Subharmonic Rumble of Channel 3 and 4

Hi,

My odyssey of things being wrong with my VH4 continues!

After some great help I received to tame the fizz of channel 2 issue, which led me to revalve everything, rebias and buy a power conditioner...

I now have a subharmonic rumble on channel 3 and 4. Deep control all the way off, bass all the way down and a variety of guitars - even low output single coils and it is still there.

So to try and deal with the subharmonic issue, I have again retubed and rebiased and it is still there.

Not audible on chords - but on lead lines it is like a sustained woof noise like you would get from a nondescript note being played through a sub-woofer.

It is there in cabs and through my ox, and through a suhr ir box.

I am not sure what is left to try. Any help appreciated.

Could you record from the send output of the preamp showing the issue and the exact same guitar dry so I could check?

It would be no odyssey if we can find a skilled tech.

For me it sounds like a bad filter cap.

Best regards,
Peter

Hi both, thank you for replying. I have just recorded two brief clips.

One with cabinet and one with the preamp output only.

Cheers,
Greg

Peter Diezel":1csfy67q said:

It would be no odyssey if we can find a skilled tech.

For me it sounds like a bad filter cap.

Best regards,
Peter

Click to expand...

Hi Peter, you can hear the effect in the clip above with the cabinet. Cheers, Greg

Please check the filter caps.

Thanks,
Peter

Peter Diezel":3pf7ya0l said:

Please check the filter caps.

Thanks,
Peter

Click to expand...

Hi, is there a test I can do on them, or do I just need to research what to buy and put some new ones in to find out?

Thanks again,
Greg

Please measure the capacity