This is The Who's Marshall History Pt 2

26th January 1966:

2 x JTM45-100 (Pete's are Tremolo models) + 2 x 8x12 Cabs each, Y splitters and
2 x 1963-100 Super P.A. amps + 4 x 4x12 1969 PA Column Speaker cabinets

With this setup the drummer was going to struggle and no audience could scream over them.

Stockholm 2nd June 1966 - Moony now has a mike and the double kit.
Presumably - Roger and John shared the left P.A. amp
and Pete and Keith the right one.

Even in the studio (head is on the floor):

3rd October '66

On Saturday July 30 The Who headlined the 6th National Jazz and Blues Festival at Windsor, England.  On Sunday it was Eric Clapton, Jack Bruce and Ginger Baker.  Originally not the headline act but Georgie Fame volunteered to drop down a notch - everyone wanted to hear the Cream of English rock.  Baker had his double kit, Jack and Eric with early production stacks but only one each.  It was raining, it was outdoors and the PA bad, it was 1966 sound.

23rd October 1966 100W Superlead (tremolo) and 200W 1967 Major

The UK bands are just starting to get into the 1959 100W Superleads and stacks and Pete and John are already using 1966 Marshall Majors - the 200Watt  "Pigs".  They also were one of the first users (with Cream) of the 1966 200W P.A. amp. With the autodestruction and destruction by volume, the speakers were now upgraded to 25W Celestions - once again pre-production.  As they moved into 1967 the single cabs were also replaced by duals - in John's case by dual stacked tall cabs (1960B then 1982B). Everyone in England looked to them for the lead on sound, and it was sending The Who broke.

In June '67 they set off for their 1st US tour after the March Murray the K debacle.  They were so broke they couldn't take the stacks - more Vox crap (oh what you do for sponsorship).  The Fillmore and Monterey performances were ground breaking in the US. A short return to UK and then back to the US in July but still Vox crap - at least Keith had his "Pictures of Lilly" Premier Kit.

19th July 1967 - Salt Lake City

Back in the UK - things were changing.  John had been talking to Sound City - a lower cost Marshall variation but as Marshall was moving ahead, the owners saw a market for a different sound.  John was ever keen to experiment and he started using modified versions of their 100Watt heads and the cabs which used Fane speakers.  Pete still experimented with Marshall including 2 1959 JTM100 Superleads::

Note: Grampian Spring Reverb on top and John's Sound City behind the destruction,
Oh and manic Moony of course

Pete started to join in because the amp sound was closer to Fender's Bassman. Sound City.  Based on their development with John and Pete - Sound City became HiWatt.

22 October 1967 - Saville Theatre

Pete with 2 x L100 Sound City Heads and Cabs (the Marshall stack is behind and was used by the Vanilla Fudge).  Interestingly Pete has Marshall heads on his stacks - covering his bets on reliability. 

From now on it was HiWatt.

Pete's standard from late '67:

Amps & speakers were upgraded, but the basic rig remained the same - 2 x HiWatt CP103 (Who customised) 100W + 1 Soundcity/Hiwatt as spare and 4 x SE4123 4x12 cabs.

John would continue to experiment with his rigs - louder and louder, but this is his classic HiWatt set-up. 2 X CP203 200W and 4 x SE4123 4x12.  1 amp with treble boost other with bass boost and fixed effects pedal.

The Classic Who Sound: Live at Leeds and Isle of Wight
Turn it Down to Deafening

Thanks to the excellent Who site for much of this information:

Notes: The Who were critical in the development of Marshall until early '67 as other bands such as Cream and Hendrix came on board Marshall spread his bets.  With Cream and Hendrix using Marshall's in the US during '67, The Who's influence and sponsoring worth declined.  Also Cream, and to a lesser extent Hendrix, were kinder to their gear.

Thewhonet site says that Pete used only the top cabs in the HiWatt rig.  I've got to question that as the P.A. reinforcement mikes and recording mikes are mostly on the lower cabs.  While the HiWatts were nominally 200Watt a cab, it was a generous rating and in modern times has been de-rated to 150W.  Also while the HiWatts were nominally rated at 120W for Pete's customised versions, this was at standard distortion ie 2-3%.  At Pete's volume it was running at 10% plus, thus closer to 200W output.

John continued to change rigs in search of the perfect loudness, Pete had found his:

25th May 1978

Graeme Pattingale, 2003