NOAD (New Old Amp Day) + Help Request

[BobKos]

I picked a new-to-me old amp last week off FB Marketplace. Like I need another amp, another project, or worse - both in one box! It is an older obscure Fender 300 Bass from around 1980. It came to me in non-working condition. After some work it is up and running - YAY! It actually sounds pretty cool!

I do have an issue I need help with. The para EQ section has stacked concentric knobs. The lower knobs have what I will call a 'Double-D' opening and the upper knobs have a single flat side. The lower knobs are all broken I think due to the pressure from the rotary selector switches they are mounted to. They were previously glued together so I see a pattern failure / crappy design possibility. I need to try to replace them but can't get the right terminology together to search them out. What are they actually called? I don't need the original vintage correct parts. I just need something that will work. Any help is greatly appreciated.

Requisite pics:

 

[gtirard]

I think there are called "stacked knobs", but changes are you'll never find the same model exactly.

In that case, you can buy a cheap electronic caliper from Amazon, take the measures and ask somebody to print them with a 3D printer.

I know smebody here in TB sell 3D printed accessories for musical gear, he could it for you (I don't remember his name, but you could find him with the search tool here in TB)

 

[beans-on-toast]

Those are really hard to find.

Check out the one on the bottom left.
Dual-Stacked Knobs

The Fender Jass bass has concentric knobs. They are available in metal and plastic. Verify the shaft size. All come with a setscrew. Might fit with an adaptor. You should be able to find a set at surplus sales.

 

[Wasnex]

Another name is concentric knobs.

I am familiar with this particular amp. I had one on order in the early 80s and cancelled it for an MTI era SVT. I think the Fender would have been a better choice for me as the B-300 was a pretty HiFi design for "the day". However, my impression is this model is not particularly reliable and some of the semi-conductors that may be needed for repair are essentially unobtainium. I think you will be able to find some suitable replacement knobs, but if the electronics have problems, you may be out of luck.

Good luck!

 

[anderbass]

The tone & balance knobs on older car radios were very similar to those...

 

[BobKos]

The tone & balance knobs on older car radios were very similar to those...

Good thinking! I will keep my eyes out for an old AM/FM radio!

 

[walterw]

i love how the thing has wooden sides like a '70s/'80s hi-fi receiver

 

[anderbass]

Good thinking! I will keep my eyes out for an old AM/FM radio!

You could probably find some car stereo, stacked knobs at a car audio shop or automotive wrecking yard.

Or from here: Invalid Link Removed