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Panasonic SA-XR 55/57 and Other Early Class-D amps

cookiefactory

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#1
Anyone here use the Panasonic SA-XR 55, 57. etc A/V receiver? They along with the T-amp were one of first “digital” amps to go viral and become an internet sensation.

I’ve been using the SA-XR57 to drive my Energy Veritas 2.4i floorstanders but recently have begun eyeing the Benchmark AHB2. My brain says I won’t notice any difference but maybe there’s something there? Curious if anyone else in a similar position.
 

taloyd

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#2
I used to and was quite impressed with the sound coming out of them relative to the cost! (Qualified by: only when fed a digital input, since it's a truly a digital amplifier. Analog in was mediocre.
 

pozz

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#4
It would be really interesting to have the SA-XR57 measured if you wouldn't mind parting with the unit for a while.
 

jhaider

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#7
I’ve been using the SA-XR57 to drive my Energy Veritas 2.4i floorstanders but recently have begun eyeing the Benchmark AHB2. My brain says I won’t notice any difference but maybe there’s something there? Curious if anyone else in a similar position.
Depending on the impedance curve on your speakers, you may well hear a difference. Their response varies quite a bit with speaker impedance.

I bought one of those when they came out. Such a cool story: blue chip TacT audiophile technology, and cheap! But it turns out there’s a reason analog Class D amps vastly outnumber PCM->PWM converters.
 

cookiefactory

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#8
Depending on the impedance curve on your speakers, you may well hear a difference. Their response varies quite a bit with speaker impedance.

I bought one of those when they came out. Such a cool story: blue chip TacT audiophile technology, and cheap! But it turns out there’s a reason analog Class D amps vastly outnumber PCM->PWM converters.
Interesting, I take it that reason is the impedance/response variability? I’m going to send my SA-XR57 to Amir for testing so I guess we’ll find out soon enough!
 

SEKLEM

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#9
If you are in US, start a conversation with me and we can take it from there.
I'm definitely interested in seeing this. I used to have one of these and it sounded good (again, when fed with SPDIF, analog inputs were just so-so).
 

cookiefactory

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#10
Same, I’m quite curious if all that hype was warranted (at least from a performance perspective). It’ll also be interesting to see how it compares to modern Class-D amps (i.e how far the industry has advanced).
 

amirm

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#11
I'm definitely interested in seeing this. I used to have one of these and it sounded good (again, when fed with SPDIF, analog inputs were just so-so).
He shipped it already so the test will come....
 
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#13
Sharp had a class-D technology similar (I think) to the TI Equibit in the TacT and Panasonic units. It debuted in the $15,000 SM-SX100 integrated amplifier and eventually trickled down to consumer-friendly products. I have two copies of the Sharp SD-EX111, which is a one-box CDP+tuner+amplifier using the same basic amplifier technology. I don't know if it's worth measuring, especially because it's a pure digital amp that has no digital inputs. It does have an analog input, which presumably goes through an A/D conversion of some sort.

Looks like Sharp kept a lot of info up on the Internet, most of it 20 years old now! It's really cool that they archived all this.
 

taloyd

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#15

While that graph looks bad (and strange - likely due to the actually digital (switching without D/A conversion) amplifier) - THD isn't a great psychoacoustic measurement for sound quality as perceived by humans without decomposing by harmonics (referencing Earl Geddes about this).

Also:
This graph shows that the SA-XR57's left channel, from CD input to speaker output with two channels driving 8-ohm loads, reaches 0.1% distortion at
77.9 watts and 1% distortion at 116.0 watts. Into 4 ohms, the amplifier reaches 0.1% distortion at
151.5 watts and 1% distortion at 204.3 watts.


...that's pretty amazing - many very expensive amplifiers don't double power output into half the impedance - and here it looks like almost exactly that. I'm curious if they used a digital connection into the [digital] amplifier or if they used the analog out from the CDP - the latter would produce TERRIBLE results as the amplifier is required to have an A/D conversion stage as it is (yes, again) a digital amplifier. I don't think it's similar to other AVRs - certainly not in its very cheap price bracket.

Subjectively, I felt it was a very enjoyable amplifier, though bested by the Tripath-based switching-output-stage pro-audio market Carver ZR1000 - one of the best amplifiers I've had the pleasure of owning, along with the Monarchy SM-70 (a completely balanced class A analog amplifier).

Cheers,
Tal
 

cookiefactory

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#16
Actually am I wrong or are those numbers significantly better than most of the AVR measurements we've seen thus far, particularly the signal to noise?
 
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#17
I still have the Panasonic 57 but haven't used it in a long time but remember when I did with some vsa vr4s in the day that a digital out of a sacd player to the digital in on the amp at 24.192 sounded awesome. I am not sure why I changed my rig but I did. With that said it did sound really good. I think between Panasonic and Sony S master they were ahead of there time. I would be surprised if when the king does a review that they fail really badly.
 

cookiefactory

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#18

While that graph looks bad (and strange - likely due to the actually digital (switching without D/A conversion) amplifier) - THD isn't a great psychoacoustic measurement for sound quality as perceived by humans without decomposing by harmonics (referencing Earl Geddes about this).

Also:
This graph shows that the SA-XR57's left channel, from CD input to speaker output with two channels driving 8-ohm loads, reaches 0.1% distortion at
77.9 watts and 1% distortion at 116.0 watts. Into 4 ohms, the amplifier reaches 0.1% distortion at
151.5 watts and 1% distortion at 204.3 watts.


...that's pretty amazing - many very expensive amplifiers don't double power output into half the impedance - and here it looks like almost exactly that. I'm curious if they used a digital connection into the [digital] amplifier or if they used the analog out from the CDP - the latter would produce TERRIBLE results as the amplifier is required to have an A/D conversion stage as it is (yes, again) a digital amplifier. I don't think it's similar to other AVRs - certainly not in its very cheap price bracket.

Subjectively, I felt it was a very enjoyable amplifier, though bested by the Tripath-based switching-output-stage pro-audio market Carver ZR1000 - one of the best amplifiers I've had the pleasure of owning, along with the Monarchy SM-70 (a completely balanced class A analog amplifier).

Cheers,
Tal
It's curious but the graph is titled for the Onkyo TX-SR504 A/V Receiver rather than the SA-XR57. Chances are it's just a copy & paste type error but does open that tiny bit of doubt.

Yesterday I found an old thread on AVSForum where the question was raised, "Is the SA-XR55/57 suitable for 4-ohm speakers?". From the above measurements it looks like it is. When one considers the Dual Amp feature (where it uses the unused Speaker B channels to double up the power) and the Bi-wire feature, you're looking at using 6 out of 7 channels to drive a 2-channel setup. That's ~453 watts into 4 ohms at 0.1% distortion for compatible (i.e. bi-wirable) speakers!
 

SEKLEM

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#19
When one considers the Dual Amp feature (where it uses the unused Speaker B channels to double up the power) and the Bi-wire feature, you're looking at using 6 out of 7 channels to drive a 2-channel setup. That's ~453 watts into 4 ohms at 0.1% distortion for compatible (i.e. bi-wirable) speakers!
Is that how that really works?
 

cookiefactory

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#20
Is that how that really works?
Pretty certain for the dual amp part. Not 100% on the “tri-amp” aspect as there is some ambiguity on the Panny’s Bi-wire functionality, particularly when active alongside the Dual Amp.
 
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