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In Reply to: RE: absolutely posted by wazoo on July 28, 2014 at 10:19:45
Obviously.
The question is if you don't need the extra power do you want the extra devices?
Follow Ups:
Dave's question was rhetorical, but I answered it anyway. I'd take his point even further and say that, at the outset, not only was reducing distortion not 'the main' purpose, but it wasn't even 'a' purpose. However, once the benefit was demonstrated, it became a design option. Even the 'little' X150 has 40 MOSFETs in the output stage - the X350 (or X600) only adds 8 more.Your question is too open ended to answer.
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My only reason for starting this sub-discussion is that I disagree with the statement that the lower powered members of a series sound better as a result of having fewer devices in the output stage. If done properly, more devices in parallel should always result in a measurable improvement. Whether or not such an improvement is audible is another matter. Is a reduction of an inaudible distortion somehow more inaudible? ;-)
Edits: 07/28/14
Maybe if I could pose the question better I would have an answer for it.
Nearly 30 years ago a DIY audiophile friend built two amps. One was a 32 transistor/ch amp for headphones but with speaker binding posts to drive his Shahanian like multidirectional monstrosity - running class A at 2 watts, the other was a single push pull pair of gigantic devices. He ran that at AB and played around with feedback, I don't know how much power it generated but it was obviously much more than the other amp. It had a much more vivid presentation and at some (low?) feedback setting there was noticeable distortion but the music just clicked and sounded real. The little 2W amp did clean detail and correct tone but lost something of the music's vividness even with AKG340 headphones.
The 2 device amp reminded me of my cousin's bin diving find of a KLH bookshelf speaker with a rotted surround that made the most communicative music I ever heard just off a 1970's SS Marantz receiver doing radio. It was obviously distorted but something there was "right".
The question is what was it that was "right" despite distracting distortion?
The other question was what is wrong with the beautiful sound of the little 2 watt headphone amp that it didn't click despite the lack of audible distortion.
My objection was to the statement that lower powered members of a series (sharing the same topology) sound better. Your example is quite a different situation and far more details would be necessary in order to proffer an answer, which I'm not likely qualified to do, in any case. :-)
Getting back to the Pass amps, the output devices of each type are drawn from the same lot# and then very, very tightly matched.
If I read correctly, you said HexFet in another post.
As a former IR Employee for over 15 years, I'll say, without fear of contradiction that lot# is nearly irrelevant, due to possible lot rework. Unless you somehow SPECIFY clean (ZERO rework at any step other than photo) lots, you are pretty much wasting your effort.
The assumption being that all wafers (100 in the case of IR) in a lot receive identical processing.
This ain't so, since some processes are SINGLE WAFER and microscopically different from wafer to wafer. Machines doing such processes are serviced at regular intervals (by wafer count, typically) and precess thru phases between such service. Even mass batch process, like diffusion, can have temp gradients across the length of the tube which effect outcomes at probe and some dopine steps.
Too much is never enough
I wouldn't presume to argue against any of your points. I'm certainly no authority on the semiconductor manufacturing process (I've spent my working life as a technician). Perhaps, part of the high cost of the Pass amps covers rejected output devices. Frankly, I have no idea, but Pass does match the devices for each amp to exceedingly close tolerances. Even if the lot code is essentially meaning less , the tight matching is still meaning ful .
I should also qualify a statement I made regarding the quantity of paralleled devices in the output section. The X150 uses different devices from its bigger siblings. The X250 has 32 output devices. So, compared to the X250, the delta is 16 for the X350 and X600 - a 50% increase instead of 20%. There is a theoretical advantage to that and measurements suggest that also translates to practical advantages.
I still maintain that comparing the slew rate of those devices to anything in the audio realm is like comparing a lightning strike to a sprinter and, as Dave pointed out, they're never really 'off'. I can honestly state that I regret selling my old X350 - it was a superb amplifier. I'm not saying that I'm at all unsatisfied with the valve amp which replaced it, but the difference in sound between the two isn't exactly overwhelming. I think that's high praise for the X350. While my Phi 300.1 was at VAC for repair and some upgrades (all at zero charge), I tried using my X150 and hardly listened to that system - same power rating (at 8 ohms), but it was anything but equal at the task of driving my 3.7s (which are spared the grunt work of sub 60Hz bass reproduction - well, that's the crossover point @18dB/oct). Even with my MMGs, I thought the X350 was significantly better than the X150 - but, that's probably not the best comparison (it would have been interesting to compare it to an X250).
I didn't intend for this to become a hot debate. I just find the position (which has been forwarded by numerous individuals) regarding the difference between the members of a series favoring the juniors hard to support (based on my understanding of the theory and my experience, albeit limited), at least for such amps as the Pass X-series. I admit that my personal experience could just as easily be affected by my belief as others who hold the opposite opinion. Perception is a brier patch.
This is an interesting hobby. Pick any issue in audiophilia and opinions will always be divided. Who is right? That's probably impossible to answer. I tend to gravitate to engineering theory, in which I do have some background (and I have a deep love for science). As long as the discussions don't get ugly, I enjoy a bit of debate. That's the best way to expose the foundations of opinions. In the end, we don't have to agree on this one - not that big of a deal. I just wanted to express my opinion on the matter, so I did.
Breir patch, indeed! No question about it. Some of these debates is like jumping Neckid into a patch of Poison Ivy. Or more to MY experience, picking figs off my tree without wearing long sleeve shirts. Man, what a RASH from that sap and whatever. Must immediately SHOWER.
Anyway, my point was simply to come up with a REAL or Realistic explanation for what some have noted, that being in a series of amps which are essentially scaled UP as you go 'upline', some actually prefer the lesser powered amp.
I HAVE to give those guys as much credence as the hobby (as a whole) seems to give those who note all sorts of differences, from Insulators (teflon=good / polystyrene=bad) or perhaps WIRE (Silver is bright sounding) or any of a dozen OTHER things of various degrees of scientific proof to outright wackiness. There are various levels of expanation ranging from 'reasonable theory' to 'let's have a s`eance!' Name your poison, stake your claim or whatever.
I floated an idea some time ago about biamping with radically different amps. My thought was that the time it takes a signal to go THRU the amp would have an audible effect. Sure enough, I got little support, but than I spotted a post from Davey which seemed to support the idea. Progress? !
cheers:
Too much is never enough
I don't know if I "supported" that concept or not, but I might have pointed out that indeed there are some amplifiers that do have built in group-delay (and other characteristics) for varying purposes. The Sunfire amps being the classic example...to facilitate the operation of the tracking power supply.
If you utilize disparate amps when bi-amping the world is not going to end, but when performing subjective evaluations it's important to understand any differences so as not to extrapolate incorrectly.
You have to really be careful when forming objective conclusions based on subjective testing. There's a couple of members here who do it incessantly. :)
Dave.
Dave
I am assuming you include me in the speculative extrapolation group. I will say that it is true that is my first tool to investigate anything. Then you delve into the physics in parallel to finding other people's observations and designer's pet theories. From there I go to picking modsters and DIY'er minds and go on to more listening experiments and figure things out or start a project, or post the speculation online for comments and to generate more ideas, or drop an issue as either too big to tackle or postpone giving it more attention.
The main limit is that I don't want to become an electronics engineer or audio engineer (or maybe I do?...). But I still want to be able to improve my own system's performance and advise friends on improving that of their systems.
"The main limit is that I don't want to become an electronics engineer or audio engineer (or maybe I do?...)."
You should. It allows to see through much of the self deception, intellectual dishonesty, and nonsense that pervades this industry.
If your first tool of investigation is speculative extrapolation then you're starting from a premise that can immediately lead you in the wrong direction....in a variety of different ways. :)
There's nothing wrong with subjective evaluations, but you can't make any objective conclusions from it. And any subjective conclusions you make from it are only valid for you and no one else.
Dave.
Unfortunately Davey, just about every industry is like this these days. Too many people hired to spin and BS their products rather than hired to make them better, combined with an uneducated public that typically does not spend any time really researching things before they buy. This industry is particularly difficult because it is technical and few understand any of the guts of these things at all (although my kids are learning about it at the elementary level at their STEM school).The A/V industry pales in comparison to the mattress industry. Talk about lying manipulating crooks.
I though this was about my first pair of Maggies....
Edits: 08/04/14
There is little alternative for an audiophile. There are aspects of sound quality we don't have effective measurement methods for so we can't rely on by the book design guidance principles and technical evaluation alone. We also need to be able to weigh the results of particular tradeoffs for our purposes.
There is no choice but to speculate on what technical aspect results in a paricular aspect of SQ being one way or another. Hence the constant need to change items in the chain.
Finally, there are simplifying assumptions behind the engineering equations that enable quantitative design that some designers try to take into account when designing with particular components in mind. Pass is one in particular who pays attention to these things in his white papers and we presume he does so in his designs, particularly for the First Watt designs.
Sorry:
It was Satie who made a related comment: QUOTE:
Davy (UK) had a listening based observation on coherence going with biamping vs single and found that for him there was something that sounded wrong with the use of different amps on bass and mids on 3.x models. For my own observation it is an issue, but careful matching of amps and XO will solve it and what little time issues remain can be adjusted for by ear with relative distances to the drivers (toe in - on the order of < <1").
The 'relative distances to drivers' remark speaks to me of time delay to fix the 'problem' of amp latency.
Too much is never enough
Yeah, that's not me. Sorry.
That guy is in the UK somewhere....I'm not.
Additionally, everything I read from Satie I take with a large grain of salt. :)
Dave.
You noted that the discrepencies between amps could often be adjusted for by panel toe which changes the distance from the listen to the various drivers…making up for 'lead' or 'lag' of a signal.
I'll see if I can find the entry again……I saw it maybe 45' ago.
Too much is never enough
Satie, these things are intriguing, are they not?It jives with an observation of mine. One of the most alluringly musical sounds may come from a basic alarm radio, or an old transistor radio. For all their relative SQ shortcomings, they have one or a few basic strengths.
The alarm radio has one speaker. Just that simple driver is capable of issuing a very cohesive -- time-aligned -- musical stream.
The transistor radio, in addition, may have the benefit of DC electronics, as opposed to AC. The same goes for an ancient cassette recorder that I used to have (in days when not even Walkmans were around). When traveling, I could enjoy Herbert von Karajan and the BPO to a surprising extent...out of a 3" speaker!
Edits: 07/28/14 07/28/14
My Tivoli #1 table radio sounds terrific. I lifted it up the other day and discovered it uses a ported enclosure! They now retail for 150$
Too much is never enough
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