Could a lower power amp actually be "better" ? (1 Viewer)

[JohnSer]

Kevin,

OK, FWIW, I went and tried this on my set-up. HK520 as pre/pro, Adcom 545II amp, and custom Peerless HDS439/Seas T25 speakers (about 84db/watt).

Test #1, Power amp on and receiver in standby
results: ear right to speaker - nothing from mid-woofer and just the very slightest hiss from tweeter. Confirmed with modified RS SPL meter. Getting only the slightest deflection at the most sensitive setting.

Test #2, Power amp on and receiver is off
results: same as above

Test #3, Power amp on and receiver is on, vol at min, source set to CD, which is using optical connection, CD player is off
results: ear right to speaker - very slight hum from mid-woofer, nothing detected from tweeter. Confirmed with SPL meter. Getting only the slightest deflection at the most sensitive setting.

Test #4, Power amp on and receiver is on, vol at -10 setting(very loud setting, I never listen at that), source set to CD, which is using optical connection, CD player is off
results: ear right to speaker - very slight hum from mid-woofer, nothing detected from tweeter. Confirmed with SPL meter. Getting only the slightest deflection at the most sensitive setting. This was a surprise, and will check latter with spl meter. I was expecting increased hiss. I suspect it is because the digital source, and because there is no bitstream lock, the receiver is muted. I will try an analog input, to see if that has different behavior.

PS: RS SPL mods are the ones on Eric Wallins site. It makes the meter more sensitive. Just touching the case or breathing can peg needle.

PSS: Ear was within an inch or two from driver. SPL meter within 1/2 inch of driver.


Gain: I pulled out service manuals for Adcom 545II (100W/8) and Adcom 555II (200W/8). Gain on both is 27db, all noise figures favor the higher output 555II. Both at each respected full output. What does it mean? Don't know, but don't have a 555II to plug in.

 

[Chu Gai]

Let's examine two hypothetical amps.
a) 10 wpc with 90 dB s/n
b) 500 wpc with 100 dB s/n

a is quieter. a, which is 10 watts, is 10 dB above one watt and b is 27 dB above one watt. S/N is the # of dB that the noise is below the full output. Although b has an output that's 17 dB greater than a, it put out about 7 dB more noise despite it having a better S/N.

Now if this noise is something that's only noticeable with no source playing and your ears fairly close to the speakers, I'd consider this a non issue and maybe your amp decision should be predicated on possible future plans which may involve different speakers in a larger setting.

 

[Dennis Gardner]

Kevin,

Do you drive your car at 85% of redline no matter what speed or gear you are in? I know that in Nascar they gear to keep their engine in the powerband which is around that 85% number in top gear.

My kids drive their rice burners this way cause their 5 inch muffler sounds better.

I would prefer the 40% method to leave ample room for those bursts in a digital soundtrack that seem to be more than 15% increase above the dialogue level.

DG

 

[Kevin C Brown]

Dennis- But remember, for now, I', assuming I'll never peg the smaller amp. (I *will* keep an eye on the LEDs. I need to ping Bryston as to what THD % they change color. I would assume 1% but obviously I have no idea.)

I think Chu is on to something. A higher power amp can have a better s/n but still have a higher noise floor. And yes, all of my own test were with my ear right up against the tweeter. The quietest amp I ever owned was that Nakamichi PA-5AII. Not only was my ear right up against the tweeter, but I had to angle it just *so*, to hear anything at all. I still have to do this test with the 4b-st and the 5b-st that's coming.

JS: does sound like your digital input is being muted. Let me know if you try an analog input. Would also be neat if you could compare from the H/K directly with the Adcom. I'd bet 50 cents the H/K is quieter than the Adcom.

 

[JohnSer]

Kevin,

I not sure how much work I am willing to do for 50 cents To test the HK will require getting into a rats nest, and moving speakers wires around.

I am not convinced that the hiss present is all amp noise. If I can find or quickly make some grounded input jacks, I'll see. It is easy to get behind the amp compared to the HK. The fact that it changes, with pre/pro powered on, indicates that it is at least not the only component. Given how hard it was for me to detect it, with ear up against driver, and the slightest ambient noise over-powered it (like when the furnace circulator pump was running), I wouldn't make an amp decission based on it.

I will try an analog source tonight, that easy.

The S/N figures are labeled as A-weighted. I don't know if that means full signal. Both of the Adcoms, according to service manual says > 110db. The HK manual says 95db IHF-A, which I assume means A weighted.

 

[John Kotches]

Mike Wilk said this a couple of days back:


You've confused human perception of output power vs the physical reality of the amplifiers operation. 200w is indeed twice the output power.

How you perceive the 3dB difference is another issue altogether.

 

[Chu Gai]

Kevin, this might be a good time to get off the floor and just pick the one you think is going to be with you for some time. Of course you can always try and find more info regarding data that represents noise as a function of output power but maybe that's getting into the point of diminishing returns. When in doubt, ask your girlfriend which one she likes and then pick the other.

 

[Felix_H]

 

[Kevin C Brown]

She wants the cheaper one.

 

[Felix_H]

Thats why you get the more expensive one like Chu says!

Thats the law of Home Theater.

 

[Kevin C Brown]

I have learned not to tell her the actual cost, unless I'm getting a big enough discount that she focuses more on the great deal I got, vs the absolute cost.

 

[Chu Gai]

There is a law of weighting things objectively here Kevin. If you're married, you might have to take the cheaper one unless you can demonstrate to her that the cost differential is outweighed by by something like her makeup expenditures. If she's your girlfriend, and I'm sure you love her dearly, go with the more expensive one especially if you're not living together. In the end, the one you want is usually the more expensive one although we try and rationalize it away. Consider the person who is looking at something like Studio 40's and Studio 100's. He's there scratching his head. He really wants the 100's so what does he do? He posts on forums like this looking for owners of the 40's that're going to wax poetically about that model. He'll mentally justify the less expensive one by rationalizing the drivers aren't that different and so forth. After a year or so, he'll be back here looking to upgrade and he will. He'll now rationalize the fact he's got to sell the 40's at a loss.
If it's the Bryston's Kevin, maybe they're cheaper to buy in Canada. Cut a deal with the signficant other and take her on a mini vacation to Canada with the thought you're going to save some money on the model you really want. A nice dinner, some sight seeing, romantic nights...

 

[John-Tompkins]

Kevin,

I still dont understand why you dont get the Lexicon versions of the Brystons (and buy used)..you could save a BUNDLE of money and get the same identical amp..Take a vacation with the funds that you saved or put it into another part of your system.

PS..your probably gonna mention the warranty differences between the lex and bryston, but more then likely you wont ever have a single problem with these amps anyhow.

 

[Charles Gurganus]

John, what are the Lexicon model's that are considered Bryston clones? Are these discontinued older amps? Thanks.

 

[John-Tompkins]

Hey whats up Charles !

The lexicon clones are discountinued now, as of a year or two ago (They do however carry a 5 year warranty).When service is needed Lexicon has them sent to Bryston. They are identical in every way except the faceplate of course and the Lex's are THX certified (because they have a trigger on them)

Lexicon 5 channel NT512 = Bryston 9BST
Lexicon 3 channel NT312 = Bryston 5BST
Lexicon 2 channel NT212 = Bryston 3BST
Lexicon 2 channel NT225 = Bryston 4BST

 

[Ricky T]

I'm Kevin's girlfriend, on email at least , and tried to convince him not to spend so much money (on new, sealed Bryston STs).

Charles,

The Lexicon NT series were rebadged Bryston ST amps with a 5 year warranty (instead of 20 years). Of course, Bryston will service them for a fee after the 5 year period. The models were: NT225 250x2, NT212 125x2, NT312, NT412, NT515. Going rate for used NT 125 wpc amps is ~ $320 per channel compared to ~ $400 for used Bryston STs. For example, a used 9b-st goes for 2000-2100; a used NT512 goes for 1700-1800 (what John paid).

 

[Ricky T]

Charles,

Here's an NT312 that might go for ~1k. While these are rated 125 wpc, they test at 160 wpc. Remember Corey Greenberg with his NHT 3.3s? Corey used to drive his 3.3s with an Aragon 4004mkII 200x2 before getting a Bryston 9b-st (aka NT512) to drive two pairs of 3.3s and one AC1.

http://cgi.audiogon.com/cgi-bin/auc....80727&auc&3&4&

 

[Charles Gurganus]

VERY tempting Ricky.

The upgrade bug is like a desease, we could make a movie about it and call it, "28 Components Later"

I am not looking to trade in my Sherbourn just yet but I do have a SVS PB2-ISD sub coming soon.
With that in mind, I may find myself not needing to biamp those VT2's with 2 200 watt channels. That is yet to be determined. If my system sounds better with all speakers crossed over at 80hz, then shooting 200 watts to the VT2 woofer would be wasted. Soooooooooo that did get me thinking about amps down the road.....

 

[JohnSer]

Kevin,

The only thing I had a chance to test, was an open analog input. The receiver was switched to one of the unused video inputs, that has a default setting of analog. No device was attached to the inputs. The results were very similar to the prior test. The hiss/hum might have been slightly louder, but I didn't try to measure, last night. It did not increase in volume with the volume control, just like the previous test.

 

[Felix_H]

And to those looking at the 3 channel Lexicon for auction.... on Ebay there is the 3 channel Bryston 5B ST.

Theres going to be 2 lucky owners!