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Re: Another Mini Review – Yamaha RX-V661
Mojo #168401 05/20/07 05:37 PM
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Hi Mojo and mdrew,

I suspect it's a thermal sensor that's shutting down the Yamaha when it gets really hot. But it could also be a current sensor into the output stage: when the low impedances of the M80s and paralleled M22s demand more current from the power supply, it senses that and, since it can't supply it, it just shuts down.

As to your Denon, Mojo, it may have a kind of "soft clipping" circuit in its output stage that rounds off the clipped square waveform and lessens the clipping distortion. It's a trick that NAD has used for years on its amplifiers which prevents the amplifier from producing the harsh, edgy distortion of a hard-clipped signal. Don't get me wrong; it's still distorting, but it's not as irritating as it would otherwise be without the soft clipping circuit.

One of the Denon AV receivers that we measured (actually, Tom Cumberland, Axiom's electronic engineer, did the bench tests) at Axiom's lab produced exactly its rated output into 8-ohm loads and the same output into 4-ohm loads. Class A/B amplifiers normally would produce much more output power into 4 ohms than into 8 ohms, so we concluded there was a circuit in the Denon that "clamped" or limited its current flow into a 4-ohm load and even when you turned it up, it wouldn't get louder. So in effect, it was a built-in limiter that prevented the Denon from going into hard clipping when presented with a 4-ohm load.

Of course, although your Denon doesn't shut down, it's still a limiter, preventing the true dynamics possible if you had a much more powerful separate amp.

I know my H/K AV receiver runs out of juice driving my 4-ohm M80s at high concert levels with really dymamic classical music. It doesn't overheat or shut down into 4-ohm loads, but on really dymamic material, the loudest orchestral peaks get a bit edgy and compressed . I think it's likely some kind of soft-clipping circuit in action. Can't wait until I get my own sample of the new Axiom multichannel amp.

Regards,


Alan Lofft,
Axiom Resident Expert (Retired)
Re: Another Mini Review – Yamaha RX-V661
alan #168402 05/20/07 05:47 PM
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Alan,

I suspect you're right about the soft-clipping circuit in the Denon. It certainly sounds distorted when it's cranked to the max but it's not nearly as bad as my old two-channel Yamaha. When the Yamaha was cranked, the sound of saw-toothed waves was unmistakable. I ended up blowing a fuse in my old Bose 601s because of that stunt.

Re: Another Mini Review – Yamaha RX-V661
Mojo #168403 05/20/07 05:53 PM
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Further to my comments above, our testing of the Denon AV receiver and a few others was during the period when we were considering taking on the Sherwood Newcastle line. The Sherwoods we bench tested did not show the same characteristics when driving the 4-ohm loads. They produced more output power into 4 ohms and didn't current-limit the power-supply stage into low impedances, so long as you didn't drive them beyond their stated limits. This aspect of the Sherwood's amplifiers really impressed us, which is why we decided to carry the line.

Regards,


Alan Lofft,
Axiom Resident Expert (Retired)
Re: Another Mini Review – Yamaha RX-V661
chesseroo #168404 05/20/07 06:33 PM
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Quote:

Quote:

And with the pre-outs, it would make a fine pre / pro to go along with the A-1400 (at least that’s what I’m thinking right now)



You know someday when i'm back in the Yukon, i'm going to take a sidetrip to Alaska to see this growing setup that you have.
Then i may have to rob you blind.




Bring some wine with you and I'll have the lil lady whip up one of here five course gourmet meals. If you want, take some of these damn Bogal indian prints hanging on the walls. Someone got a bit carried away with them.....

and bring that fancy switcher of yours. we'll do some drunkun blind wine testing.

And if you wait another couple weeks, I'll have my new modified Oppo 981. I'm having an SDI video output card installed. I'm pretty curious to see how it compares to my Oppo 970. {480i 4:2:2 via sdi verses 480i 4:4:4 via hdmi into the VP-50}

Re: Another Mini Review – Yamaha RX-V661
michael_d #168405 05/21/07 06:52 PM
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Got around to doing some more testing / listening after everyone vacated the house this morning.

I decided to forgo the earmuffs so that I could listen for straining and clipping better. I turned the sub off and set the receiver to pure direct stereo with the M80’s set to large and LFE to the front.

I put DSOTM back in and gave it a whirl. Although this a great sounded CD, it isn’t very dynamic, or loud. That being said, I was able to pin the volume on the receiver without it shutting down. Peak DB’s were 110. That’s the positive. The negative is it sounded like crap. Sound quality started to go south at -10 db on the volume control which was an average db of 95 with peaks to 100. After around 95, I could noticeably tell that things just sounded strained, not clear and the mids just lost their slam. As I turned the volume up, it just kept getting worse. I didn’t leave it pinned for but a few seconds for fear of long term hearing loss and fear that it was screwing up my drivers. At full volume the average DB was 104 db with this CD. The track I used was “Time” and I didn’t crank it till after all the clocks were done ringing.

After DSOTM, I put in one of my favorite new disks. Carbon Leaf, Indian Summer. I think Mark Johnson would even approve of this disk. It’s mastered well for an Alt Rock type CD. Plus, I just like the music and if I’m going to go deaf listening to something, I want to like it. The second track “What About Everything” has a lot of vocals but also has some pretty dynamic drums and guitar. This track has about an 8 DB range. Not so surprising, it sounded very good till the average db was about 95 with peaks around 103. Clarity and detail just started to fade into a muddled mix of crap and even at this volume; the peaks were starting to loose clarity and slam. I didn’t even try to pin the volume with this CD – what’s the point? Out of morbid curiosity, I still bumped up the volume to where the average was 105 db’s with peaks around 112. This was at a +5 of a max +15 on the control knob. It did not shut down, but again, I did not leave it there for but a few seconds. At no point during any of this foolery did the speakers go into a hard clip. The music just sounds like crap.

Seeing how my ears were already buzzing, I decided to pop this CD in my two channel rig. This one has a Rotel RB 1080 / RC 1070 comb driving a pair of Wharfdale Opus 2’s in a 32’ X 28’ space with vaulted 22’ ceilings. Ya I know, completely different speakers and electronics, but I was still curious. At about 7/8 volume, even though it was very loud (114 – 120 dbs) and it was hard to not wince, sound quality was starting to degrade. I did not try to pin the volume for three reasons 1) sound was degrading 2) it was simply too dam loud 3) my neighbor across the street was giving me a really bizarre look. Now I’m wondering if I need a different amp for this set up another set of M80's because I could pin the volume when I had them in this room.

So for you engineer types, here’s the specs off the Yamaha for you to ponder and speculate over.


AUDIO SECTION
• Minimum RMS Output Power for Front, Center, Surround,
Surround back
20 Hz to 20 kHz, 0.06% THD, 8 Ω ...................................... 90 W
• Dynamic Power (IHF)
Front L/R, 8/6/4/2 Ω ..................................... 120/155/190/235 W
• Maximum Useful Output Power (JEITA)
[Asia, General, China and Korea models]
1 kHz, 10% THD, 6 Ω ....................................................... 130 W
• Maximum Output Power [U.K., Europe and Asia models]
1 kHz, 0.7% THD, 4 Ω ...................................................... 140 W
• Dynamic Headroom
8 Ω ....................................................................................... 1.4 dB
• IEC Output Power [U.K., Europe and Asia models]
Front L/R, 1 kHz, 0.06% THD, 8 Ω ................................... 100 W
• Damping Factor (IHF)
Front L/R, SPEAKERS A, 20 Hz to 20 kHz, 8 Ω
.................................................................................. 120 or more
• Input Sensitivity/Input Impedance
PHONO (MM) ........................................................ 3.5 mV/47 kΩ
CD, etc. ................................................................. 200 mV/47 kΩ
MULTI CH INPUT ............................................... 200 mV/47 kΩ

Re: Another Mini Review – Yamaha RX-V661
michael_d #168406 05/21/07 09:34 PM
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Your Yamaha isn't much different than my low-end Denon. Actually, it's dynamic rating is higher than my Denon. You should be pretty happy with it as it provides you with more than enough power.

I wouldn't spend any more money on the 2-channel rig. Save up and buy an EP600 instead .

I am curious how you like the Wharfedales in comparison to the Axioms.

Re: Another Mini Review – Yamaha RX-V661
Mojo #168407 05/21/07 10:32 PM
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Quote:

Your Yamaha isn't much different than my low-end Denon. Actually, it's dynamic rating is higher than my Denon. You should be pretty happy with it as it provides you with more than enough power.

I wouldn't spend any more money on the 2-channel rig. Save up and buy an EP600 instead .

I am curious how you like the Wharfedales in comparison to the Axioms.



Mojo -

Mike already has an EP600!

Re: Another Mini Review – Yamaha RX-V661
Sutter Cane #168408 05/21/07 11:09 PM
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Uhmmm...I meant yet another EP600 .

Re: Another Mini Review – Yamaha RX-V661
michael_d #168409 05/22/07 01:27 AM
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Mike, it hasn't been mentioned yet, and in case you haven't studied it, here's the lab report and review on the 661 from the new June S&V(presumably you also set the impedance to 8 ohms rather than the lower setting).


-----------------------------------

Enjoy the music, not the equipment.


Re: Another Mini Review – Yamaha RX-V661
JohnK #168410 05/22/07 01:41 AM
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sounds like a pretty good receiver..

Would this receiver be likely to shut down when powering the 6ohm vp150 and 2 qs8's combined with m60s and ep 500; or could I crank these speakers up to their full potential with this receiver?


-David
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