Replacing the stock linear pin shaped NJM4558L / JRC4188 to a TL072.
This which suggested and described to me by Bajaman because I found the buffered bypass to be less than satisfactory. I tried this mod today and took a few pics along the way. Even a n00b like me can do this.
1). Locating the NJM4558L / JRC4188:
https://i220.photobucket.com/albums/dd2 ... atone0.jpg
Look Ma! No SMD!
2). Removing it:
https://i220.photobucket.com/albums/dd2 ... atone1.jpg
3). Preparing the TL072 (2 rows of 4 pins) to fit 1x8 layout:
https://i220.photobucket.com/albums/dd2 ... atone2.jpg
Looking up the datasheets, the pins layouts for both ICs are numbered the same on the 2x4 versions - which makes it easy for us. In the pic, the pink stripe is on pin 8. I bent pins 1-4 so that I could lay the TL072 on its side. I cut off pins 5-8 and then soldered their base to a chunk of old floppy drive cable. Whoops, I heated it a little too much.
4). The IC is in place:
https://i220.photobucket.com/albums/dd2 ... atone3.jpg
Back to the board, pins 1-4 of the TL072 fit where pins 1-4 of the old IC were located. The ribbon cable attaches pins 5-8 to the board. A bit of insulation tape around the chip because the bent pins 1-4 seem quite close to 2 nearby resistors -which I bent out of the way a little to squeeze in the IC.
I haven't had a decent test of this mod, but so far just as much sparkle is there when bypassed as is when the pedal is removed. The test will be with my other pedals, because the stock bypass did bad things to some of my other pedals.
Guyatone ST-2 Compression Sustainer
Tweaking the Dry [On/Off] modes:
There is a 150k resistor [R17] in series with a 22k [R16] making it 172k. When Dry is set to On, the 150k is bypassed leaving just the 22k. On Dry mode, the sound is more open, and less muddy and squishy. No majorly, but still noticable. I swapped the 22k to a 10k to see if that increases the clarity. I guess I need to A/B with a stock pedal to tell now.
To increase squishy mode (i.e. when Dry is set to "Off"), one could replace the 150k with something higher to really make a stronger contrast between the modes.
Somehow, this design doesn't seem to be the equal blend of dry and compressed signal that is claimed. But it still sounds good. I leave Dry set to "On" all the time.
There is a 150k resistor [R17] in series with a 22k [R16] making it 172k. When Dry is set to On, the 150k is bypassed leaving just the 22k. On Dry mode, the sound is more open, and less muddy and squishy. No majorly, but still noticable. I swapped the 22k to a 10k to see if that increases the clarity. I guess I need to A/B with a stock pedal to tell now.
To increase squishy mode (i.e. when Dry is set to "Off"), one could replace the 150k with something higher to really make a stronger contrast between the modes.
Somehow, this design doesn't seem to be the equal blend of dry and compressed signal that is claimed. But it still sounds good. I leave Dry set to "On" all the time.