Cupcake aka Orange Squealer?

[anonymous]

I just built the Cupcake. Everything works but I have a few questions:

1. Is the 10K pot supposed to be at 0 volume at it's lowest setting, then peak midway, then return to 0 volume when at its highest setting?
2. I am getting wild squeals with the trimpot in most settings (persistent, throughout notes being played) that change pitch and intensity if you roll the guitar volume/tone up or down. What is going on?

Now I admit - I ordered my IC from Tayda and they did not have something called JRC4558, but "NJM4558" (which has 4558D / JRC / 0058T). That is the IC I am using and getting these weird results. There is a setting I can reach where there is no squealing, but it seems to not be doing much as a compressing effect. Again, the volume is at 0 when the level pot is at 0 and returns to 0 when the level pot is maxed.

I also bought another "4558" IC from Tayda - the TJM4558CN - do not know what kind of difference this will make. It's tough to desolder ICs. Any pointers on that, while we're at it!?

Josha

[midwayfair]

Your IC is fine. It's just made by a different manufacturer, and almost any dual op amp will work in this circuit in any case.

1. Which 10K pot? If it's the volume pot, no it's not supposed to act that way, and you need to check that you didn't mix up two of the wires.

2. Some settings on the trimpot are going to be noisy, but squeals are not normal. What you've described sounds like positive feedback, where the output of the signal is fed back to the input. Check all your off-board wiring.

You should post voltages and pictures.

[anonymous]

Here are the voltages:
1) 5.12
2) 5.09
3) 4.98
4) 0
5) 0
6) 8.76
7) 8.76
9.33

So something is amiss with pins 6&7 but according to my understanding of the schematic (IC1B) don't they simply connect to each other?

Pics

[anonymous]

Pin 8 is waaay cool.

I wanted to mention R5 is a series of 2k and 390 ohm resistors, and the pot I first referred to is the external pot. The wiring on that checked out.

Here's a link to the squealing sounds, if you're interested. I was wondering what is causing this effect in case it could be harnessed in some way for another project.
**Please make sure to keep your volume low!**
http://youtu.be/tP2IlPtKNFA