From formercakid@yahoo.com Wed Jun 19 15:35:17 2002
Subject:Re: Swapping Out the H&K Rotosphere Tube
Thx for the advice. The idea was to lower the gain. I
checked with H&K first and they reported some players
do swap out the 12AX7 for a 12AU7, guess it backfired
in my case. Cause the hiss is definately louder, I
will stick to 12AX7's, I have a couple of spares I can
try. But I agree with you regarding the design and I
am sure H&K must have tried numerous tubes before they
decided on the Ruby 12AX7. But then again it's gotta
be the tube that is producing the white noise. I had a
recommendaton do try old NOS 12AX7 tubes.
--- sgtpepper@rcsis.com wrote:
> IIRC from my guitar-amp-building days (in the late
> 60's), the 12AU7 is a much
> lower-gain tube than the 12AX7. If the Rotosphere
> is designed for the 12AX7,
> shouldn't you stick with that type? I think (this
> is a guess) you are now putting
> out a lower-amplitude signal, but the white noise
> level is the same as before--resulting
> in a poorer signal to noise ratio.
>
> --smc
>
>
>
>
> I recenly swapped out the Rotosphere tube. Going
> form the stock Ruby
> 12AX7 to a JAN-Philips 5814 12AU7. Although the tone
> became a little
> warmer after the swap I noticed that the hiss(white
> noise)that the
> Rotosphere produces got a little louder.
>
> Has anyone out there experimented with swapping the
> Rotosphere tube
> out with other brands/makes/types of tubes? If
> anyone has I would
> appreciate their feedback as to how the tube swap
> affected the units
> noise(hiss) level.
>
> We could all save each other alot of money if we
> share are results,
> ause tubes are really expensive these days.
>
>
>
>
>
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