Re: Adding Tone Stack Caused Whistle?

On Wed, 25 Mar 2009 01:38:51 -0700 (PDT), "Mr. Green"
<cliff@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote:

On 23 Mar, 18:21, "Stephen Cowell" <scow...@xxxxxxxxxxxxx> wrote:
"Mr. Green" <cl...@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote

Would the oscillation be caused by the pretty basic filtering or would
there probably be more to it than that?

Could be design, layout, the way you hold your lips...

Suppose I should ask if this
sort of oscillation will cause any harm to any components.

Yes... your ears.  Also causes funky wolf-tones even when
it's not happening... like bad noise on volume peaks (down-strokes).



If the whistle originates in the second stage then gets leaked into
the first stage which sends it back to the second stage etc. I can see
what the problem is.

It's the two stages working together... the second stage amplifies
a high frequency, that makes it back into the first stage, then round-
and -round we go.

Sorry about all the questions. This is interesting stuff for a
beginner like me. Now I know what to look up, I'll see what I can find
in the books I have.

Many thanks for the help, Green

GL!  If something makes it worse, do the opposite...
__
Steve
.

After a bit of reading on the subjects of oscillators and grid
stoppers, I fianlly had a chance to get my soldering iron out last
night. I tried a few caps in parallel here and there. I found one cap
in parallel with a resistor (4.7nF/470K) just before the second stage.
Changing that cap value changed the pitch of the oscillation. Taking
the cap out made the problem worse. Without the cap a hum started as
soon as i turned up the master volume. Well finally I tried the first
thing you suggested. Swapped the OT primary leads. Problem solved
LOL :-)

The amp even sounds better. It's a little tamer in a good way. Less
mids to the tone and more clarity. Before the sound was good with my
strat but, too muddy with my hollow-body humbucker equipped jazz box.
Now the jazz box sounds fine too.

Many thanks for your help. I now feel my first amp build has been a
100% success.

Cheers, Green
You would be surprised how many times that happens...even on OT
replacements...makers seem to not be systematic on lead colors...
.

Relevant Pages

  • Re: Adding Tone Stack Caused Whistle?
    ... the first stage which sends it back to the second stage etc. ... Changing that cap value changed the pitch of the oscillation. ...
    (alt.guitar.amps)
  • Re: Adding Tone Stack Caused Whistle?
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