Home Theater A/V Receiver & Amp Help Needed

[Cpt_John]

I was in the process of completing a home theater setup this weekend when my new Denon A/V Receiver crashed. It made it through one movie and about an hour of television watching the next day before it shut itself down (at very moderate volume levels) and I could smell a "burning smell". I do not believe there are any shorts in the speaker wiring. The Denon is a model AVR-2808 (110Wx7) that was an open box buy. I am fortunate that my retailer had a new floor model (recently opened) that I was able to swap it for. I am using it in a 7.1 system with KG 4's as my front left/right with a C-6 center channel and the large Klipsch dispersion speakers as surrounds. Before I hook up the replacement receiver my questions are:

1) What do you think would cause the first receiver to crash (i.e. overloading, fluke, etc.) and is this common?

2) Do you believe I am overloading the receiver's amp trying to run all 7 channels even though I could hear no distortion, etc. and was only using moderate volume levels?

3) I was previously driving the front KG 4's with and older Nakamichi TA-3 (75Wx2) with its internal STASIS amp and never had any issues (at much louder volumes). That receiver is capable of using it as an amp only. Would I be better of using the front L/R pre-outs on my Denon 2808 to feed into the Nakamichi TA-'s amplifier to drive the Klipsch Kg 4's or would just continuing to use the Denon's internal amplifier be just as good or better?

4) Are there any other A/V receivers in the same price range as what I paid for the Denon AVR-2808 (<$400) that would be a better choice for my setup? (I chose the Denon mainly for its bargain price on a normally $1200 MSRP receiver).

Thank you in advance for you replies!

[Youthman]

The Denon is definitely capable of driving 7 speakers at the same time. My guess is just a fluke or manufacturer defect (assuming that you had everything hooked up correctly and no shorts in the wires).

[InVeNtOr]

agree with youth, i wouldn't think anything was hooked up wrong, if you did, you would have found out real quick. if something shorted, you should have seen some kind of spark.

your "open box" buy was a dud. that receiver shouldn't have any issues powering klipsch speakers.

if you want a different AVR at that $400 price, i would suggest the onkyo 805. i have it. i am happy. does the job very well. not much of a CD person, just HT in my house. i use an emotiva lpa-1 amp to power the front 3 and the onkyo powers the 4ea RS-42's. it's overkill on the onkyo's part, (130w X 7, powering 4ea RS-42's @ 75w each).

[Cal Blacksmith]

For just a few $ more, the Yamaha RX-V663 is a very nice unit. I love the heck out of mine.

[Cpt_John]

Thanks for the replies!

It looks like the opinion is that my receiver "crash" was just a fluke and that it should normally drive the speakers without a problem.

I will plan on just hooking up the replacement Denon 2808 unless I read another reply that recommends against it.

Thanks again for your help!

[Fish]

It may be a good idea to confirm elec supply is not overtaxed,cables etc..are all good.If you feel that's all good,the Denon should be capable,as a rule they are sturdy radios from 28xx unit up.

[carbon summit]

For just a few $ more, the Yamaha RX-V663 is a very nice unit. I love the heck out of mine.

I agree. Very happy with mine.

[carbon summit]

if you want a different AVR at that $400 price, i would suggest the onkyo 805. i have it. i am happy. does the job very well. not much of a CD person, just HT in my house. i use an emotiva lpa-1 amp to power the front 3 and the onkyo powers the 4ea RS-42's. it's overkill on the onkyo's part, (130w X 7, powering 4ea RS-42's @ 75w each).

I've been thinking of adding a three channel amp for my Forte II/Academy/Forte II front and using the Yamaha to power the rears. Did you notice any real improvement in sound quality and dynamic range? I have everything set to small and have subs for HT so I' m not really taxing the Yamaha when I watch movies. I'm more thinking of when I listen to music giving the Forte IIs a little more juice might really wake them up.

The Yamaha 663 is 95 watts x 7. I'm thinking of putting a pair of Forte IIs in for surrounds so then I'm thinking the Yamaha will have less work to do. Regardless of what its rated per channel it shares the same power supply with each amp inside of it. Thinking less amps drawing on that current pool means better results. I could be wrong. This could be another justification to spend money on AV stuff.

[wuzzzer]

I had a Harman/Kardon two channel integrated amp and added a Rotel two channel power amp using the H/K as a pre. I didn't notice a difference in sound quality, rather a difference in sound quantity. When I bought a Rotel pre-amp I noticed a huge difference in sound quality. I think a pre-amp makes a much bigger sound quality difference than the amp does.

[carbon summit]

I went with the Yamaha because in doing my Google based research I found a lot of people were buying them to use as cheap pre/pro's.

To buy a "real" pre/pro with all the surround sound stuff was so much more expensive I knew I'd never buy one but I'd try the Yamaha as my primary source of power and if it wasn't enough then it was comforting to know that it was easy to add amps down the road. I don't know if the Yamaha isn't producing enough power for me as much as I'm curious what results the next step will bring. What am I missing?

[carbon summit]

I emailed a Rotel dealer that is in my area and this is what he said about using an external amp vs the Yamaha as the source of power:

Jeff,

Like I said when we spoke, the RMB 1066 in bridged mode is 150 watts rms for 3 channels.

The RMB-1075 100 rms x 5 is $999.00 and the RMB-1095 200 rms x 5 is $1999.00.

It's not the power that will impress so much as the quality of the sound. Any of the above will be infinitely preferable to the internal amps in the Yamaha.

Thanks,

Rick

Truth or saleman talk?

[htxpert]

You may want to consider this when
talking about amplifier power ratings. Doubling the amplifiers power will
produce a very minimal net 3 dB gain which is only slightly louder than not
doubling it. I seriously doubt you have a hard time driving any of the Klipsch
offerings even with a receiver capable of 75 watts per channel. Many believe that adding an addition power
amplifier and using a receiver as a pre amp is a good idea to gain amplifier
head room when this could be a major step backwards depending on the receiver
pre amplifier. Some receiver’s pre outs
have a very weak output voltage say around 2 volts or so before clipping.
Ultimately a pre amplifier should be able to output 4volts or more without
clipping to effectively drive an amplifier to full power without adding any unwanted harmonic
distortion.

[carbon summit]

Some receiver’s pre outs have a very weak output voltage say around 2 volts or so before clipping. Ultimately a pre amplifier should be able to output 4volts or more without clipping to effectively drive an amplifier to full power without adding any unwanted harmonic distortion.

I thought the gain on the amp is what adjusts for this? I googled and found this which kind of says what I thought was true:

http://www.installer.com/tech/preamp.html

Not to say that everything on the net is true of course but this is how I always understood it.

[htxpert]

This is dependent on the amplifier some like the Emotiva can be driven to full power with as little as 2 volts RMS while many others, Kinergetics and Newcastle come to mind require more input voltage to achieve full power. It would be very easy to make a mistake and many do by selecting the wrong combination of receiver and amplifier for use as a pre/pro. For example just off the top of my head using older Yamaha’s that predate the RX-V2600 and Kinergetics THX amps would be a poor combination.

[carbon summit]

I checked on Rotel's website and thier pre/pros only put out 1 volt as does my Yamaha 663 so I should be in good shape with Rotel amps I'd think.

[nzorn]

For just a few $ more, the Yamaha RX-V663 is a very nice unit. I love the heck out of mine.

It's a nice receiver, my dad just bought one. I have the RX-V3900, but that's out of your price range.

http://www.6ave.com/shop/Product.aspx?sku=YAMRXV663BL

Use aflaud25 coupon code and get it for $375 shipped.

[htxpert]

Carbon,

Where did you get the 1v rms specification for the 663
preamp output? It is my understanding that the 663 outputs 4-4.3 volts
rms without clipping or harmonic distortion. Mabye I am thinking of the 863 or 1900?

[carbon summit]

If anyone is considering buying a current Yamaha receiver I'd wait until March. The new models come out then so you can either get the latest and greatest or pick up a deal on the closeouts of the older line.

[carbon summit]

Page 128 in the 663 manual.

[htxpert]

Here is a good reference regaurding preamp output voltage written by Gene at AH and this is exatly why you have to be cautious.

Preamplifier Tests

Frequency Response



The frequency response out of the preamp
was ruler flat in the audio band (20Hz to 20kHz +-0.1dB) with a -3dB point around 120kHz.
I also
observed no measurable difference between "Straight" and "Pure Direct".

FFT Distortion Analysis

When the analog preamp was driven at 1Vrms (typically ½ signal strength to achieve ½
of max power of most power amps with voltage gain of 29dB) distortion levels were (+0.497 + 88.955 =
89.452dBv) or 100*alog(-89.452/20) = .00337%
This is certainly a commendably low
distortion
figure.

At 2Vrms, the preamp section of the RX-V4600 faltered.
This is because Yamaha
was likely using only a single rail 5V supply for the preamp section. I
would prefer to see a preamp have the ability of driving 2Vrms
undistorted to accommodate a wider assortment of power amplifiers.
Though this didn't present any audible nasties when I used the RX-V4600
as a preamp to my
Emotiva MPS-1
power amp, my advice here is to choose a power amp that can achieve
maximum power output with about a 1.5Vrms input should you decide on
buttressing your system with external amplification.

Signal to Noise Ratio

• 
  The Inputs can handle 3Vrms unclipped!
  
• 
  Outputs Deliver nearly 2Vrms output unclipped! But FFT distortion becomes very
  high once output exceeds 1.5Vrms.
  

Ch-A Signal to Noise Ratio (SNR)

• 
  
  
  -106.85 dB below 4.23 dBV
  Reference Level (at 0.10 %
  THD+N)
  
  
• 
  
  
  <
  10 Hz - 22k Hz bandwidth , no option filter and no weighting
  
  

With a 200mV Input Signal, I adjusted master volume for 1Vrms out, preamp gain
(Av=5 or 14dB), I measured as follows:

• 
  18.5dBrA with signal
  
• 
  -74.6dBrA without signal
  
• 
  SNR: 93dBrA
  (commendable performance for a preamp at any price
  class)
  

RX-V4600 Power Amplifier Tests

Frequency response uniformity over all power levels was excellent (within +-0.1dB
from 20Hz to 20kHz).

RX-V4600 Distortion Tests

of Channels	8-ohms > 0.1% THD	8-ohms > 1.0% THD	4-ohms > 0.1% THD	4-ohms > 1.0% THD
RX-V4600 1 CH	134 wpc	144 wpc	210 wpc	225 wpc
RX-V4600 2 CH	116 wpc	128 wpc	175 wpc	184 wpc
RX-V2500 1 CH*	NA	146 wpc	NA	199 wpc
RX-V2500 2 CH*	NA	135 wpc	NA	119 wpc

*Line voltage was lower during testing of the RX-V4600 which accounts for the
negligible edge to the RX-V2500 in 8-ohms.
We did not test the RX-V2500 at 0.1% distortion so
those measurements are unavailable.

Upon first inspection it would appear the RX-V4600 delivered similar
power measurements to the RX-V2500 (see
measurements and analysis
), until you take a closer look at the RX-V2500 power into 4-ohm loads.
In the case where 2CH are driven into 4-ohms, the RX-V4600 delivered
184wpc @ 1% THD (onset of clipping) while the RX-V2500 delivered about
119wpc under the similar testing conditions.
What's most impressive is the RX-V4600's apparent better handling of
low impedance loads when compared to the lower priced RX-V2500 as can
be seen in our output impedance and damping factor measurements.

RX-V4600 Signal to Noise Ratio Tests

With 200mV in and 2.82Vout into an 8-ohm load,

• 
  <
  10 Hz - 22k Hz bandwidth , no option filter and no weighting

Measured at 1 watt:
200mV input:
Master Volume: -3.5dB

• 
  At 1 watt: -21.69 dBrA
  
• 
  At idle:
  -103.46 dBrA
  
• 
  SNR:
  
  81.7dB at 1 watt
  
  This is very good
  performance