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Old 21st April 2004, 04:44 AM   #1
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Join Date: Apr 2004
Location: Houston
Default Question for Nelson Pass

My Pass, I have struggled to get some answers about your current line, so a friend told me you hung out here, and so here I am. I used an old Threshhold amp years ago, a 2 channel A/B amp that was 200 x 2 and was the technology that got copied by a company. I liked it and didn't know you were still doing business as Pass Labs, because there are no dealers in Houston, where I live. I saw an ad in a magazine and than looked on your site and finally got so interested that I was thinking of trying your X3. I recently got new Infinity Kappa 600's and sold my Kappa 7's from yesteryear, and have noticed I don't need close to the 250 into 8ohms I once did to effectively drive these newer speakers. I decided to down my power a little, but without my quality, in fact I thought maybe I could move up a little there if I went used to used. I read about your X3, and the low power output at class A and very high dynamic range, giving justice to SACD, DVD a and future things was exactly what I had hoped for.

I ordered it today and get it on friday, and can hardly wait. I get confused somewhat when I read about your symetric circuit and specifically it reads like you may need to have it hooked up through the balanced connections for this additional order of noise suppression to be realized. I know that balanced is inherently more quite, but I do not know why this technique would be tied to that where the entire order is only working if you are hooked up balanced. I called and asked one of your people because you were out, and they also said that was the case. I called again and you were out, but this guy was kind of in the middle on it, so I think I have a very good question, that needs an answer, but also I was hoping for an explanation of why, that a regular non expert could understand.

Either way, I am so excited about trying this amp, and if it works out like I hope, I may finally do what I had planned when I started which was to get either mono blocks on the front, or a great stereo amp, and than a same brand, but lessor powered amp for teh center and surrounds, making the X250 a good candidate.

Other questions
1)Your amps say they are A to a small part of their power than A/b from there, but they also say seriously biased toward class A. This makes me think that even in the A/b mode, they are still going to share characteristics of Class a performance more than those that aren't biased this way. Am I corrrect in that, or just to the point where they go A/b?
2) You list different amounts of power output for bias like just a random example: You say a 250 watt amp may be class a till 40 watts, but is biased to a 100 watts. What does that part between 40 and 100 represent to us?
3) Dynamic range- 1st occurred to me as more important when SACD and DVD a came out with their 120db instead of traditional CD at 96db, when I would hear a amp with only say 100 db dyamic range than one of equal level of price and I thougth build with say 118 and I noticed much more smoothness on the details, and your amps range from 140 to 156 on the X600 and 1000 and I wonder when you say the X600 is 156db dynamic range and up to 26bit recordings, is there some accuarial calculation that brings us to see that? What is the limit for the models that achieve 140db instead that you make?

Lastly, the only other amps that I have seen with such incredible dynamic ranges is the Classe brand, but when I finally heard them in the Omega line , I found them quite edgy and grainy, which really confused me on how they measure so well, but sound so harsh. I guess a better understanding on how dynamic range impacts the whole deal would be helpful and maybe what other factors could make it pass that so high, but sound so much harsher than even cheaper mid fi amps which much lower range.

Thank you in advance for your assistance, and I hope to be a long term pass customer shortly.
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Old 21st April 2004, 05:51 PM   #2
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Default Re: Question for Nelson Pass

"1)Your amps say they are A to a small part of their power than A/b from there, but they also say seriously biased toward class A. This makes me think that even in the A/b mode, they are still going to share characteristics of Class a performance more than those that aren't biased this way. Am I corrrect in that, or just to the point where they go A/b?"

The X series is heavily biased Class AB, the XA and Aleph series
are Class A. It is true that if a push-pull Class AB amplifier has a
high bias it will pretty much act like a Class A amp until the
output current hits twice the idle current. Often this value
encloses the entire listening experience. In any case, we regard
the performance at low levels to be the most important.

"2) You list different amounts of power output for bias like just a random example: You say a 250 watt amp may be class a till 40 watts, but is biased to a 100 watts. What does that part between 40 and 100 represent to us?"

Taking the example of an ordinary push-pull output stage, 250
watts means that supply rails are about 65 volts, and the 100
watt bias would be about 0.75 amps. The amplifier will leave
Class A at twice this figure, which is 1.5 amps, which is 18
watts (peak into 8 ohms) and 9 watts rms.

This does not describe an X250, however, which idles at over
200 watts, not 100, and gives 40 watts peak, 20 watts rms into
8 ohms.

"3) Dynamic range- 1st occurred to me as more important when SACD and DVD a came out with their 120db instead of traditional CD at 96db, when I would hear a amp with only say 100 db dyamic range than one of equal level of price and I thougth build with say 118 and I noticed much more smoothness on the details, and your amps range from 140 to 156 on the X600 and 1000 and I wonder when you say the X600 is 156db dynamic range and up to 26bit recordings, is there some accuarial calculation that brings us to see that? What is the limit for the models that achieve 140db instead that you make?"

The dynamic range is considered (by us) as the highest peak
output power divided by the noise floor of the amp (this is the
noise at any particular Hertz, and is expressed as square-root
Hertz). We try to make this number as high as possible, which
generally means rooting out as many noise sources as we can.

"Lastly, the only other amps that I have seen with such incredible dynamic ranges is the Classe brand, but when I finally heard them in the Omega line , I found them quite edgy and grainy, which really confused me on how they measure so well, but sound so harsh. I guess a better understanding on how dynamic range impacts the whole deal would be helpful and maybe what other factors could make it pass that so high, but sound so much harsher than even cheaper mid fi amps which much lower range."

There's no particular reason to assume a correlation between
dynamic range and "edgy/grainy/harsh" sound. More often than
not, edgy/grainy/harsh is a function of circuit complexity, non-
linearity and high feedback (This would be my humble opinion).

The attraction of the Super-Symmetric circuit is that it gets high
performance from very simple circuits and low amounts of
feedback, and so we get an improvement in the edge/gain/harsh
department.

The excellent noise rejection of the balanced circuits gives us
the dynamic range, and by this I mean the circuit itself, not
whether you are using the balanced inputs or not. With the
exception of the X600 and X1000 when you use a single-ended
input with an X amp, you set the - input at ground, and the
amplifier works with the difference between the + signal and
ground. In this case, the system is more susceptible to ground
loops outside the amplifier, but that is not particularly under my
control. Otherwise the performance is pretty similar, although
quieter and slightly better in other specs and sound when used
with balanced inputs.
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Old 21st April 2004, 07:48 PM   #3
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Join Date: Apr 2004
Location: Houston
Default Thank you for answering

I had no idea this was the best way to get you, lucky my friend knew that. Thanks for teh ensight, and I hope the manual talks more of this set ground stuff, because I had not heard that. I am a balanced guy for over a decade, but I decided I didn't want to buy Theta's xtreme dac to get to 24 bit, sold my dual superior balanced dac model and after a year decided I really liked Theta best, so I got back in one wiht dual basic dacs with the idea being upgrade to xtreme without still having cost in superiors. I am not going to upgrade till I decide if the 3 version is for me, because now debating new one of those or this with xtreme and updated, so I actually have some 1000 dollar for 3 balanced connects in a box I can't use, but till then I won't get that benefit of your X3.

I was just shocked when I heard the Classe and the only amp higher than 120 db dynamic range was one of the most whiny amps I have heard to date, so I had to ask that question because of that.

One thing I didn't get answered or I didn't get at least was when you say the X600 and 1000 are 156db, up to 26 bit, how do you get that number and if the other models are 140 db does that mean they are good up to 24bit, and lastly not knowing that calculation what are say 120db and 100db the more usual average and peak ratings in common amps good for as far as bits?

Thanks again for answering so quickly and looking forward to my X3 coming friday. I also am not interested in what all these amp makers are doing here? Do you have some sort of Do it yourself division going on?
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Old 21st April 2004, 11:55 PM   #4
The one and only
 
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Like amplifier sensitivity, the question of dynamic range has
a lot to do with who is asking and who is answering, which
is why it's helpful to define your terms.

The dynamic range will vary with otherwise identical amplifiers
on the basis of their rated power. There are other considerations.
but in truth we did not particularly set out to design an amp with
wide dynamic range as such. The figures we quote (of course
presented in their best light - noise floor to peak ratio) are simply
what we measured.

I don't know how well this corresponds with DAC measurements,
but probably they present the data in its best light aso.

Picking a product solely for dynamic range is kind of a limited
approach. I would just live with a product for a while and see
how happy I was.
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Old 22nd April 2004, 12:26 AM   #5
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Location: Houston
Default My real question though

Is that on your general descriptions of your amps you mention 140 dynamic range in one of them in line with the current new world of high resolution 24 bit recordings, while on your x600 and 1000 adds you say 156 up to 26 bit, as if there is some kind of distinction related to one to the other.

My question related to that is how does that relate, and if a formula what that is. My last question is that I notice many people talking about making amps and a little area on your pass labs sight about do it yourself, so do you have some kind of build it yourself type of stuff you sell and advise now?

As far as opinions and qualifying your opinion to others, I realize that, and appreciate you qualifying that, but when I had my old Thresh, I concluded that you are one of the pioneer's of amplifier theory and at that time were producing very high quality and unique amplifiers, clearly made technically sound, but at the same time with some passion, which in today's market seems lost or maybe it was never even present with many of the high end companies. I did notice that Pass is much more expensive relative to teh old days, but maybe the level of performance is still a great deal relatively speaking, I won't know till I hear them.

On another subject, I know Nakamichi copied you on that PA 7 model and I hope you made allot of money for that, but one product other than their dragon's I really was impressed with before they became clarion with a faceplate, was the CA1- the 100 watt by 5 amplifier that was out in 1994 to 98 that featured the Harmonic time allignment. It really shined for it's price point and was great on music for an HT amp and it's price point, and I was wondering if you ever heard that and if so what you thought?

I will give you a rest now, but I am so glad you are still in the game, and now I really can't wait for my X3, because I really think I won't miss the extra 100 watts, and my current Krell has nothing wrong with it, but for reason's I can't put my ear on , it just does nothing to make me love to listen to it either. Past Krells' have had more bass slam and a sound you either liked or didn't, which the current line has more range and seems more extended, but without anything really drawing you in. Kind of like the way Proceed's HPA line or some of their other amps on Levinson's line have been described, where not to this and not to that, but great specs on paper, and in the past your amps have always been fun to listen to, especially on accoustic music.
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Old 22nd April 2004, 03:34 AM   #6
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Location: Seattle, WA
The real high resolution recordings now are 1-bit

All this sort of misses the point, though. Humans are not capable of hearing the difference between 24 bit and 26 bit recordings, all other factors being equal. Mr. Pass seemed to all but state that the whole specification of dynamic range in this context is a marketing exercise, and at the ranges his amps reach, that is doubly true.

Less concern for marketing, more listening to music
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Old 22nd April 2004, 04:05 PM   #7
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Location: Houston
Default Boy did you miss the point

The point is if you make a distinction between one amp being good till 26 bit, while others are only 24 bit, than what you have is a defined and apparently linear relationship within a line for calculating this relationship, and as such, I am curious what that is, and how it is calculated, thus my question.

Your answer really doesn't address that, although I am familiar with one bit type recordings. 24 versus 26 may be marketing, but he doesn't say anything that can't be supported, so you could be right it is meaningless in the scheme of things, but it would also be supportable if he lists it on his site.

I read a great deal about amplifiers and this is the 1st time that I have seen a non digital amplifier ever list Bit's, and so that is where my question stem's from.
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Old 22nd April 2004, 06:29 PM   #8
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Default Re: My real question though

"Is that on your general descriptions of your amps you mention 140 dynamic range in one of them in line with the current new world of high resolution 24 bit recordings, while on your x600 and 1000 adds you say 156 up to 26 bit, as if there is some kind of distinction related to one to the other."

Not really. We just measure the peak output and the noise
floor, and that's where the figure comes from.

"My question related to that is how does that relate, and if a formula what that is."

Every bit adds 6 dB to dynamic range.

"My last question is that I notice many people talking about making amps and a little area on your pass labs sight about do it yourself, so do you have some kind of build it yourself type of stuff you sell and advise now?"

We have some stuff, but mostly we provide intellectual property.
We don't really intend to be in the business of kits as such. It's
much cheaper to print instructions and maybe PC boards than
it is to provide whole kits and support them also.

"I did notice that Pass is much more expensive relative to teh old days, but maybe the level of performance is still a great deal relatively speaking, I won't know till I hear them."

You are thinking about 25 year old prices. Inflation pretty much
took care of that.

"On another subject, I know Nakamichi copied you on that PA 7 model and I hope you made allot of money for that, but one product other than their dragon's I really was impressed with before they became clarion with a faceplate, was the CA1- the 100 watt by 5 amplifier that was out in 1994 to 98 that featured the Harmonic time allignment. It really shined for it's price point and was great on music for an HT amp and it's price point, and I was wondering if you ever heard that and if so what you thought?"

Nakamichi was most generous in paying for the rights to build
Stasis amps. The Harmonic Time Alignment was not from me -
that would be some other design weasel.

I wasn't aware that Nakamichi was now a Clarion. I believe
that Clarion had purchased McIntosh, and have heard that more
recently McIntosh has been acquired by yet another company.

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Old 23rd April 2004, 01:18 AM   #9
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Location: Houston
Default Not aquired

When Nakamichi brought out there current HT line, a much lower level than in the past, they were initially at least made by Clarion, and I thought because of Clarion's history, that they were only making their car line, but than several people told me it was the whole line.

I still don't know for sure, and given Clarion has no history in home, maybe it is just the car line. I knew you didn't make the Harmonic time allignment, because they gave allot of credit to some engineer from MIT for coming up with teh technology, but that question was more directed at your enthusiast side, because it was really one of those rare wow's for it's price point, and if it had about 50 more watts, I think it would have dominated it's segment. My X3 is slotted to arrive tomorrow and all this talk with you, has really gotten me even more excited about hearing this newest breed of Nelson Pass designs.

I will follow up after about performance once I spend a weekend of using it, but I plan on listening to just a ton of music between now and than.
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Old 25th April 2007, 04:31 PM   #10
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Join Date: Jun 2005
Location: Northern California
Default Where to Find a Pass Labs Dealer?

I am reduced to asking the inventor...

Where can a person with hot cash and a desire for great sound sample Pass Labs equipment in the flesh?

I can't seem to find a dealer in Northern California that handles your gear.


Please advise!

Thanks, dragonhands
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