New member hoping for advice on Plexi build! (Resolved)

[TheMagicEight]

Hello,

I've just build myself a '68 Plexi clone with a Metro spec choke and 50W OT. It sounds pretty good, but when cranked - and it's mostly / more noticeable on high notes - I get this weird crackling distortion over the regular tone. Almost sounds like a needle scratching lightly on something. I'm wondering of it might be parasitic oscillation? Maybe there's something to check for with this type of thing that I've overlooked? I've gone over everything and am quite sure I've assembled it correctly, but I am using my own layout so I can add / mod in the future, and perhaps I've placed something in a bad way. Would it help if I've recorded a clip?

Also - and I definitely should have check this before I ever started - but the Metro spec Heyboer OT...which wires are which on the secondary? I think I have it correct - orange ground, yellow 4 ohms, green 8 ohms, and grey 16 - but I'd love to have a confirmation if anyone knows.

Thanks so much for any help or tips!

[neikeel]

Correct.

Crackling is more often a ppor contact or iffy preamp valve.

Cutting out and whining is more like PO.

Might be worth 5k6 0.5w grid stoppers on pin 5 of output valves tho'

[TheMagicEight]

Correct.

Crackling is more often a ppor contact or iffy preamp valve.

Cutting out and whining is more like PO.

Might be worth 5k6 0.5w grid stoppers on pin 5 of output valves tho'

Thanks!

I actually figured it out before my post was approved. I have been building 6L6 amps and forgot you need to ground the screen suppressor grids with EL34s.

Sounds fantastic now!

[neikeel]

I actually figured it out before my post was approved. I have been building 6L6 amps and forgot you need to ground the screen suppressor grids with EL34s.

Sounds fantastic now!