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Old 11th April 2006, 02:28 AM   #1
ttan98 is offline ttan98  Australia
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Default Various Pass Amplifiers Topologies-Comment

I am new to this website and I am interested in Audio.

I understand there are many Pass amp. topologies in Mr Pass's many years in this industry.

Can anyone out there be able to give a brief summary of the various types circuit topology and their impact on sonic differences?

an example would be the Aleph 30 amp, which seems to be a popular one, I have not seen the circuit diagram and I don't know the details. I know it is SE ended and why is is it so popular? Does it sound different from other amplifiers? Any comments..

thanks for your time
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Old 11th April 2006, 05:28 PM   #2
moe29 is offline moe29  United States
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Stereophile review by Muse Kastanovich

I liked reading Muse's reviews, and he's built a Zen too. Should give
you some good background on the 30.

(The Aleph 30 was a refinement of the Aleph 3.)
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Old 11th April 2006, 09:59 PM   #3
JCM is offline JCM  United States
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I don't know about all the Pass topologies, but can say a few things.

The reason for the superiority of some Pass designs as opposed to others :

* Class A bias, of course, as you know, thus giving these benefits :

*No crossover distortion.

*Great reduction if not elimination, of power supply modulation, and consequent distortion, something even a great Class AB design MUST deal with in one way or another - and many lesser quality designs don't deal with it at all, the result is very audible. On a typical sine wave analysis, this doesn't even show up, since the signal is at a constant amplitude, yielding much lower distortion than it really has. Maybe it measures .04% THD with a constant amplitude sine wave, but in real life, it will be more than that.

*The transistors work less the louder the volume - the opposite of Class AB.

Other benefits :

*The patented Aleph current source, giving ten times less distortion compared to non-Aleph, as documented in Zen variations 3. It also gives much better efficiency.

*The use of mosfets, heavily biased, the best way to use them.
Since they are voltage controlled devices, they are easy and simple to drive, eliminating additional and/or more complicated circuitry.

*Minimal local and overall degeneration.

* The simplest practical designs - fewer gain stages, and therefore fewer chances for the signal to be corrupted.

*Balanced designs - the sonic benefits of which are well known. Greater dynamic range, lower noise, higher gain.
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Old 12th April 2006, 03:51 PM   #4
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Various Pass Amplifiers Topologies-Comment

Hi, ttan98,

You mean all that Mr.Pass has done? You cannot get a "comment" from this question. If it could be described in words (which I think it couldn't) it will be thicker than a dictionary
The best way to find out all yourself and experimenting with all the variables of each topology.........may take years I'm afraid
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Old 12th April 2006, 06:02 PM   #5
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I think I counted somewhere around 500 permutations of
a single-stage topology. Many are trivial, but I also probably
left some out.

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Old 13th April 2006, 12:28 AM   #6
ttan98 is offline ttan98  Australia
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I am a little vague in my posting, to be more specifiic for example, looking some of my Pass topologies, the DIY kit has very few components and biasing circuitry is very simple, no added output resistors, when compared to the commercial amps eg, Aleph 30 where biasing circuitry is more complex, differential inputs, , more components,

However their basic topology remains unchanged.

My question :

1. How isthe sound quality of DIY kit compared to commercial ones?

I "suspect" the sound quality is different, but their basic characteristics remains unchanged, eg the commercial amp may have better image(because of better biasing) and better control of the speakers as the output of comm. amp is different(better damping factor). For basic characterics remain the same because both are single ended with a current source.
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Old 13th April 2006, 05:24 PM   #7
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All amplifiers are different, and no amplifier is best for all
situations. Some of the DIY projects are made deliberately
simple to encourage people to build them, but that does not
necessarily make them sonically inferior - often it trades off
against power and type of loudspeaker.
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Old 14th April 2006, 01:13 AM   #8
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Hi, ttan98,

1. How is the sound quality of DIY kit compared to commercial ones?
Sometimes (not everytime) the DIY design sounds better than commercial design. DIY has no "minimum requirement" of measurement has to be passed, like standard of THX or Stereophile's AP machine. So, DIY design have more freedom to tailor the specification you like, usually only for meeting the sonics. More freedom in this side. This freedom cannot be brought to commercial units that will be measured by Stereophile, for example, too bad measurement will invite bad review

your question in this thread, is it comment about various Pass amplifier topologies restricted to single transistor ones (Zen-alike) or do you mean various topologies of all that Mr. Pass has made?

Mr. Pass is often mistaken as a person who "only" builds Zen (single transistor amp). Some "thinks" that Mr. Pass has no abilities to make a more complicated design. Well, they are surely wrong The most clever audio amplifier patents and audio cct's are made by Mr. Pass, and they are not single transistor ones SuSy, Smart Bias, Efficient ClassA, Aleph CCS, Statis patent etc are the most basic yet most elegant approach one can think of when designing power amps. I haven't seen patent(s) from another single gentleman that is more elegant than Mr. Pass' thinking.
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Old 14th April 2006, 04:31 AM   #9
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Hi TTan98,

Craftsmanship plays a big role in how an amp sounds. All things being equal, two people buildig the same amp with the same parts can sound different or have negative characteristics to each other like noise or hum due to the quality of the soldering job.

Sometimes placement of components also impact the final amp.

A skilled craftsman can oftentimes make a better amp than commercial products. A lot of DIYer's like to overkill with exotic parts or wire that would not be profitable with a commercial product. Does fancy wire or solder even matter? Sometimes yes. For me that's part of the fun of tinkering and substituting parts to get it right.

Great hobby! Keeps me off the streets and annoys the neighbors by rattling their windows.

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Old 14th April 2006, 07:01 AM   #10
lineup is offline lineup  Sweden
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Originally posted by Nelson Pass
All amplifiers are different,
and no amplifier is best for all
i agree and think it is the truth

i often call amplifier an 'adaptor'
between a specific source and a special load

the later 'load' is a sound reproducer of some kind
the source is some type of 'sound data storage' medium
in which somehow an attempted description of sounds is saved
for future use, and recreation, reproduction

now to reduce number of adaptors, amplifiers
designers try to make them universial useful
so compromise and increase their general usability

the ultimate sound system
uses one specific sound source
adpted, without compromise, to a very specific reproducer ( loudspeaker, headphone)

that is, a custom amplifier, trimmed and with very specialisized function
in one specific static environment

source, power supply, load
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