DEMO Harry Klippton's 1590a builds

This post contains an audio or video demo
The 1590a apocalypse is nigh. Here's one of my last ones. When I bought it, it was called the El Guapo, but Brian has since changed the name to LETFA. According to the build doc, it's based on but deviates a bit from the Os Mutantes fuzz. I like Os Mutantes a bit and I want to build every fuzz ever so I figured why not.

I left the switch off because I decidedly didn't like one side. I'm also not 100% sure on the behavior of this pedal. I swapped Q2 a couple times after reading lots of stuff about this circuit from around the web, but I still couldn't quite get the bias low enough. Anyway it sounds pretty good but makes some awful noise with the volume up too high. It sounds like the pedal has a lot of output and is clipping my headphone setup real bad. The bad sound goes away with the volume lower. I haven't gotten to try it with an amp and speaker yet to confirm.

According to the build doc, the left knob pans between symmetrical and asymmetrical diode clipping, the right knob controls the output volume. It's very thick and velcroey in a pleasant way. Green 1590a, green LED.

1000001985.jpg 1000001971.jpg
 
I've spent the last couple days fucking around with this pedal again. It's back out of the enclosure and I've swapped out both transistors again.

I've read a couple places that Q1 should be around 200 hfe and Q2 around 40. The best I could do for Q2 was 84 hfe. That brought the collector voltage down to about 1.5v. next I'll try swapping out R5 to see if I can get it any lower. @bean got any advice for this?
 
Ok I neglected these for a few months but they're done, and really fun to play. Had to go back and check my notes on what I changed. I put in a 330ohm resistor in place of the 1k in the power supply to make it less noisy, and I used a 68p cap in place of the 51p in the first stage. I don't remember how it sounded different but I liked it better. I also tried a 2M resistor in place of the 1M in the second stage as in the ample alpaca schematic but noticed no difference. I own a 25th anniversary red llama, so when I was breadboarding this, I had the 25th plugged in next to it to compare, but that was like 6 months ago so I don't remember much about it. I like these enough though. I think the llama is a fun circuit to play around with. It can get pretty loose and gainy which I like, but sounds good at lower gain settings, and cleans up well with the guitar volume rolled off. Maybe I'll post a demo if I get a chance
1000004115.jpg 1000004114.jpg
 
Back
Top