Pass Then vs. Pass Now

@twoleftears

in my 17x20 room, i have a listening triangle roughly 11 ft equilateral, i don’t listen real loud, rarely exceed mid 80’s db peak loudness

in that context, with my mon 40’s all pass amps drove the speakers very satisfying for my listening... bass control is also excellent... i had an f6 for a time, felt that one was maybe just a touch loose gripping the woofers... my f5 is modded with extra power supply capacity (bear in mind the f5/f6 are push pull amps, not single ended as most lower powered fw amps are) so that one does fine too, xa25 xa30.5 and up all sound effortless

parenthetically, i would say my favorite for driving the mon 40’s is the linear tube audio zotl40 reference, with a pair of rel subs augmenting the deep bass crossed over very low.... that is a hella sweet combo... clarity, purity, vast spaciousness, excellent impact and of course, the midrange magic in spades...

hope that helps

i think @liquidsound ’s post highlights a very important point

and that is that amps of certain power levels do better or worse within some range in their power band -- for instance, using high efficiency speakers with paper cone drivers etc, very sensitive to that first watt, fractions of the first watt they ever get from the amp (btw - that’s the reasoning behind the choice of name, for those that didn’t realize...)

versus something like a modern x250.8 - designed to deliver 250w into 8, 500w into 4... amps like that operate in their sonic sweet spot when they are doing some real work, and they are at their best, they show the strengths intended by the designer when they are delivering some serious current, applying their high damping factor on woofers that need it, and so on.... you get my drift...

so given the wide range of amps offered by pass, from the (relative) fleawatt fw’s to the mega x series amps, one still needs to think carefully about speaker/room matching -- that is the key to sonic happiness

all the above said, it is also important to note that the smaller xa series amps, in my opinion, give somewhat the best of both worlds.... they are rated very conservatively at 25-30 wpc but can actually deliver well over 100 wpc on transients....

i have had the fw f5 and f6 as well as the pass models i mentioned earlier (currently have the int150, xa30.5 and a modded f5 in my collection of amps)

nelson pass has been interviewed many times, these vids are on youtube, he speaks at length to steve guttenberg and others about how each gen of pass amps, different generations of them, and different fw amps are all his playing with available components (especially various transistors, some no longer available) in various ’less is more’ circuits to produce amps of different capability levels and with varying sonic traits... he is very articulate about how different types of distortion leads us to hear certain attributes in the music

there is also a terrific thread on one of the other forums where he directly participates, and he speaks about his take on how various first watt amps sound different within their respective power envelopes...

these interviews are worth watching, easily found on youtube with a basic search, as is that excellent discussion thread where you hear the sound of various of his described by the man himself

here are some very informative threads that i have personally found helpful in the past

https://forum.audiogon.com/discussions/pass-labs-amp-s-what-is-the-best-pass-amp-sound-for-you-from-past-10-y

https://forum.audiogon.com/discussions/are-pass-labs-amps-probably-the-best-ever-you-can-buy

https://forum.audiogon.com/discussions/comparing-the-pass-labs-xa30-5-to-the-xa-30-8/post?highlight=xa30.8%2Bvs&postid=1298467#1298467

https://forum.audiogon.com/discussions/which-amp-would-you-choose-and-why-pass-labs-xa-25-or-first-watt-f8

@4krowme

Don’t mean to derail the thread here, as I am interested in other peoples’ experience with the big NP amps.

i have to say, reading your entries on this thread it seems you are doing just that

you have owned pass kits and really old pass stuff, you don’t have experience with modern pass/fw gear, you say you are interested in other’s experiences with big pass amps

given that, it would make sense that you should perhaps say less and read more? this thread and numerous other threads comparing modern pass amps exist on this forum. with many many happy users reporting and discussing their experiences... just seek and you will easily find...

@swede58 

Thanks, I’m hesitating between a Pass XP22/X260.8 or X350.8 combo or the Gryphon Diablo 300.

i don't know the size of your room, how loud you want to play your maggies

those are very powerful options you are considering... for my application they are clearly overkill

i also prefer the slightly better (to me) tone, delicacy and saturation of pass' class a amps - of course, very high power xa versions of those are also made... but they are expensive, generate a lot of heat, use alot of power...

@swede58

in my 17x20 room, maggies 4+ ft into the room, 10-11 ft listening triangle, all three amps drove the 3.7i’s just fine, never felt strained

but i don’t listen at headbanging levels, mid 80 db transients

know that the xa25 and xa30.5 have been tested to deliver 130 wpc and 190 wpc into 4 ohms respectively without clipping... the maggies are a purely resistive 4 ohm load, as such they draw current, but phase angles are completely benign, no stress on the amp in that respect unlike cone/box speakers with reactive phase angles and severe box resonances amps must often contend with

i have had the xa25 along with an int150 (x150.5 with pre front end) and also xa30.5 - have bought the xa25, sold it, bought it back, sold it again through speaker evolutions...

all three are truly excellent but of course, they sound different, do different things well

xa30.5 sweetest of the three in the treble and upper mids, most tube like, if you will -- with excellent tonal density and very good bass control, and ever so slightly softened transients

xa25 is less sweet, more ’straight wire with gain’ in the treble, but still tonally dense, and slightly better bass control, sounds faster more like an x series, than xa

int150/x150.5 similar to the xa25 in treble extension, tonally a bit less dense/saturated, tremendous bass impact and control, mids slightly leaner (just slightly), and of course, a notch greater headroom

i think the differences above capture the essence between the xa25 (which i consider a middle ground between x and xa amps for reasons enumerated above), and what would be consider typical xa vs x series amp’s sound

basis for my commentary is driving the following -- spendor sp100 r2, harbeth mon 40.3/40.2, magnepan 1.7i/3.7i and most recently, laufer technik notes

op

don't rule out the xa25 either, it is excellent, plenty of power for your gibbons

kind of a lovely mid ground between x and xa series sound...