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Marantz PM-90 Review (Vintage Amplifier)

So, this amp's Class A mode is effectively a con for the many gullible audiophiles who imagine(d) they can hear an improvement.
Basically, yes. A feature to push sales of a more expensive product, to make it look "better" than the cheaper one. I've once had the PM80, same feature, I ended up using it in class AB, not being able (back then - 30 years younger than now) to hear much difference. It even seemed to me the AB sounds better (probably because it was a touch louder), and the amp was running cooler.
 
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It's a neat unit. I especially like how there is a minimum of circuitry. The amp PCB are populated with a minimum of components and the rest of the unit is the same.
Straigtforward, without weird experiments, using decent parts = usually a recipe for success.
BTW, it also shows, the simplest (exterior) designs are the most timeless ones.
If it came out today, nobody would notice the design is 30 years old.
Maybe Marantz should reissue it ? (but please with a remote, and without HDAM and such)...
 
Was this amplifier in use till recent past or not in use ?
thanks for the review
It has definitely been used. It has some fine scratches and such but taken good care of.
 
It is a nostalgic amplifier.
Thank you very much, Mr. amirm, for the detailed measurement.
It will be very helpful.
 
I love this on old amplifiers. Allows you to just use the power amp alone, use it as a pre-amp, get subwoofers in there or slap a miniDSP in between it.

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My old PM-16 didn't have it though, which made me kinda sad. The PM-16 did had HDAM, so I guess its technical performance wouldn't have been great.
 
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I hope the company goes back to these roots rather than horrible looks and performance of much of their AV line.


People that make the device you just reviewed are long gone. I think the amount of people they'd need to fire and hire to get back to their pedigree is something they can't stomach.

Kinda reminds me of people awaiting great software titles in gaming by once venerated development studios. Those folks are simply gone after all this time, and a bunch of clowns are left it seems. It's really telling when a supposed high end company like Marantz is filled with designers and executives that greenlight such dumb looking modern designs. Even if they had the engineering people, they probably have some bum over their shoulders telling them to do dumb things even on the performance front.
 
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To see if there is a difference at all between Class AB and Class A, I turned on the residual mode of Audio Precision in the scope display. This shows us the difference between input and output waveforms. If there is zero crossing error due to class AB operation, we should see more difference around that part of the waveform but we don't:

Crossover distortion (cross-over between classes of operation) does not appear at zero crossing, but at the level where is the transition point from class A to class AB. This transition point, for push-pull output stage, depends on:
1) idle current
2) load impedance
It appears at zero crossing only with class B output stage with zero or minimum idle current, thus it was "popular" to seek for it near zero as many class B and AB amps had minimum idle current.

Several examples of transition point at different idle currents Iq and 4ohm load:

Iq = 10mA, 0.0008 W
Iq = 100mA, 0.08 W
Iq = 0.5A, 2W
Iq = 1.5A, 18W

These are the points where you have to look for crossover distortion. In this Marantz the Iq would not be low in class AB mode.

I have explained how the crossover distortion looks at transition point on a high Iq (1.4A) example here:
https://www.audiosciencereview.com/...they-really-sound-different.18415/post-914699

High transition point (high idle current) means that the amp operates at class AB, i.e. in the crossover distortion mode only during peaks of high power. Minimum idle current makes it operate in crossover distortion area all the time.
 
People that make the device you just reviewed are long gone. I think the amount of people they'd need to fire and hire to get back to their pedigree is something they can't stomach.

Kinda reminds me of people awaiting great software titles in gaming by once venerated development studios. Those folks are simply gone after all this time, and a bunch of clowns are left it seems. It's really telling when a supposed high end company like Marantz is filled with designers and executives that greenlight such dumb looking modern designs. Even if they had the engineering people, they probably have some bum over their shoulders telling them to dumb things even on the performance front.
I wish you were wrong, but I'm afraid your're right, this is not new, but disastrous in the long run...
 
Allows you to just use the power amp alone, use it as a pre-amp
According to this block diagram the processor loop is before the pre-amp section, the bass and treble control and the volume control. So if that is the case it is strictly a processor loop and not a pre-out.
SE90 - 3.png
 
Has it been revised (new caps and such) or is everything in it 30 years old?
This is interesting as well, just to debunk the myth of replacing old capacitors, considering the parts used in these amplifiers at the time, were the best of the best..
 
Myth, IDK, it depends - mainly on temperature. Even the best parts do age. While I would not necessarily do a re-cap automatically, in an amp from a time before the "bad caps era", it's interesting to know in cases like this one.
 
These are the points where you have to look for crossover distortion. In this Marantz the Iq would not be low in class AB mode.
Only if you understand electronic design and amplifiers. Lay audiophiles are sold on it being zero crossing error and that is what I tested to show it was not.
 
Thanks for the review.

Interesting how well this.holds up when compared to today's offerings.
 
Being a now old UK based bod and in the industry at this time, I feel very sad indeed that these massive top line amps never really found their way over here in large numbers, although maybe they could be found in London's Tottenham Court Road stores which has huge ranges of everything except the smaller 'enthusiast audiophile' brands. I seem to remember the last was a PM94 which was black with gold lettering and wooden? end cheeks. Our upper-mid level market was mostly UK made badly measuring tat basically I now understand, with a shouted story (and contrived sound quality) to tell that we lapped up in our ignorance. Sony, JVC, this era Marantz, Yamaha and no doubt others, made good solid meaty stuff like this but were not to be seen in higher end HiFi stores as I believe 'we' had to buy in the entire range rather than cherry pick - not all of it was good and it rarely lasted for sale beyond a season or two if we were lucky. In any case, big-box amps like this were right out of fashion. Looking back I could weep at my/our ignorance :(

We did see the upper end Marantz CD players though - CD80 and 85, CD10 (which I owned for a short while) and the golden slimmer CD 17? from a later generation, which 'KI' had apparently looked at to deserve a 'Signature' badge (usually the kiss of death away from the press fervour).
 
Wow! Japan has two power system networks! I’m shocked!
Previous turntables were often distinguished between those for eastern Japan and those for western Japan. Although the voltage was the same.
Now it's less.
New purchases are specified when ordering, but second-hand purchases must be careful.

Although it is a small country, attention should also be paid to air conditioners, electric fans, refrigerators, washing machines, fluorescent lights, microwave ovens, sewing machines, etc.
 
According to this block diagram the processor loop is before the pre-amp section, the bass and treble control and the volume control. So if that is the case it is strictly a processor loop and not a pre-out.
View attachment 154285
Ah I guess that's why its labeled processor and not pre-out or something like that. How nice of them to think about all those MiniDSP users ;).

Previous turntables were often distinguished between those for eastern Japan and those for western Japan. Although the voltage was the same.
Now it's less.
New purchases are specified when ordering, but second-hand purchases must be careful.

Although it is a small country, attention should also be paid to air conditioners, electric fans, refrigerators, washing machines, fluorescent lights, microwave ovens, sewing machines, etc.
Japan is not really a small country, 126 million inhabitants (11th in the world).
 
Unfortunately our measurements are polluted by high mains noise and harmonics. I tried every which way but could not reduce that impact much. Whether this is due design of the amplifier or longer AC mains connection due to use of lab AC gen or Variac, I can't tell.

It seems like this amp is begging for new electrolytic capacitors.
 
Being a now old UK based bod and in the industry at this time, I feel very sad indeed that these massive top line amps never really found their way over here in large numbers, although maybe they could be found in London's Tottenham Court Road stores which has huge ranges of everything except the smaller 'enthusiast audiophile' brands. I seem to remember the last was a PM94 which was black with gold lettering and wooden? end cheeks. Our upper-mid level market was mostly UK made badly measuring tat basically I now understand, with a shouted story (and contrived sound quality) to tell that we lapped up in our ignorance. Sony, JVC, this era Marantz, Yamaha and no doubt others, made good solid meaty stuff like this but were not to be seen in higher end HiFi stores as I believe 'we' had to buy in the entire range rather than cherry pick - not all of it was good and it rarely lasted for sale beyond a season or two if we were lucky. In any case, big-box amps like this were right out of fashion. Looking back I could weep at my/our ignorance :(

We did see the upper end Marantz CD players though - CD80 and 85, CD10 (which I owned for a short while) and the golden slimmer CD 17? from a later generation, which 'KI' had apparently looked at to deserve a 'Signature' badge (usually the kiss of death away from the press fervour).
British Hi-Fi pretty much "owned" the review press in Europe at that time, the Germans following but behind, even in their own country.
In countries like Poland there is still a preference for British stuff, at least it was last time I checked (which was before Brexit).
Maybe one of the reasons is/was, similar living rooms, rather small for the most, not much need for beefy amps and speakers.
Money was the other factor, not so many were able to afford Marantz, Accuphase, T&A etc.
 
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