DeArmond - Square Wave Distortion Generator  [schematic]

Discussion regarding early stompbox technology: 1960-1975 Please keep discussion focused and contribute what info you have...
User avatar
Tulrich
Information
Posts: 7
Joined: 03 Jan 2022, 15:16
Has thanked: 1 time
Been thanked: 4 times

Post by Tulrich »

ppluis0 wrote: 07 Jan 2022, 14:26 Hi folks,

This stompbox is in all aspects equal to MXR Distortion+, so the following link explain how this design works if someone here don't knew that already :)

https://www.electrosmash.com/mxr-distor ... s-analysis

Cheers,
Jose
I had an MXR Distortion+ quite a long time ago. (As far as I rember it was a late 70s/early 80s block logo.) But I did not like it. Too harsh for me.
Could it be the magic lies in the NTE941 IC? The distortion it gives is smooth, yet the pedal has bite. And in low settings it just adds distortion (to the tube amp distortion of my 5E3 Deluxe) in a very neutral way. It is just more distortion, not another kind of distortion.
The other Square Wave with the LM741CN (just like the Distortion+) I did not like either.
Just later I realized that the clips are different. So, this seems the be the main difference.

User avatar
Tulrich
Information
Posts: 7
Joined: 03 Jan 2022, 15:16
Has thanked: 1 time
Been thanked: 4 times

Post by Tulrich »

modman wrote: 07 Jan 2022, 13:08 Time to desolder the pot and measure again to be sure...
Let's hope the intensity pot is about 500k
If you care about performance of the unit, perhaps replacing the electrolytics on this 40+ year old pedal may be an improvement too.
I desoldered the pots. Intensity is 500k, Output is 10k. Electrolytics are ordered.

User avatar
Tulrich
Information
Posts: 7
Joined: 03 Jan 2022, 15:16
Has thanked: 1 time
Been thanked: 4 times

Post by Tulrich »

I changed the electrolytics (no difference with regard to output or whatsover). After installing an 8 pin socket I put in an other NTE941M. It sounds terrible, very harsh. The original NTE941M says 971E in the second line. This one says LF205K. Don't know what this means. Also, this one is not louder in low distortion settings (that's what I am looking for).

Then I tried out a uA741CN I got from musikding.de (highly recommended). It says 13AER5M UA741CP, and I see the sign of Texas Instruments. Sounds better than the other new one but still too harsh to my ears (reminds me to the Distortion+ I had many years ago), and still is not louder in lower settings.

I would say, the original NTE941M 971E is magical, very musical, has bite, without being harsh. If you have a Square Wave with another IC, its like having a different pedal.

Is there any (easy) way to increase output in lower distortion settings without altering the tone in any way?

Post Reply