EFX layout in tube amp ?

[petemoore]

  Troubles with noise here:
   120vac : 12vac transformer feeds 7809 regulator and associated filtering, noise = humm.
    Should'? [of course it 'should', it's following the 'rules'] but...it seems there is a good bit of hum right in the supply line [I tried it with an 18v battery 'a 'la carte' [off to the side w/floating supply] and the regulator circuit..seemed to be regulating.
   Perhaps I"m missing something with the layout or the filtering amounts, I can't seem to get the hum-ripple out from the filtered regulator output.
Here's a question about the transformer inducing signal into the effect circuit, rotate/twist or moving the circuit 'tunes' in the hum...I know there's no sure-kill way to work with noise, but would a separate shielded/grounded enclosure say under the amplifier bottom plate be worth testing out as a way to keep effect inputs shielded from amplifier related tranformer induction [or whatever else would produce noise?
     How do 'they' do it ? ['they' being amps which have say...a well behaved built-in distortion ?
  I've been using my little 2w 6sn7's amp to test out the 12vac secondary>FWR>7809>Filter supply for 9v efx with too much humm, resorting back to batteries to fix it.

[defaced]

Sounds like either not enough filtering, or grounding is pooched somewhere on the PSU board.  Can you post a schematic/pics?

[maarten]

Between the rectifying diodes and the regulator there should be a large capacitor (about 2200 uF when you want to draw 1A max.). Immediately after the regulator there should be a 10uF cap and also a 100 nF cap (sometimes I see schematics where they have omitted these caps, which might be all right when working with batteries, I guess). As you wrote about tuning the hum by rotating the powertransformer, there probably is something wrong with the layout.

When you are sure that the regulator itself is working fine, then you can check out whether there is a problem with your lay out by using a second powertransformer (probably something like 120: 6 volts) as a pick up for the humsignal: connect headphones or an earphone to the secondary side. Don't connect the primary to anything: the primary winding will pick up the hum by itself, without being connected to anything. Move this pickup transformer around the powersupply and regulator to see whether there is hum around the power transformer and the connections to the regulator, once you have fired up. You will find that you are picking up hum at quite some distance, at certain angles. From other angles you will be able to get very close to the power transformer without picking up hum at all. Hopefully this will help you in locating the problem.

Maarten