I got yo big ol' Ultra Linear right here.

[matt h]

Rt66= Leak TL25 + Selmer (or was it ampeg?) forget which model) tone controls, possibly with a bumped "mid" lift.

there may be some Z scaling as well, it's been a while since I went hunting- but I seem to remember the tone controls not actually being original either.

[talbany]

Ultra-linear operation uses local negative feedback to the screen grids of the output stage by means of a tapped output transformer primary..
How does this effect tone and feel?

Negative feedback makes the amp sound tighter, especially in the low end..(Which is why the hardcore metal guy's love them,especially for drop D tune-ings!) where the speaker resonant hump has the most effect on the output section. This is fine for ultra clean playing, while a non-negative feedback amp has a much looser feel,. The other disadvantage of a negative feedback amplifier is that the transition from clean to distorted is much more sudden, because the negative feedback tends to keep the amps harmonic distortion characteristics to a minimum until the output stage clips, at this point there is no more gain" available to keep the feedback loop operating properly, which means that the clipping occurs suddenly. The non-negative feedback amp will transition more smoothly into distortion.. Jimmy Page was another player that used a Major loaded KT-88 and his amp was converted "Marshall 100's which are customized by Tony Franks in New York (he customized Hendrix's amps too actually) AFAIK..Both Page's and Blackmores Majors had UL tap output transformer upgrades when they installed the 88's..This was done right before the 73 Tour..
If you listen to The Song Remains the Same you can hear the difference..That amp sounded pretty good ( run clean) with a little pre amp/speaker (MXR Dist +)breakup... Oh and a 59 Les Paul..
Blackmore got his pre amp breakup through an Akai Tape deck..Again output section run clean..

Tony

[teemuk]

Blackmore got his pre amp breakup through an Akai Tape deck..Again output section run clean..

And let's not forget that he, like many other guitarists of the era, was a keen user of treble booster pedals, which not only distorted in their own right but also tended to ovedrive the second effect in the chain, like the tape delay preamp in Blackmore's case. Jimi? He reputedly turned his distortion/fuzz pedal off when he played the "Wind Cries Mary" and guess what happens to that "cranked Marshall" tone.... oh, turns out the amp was practically running clean all the time. Lion's share of distortion came from the effects.

[jazbo8]

Blackmore got his pre amp breakup through an Akai Tape deck..Again output section run clean..

And let's not forget that he, like many other guitarists of the era, was a keen user of treble booster pedals, which not only distorted in their own right but also tended to ovedrive the second effect in the chain, like the tape delay preamp in Blackmore's case. Jimi? He reputedly turned his distortion/fuzz pedal off when he played the "Wind Cries Mary" and guess what happens to that "cranked Marshall" tone.... oh, turns out the amp was practically running clean all the time. Lion's share of distortion came from the effects.

When you say the amp was running clean, do you mean just the (UL) output section or the rest of the gain stages as well?

[talbany]

Blackmore got his pre amp breakup through an Akai Tape deck..Again output section run clean..

And let's not forget that he, like many other guitarists of the era, was a keen user of treble booster pedals, which not only distorted in their own right but also tended to ovedrive the second effect in the chain, like the tape delay preamp in Blackmore's case. Jimi? He reputedly turned his distortion/fuzz pedal off when he played the "Wind Cries Mary" and guess what happens to that "cranked Marshall" tone.... oh, turns out the amp was practically running clean all the time. Lion's share of distortion came from the effects.

When you say the amp was running clean, do you mean just the (UL) output section or the rest of the gain stages as well?

AFAIK.. There were several versions of the Major..The early ones used a different tone stack (possibly a version of a Bax/Orange/Hiwatt) and some LNFB in the preamp stages.These amps also used a cathodyne PI and a 12AU7 to drive the 88's..Although I've never heard one of these early BEASTS!! I did hear a later one..I would imagine not much pre amp gain (if any at all) could be had with such a topology..Textbook clean
Later on the design shifted back to the standard Marshall pre amp section and tone stack but still kept the cathodyne, and UL taps.. I would imagine you could get a bit more pre amp gain from these later versions although the cathodyne imparts very little PI breakup ( until you get to ear splitting, dog howling, clear the neighborhood, cops on the way over volumes!!)...
Since Page's was modified to a Major there's no telling how far Tony went with the modifications (tone stack/PI/feedback loops)..Jimmy usually ran 2 Marshalls at once, the major and a stock 59 Superlead so he most likely got some of his breakup live from the SL and combined the clean big tones from the Major (sound man would blend accordingly)..There is no evidence that Jimmy used just the Major on any famous recordings (other than the live Song Remains the Same)..BTW..If you want to hear what the Major sounds like pushed in the mix listen to Rain Song/Stairway/violin bow on lotta love live..
Apart from the added power dissipation from the 88's these ran at very high voltages 600+ (mo headroom!) and even with the UL taps to help regulate the screen supply they were probably running on the ragged edges of the curves..The older more well built GEC that were used held up well with those high voltages but even then those amps were prone to screen melt downs and internal arching,transformer failures which ultimately ended their production..
As far as clean headroom..I vividly remember a friend and fellow musician back in the 70's having a major (loaded 6550's) and going over to hear the amp one day..Through 4X12 Marshall cab and literally shook the room with air pressure (loudest amp I have EVER heard) and could not get the thing to break up (speakers went first)..UNBELIEVABLY LOUD!!..What a fun amp though..Whew!!

Tony

[roberto]

a ltp without fb sounds much better to me; you can dial it in for nicer distortion without the feedback tap.

Second very old thread I resume today.
I was thinking exactly about a 20% UL design with a potentiometer to add positive to zero to negative current feedback to the amp (to lower even more, or keep it low, or increase the output impedance of the amp).