Weber 6A14 Trouble

[c_sulla138]

Hello All,

First post.

I built a weber 6A14 kit (using some of my own parts with some hints from the amazing robrobinette website).

After much tinkering I have a pretty quiet good sounding amp with one problem.

When I play an A (either the A srting or fretted on the E string) - I get a feedback like sound - I have already double checked that the speaker / baffle is tight - As I am very new to amp building, I thought I'd ask around to see if this is a problem with the weber cabinet or maybe there is a trick that I don't know (likely).

If it helps, when I dime the treble and bass controls, the feedback-like resonance lessens considerably.

thanks!

 

[tubedude]

Did it come with a Sig series speaker? If so, try another speaker.

 

[schmee]

Could be the speaker. Could be a microphonic tube. What kinda tubes are in it?

 

[TequilaCaster]

Probably a microphonic JJ preamp tube.

 

[Phrygian77]

Probably a microphonic JJ preamp tube.

I've had Xpo-Pul tubes go microphonic on me too.

 

[Lowerleftcoast]

Might it be blocking distortion?

 

[corliss1]

Welcome to the forum

Isolate - is it the speaker or the amp? Try the amp through another speaker or speaker cabinet. Weird sound is still there? It's the amp? If not, it's the speaker/cabinet.

You can also try another amp through that speaker.

That's where to start.

If it turns out to be the speaker/cabinet...keep on isolating. Make sure all hardware is screwed down well. Make sure the speaker is solid, but not too tight - overtightening can result in weird sounds since you warp the speaker frame. Stuff like corners, handles, logos, jacks, can all vibrate.

If it's the amp, keep on isolating. Try swapping preamp tubes to see if that makes a difference. If not, swap power tubes if you have them. If that doesn't change the symptom, it's something in the circuit itself.

 

[King Fan]

What he said ^^^ for sure. Keep us posted. The fact it occurs on just one note tells us it's most likely mechanical or sympathetic vibration -- many of these are loud and sound amplified or electronic. This could be inside a tube for sure -- V1 is always suspect -- but it could be a *ton* of other things all the way to the speaker.

 

[c_sulla138]

Thanks for all your suggestions - this on was total noob error - I had me negative feedback coming from the ground side of the speaker jack instead of the tip side.