1st attempt at OpAmp..

[Cvp1969]

I am learning OpAmps now. My first attempt is a Dan Armstrong Blue Clipper. I really think that I have it wired correct on the breadboard. I’m using an RC4458 IC chip. When I switch it on- I get a beating hum and gated sound. When I switch the power on the chip to 18v- it works fine. I tried a tl072 and the same thing happens… thoughts?

(I tried to post videos but they won’t take. Just trust me- 18v works.)

 

[jwin615]

R1/R2 values look off
Sub a 20k for R2 and try again.

 

[Cvp1969]

I’ll try this.. thanks.

I pulled another schematic and R1 is 200 ohms.

 

[Cvp1969]

R1/R2 values look off
Sub a 20k for R2 and try again.

Changed R1 to 220k and it works.. schematic was wrong

 

[drew.spriggs]

Changed R1 to 220k and it works.. schematic was wrong

Op-amps get biased to roughly half the supply rail - so you want the voltage divider to have two equal(ish) resistors for R1/R2 so the middle of these will be ~4.5v.

 

[jwin615]

Unless you want asym opamp Distortion, which is possibly the goal (or it's a typo). But, a 1/10 voltage divider seem really extreme.

 

[spi]

LOL "fairly unremarkable op-amp booster" is not selling it for me.

I see many schematics are using 200K for R1.

Try a dist+, it's not much different component-wise, but people actually like it.

 

[Cvp1969]

LOL "fairly unremarkable op-amp booster" is not selling it for me.

I see many schematics are using 200K for R1.

Try a dist+, it's not much different component-wise, but people actually like it.

I actually dig this circuit now its working and I’m doing all the Dan Armstrong circuits.

Theees quite a few mods you can do to this circuit.

 

[BuddytheReow]

To learn the basics of opamps try breadboarding a mini muffin fuzz (inverting) and a Dist + (non inverting). There are breadboard tutorials in the Test Kitchen here to guide you in the right direction.

 

[Cvp1969]

To learn the basics of opamps try breadboarding a mini muffin fuzz (inverting) and a Dist + (non inverting). There are breadboard tutorials in the Test Kitchen here to guide you in the right direction.

Thanks-

 

[Feral Feline]

Changed R1 to 220k and it works.. schematic was wrong

Some times stuff gets posted before it's fully/properly traced and then it becomes entrenched as being original (even though it was just a rough draught that got posted).


When I was diving deep into the Blue Clipper pool I came across this ROG schematic:




An aside: that 10k after the clipping diodes threw me when I was trying to build the Blue Clipper on a Dist+/250 board. I drilled a hole in the board to cut the trace to the VOL pot, when all I needed to do was run the Beavis R6 resistor between the PCBs pad for VOL3 and the volume pot, and then add the Beavis C4 33n right on the pot from LUG3 to LUG1. I was very forest-green to pedal building / modding at the time. Now I'm just a minty green. Anyway...





Here's a cool mod for the Blue Clipper by Nicholas Kula, it uses up the other op-amp in the 4558 (you posted it as a "4458"), by way of a Baxandall EQ (I've added the New Clipper info to the schem):




You can breadboard Kula's mod, and if you like it there's a vero layout from him to match.
I might have a perf layout of it somewhere, or you could (heavily) mod Storyboardist's BC layout.
As mentioned, pretty easy to transform a Dist+ board to the Blue Clipper, but NOT with an added Baxandall EQ.