The Natural Philosopher schrieb:
Phil Allison wrote:
"The Natural ****** "
I reverse engineered a couple of marshals. Triumph of overrunning
components and cost reduction over correct design.

The marshal 100W valve is based on an overrun Mullard 50W design,

** Nonsense.

The first Marshalls were clones of the Fender Bassman of 1959, the
5F6-A schematic.

Subsequent models all followed a very similar pattern.

Well just look at the Mullard 50W circuit with 4xEL34 and compare and
contrast.

** No relevance to Marshall whatever.


American tube amps were all based on different valves entirely..beam
tetrodes mainly, not pentodes.


** All the early 60s Marshalls used beam tubes, 5881s and KT66s.

Marshall Majors used 4 x KT88s.


None of the marshalls I ever saw used KT88's

All EL34s.

Maybe that was a US export model you hade.


USA models used mainly 6550s.

EL34s were later substituted with a bias change and little else, as an
a economy measure.


They are not cheap, and never were.

Read the Wiki & check out the schems.

http://en.wikipedia.org/wiki/Marshall_Amplification

http://www.drtube.com/marshall.htm

You are totally WRONG.



Or teh Wiki is..




...... Phil







Hi Mr Philosopher,

it's very remarkable that you don't recognise one of the most polite
answers Phil.A ever made.

Let me assure you - his statement's correct, yours' not so...

There also were KT88 Marshalls, although they are a completely different
story. IIRC the indeed evolved from generic Mullard or the GEC designs.
But - the bread and butter Marshall began 1962 with the 5881/6L6/KT66
equipped JTM45 - an almost 100% copy of the 5F6-A - and they (Ken Bran)
have publicly admitted that they were clearly aware of that fact. The
evolvement to the usage of pentodes (EL34s) was mainly driven by
economical reasons. The similarities to the mullard designs may come
from the fact, that there ain't so many possibilities to connect a
pentode or a beam power tetrode to a circuit - and - the 5F6-A was also
based on a common available basical circuit (from WE or RCA IIRC).

The preamp of the marshall *was* the same as a 5F6-A and the future
evolvement was only incorporated by the addition/alteration of some
components to fit the sonic tastes of the upcoming rock musicians
(cathode Cs, mixer Rs, bypass Cs, different B+ filtering etc). Even the
MV Marshalls just rewired the existing preamp circuit to a cascaded
design. OK some Rs and Cs were added but that was all. Up to the generic
JCM800 the circuit still clearly showed it's origins.

regards

Jochen