clock. Level knob more operational but loses utility after 12:00 o'clock position. Tone knob has improved but still not to my liking. Diode mod report forthcoming.

[PRR]

> google "resistor parasitics"

"Everything" is ~~100 Ohms above 1GHz.

Small-value resistors have inductance. Large-value resistors have capacitance. The universe tends to be about 100 Ohms over parts-size space.

> my work is with processors

The faster ones are already up against parasitics, and the external parts tend to be in the 100r-1K range. No 1Meg resistors unless it is on some very slow external input (waiting for the user's slow finger).

680 Ohms is 680 Ohms to far above the audio band. Doing it with a pot does not change things a lot. Wiring capacitance will have more effect. Here this may be swamped by diode capacitance(?) and the low-pass you almost always want after a clipper.

So a "1 Meg" is dropping by 100KHz; a "0.1 Ohm" is rising by 1MHz (sooner if it is curly inside).

[gmaslin]

PRR
Thanks for the elaboration. I conceded the point but in my defense, I didn't think optimizing R9 was the best approach when D4 and D5 contribute so much to the clipping. The 680 ohm value was a nice center point and I had one available so I went with it. By the way, here is the report on the diode change:
DO THIS MOD
It's still not as good as the AnalogMan original to my recollection but it's a vast improvement over what it was. It's still a bit too noisy and the knobs don't range as nicely as on his mod but definitely a worthwhile mod to do. I put the two existing diodes in series and placed an IR LED on the other side. This is about the best bang for the buck mod I can foresee. You get 70% of the AnalogMan mod sound for one LED and one resistor.

[Hatredman]

Hatredman
What makes you believe the components on this circuit are operating <6kHz?

Humm... the fact that it's a guitar pedal?