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Is more power really needed?


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#1 of 53 OFFLINE   MikeNagy

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Posted August 02 2003 - 07:23 PM

I am trying to decide between buying a NAD T752 and a NAD T762. I can get them for $600 and $900, respectively. I don't really need any second zone capablities, I don't need amplification for 6 or 7 channels (I'm only going to be running 5.1 at the most), and I don't listen to music or movies super-loud, but I'd like movies to have pleanty of dynamics at medium levels. I'm going to be running a 2.1 system until I can afford surrounds and a center, most likely around Christmas time, at which point I very much intend to move up to 5.1.

Currently, I have the following components (in case any of this makes any difference):
PSB Stratus Silveri's (mains)
SVS 16-46PCi (sub)
Sony NS900V (dvd/sacd/cd player)
Kimber Kable 8VS (speaker wire)
Belden 1694A, 1505F, and 7710A (interconnects; digital coax, stereo, and component video respectively)

Basically I want to know what the differences are between the 752 and the 762 other than the multi zone and amplification for more channels (also, what the heck is a toroidal power supply??). I'm also interested in people's opinions as to which would be the better buy. Meaning, in YOUR opinion, is the extra $300 worth the increase in power (and whatever other extra features there are)?


#2 of 53 OFFLINE   keir

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Posted August 02 2003 - 09:38 PM

It doesn't take a whole lot of power to get good movie playback levels, especially when you have your speakers set to small and a capable sub like an svs. I think theres a good chance that you would be more than satisfied with the cheaper NAD with 80 WPC. It takes a doubling of power to gain 3 dB in volume, so the extra 20 watts isn't going to get you much in my opinion.


heres a link on toroidal power supplies:
http://www.audiovide....ctionaryid=445

I'm guessing that both receivers probably use a toroidal supply, maybe the 762 has a different one for the higher power it puts out.

#3 of 53 OFFLINE   MikeNagy

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Posted August 02 2003 - 09:56 PM

Hmm...so torodial psu's give better current with less noise. Less noise at high current would matter to me, I think, since the PSB's are 4-ohm speakers, so they'd be drawing a relatively larger amount of current than typical 8-ohm speakers. But in the product specs, both receivers claim to have the same %THD, 0.08%. Ok, I think I just got myself more confused...

#4 of 53 OFFLINE   Chu Gai

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Posted August 03 2003 - 02:29 AM

A large number of companies are using torroidal power supplies and that makes sourcing them fairly inexpensive. However, even if they weren't, I don't think it ought to be a major factor in your purchasing decision.

What're you currently using and how big is your room?

#5 of 53 OFFLINE   Mark Dickerson

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Posted August 03 2003 - 04:50 AM

First off, let me congratulate you on excellent gear. Those PSBs and the SVS sub are pretty awesome, and the choice of an NAD receiver I think is the right one.

The differences are as follows:

1. The 762 has a Holmgren Toroidal power supply, which is a high quality outside brand. The 752 does not have this. A toroidal power supply has a large circular magnet, which is supposed to provide higher power and better transients when used in a receiver.

2. The 762 also has a sixth channel, which may or may not be of any interest to you.

3. The 762 has 3 component video inputs instead of two.

4. The 762 has switching between Main A and Main B speaker outputs

5. The 762 has 3 12v output triggers vs only 2 for the 752.

6. The 762, when connected to a CD player by digital cable, will read HDCDs, but the 752 will not.

7. Finally, the 762 has a RS-232 port interface "for advanced control systems."

Only you know if there is anything on this list that will be of value to you. But it must be noted that both models have the same pre/pro section, so there is no advantage there and since you are running 4 ohm speakers, the difference in dynamic power into 4 ohms is pretty negligible (200 wpc vs. 230 wpc). Personally, I don't think there will be any difference in the quality of the sound, especially when running only two speakers (plus sub). I hope this helps you.

#6 of 53 OFFLINE   Jason.Soko

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Posted August 03 2003 - 05:21 AM

I posted this in another thread. I think it will help.

Thing you have to realize is that say for instance you have some speakers with a sensitivty of 90db. So that at 1meter from the speakers at a SPL of 90db you will be using 1 watt of power. 90db is loud. That is the sound of a lawnmower with your ear 3ft away from it. My fathers old Onkyo receiver used to have a wattmeter on the front that rarely if ever went past 1 watt. The extra power is needed for all the dynamic headroom and what not. A 10db increase is what usually people distinguish as twice as loud. So I suppose if you are blasting the things then you might use somewhere near the potential.


Note that for every 10 db increase in POWER you get a decade
increase in Wattage:

0 db increase = same power
3 db increase = 2 x power
10 db increase = 10 x power
20 db increase = 100 x power
30 db increase = 1000 x power
40 db increase = 10,000 x power
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#7 of 53 OFFLINE   MikeNagy

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Posted August 03 2003 - 07:08 AM

Chu: Currently I have nothing powering this system. It's been my summer project to research and slowly piece together a system by the time school starts back up in the fall. My HT "room" is only about 12'x14', but it has almost full-width openings into my dining room, kitchen, and living room, which makes it more like a system in the corner of a 23'x30' room. Ceiling height is standard... 10' I think.

Mark: They have the same pre/pro section? Does that mean that all the logic chips and DAC's and etc are the same? Man...the 752 is looking a lot better. I agree that I won't have to worry with 2-channel audio, but I'm only going with 2.1 right now because I can't afford to fill the system out with 5.1 quite yet, although it is my intention to do so. So I'm slightly concerned that with all 5 channels driven, the 752 won't be able to fill out dynamic sound as well as the 762...But then again, the 762 only has 30 more watts dynamic and 20 more watts continuous. But will it sound cleaner with 5 channels driven than the 752 with 5 channels driven? Gaah! heh

Hmm...I think the ONLY thing that's appealing to me is the larger power supply...I don't particularly need the other features. So it boils down to $300 for a torodial power supply which brings in an extra 20 watts and maybe a little more smoothness. Decisions, decisions....


#8 of 53 OFFLINE   DanielMan

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Posted August 03 2003 - 04:50 PM

Mike,

Go with all the power you can afford or willing to spend; not because you listen at high volumes, but for musical dynamics. You need lots of reserve power to replicate dynamics such as orchestra hits, explosions, etc.

If you listen mainly to HT, you may not notice it much. But if you listen to music at all, especially classical, you will notice the difference.

Just my 2 cents...

#9 of 53 OFFLINE   MikeNagy

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Posted August 03 2003 - 05:23 PM

Yeah, I'll be using the system 75% music, 25% movies. I do listen to classical and jazz, among other genres. :-/ Being on a tight budget sucks. Either I splurge on the bigger amp and make up for it by eating ramen more often next quarter, or I stay with the 752 and eat out more often. Being a collidge stoodent is such fun! Posted Image

#10 of 53 OFFLINE   Ferran Mazzanti

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Posted August 04 2003 - 02:59 AM

Uhmm... that thing about power is surprising me. I have a Marantz SR6200 which is claimed to have lots (more or less) of watts and it sounds nice and low at reasonable levels. However I'm running also a 2 channel amp Puccini which is rated at 40 watts per channel only and I can tell that it delivers plenty of sound (as loud as you want) at 1/3 of its max volume. Also sound is hundred times nicer than the 6200, more detailed etc etc... so waht's up with wattage?
Just 40 watts and I'm in nirbana. My room is 6x5 square meters, so not small at all. Why would I need more watts?
I wonder if somebody can put some light in this point...
Thanks.

#11 of 53 OFFLINE   Jason.Soko

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Posted August 04 2003 - 04:40 AM

Ferran, current drives your speakers, not wattage. It is total nonsense. I guarantee you are very rarely ever going over 1 watt of power in the first place. The Puccini is obviously a quality high current amplifier. My Moon costs about $2500 retail and only does 70w x 2. But it is capable of 9amp continous with peaks at 16. There is a reason you can goto walmart and buy a supposed 600watt amplifier for $100. There are 2 ways of getting to 600watts, high current or high voltage.
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#12 of 53 OFFLINE   John Garcia

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Posted August 04 2003 - 05:22 AM

Quote:
There is a reason you can goto walmart and buy a supposed 600watt amplifier for $100.

Hahaha. Too funny, and too true. 600w PEAK for 1 second, just before it melts.

I looked at the 752 and 762 also. That 30W doesn't sound like a lot, but IMO, it will be worth it. I moved from a Marantz 6200 to an 8300, which, on paper, is only a 15w increase, but I can tell you there is a significant difference between the two.

I don't want to spend your money, but long term, I am going to say the extra current from the huge power supply in the 762 will be worth that $$$ and eating ramen + mac & cheese.

I went with the 8300 over the 762... (but it also cost me about ~$300 more).
HT: Emotiva UMC-200, Emotiva XPA-3, Carnegie Acoustics CSB-1s + CSC-1, GR Research A/V-1s, Epik Empire, Oppo BDP-105, PS4, PS3,URC R-50, APC-H10, Panamax 5100 Bluejeans Cable
System Two: Marantz PM7200, Pioneer FS52s, Panasonic BD79
(stolen) : Marantz SR-8300, GR Research A/V-2s, Sony SCD-222ES SACD, Panasonic BD-65, PS3 60G (250G)

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#13 of 53 OFFLINE   MikeNagy

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Posted August 04 2003 - 05:59 AM

Jason: Very good point about watts vs amps. Doing a quick search online shows that most manufacturers (read: all the ones I've seen) do not quote their maximum continuous current output, neither for stereo nor for all channels driven. NAD does claim that the 762 is capable of 45 amps peak current. That sounds awfully high, but it is around what your Moon would do if it had the same amplification for 6 channels instead of 2.

John: I'm leaning towards the mac & cheese / ramen route now. I don't think I'd be happy if I bought the 752 and if just once I could tell that it didn't have enough power, because then I'd know I should have bought the 762 and would then be unable to do so. I might be kicking myself in two months, but it'll be worth it in the long run. (yeah...that's what I have to keep telling myself Posted Image )


#14 of 53 OFFLINE   JackS

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Posted August 04 2003 - 06:07 AM

Mike -Stay off the Ramen. Too much sodium and more saturated fat than you might imagine for such a product. Heres a vote for the 752 and your continued good health. Jack

#15 of 53 OFFLINE   John Garcia

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Posted August 04 2003 - 06:39 AM

Salad and fruit are inexpensive. Posted Image

I was in the same boat with the 7300 OSE vs 8300. The OSE is less expensive (about the same as the 762), but was rated at the same output as my 6200 (though I know it's current delivery would be higher), however the point of upgrading for me, was to gain some added power and processing. I didn't want to spend as much as I did on the 8300, but I am VERY happy with what I got Posted Image I don't expect I will need to upgrade this receiver for quite some time (and it is upgradable via RS232 as well).

Then the 762 vs the 8300...20w difference, but the 762 is 4 Ohm stable and weighs in about 10lb heavier; it is even heavier than the 9300, which suggests to me a serious power supply.

Of note is that the 762 was not upgradable via it's RS232, but the new models do appear to be.
HT: Emotiva UMC-200, Emotiva XPA-3, Carnegie Acoustics CSB-1s + CSC-1, GR Research A/V-1s, Epik Empire, Oppo BDP-105, PS4, PS3,URC R-50, APC-H10, Panamax 5100 Bluejeans Cable
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#16 of 53 OFFLINE   Jonathan M

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Posted August 04 2003 - 10:04 AM

Hey MikeNagy,

I have a T752 and it does the job well for me running 5 custom built speakers all small with a decent sub (My own design).

If you are only going to be using 2 channels, then I see no reason to go for the T762.

As far as power output goes, the 762 does have more (Total 600W compared to 400W), but the way the NAD stuff is rated means that you'll probably not need it.

My home page has pictures of the guts of the T752 so you can see the size of the power transformer. And YES, the pre/pro sections are basically identical except for the lack of HDCD and multizone stuff. Note that the T752 has 2 12V trigger out sockets, but they are wired in parallel, so there is only 1 actual output. (The T762 has 3 outputs but 2 are in parallel giving 2 actual outputs).

One question: When do you see yourself next upgrading your receiver/amplification? If it is less than 3 years away, go with the 752 - it'll easily perform well enough to not warrant the extra cash on the 762 - you can save that $300 for your next upgrade.

My homepage can be found via the www link or the link in my sig.

Cheers,
Jonathan
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#17 of 53 OFFLINE   MikeNagy

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Posted August 04 2003 - 10:07 AM

Jack: Yeah, ramen is pretty bad. Actually, really bad. Plus it tastes awful IMHO. I was just using it as an example of cheap food that I'll be living on soon.

John: Salad, fruit, and bread. And some cheese now and then. Mmmm... Can't get a cheaper meal that tastes as good. But I digress. It's interesting that the 762 weighs more than the 9300. I always thought it would be leaps and bounds better than a "humble" 762. Not like I have a choice, really, when it comes to powering 4-ohm loads. From what I've seen/read/heard, NAD is the best choice for 4-ohm speakers in this price point.


#18 of 53 OFFLINE   Jason.Soko

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Posted August 04 2003 - 11:07 AM

MikeNagy.

Spec sheets for my I-5.

http://www.simaudio.com/mooni5.htm

Output Power @ 8 ohms 70 Watts per channel
Output Power @ 4 ohms 110 Watts per channel
Output Impedance 0.04 ohms
Damping Factor > 200
Gain Control RBG cs version
Gain 30dB
Dynamic Headroom 3dB
Signal-to-noise Ratio 97dB @ full power
Maximum Output Voltage 23.5 Volts
Slew Rate 20V/µs
Maximum Current - Peak 16 amperes
Maximum Current - Continuous 9 amperes
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#19 of 53 OFFLINE   Wayne_T

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Posted August 04 2003 - 11:32 AM

I'm going to refer to two posts above which together really get to the heart of the matter - how much power do you need?

DanielMan said:

Go with all the power you can afford or willing to spend; not because you listen at high volumes, but for musical dynamics. You need lots of reserve power to replicate dynamics such as orchestra hits, explosions, etc.


Daniel is spot on. That is exactly why you want as much power as you can get/afford.

Jason gave us this table:


0 db increase = same power
3 db increase = 2 x power
10 db increase = 10 x power
20 db increase = 100 x power
30 db increase = 1000 x power
40 db increase = 10,000 x power


And Jason also gave us this (approximate) fact... that

A 10db increase is what usually people distinguish as twice as loud.


So lets put all this in perspective. If we listen at a normal average level of 5W (for example), and the drummer hits a drum which is (conservatively) twice as loud as the median sound level, you momentarily need 50W to reproduce that sound without clipping. For an explosion which is twice as loud again as the drum, you will now need to momentarily have 500W at your disposal to play that sound without clipping it. This is what we mean by dynamic range. To reproduce the dynamics of a live performance, at a listening level of 5 watts, would take in the order of 500W.

The reason more power is important is not beacause we want to play the music louder. God forbid! 25 watts average power would be unbearably loud in most rooms, but a 25 watt amp would be terribly underpowered if you wanted to listen at an average 2W with decent dynamic range. More power gives you cleaner, truer sound, not louder sound.

My advice (for what its worth)... get all the power you can afford.

Wayne
The bitterness of poor quality lingers long after the sweetness of low price has passed.

#20 of 53 OFFLINE   MikeNagy

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Posted August 04 2003 - 12:18 PM

Jonathan: I won't be using this for two channel audio. I only have two channels right now because I am poor. I will get more in the near future. I hope I'm not going to need to upgrade in less than 3 years. If the past four years are any indication of the next four years, then I'll probably want to upgrade my pre/pro for the latest and greatest formats. Grr...getting seperates makes so much more financial sense than getting new receivers. Then I could get a sweet amp, keep it for a long time, and only upgrade the pre/pro as necessary. From this standpoint, I agree the 752 makes better sense...

Wayne: ...however, Wayne makes a valid and very solid point, and it is summed up by the quote in his sig. But let me see if I get this right:

Say average listening volume is about 3 watts / channel at 4 ohms. Along comes a drum hit which needs twice the volume to not be clipped. So then it would need 30 watts / channel. Then if an explosion 2x as loud as the drum happens, it would need 300 watts / channel to not be clipped. Okay, so the max dynamic power on the 762 is 230 watts/channel at 4 ohms, and the 752 has 200 watts/channel. Neither of them are very close to the necessary 300 watts. The 762 would have 76% of the necessary power and the 752 would have 66% of the necessary power. If we look at your sample figure, it's even worse, and the two amps get closer to each other.
...or am I on crack? I made some huge assumptions there, such as, +10dB = double volume, avg listening volume = 3 watts, that a drum is 2x as loud as regular volume, and that an explosion is 4x as loud as regular volume.

I guess its just a case of diminishing returns. At what point does the marginally better power not make its own cost worthwhile? (rhetorical question)

The test I like to do for dynamic range is the big battle scene at the beginning of Gladiator. You have the surging orchestral score behind the clamoring warriors fighting, with big explosions in the background. The first two pretty much demand a lot from amps, and then to throw massive explosions on top of it...clipping becomes painfully obvious on just about everything I've heard (although, I haven't heard very many serious audio systems play this scene). I wish I could listen to this scene on both receivers in the same room with the same gear. But my prediction is that they're going to be pretty close.