Re: Swapping 12AX7s to a 5751, 12AT7 or 12AU7?

On 30 Aug 2006 16:33:00 -0700, "grolschie" <grolschie@xxxxxxxxx>
wrote:

Hi there,

I have a Laney LC50-II. It's all good, however, it seems like the the
first stage of the pre-amp is a little harsh. Tried various 12AX7's
(EH, JJ, Ei, Chinese) and settled on chinese. On the clean channel with
distortion pedal, or gain channel without a pedal, the loudest notes
played are harsh. Harsh upper mids. When using a limiter/compressor, it
is much better. Boosting the signal obviously worsens things. It makes
me think something is bad at V1 stage. Sounds a little better when I
turn the mids right off, but then its too scooped.

I read a review where a guy replaced V1 with a 12AU7a (NOS british -
whatever that tube is) and V2 with a 5751 and it tamed both channels
nicely. The gain channel has plenty of gain to spare. I never have it
over 60%.

Is it safe to swap pre-amp valves like this? Recommendations?

I know that the speaker is a big factor in the harshness of the mids.
It's a bright amp. Any recommendations on a speaker swap to smoothen it
somewhat?

TIA,
grol
I have a '73 Vibro Champ that I put a real Mullard ECC81 in and it was
surprising how much it changed the tone. Really sounds nice now and
people comment on the tone...J.P.
.

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