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Post new topic Pedal Steel Played Through A Gibson GA-40 Les Paul Amp
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Author Topic:  Pedal Steel Played Through A Gibson GA-40 Les Paul Amp
Greg Cutshaw


From:
Corry, PA, USA
Post  Posted 9 May 2018 10:17 am    
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This was a 60 year old amp that I repaired a few years ago and at lower volume levels it still has a great warm tone.

http://www.gregcutshaw.com/Samples/My%20Shoes%20Keep%20Walking%20Back%20To%20You.mp3


http://www.gregcutshaw.com/Gibson%20GA-40%20Amp/Gibson%20GA-40%20Amp.html

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Lee Baucum


From:
McAllen, Texas (Extreme South) The Final Frontier
Post  Posted 9 May 2018 2:23 pm    
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That sounds great!

I've got it's little cousin, a GA-5 Skylark.
My parents bought it for me, used, back in the mid 1960s.

I see the bottom of the G in Gibson is broken.
It looks like Cibson.

The top of the G is broken on mine.
It looks like Yibson.
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There are only two options as I see it.
Either I'm right, or there is a sinister conspiracy to conceal the fact that I'm right.


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Greg Cutshaw


From:
Corry, PA, USA
Post  Posted 10 May 2018 7:32 am    
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I have heard that the Yibson amps are a direct copy of the Gibson amps and even sound the same LOL.

At low volumes a flabby old speaker can sure sound mellow!

Lots of personality in these old cabinets. I loved the look of my old Emmons amp with the shiny silver knobs and Emmons logo but couldn't keep transistors in it. Years later we all found out that the RCA transistor manual was full of uncorrected errors later corrected by Peavey designs. Thermal runaway in germanium power transistors was rampant. I wonder if anyone is still using one of those Emmons amps? Mine was traded back to Washington Music Center for a Fender twin with JBL's.
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Alan Bidmade


From:
Newcastle upon Tyne UK
Post  Posted 10 May 2018 9:14 am    
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Thermal runaway in germanium power transistors was rampant.

Please tell me this is bollox.
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First name Alan, but known as Nick
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Greg Cutshaw


From:
Corry, PA, USA
Post  Posted 10 May 2018 9:50 am    
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From here:

https://peavey.com/support/technotes/hartley/Chapter_1.pdf

THROW OUT THE MANUAL:

"I will never forget that first day in 1972 when Jack came
into work. He came in my office and announced that
“we are going to throw out all your power amp designs
and start all over from scratch!” I told him that
he was crazy, that I’d worked for seven years and
had finally gotten my solid-state amps where they
were reasonably reliable… Much more so than my
competition, in fact. I told him that what he was asking
was not reasonable because it would be a huge
amount of design work, circuit board layout, etc. In
addition, I told him that I had very carefully followed
the RCA TRANSISTOR MANUAL parameters precisely…
He said, “Yes I know, that’s the trouble…..
all that information is pure bullshit!” I asked him how
did he know that. He replied, “I helped write it!” I
could only mutter “well I’ll be damned.” Then and
there, Jack and myself proceeded to redesign all
our output stages.
Jack taught
me that tube
manuals were
pretty much
“right on” and
that most engineers
then
were quite
comfortable
using the
specifications
in tube manuals to design their products. This modus
operandi almost always produced acceptable
results with tubes, and since this was the established
way of doing things, it had more or less become
“standard practice.” It was only natural that engineers
then used this same practice with new transistor
designs. RCA’s transistor manual indicated that
you could achieve 100-watt power levels with two
RCA 2N3055 transistors. A lot of companies tried
(Fender, others, and myself) with disastrous consequences.
Jack’s sage advise saved the day for
Peavey and the lessons he taught me (beginning in
‘72) are still applied at Peavey today… He told me
that you can overdrive a tube and the tube could
easily recover, but if you overdrive a transistor, you
only do it once! If the manual calls for two output
devices, use four! If the manual calls for six, use 8 or
10 (i.e. provide 100% ADDITIONAL capacity and the
amp will stay together). This was a total departure
from generally accepted tube-amp design practice!
It took most of Peavey’s biggest competitors another
20 years to learn this!"



"Shortly thereafter, I built a case for
the chassis and unfortunately I discovered that as
the heat built up inside the chassis (now encased
8
Lear’s Eight-Track Tape
Phillips Compact Cassette
9
in a cabinet), the transistor bias started to “drift” all
over the place. The amp that sounded so good in
an open chassis was hardly operable when put inside
a case! After another trip to Orradio wherein I
demonstrated the problem, it was decided that we
would scrap the Germanium design in favor of the
latest silicon transistors. We used GE 2N3391A signal
transistors and RCA 2N3055 “Homogeneous”
silicon power transistors. "
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Alan Bidmade


From:
Newcastle upon Tyne UK
Post  Posted 11 May 2018 9:48 am    
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As I thought!
_________________
Ben-Rom #017 'Lorelei', Guild D25, Epiphone 'Joe Pass', Roland 40XL, Hilton VP

First name Alan, but known as Nick
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Larry Dering


From:
Missouri, USA
Post  Posted 13 May 2018 4:21 am    
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Greg that was a wonderful sounding track for a old low watt relic. You had to be hard pressed to give it back. Great info on the transistor evolution. Thanks buddy.
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