Sound of various Pass designs
Nelson,
It would be interesting to know your thoughts on how the Sony VFET amps sounded vs the Pass SIT amp vs the current (and maybe past) Pass 240 based products, the F series and maybe even the Aleph sound.
Perhaps a short description of each and what that design did really well and perhaps what it could have done better. Also perhaps how it performed into low impedance loads.
I realize how each sounds is subjective and all have sounded good. However, since you're likely one of very few people who have heard each topology, your perspective on each would be great info to know. I also think it could be useful for folks buying Pass equipment (new or used) who are wondering how a particular piece might fit into their system. Finally, it would also help those interested in DIY who may be trying to determine what to build. Essentially, it could serve as a guide that would evolve over time and could even perhaps be a sticky.
I realize you have a long list of to-do's, but given the number of designs over the last five years or so, I think it would be very useful. As this site has grown, it's become very challenging to wade through thousands of posts on each design to try to determine how each compares to others.
Thanks,
Steve
Nelson,
It would be interesting to know your thoughts on how the Sony VFET amps sounded vs the Pass SIT amp vs the current (and maybe past) Pass 240 based products, the F series and maybe even the Aleph sound.
Perhaps a short description of each and what that design did really well and perhaps what it could have done better. Also perhaps how it performed into low impedance loads.
I realize how each sounds is subjective and all have sounded good. However, since you're likely one of very few people who have heard each topology, your perspective on each would be great info to know. I also think it could be useful for folks buying Pass equipment (new or used) who are wondering how a particular piece might fit into their system. Finally, it would also help those interested in DIY who may be trying to determine what to build. Essentially, it could serve as a guide that would evolve over time and could even perhaps be a sticky.
I realize you have a long list of to-do's, but given the number of designs over the last five years or so, I think it would be very useful. As this site has grown, it's become very challenging to wade through thousands of posts on each design to try to determine how each compares to others.
Thanks,
Steve
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You may not be able to name a favorite child, but a parent always has an
opinion about the characteristics.
I always keep in mind that someone else's experience will not duplicate mine.
Speaking strictly of the the FW amplifiers, my listening is generally restricted
to 90+ dB sensitivity and no tough loads, as the amps are low power and
typically low damping factor.
F5: Dynamic, accurate, a little unforgiving. On speakers with peaks in the
top end, it will reveal as too bright and annoying. On speakers with a slightly
diminished top end, it adds a little sparkle, this in spite of being flat out at
high as 500 KHz. Good control - if your speaker is a little boomy, it will tend
to tighten it up. Overall, probably the most neutral of the FW amps. It will
drive 4 ohm loads without particular issues. Oh, and it does sound very good.
J2: A more relaxed version of the F5. Decent bottom end control, a warm
midrange, excellent depth. Overall, one of the most popular pieces. Still
in production, it best hits the mainstream taste of the FW audience, probably
because it delivers a consistently pleasant sound. Not intended for 4 ohms
unless the speaker is particularly efficient, which is rare.
F3: An even more relaxed version of the J2. Not much power or control. Popular
with Avant Gardes and other horn drivers, and does smooth out the peaks in
the tops of a lot of full range drivers. Used to be my favorite for the
Feastrex and Lowthers over the F5, now has to compete with SIT-1 and
SIT-2 for that spot.
M2: Some people just like the sound of push-pull output stages, transformers
and no feedback, and this is what the M2 delivers. Limited bandwidth and
control, but a pleasant sound, and it will drive 4 ohms. Has a bit more noise
than the other amps due to hum pickup on the input transformers, although
nobody seems to mind very much.
SIT-1: Broke the mold in the ability to play with the load line of a no-feedback
Common Source amplifier that still has any damping factor. A very unique
harmonic signature that can be dialed in to taste - Lots or little of 2nd
harmonic of either phase. Literally the sound of one transistor clapping -
without the input buffer (which no one seems to use) there is only 1
transistor in the amp. Has tremendous clarity and depth, depending on
setting, spectral consistency with warmth and detail. It allows you to focus
on a single instrument in an ensemble, almost to the exclusion of all else if
you want. This is the amp that convinced me that absolute phase is not
such a subtle factor.
SIT-2: A SIT-1 with a constant current source load instead of a stack of
power resistors. More efficient but similar to the SIT-1, it is set at a single
load line setting, so is not quite as flexible or fun.
Sony SIT amp (the big one shown at CES): This is a push pull VFET follower
output stage. Dynamic, high power, good control, drives the crap out of 4
ohms. It was voiced around AR-1's, and shows them to good advantage. It
is primarily 3rd harmonic in character, so the aspect is a little different than
the single ended SIT designs, but it is very impressive, detailed and easy to
listen to.
You realize that the original VFET (SIT) designs from the 70's were not
Class A and had more complex gain paths. I speculate that things might have
turned out a little different if they had gone for simple Class A designs that
play more to the strength of these parts.
Of course tastes have changed over time.
opinion about the characteristics.
I always keep in mind that someone else's experience will not duplicate mine.
Speaking strictly of the the FW amplifiers, my listening is generally restricted
to 90+ dB sensitivity and no tough loads, as the amps are low power and
typically low damping factor.
F5: Dynamic, accurate, a little unforgiving. On speakers with peaks in the
top end, it will reveal as too bright and annoying. On speakers with a slightly
diminished top end, it adds a little sparkle, this in spite of being flat out at
high as 500 KHz. Good control - if your speaker is a little boomy, it will tend
to tighten it up. Overall, probably the most neutral of the FW amps. It will
drive 4 ohm loads without particular issues. Oh, and it does sound very good.
J2: A more relaxed version of the F5. Decent bottom end control, a warm
midrange, excellent depth. Overall, one of the most popular pieces. Still
in production, it best hits the mainstream taste of the FW audience, probably
because it delivers a consistently pleasant sound. Not intended for 4 ohms
unless the speaker is particularly efficient, which is rare.
F3: An even more relaxed version of the J2. Not much power or control. Popular
with Avant Gardes and other horn drivers, and does smooth out the peaks in
the tops of a lot of full range drivers. Used to be my favorite for the
Feastrex and Lowthers over the F5, now has to compete with SIT-1 and
SIT-2 for that spot.
M2: Some people just like the sound of push-pull output stages, transformers
and no feedback, and this is what the M2 delivers. Limited bandwidth and
control, but a pleasant sound, and it will drive 4 ohms. Has a bit more noise
than the other amps due to hum pickup on the input transformers, although
nobody seems to mind very much.
SIT-1: Broke the mold in the ability to play with the load line of a no-feedback
Common Source amplifier that still has any damping factor. A very unique
harmonic signature that can be dialed in to taste - Lots or little of 2nd
harmonic of either phase. Literally the sound of one transistor clapping -
without the input buffer (which no one seems to use) there is only 1
transistor in the amp. Has tremendous clarity and depth, depending on
setting, spectral consistency with warmth and detail. It allows you to focus
on a single instrument in an ensemble, almost to the exclusion of all else if
you want. This is the amp that convinced me that absolute phase is not
such a subtle factor.
SIT-2: A SIT-1 with a constant current source load instead of a stack of
power resistors. More efficient but similar to the SIT-1, it is set at a single
load line setting, so is not quite as flexible or fun.
Sony SIT amp (the big one shown at CES): This is a push pull VFET follower
output stage. Dynamic, high power, good control, drives the crap out of 4
ohms. It was voiced around AR-1's, and shows them to good advantage. It
is primarily 3rd harmonic in character, so the aspect is a little different than
the single ended SIT designs, but it is very impressive, detailed and easy to
listen to.
You realize that the original VFET (SIT) designs from the 70's were not
Class A and had more complex gain paths. I speculate that things might have
turned out a little different if they had gone for simple Class A designs that
play more to the strength of these parts.
Of course tastes have changed over time.
You may not be able to name a favorite child, but a parent always has an
opinion about the characteristics.
I always keep in mind that someone else's experience will not duplicate mine.
Speaking strictly of the the FW amplifiers, my listening is generally restricted
to 90+ dB sensitivity and no tough loads, as the amps are low power and
typically low damping factor.
F5: Dynamic, accurate, a little unforgiving. On speakers with peaks in the
top end, it will reveal as too bright and annoying. On speakers with a slightly
diminished top end, it adds a little sparkle, this in spite of being flat out at
high as 500 KHz. Good control - if your speaker is a little boomy, it will tend
to tighten it up. Overall, probably the most neutral of the FW amps. It will
drive 4 ohm loads without particular issues. Oh, and it does sound very good.
J2: A more relaxed version of the F5. Decent bottom end control, a warm
midrange, excellent depth. Overall, one of the most popular pieces. Still
in production, it best hits the mainstream taste of the FW audience, probably
because it delivers a consistently pleasant sound. Not intended for 4 ohms
unless the speaker is particularly efficient, which is rare.
F3: An even more relaxed version of the J2. Not much power or control. Popular
with Avant Gardes and other horn drivers, and does smooth out the peaks in
the tops of a lot of full range drivers. Used to be my favorite for the
Feastrex and Lowthers over the F5, now has to compete with SIT-1 and
SIT-2 for that spot.
M2: Some people just like the sound of push-pull output stages, transformers
and no feedback, and this is what the M2 delivers. Limited bandwidth and
control, but a pleasant sound, and it will drive 4 ohms. Has a bit more noise
than the other amps due to hum pickup on the input transformers, although
nobody seems to mind very much.
SIT-1: Broke the mold in the ability to play with the load line of a no-feedback
Common Source amplifier that still has any damping factor. A very unique
harmonic signature that can be dialed in to taste - Lots or little of 2nd
harmonic of either phase. Literally the sound of one transistor clapping -
without the input buffer (which no one seems to use) there is only 1
transistor in the amp. Has tremendous clarity and depth, depending on
setting, spectral consistency with warmth and detail. It allows you to focus
on a single instrument in an ensemble, almost to the exclusion of all else if
you want. This is the amp that convinced me that absolute phase is not
such a subtle factor.
SIT-2: A SIT-1 with a constant current source load instead of a stack of
power resistors. More efficient but similar to the SIT-1, it is set at a single
load line setting, so is not quite as flexible or fun.
Sony SIT amp (the big one shown at CES): This is a push pull VFET follower
output stage. Dynamic, high power, good control, drives the crap out of 4
ohms. It was voiced around AR-1's, and shows them to good advantage. It
is primarily 3rd harmonic in character, so the aspect is a little different than
the single ended SIT designs, but it is very impressive, detailed and easy to
listen to.
You realize that the original VFET (SIT) designs from the 70's were not
Class A and had more complex gain paths. I speculate that things might have
turned out a little different if they had gone for simple Class A designs that
play more to the strength of these parts.
Of course tastes have changed over time.
Nelson, thank you for your very interesting discription.
But how about your FW designs compared to actual PL XA.5/XA.8/Xs-amps?
Yes, PL-amps can handle heavier loads - but can you give us an impression how they sound with similar loads?
Make a house party use First Watt amplifiers is garantie of everybody dancing on the floor and beauty chicks become very relaxed
horns <100dB efficiency for pop up the volume and we go wonder
horns <100dB efficiency for pop up the volume and we go wonder
Attachments
It is amazing how many flares of outstanding there is. Each one of those amps are simply rare and unbelievable with the sound they produce. It is really important knowing speakers to make the right choice. I have built F5, F2, F3 and FJ2 in addition to Aleph 2, Aleph 30, and X600. My favorite is FJ2 and that is what I am listening with the utmost pleasure. The closest comparison is to the best SE tube amp minus disadvantages that tubes have. This amp has solid bass, very lovable mids and the best and most natural top I ever heard in an amp. On the brightness level, F3 is softest, followed by FJ2 with F5 leading. Yet, with not as bright speakers, F5 would be what doctor prescribed. It is pleasantly analytical and extended and it is very interesting comparing it with FJ2. That is maybe the best example that there is no universal best amp, just best amp for the job. I have not have opportunity to build or to do much of listening of SIT amps, but they suppose to be the next advancement to FJ2, which is really hard to believe to be possible. Nelson for Nobel, I tell ya... Hold on, add Zen Mod to it too.
Mr. Pass, I would like to thank you for sharing your ideas with the community.
I recently realized that some of the equipment I've worked on, some of the equipment I personally own, and some of the circuits I have emulated in my own designs are your circuits. I personally like the Stasis topography; it works very well with "difficult" loads. I think that is because the feedback is not taken from the speaker output, so the input stage is buffered from speaker back emf (and thus it not amplified). Please correct me if I'm wrong.
I haven't looked in this forum that much, but I will check it our from now on.
I recently realized that some of the equipment I've worked on, some of the equipment I personally own, and some of the circuits I have emulated in my own designs are your circuits. I personally like the Stasis topography; it works very well with "difficult" loads. I think that is because the feedback is not taken from the speaker output, so the input stage is buffered from speaker back emf (and thus it not amplified). Please correct me if I'm wrong.
I haven't looked in this forum that much, but I will check it our from now on.
to be frank , my AR2 was first impressed with Mili BJ2 (not Mini)
, later advancing to sort of Turbo BJ2Turbo - as typical scavenger , he had 2x24Vac xformers , not 2x18Vac , as prescribed .......... he had no space enough in case for proper stereo amp , so he just use two cases , as monoblocks
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Aleph models
Found this post from 2003 describing the various Aleph models and thought I'd add it to this thread.
Found this post from 2003 describing the various Aleph models and thought I'd add it to this thread.
Power Mosfet Choices
While slightly off topic, I found this post from 2003 describing the sound of various output devices and thought I'd add it to this thread as well:
While slightly off topic, I found this post from 2003 describing the sound of various output devices and thought I'd add it to this thread as well:
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