Is there anyway to mod the blend function? I like to blend the dry sound with the echo. IMHO there is a very small range that I can use with the stock blend pot.
For me to have the option of echo/repeats ONLY is a waste.
Sonic are you referring to the same 100K resistor when you say you changed it to 470K and installed the 1M pot? I assume you used the 470K to equal the pot set to 1/2 of it's limit.I changed all the NE4558's in my early 80's DMM with TL072's as well as changed the 100K input resistor with a 470K and it made very noticeable difference.
I think the input resistor swap made an even bigger difference than the opamp swaps. I used to get a lot of distortion on repeats but this helped it a lot and made everything clearer and easier to setup as far as the input gain and blend knobs go.
It was posted over at diystompboxes.com a while back.
"Now, the stock input impedence is really low and there's a ton of potential gain on tap - much more than is needed, even using the DMM as a boost. So replace the 100K resistor in the input with a 1M pot. Here's the schematic: http://www.freeinfosociety.com/electronics/schemview.php?id=381.
The stock gain structure has a 100K resistor before the opamp and a 1M pot in the feedback loop (this is the volume pot). By changing the 100k resistor to a 1M pot, you can set it to the stock impedance and when the volume pot is on full, have 10x gain. But you don't need 10x gain, and the stock impedance is really low and loads down the pickups in a passive guitar (particularly with single coils). Put in the 1M pot and you can raise the input impedance and lower the overall gain available, finding a balance between a higher input impedance and still having enough gain on tap. I liked the input pot set to about 500K, which still had enough gain (2:1 at max though I didn't use it on max) for a nice boost. Really improved the sound and gave it more depth."
The 1M from input to ground is a pull down resistor to prevent the footswitch popping. Maybe sometimes they use a 2.2M. But you want to change the 100K with either a 1M trimpot wired as a variable resistor or a fixed value resistor somewhere between 100K and 1M. I initially used a pot and found that about 500K worked well so I put in a 470K. The lower the resistor the more gain you have and the higher the less gain.Sonic are you referring to the same 100K resistor when you say you changed it to 470K and installed the 1M pot? I assume you used the 470K to equal the pot set to 1/2 of it's limit.
My unit has a 100K resistor, but it does not have a 1M (from input to ground NOT the pot) as shown in the schematic. Mine has a 2.2 meg. I assume the 2.2M would also raise the gain.