JRC 4558, Is That Still The Current Op-Amp for Activators?

[Football]

Wondering if there is a quieter op-amp in the circuit for Activator guitar pickups these days.

Getting more hiss than I'd like.  I figure maybe turning down the trim pot down may help, but am also wondering, since I have really old pickups, if that is still the same op-amp in use today.

Thank you.

[lbpesq]

I'm not sure if they have changed op-amps, but Alembic does a standard upgrade to older instruments that are experiencing RF interference (apparently there is substantially more RF signal in the air these days than back in the 70's).  Some older instruments need it, some do not.

Bill, tgo

[xlrogue6]

Even with the trim maxed, you shouldn't be getting excessive hiss. Your 4558 may be bad, or a passive component may be failing.

[Football]

Thank you for the tips.  Thinking of bringing it to a local tech to see what he can uncover from here.

[keith_h]

Any of the 4558 chips should work and are readily available. I might have a few MC4558's still lying around from my younger years in the 70's when I used them in pedals and preamps. The NE5532 is also a direct plug replacement and is what I ended up using in preamps but it does use more power as I recall. Things might have changed but back in the day I would swap several MC4558 to find the one with the lowest noise and that sounded best to my ears. I don't know if they are more consistent now but it is something to keep in mind. I will look around to see if I still have extra chips. I cleaned out a bunch of my old electronics parts a few months back but if I still have some you are welcome to them. It might take a few days but I will let you know. 

[gtrguy]

The 4558 chip is an often used one in older electronics and can be found on many circuit boards.

[mica]

Activator circuits have used a TLE2022 for decades now.

What controls are in your circuit? Are they the bass and treble or the filter type? Is your electronics cavity shielded? Has the noise level changed over time? Can we see an image of how they are installed?

[gearhed289]

The 4558 chip is an often used one in older electronics and can be found on many circuit boards.

It's the heart of the legendary Tube Screamer and all of its clones.

[Football]

Thank you for the replies.

Using it for gigs this weekend.  Am scheduled to bring to a tech on Monday.

I think the guitar cavity and pickguard could use more shielding.

It's a volume/filter and a three way q-switch.

[Football]

This is a pic from one of my sets of pickups.  Showing the 4558.

Will dive more into this Monday.

Thank you for the input.

[Football]

Activator circuits have used a TLE2022 for decades now.

What controls are in your circuit? Are they the bass and treble or the filter type? Is your electronics cavity shielded? Has the noise level changed over time? Can we see an image of how they are installed?

Will you please let me know if the 2022 is the only thing that would need to be upgraded?  Or some additional parts in the circuit as well?  I put in a TLE2022 and it was picking up a lot more noise, like RF interference type things.  I do have the control cavity shielded.

I believe my original 4558 chip was from 1983.  My Alembic Activators I'm guessing are from somewhere in the 1980's.  Volume and tone pot numbers may indicate 1984?

Also, I'd be happy to pay to have it updated there, if possible.

Thank you

[Football]

Chiming in to mention that although I like the sound with the 2022 that replaced the 4558, it's making oscillating sounds.

Wondering if bypass capacitors might help that?

[mica]

We have a replacement chip for Activators for dealing with the increased RF noise sources since these circuits were designed. 2024 compared to 1984 saw an enormous increase in high frequency noise sources.

You replace the chip you have with a small circuit board the same foot print that plugs into the original socket. There are other components on the board that provide the RF filtering. This tiny board runs $125 to ship. Email me if you'd like to arrange to get one of these.

You're also welcome to send you electronics in for testing to see if there are any other problems, but it's best to test in the bass, to make sure that the installation doesn't present any additional issues.