From frederick.somerville@gmail.com Fri Apr 05 14:19:41 2013
Subject:Re: Converting a 147 amp to 122 negative feedback standard - earlier distorsion

Hi David.

The schematics looks exactly like the rebuild I have done.
Nice drawing - looks very professional.

What I have done on my 147 is to replace r9 with a trimpot (47k Ohm). This
way i can balance the two tubes to clip at the same time.
Or unbalance them for more distortion.

2013/4/5 palmquistdavid

> **
>
> Frederick - I'm interested in your experiment. I don't know when I'll have
> the ambition and (to put it politely)courage, but I may give it a try. I
> had drawn a 147 schematic for myself already. I went ahead and replaced the
> power tubes with the 122 section from the Captain Foldback manual library.
> I put this in the files section. IMPORTANT NOTE: I have not tried this or
> carefully checked the drawing. Do not try this until I confirm it works.
>
> http://launch.groups.yahoo.com/group/CloneWheel/sfedit?path=/DIY/Visio-147-122%20Split.pdf
>
> Fredrick, please take a look and tell me if this is what you did. If its
> close, tell where you differ. If I'm all wet, tell me I'm all wet. If you
> have alternative schematic, please post it or send it to me directly.
>
> Thank you in advance and thank you for sharing your experiment.
>
> --- In CloneWheel@yahoogroups.com, "frederickc2d"
> wrote:
> >
> > this weekend i converted my 147 Leslie amp to the negative feedback
> system of the 122.
> > The 147 gets negative feed back from the secondary winding of the output
> transformer.
> > Negative feedback cancels out a lot of the distortion in an amp.
> >
> > When the 147 was released I think it was considered an improvement.
> >
> > My experiments this weekend proved the point that the 122 configuration
> distorts earlier but also in a much more gradual way.
> >
> > It would be possible to have a 4 pole switch to select either
> configuration.
> >
> > Do not do this unless you know what to do inside a Leslie amp. The
> highvoltage caps keep their high voltage even with the power off.
> > The have a long memory.
> > They can kill you.
> >
> > Regards Frederick
> >
>
>
>

--
MVH Frederick Somerville

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