What is a high current amp??

[Zen Traveler]

Does any of the information I provided give a sense of the quality of amplifier it is in regard to running the speakers in my Home Theater (2,000 cu ft) listed in my sig? [^o)]

Preamplifier

Maximum RMS Output Voltage at Pre-Out

6.34 volts RMS

10 Points

We prefer at least 1.0 volt RMS, and 2.0 volts RMS is best. The AVR-4806 has outstanding voltage output. The maximum pre-out voltage was obtained using 1 kHz analog input, 2.44 volts RMS output from the sound card, and a volume setting on the AVR-4806 panel of +11.0 dB.

Power Amplifiers

2 Channel Maximum RMS Power Output

182 watts x 2; 0.14% THD; 2.44 volts RMS input

10 Points

To get the full 10 points, the 2-channel maximum output must be at least 30% above the rated output for all channels driven. This would be at least 169 watts per channel for the AVR-4806. This capability is tested with a variable transformer that keeps the input voltage at 120 volts when the amplifier is delivering its maximum output.

7 Channel Maximum RMS Power Output

114 watts x 7; 0.06% THD; 2.44 volts RMS input

0 Points

Output with all channels driven must be at least 95% of rated output, when testing with a variable transformer that keeps input voltage at 120 volts. For the AVR-4806, this would be at least 123 watts per channel (the 4806 is rated at 130 watts RMS x 7).

[pauln]

I see, you meant the amp won't burn up when it plays peaks of some duration...

guess that would allow the amp to survive passing DC to the unfortunate speakers when the Green Day CD's signal hits 1111111111111111

http://www.hydrogenaudio.org/forums/lofiversion/index.php/t28711.html

[Zen Traveler]

I forgot there were some graphs on the Denon AVR 4806 Benchmark Test:

http://www.hometheaterhifi.com/volume_12_4/denon-avr-4806-receiver-12-2005-part-6.html

.

I don't know what I'm looking at but the dudes comments looked good. [8-|]

1) Does this AVR look like a good match for my RF-7 based HT?

2) Are those numbers comparable to lower end AVRs (pre $1,000)?

Any help would be appreciated.

[mas]

I'm a bit confused as to what magic quality you are looking for...(but that's OK, don't tell me...) []

It will work fine!

[DrWho]

And then there are Class D amps. While most "ideal" Class A or AB amps double their wattage as impedance is halved (500W into 8 ohms, 1000W into 4 ohms, etc.), even high-end Class D amps don't. 500W into 8 ohms, 650W into 4 ohms is more typical. Could this be caused by an inadequate power supply, or is it just the nature of that amplifier type?

If you think of amps as voltage amplifiers (which is what they are), then you'll find the answer to your question in the fact that current is the reason for thermal failure (which is the limiting factor in this case).

[Arkytype]

Garyrc---

1) Your continuous average sine wave power (CASP) would be 171 watts (just below clipping). That's about 13% above the rated output. Depending upon the program material, the actual peak power would be higher on short transients.

2) I'm not sure if you meant RMS instead of ROMS. A root mean square value as applied to a voltage is derived by taking the square root of the mean of the sum of the squares of a voltage. A true RMS voltmeter will sample the positive and negative values of a waveform, square each sample, add the squared values together, compute the average (or mean) of all the squared values, divide the sum by the number of values squared and finally, taking the square root of the last step. Simple, huh?

The primary advantage of a true RMS voltmeter/ammeter is that the result is independent of the shape or symmetry of the waveform and that value can be used to compute the average power or DC heating equivalent of a load.

3) Bob Crites correctly answered this point.

Are you looking for this type of 30-ampere receptacle?

http://www.internationalconfig.com/icc6.asp?item=L530-R

IMHO that's overkill. Be aware that the National Electrical Code requires you to run #10 wire for a 30 ampere circuit. You can't legally use #12 wire which is rated for 20 amperes and connect it to a 30 amp receptacle. Also the circuit breaker has to have a 30 ampere rating as well.

I'm installing 20 ampere receptacles in the house I'm building and wiring with # 12 wire. A 20 ampere receptacle has a little more metal where the plug mates compared to the usual 15 ampere receptacle. For you, I'd recommend asking for 20 ampere service with an isolated ground receptacle (usually orange). Bring the ground wire back to the service entrance without tying in to any other ground and connect to the grounding bus bar. That will help system noise and interference from other household appliances.

Lee

[garyrc]

Lee,

Thanks for your reply!

RMS is sure reminiscent of the Standard Deviation in statistics, which, as you probably know, is the square root of the average of all the squared deviations from the mean, with the squaring apparently done for the same kind of reason, to avoid the positive and negative values summing to a useless 0. In stat, the final square root is to return the value to a size that makes intuitive sense within the data set. If one does nothing at the end to undo the squaring, what you have is a variance, which has its own uses, but is intuitively unsatisfying.

I'm surprised that manufactures don't all flock to using CASP, since the power figures would look higher than with RMS.

[oldtimer]

Refresh my memory Gary, is variance the same as rsquared?

[garyrc]

Oldtimer,

I'm not a real expert, but;

Many things go under the term "Variance."

The most commonly seen one may be "the average of all squared deviations from the mean." The square root of that is the Standard Deviation. There are specialized forms of both for estimating population values from samples, with slightly different formulas, e.g., with N -1 as the divisor to get the average of squared deviations, instead of N.

If "r" is the Pearson correlation coefficient, then "r squared" is the proportion of variance [some would prefer the word "variation"] "explained" by the correlation. If the correlation between two variables is 0.50, then the proportion explained is 0.25, or 25%. "Explained" -- that's a good one -- it doesn't by itself imply causality, only that it is the the part of the association that is not error variation (in social, behavioral, and medical science, most people would say one can't infer causality -- instead of mere association -- unless there is an experimenter manipulated independent variable and random assignment to conditions -- most are happiest with double blind and other refinements)

There are specialized uses of the word "Variance" as in Analysis of Variance (ANOVA) in which the variance is split apart (in the simplest case) into

variance within groups vs. variance between groups.

Then there is "homogeneity of variance" as in the homoscedasticity one looks for in scatter diagrams, the similarity of scatter of the dots along the length of the regression line (rather than them forming a bowed shape, say). This seems to be vitally important to some people, and not to others. At SFSU, there was a little man with a briefcase who would show up about twice a semester to offer his services in examining one's data ... he earned the name "Mr. Homoscedasticity,"

[oldtimer]

Got it, thanks. I was thinking of the Pearson correlation coefficient.

[MrMcGoo]

tkd,

As receivers go, your Denon is way above average. However, the wattage figures given are likely for 8 ohm load resistors. The issue would be easier to analyze, if 4 ohm and 2 ohm figures were given. Per Ohm's law, when impedance falls in half, current requirements double to maintain a fixed voltage (fixed SPL level). If the current does not double, then frequency response suffers as the proper voltage cannot be maintained.

The bottom line on any receiver is to run all speakers as small. The bass frequencies are much more demanding than high frequencies, i.e., more wattage is require to play 100 Hz than 10,000 Hz at a given SPL. Subwoofers usually have their own amps, so spreading the load between the receiver and the subwoofer is an optimal strategy, when the sub(s) is/are properly integrated.

Bill

[Guest " "]

I like the explination provided in the attached PDF.

In one sentence....a high current amplifier is an amplifier that can drive low impedance loads......drive in the sense of power...that means watts...so yeah...it's a high wattage amplifier at low impedances.

high%20current%20amps.pdf

[michael hurd]

You can replace "watts" with high voltage source that can also deliver high current. Amps are voltage multipliers, and when given differing loads, the current flow changes, but the voltage gain stays the same. As the load impedance drops, current rises.

Amplifiers don't make more "watts" at low impedances, but they do put out more current. Adequate heatsinking, multiple output transistors, and low output resistance are factors in an amplifier's load tolerance, as well as having a good power supply.

[Guest " "]

Thia is going to be one of those threads that will  run forever, below, my SS map, has a different "watts" or "power" rating as the load drops.....the "watts" or "power" does not stay the same.  I don't know how to compute "watts" or "power" with out using a variable for current.   Maybe some examples would be helpful that would show how current can increase independent of "watts" or "power".  It would be very interesting to include a fuse value for each impedance step.

 

Amplifier Section
Power Output* (8 ohm, 20 Hz-20 kHz, FTC)
Front L/R		150 W/Ch
Center		150 W
Surround L/R		150 W/Ch
Surround Back		150 W/Ch (L/R)
Power Output* (6 ohm, 1 kHz, FTC)
Front L/R
Center
Surround L/R
Surround Back
Dynamic Power** (front)
3 ohm		340 W/Ch
4 ohm		260 W/Ch
8 ohm		175 W/Ch

[pocket.change]

Per the question and for the investment, consider a Pioneer SX1250.

Covers the question without "question".

Will a Denon (whatever) have the value of a Pioneer SX1250 in the future (i doubt it)?

pc

[Zen Traveler]

why bother

Ouch! [:S] I appreciate the responses and gave it my best shot at trying to understand how it pertained to my situation. Unfortunately I suck at math, but it did help. ;-)

On a side note, I got in deeper than I felt comfortable on this thread concerning Klipsch speakers, Separates and AVRs : http://www.avsforum.com/avs-vb/showthread.php?t=882655 and was trying to learn more about the topic. {edit: I am NOT the OP in the linked thread}

I can see where Separate amplification may be beneficial, but I was also trying to confirm that all AVRs are not alike.

Btw, thank you also Mr. Mcgoo.

[Guest " "]

Per the question and for the investment, consider a Pioneer SX1250.

Covers the question without "question".

Will a Denon (whatever) have the value of a Pioneer SX1250 in the future (i doubt it)?

pc

3200 for a model 5805.......what's a 1250 brining in 1200 - 1500?

[Islander]

The bottom line on any receiver is to run all speakers as small. The bass frequencies are much more demanding than high frequencies, i.e., more wattage is require to play 100 Hz than 10,000 Hz at a given SPL. Subwoofers usually have their own amps, so spreading the load between the receiver and the subwoofer is an optimal strategy, when the sub(s) is/are properly integrated.

Bill

That's a generalization that does not apply in all cases, especially if the sub is set to roll off at a relatively high frequency, as is required with speakers like La Scalas, for instance. Setting all the speakers as 'small' cuts off their low end, which may make little difference with a 60 Hz sub cut-off, but will not sound ideal with a 100 Hz cut-off, for example.

The sub roll-off needs to match the needs of the speakers and the room to integrate the sub properly. It amazes me when people who should know better, like reviewers in magazines, will sometimes set the sub cut-off at 80 Hz "because that's the THX spec", regardless of what kind of speakers the sub is working with.

In certain cases, setting all the speakers as 'large' will give a fuller and better sound. Let your ears be the judges.

[mas]

You can replace "watts" with high voltage source that can also deliver high current. Amps are voltage multipliers, and when given differing loads, the current flow changes, but the voltage gain stays the same. As the load impedance drops, current rises.

Amplifiers don't make more "watts" at low impedances, but they do put out more current. Adequate heatsinking, multiple output transistors, and low output resistance are factors in an amplifier's load tolerance, as well as having a good power supply.

Well put. And what the formerly attached pdf explored in more detail...which either was ignored or simply confused folks as its example (with answers!) happened to employ multiplication and division. I suspect that Mike's comment too will be lost in the immensity of the conflagration.

I wish I could say that it is seldom, but this is a prime example of a thread gone terribly awry with the oddest compendium of of personal hangups, off the wall specs and 'standards' (right...) derived from product marketing sheets, and non sequitur emotional product endorsements that we have had in a short while.

One can only hope that the time between this and the seemingly inevitable next one is long.

But then, hope springs eternal....despite the foreknowledge of the complete and utter futility of the venture.

[Rivendell61]

And then there are Class D amps. While most "ideal" Class A or AB amps double their wattage as impedance is halved (500W into 8 ohms, 1000W into 4 ohms, etc.), even high-end Class D amps don't. 500W into 8 ohms, 650W into 4 ohms is more typical. Could this be caused by an inadequate power supply, or is it just the nature of that amplifier type?

Islander: The specs you quote are not good but.....no, there is not a topological reason for Class D amps not to perform well.....there are however *lots* of poorly designed Class D amps. Here are specs from a good 'high-end' Class D amp spec sheet: 350W 8 ohm/600W 4 ohm/1200W 2 ohms.

When actually based on measurement even high-quality linear amps do not usually fully double. For instance-- Bryston 14B: 690W/8 ohms and 1000W/4 ohms. Or Mark Levinson #431: 234W/ 8 ohms and 400W/4 ohms.

Here are two Class D amps (measured): 290W/8 ohms and 540W/4 ohms (Logic MC-20) Another: 110W/8 ohms and 200W/4 ohms(CIAudio). So.....they perform reasonably well when compared to actual AB amp ratios.

Mark