Gross loudspeaker cone movement when using tube amps.

[SY]

Glad it all worked out OK. Let's hear about that hum and see what we can do to fix it.

 

[colinB]

Hi SY

Let's hear about that hum and see what we can do to fix it

Thanks for your offer of further help - let's hope you don't regret this
I've been playing with pre-amp tonight looking at earthing and heater bias in an attempt to track down the background 'noise'.

I raised the heater bias as you suggested in an earlier post (#16) but this had no noticeable effect on the noise.

I then turned the pre-amp off and just had the EL84 PP Power amp on connected to speakers. It seemed to me that the background 'noise' was still there which suggests the power amp is the culprit or is at least contributing significantly to the 'noise'. I also noticed that the 'noise' is louder in one channel than the other.

At the moment I think the noise is more buzz than hum but I really wished I had a 'scope so I could be more specific on this.

Ok, my question is do you have a checklist/ procedure for reducing such hum/buzz that I could follow bearing in mind I don't have an 'scope or is it trial & error again - probably mostly error in my case!

Anyway I've attached a photo from the underside of the EL84 power amp so you can see the layout/earthing etc - something obviously wrong will probably stare you in the face and I'll learn some more!

BTW if you think this ought to be a new thread then I'm happy for you to make it so.

Once again, thanks for your help.
Cheers
Colin.