Bassballs Radio Signal

[peterg]

I recently completed building 2 EHX Bassballs clones using this schematic:

http://topopiccione.atspace.com/pjimages/EHBassBalls.sch.gif

They generate a lot of radio signal. Adjusting the settings does not have any impact. Using a battery as opposed to a Boss PSA 120  adapter does not help. None the less I tried adding caps of varying values from 9v to ground and adding a low value in line resistor to the power input as well as adding small caps from circuit input to ground. I designed the layout and home etched the boards.

Any ideas of next steps would be appreciated.

[PRR]

> They generate a lot of radio signal.

Actually transmit??

If they pick-up radio, that's your built-in Karaoke feature. (?)

Have you picked-up radio in your audio before? (Some places it is inevitable.)

Re-check input jack shielding and grounding. If radio signals have to run the long way around before going to circuit ground, they will bleed off the ground wire and get in your audio circuits.

I have fought RF on slightly-dirty plugs and jacks. Long cables are begging for pick-up.

The input RF suppression could be more robust. Increase a resistor and add an explicit capacitor right back to the input jack.

I have to wonder about those 560pF directly on the opamp outputs. Many opamps are destabilized by that. The trouble may show up in the RF range, but then that beats the external RF down toward the audio range. The 560 are not essential. If they are to slow response and smooth the clipping, a 0.01u at the out jack (after the 2.7K resistors) would do similar without bothering the opamps' stability.



This image does not say what opamps to use? The connection of IC1b will not work as-expected for all opamps. It has been known to work reliably with older BJT chips like 4558. The TL0 series may do very strange things with inputs tied to rail (tho I thot the problem was with non-inverting abuse).

[peterg]

Thanks Paul

I do pick up radio often but never like this.

You can see on the attached link that all the wires are on one side of the board. I will separate them so provide some distance between the in and out wires and the ground wires as well as trying out your suggestions.

IC1 is a 1458 and IC2 is a 4558. I found these recommendations at a number of sources.

http://www.diystompboxes.com/smfforum/index.php?topic=36392.msg1051208#msg1051208

[thermionix]

Are you picking up the broadcast of a baseball game?

[peterg]

Ha! No I'm not pick up a base ball game. At least it would make sense if I was! Unfortunately it's mostly opera.