Signal to Noise Ratio and Amps (current!)

 

New member
Username: Feminazi

Post Number: 13
Registered: 12-2003
I am reading different numbers on signal to noise ratios for different receivers. The Marantz receivers seem to have high numbers of 105, the Onkyo TX-SR600 I have is listed as 100, and the Yamaha I am demoing (blech!) has a 96 dB rating. What does this measure mean in the real world?

Also, how do I find out what kind of amps or current that receivers have? I read that the H/K 7x00 series receivers have 75 amps, and that the NAD T761 has 45 amps, which both sound like a lot, but I don't see this posted for other receivers, perhaps because the numbers are not very impressive? Please illuminate me! :-)
 

New member
Username: Geekboy

Post Number: 21
Registered: 12-2003
I can't go any justice explaining S/N ratios!

Anyhow, I too find that most of the receiver manufacturers don't like to talk about their power supply in the receiver. All of the "high current" receivers are PROUD to show this off and flaunt it. H/K 7200 is 75amps, H/K 525 is 45amps... NAD T76x at about 45amps.

You don't see Sony or the others doing this, because they don't offer the high current capability of the amplifier section of the receiver. It costs more for a high current amplifier. Bigger power supply, capacitors.... and quality ones too! :-)

I think the numbers are not illuminating. I wish they would.
 

New member
Username: John_a

Post Number: 28
Registered: 12-2003
D. Spitzig,

About power. I think the T761 is rated at 60W x 5 into 8 Ohms, all channels driven. NAD rate power of amplifiers/receivers conservatively and honestly. The qualifications are important if you wish to compare paper specifications (every amplifier give more Watts at less Ohms; more Watts per channel into fewer channels). There is also the question of whether the power is delivered to an ideal electrical test load or into real loudspeakers, working at full frequency range. I recommend the web page NAD power; it makes a case that applies not just to NAD but to other honest manufacturers. Dishonest ones are aware that power is one of the first things people look for, and will do anything to keep the numbers high even at the expense of real-world power and sound quality. It is largely a question of how much current (measured in Amps) the amplifier/receiver will sustain, as geekboy says.

About S/N ratios. A sense of perspective. Years ago these were something to think about. For modern amplifiers, there will be no audible different between your quoted, measured test figures - the makers are playing a meaningless numbers game. The honest ones cannot quit the game, in case prospective purchasers think they are hiding something.

I have the blurb for a turntable I bought in 1979. It was proud to quote rumble of -70 dB: that is, the throbbing from the bearing was 70 dB lower than the signal from the LP record being played. It was a cr*p turntable for other reasons - 70 dB was a good figure.

Still in use; a pretty good analogue tape cassette player, Sony Walkman Professional. S/N ratios: from 71 dB with metal tape and Dolby C noise reduction, down to 54 dB with Type I tape and noise reduction off.

Moral? S/N noise ratio figures are obsolete, like wow and flutter. Figures above about 85 dB have no meaning in terms of what you will hear. Your amplifier will only give lower values if it has a serious and obtrusive source of noise, like hum, or a component failure. Total harmonic distortion (THD) is still something to consider, but it has to be at a stated power, and then they have to tell you if it is DIN or (W)RMS. Even then, for most reasonably-powered amplifiers it is also negligible, today - you can probably forget it.

Beware paper specs. You need to know what the makers do not say - it is more revealing than what they do.
 

New member
Username: Geekboy

Post Number: 23
Registered: 12-2003
John_A wrote: Beware paper specs. You need to know what the makers do not say - it is more revealing than what they do.

Exactly... I don't like what they DON'T say. I find that B&K, H/K, and NAD (somewhat), show every single measurable aspect of their components in their "specifications" section.

It is too difficult trying to hunt down information which should be readily available, and as you said it John_A, if H/K DID NOT show the S/N ratios -- although they are useless today -- *I* would think they're hiding something!

How many 110W x 7 receiver manufacturers are going to put, in their specifications, that they can peak to 5amps and that their receiver draws at most 265W out of the plug socket (2.2A)? (By the way, I just describe the Sony STRDE995.) But then you have the manufacturers that say they only deliver 70W x 7... BUT... peak at 45amps and draw 1040W out of the plug socket (8.66A)? (That's the H/K 525 just describe.)

Powerful numbers if you just look.
 

New member
Username: John_a

Post Number: 29
Registered: 12-2003
Great point, geekboy. A 110W x 7 receiver all channels driven has to be able to draw at least 770 W from the supply, and that is if it is perfectly efficient. If it draws 265 W then it cannot deliver more than about 132 W x 2. I suspect the figure 110 W x 7 is 100 W for each of two channels driven, with seven channels to choose from. With all 7 channels driven equally, it cannot possibly give more than about 38 W per channel. What a con.
 

New member
Username: Feminazi

Post Number: 15
Registered: 12-2003
Great reading here, thanks for the info. guys! I just picked up a Marantz SR-6200 at a great price from a local dealer. My dealer told me that the 6200 I bought was made in Korea, not one of the ones that were made in China that were recalled for a SVHS connection fault or something like that. It weighs 32.6 pounds and has a pretty solid transformer, he said. For the same price, I would have only been able to get a 4400, probably. He said to go with the 6200 as it has a lot more power and that he called Sound and Vision about the test saying it was underpowered and that it wasn't published, or something to that effect. I plan on seeing if it can cut the custard tomorrow afternoon! :-) I am going to throw some 5.1 stuff on and crank it for awhile.

Does anyone know what the amps are on that bad boy, I think he said it is something like 12 or so, does that sound right? I don't know what it is drawing out of the socket, but I am pretty sure that it has seperate amplifiers for each channel.

On another note, I know someone who has an old Pioneer 4 channel (I think)integrated amp that does 4 channels with a total of 450 into 8 Ohms and that can be switched to run 4 ohms. Apparently it can really put some power out, so maybe it is underrated. It says on the front of it that it has 3 transformers and 7 power supplies, I think! I think it is the 770 or something like that.
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