Page 2 of 2

Re: JP amp - parasitic oscillation

Posted: Wed Aug 12, 2020 6:43 pm
by shakti
I don’t have a switch for my amp yet, still need to find a nice looking footswitch box. I think the ones Marshall uses for their HW 18 amps looks close to what Page had for his amp. I need something that matches that nice Cannon XLR inlet I found (which is an exact match with what Page’s amp had).

I noticed that noise issue with the Royal clone I used to have - if the footswitch wire was close to a mains power line, it would induce hum and squeel. To be honest, I rarely use the footswitch anyway, it’s always in cascaded mode and then I use the guitar volume control.

Re: JP amp - parasitic oscillation

Posted: Wed Aug 12, 2020 7:17 pm
by gtomax
I have mine wired per stock:
  • No switch inserted or inserted with contacts connected: quiet mode
  • Switch inserted and engaged/contacts broken: loud mode
I considered reversing it so the default state of the amp is cascaded but I think I'll leave well enough alone, source some nice coax and see if I can make a reasonable footswitch setup that doesn't cause the problem. Otherwise I'll use the blank 'shorting' (though really 'opening') plug. Let's face it i'm not playing RAH anytime soon.

I love the Marshall 18w footswitches, they're very difficult to find. I got one for a series 1 18w clone I made with NOS RS transformers and it took a few months to find one available as spares. Gorgeous look and feel on it. Part number is Marshall PEDL-10034, looks like there are a couple stores with them in stock in Europe. Cheapest looks to be about $80 US shipped all the way up to $130 pre-shipping :shock:

Re: JP amp - parasitic oscillation

Posted: Tue Aug 18, 2020 5:40 pm
by shakti
Do you have a link to some of those? I am looking for a few, both for these two JP Hiwatt conversions I did and for a Bluesbreaker restoration.

Re: JP amp - parasitic oscillation

Posted: Tue Aug 18, 2020 7:25 pm
by gtomax
@shakti emailed ya!