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Powering rf7iis+rc64ii


Destiny

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the adcom amp gfa 7805 should do the trick, i think..

 

Probably a good solution.

 

 

 

the reason for the pre amp without amps is to save power(assumption only)...

 

Maybe that but usually flagship or near flagship pre/pros use better parts(DACs, analog section, lower noise floor, etc.) than mid level AVR's with preouts.  Some mfr's flagship pre/pros have the same guts(minus amps) as their flagship AVR's.

 

Bill 

Edited by willland
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the adcom amp gfa 7805 should do the trick, i think..

 

Probably a good solution.

 

 

 

the reason for the pre amp without amps is to save power(assumption only)...

 

Maybe that but usually flagship or near flagship pre/pros use better parts(DACs, analog section, lower noise floor, etc.) than mid level AVR's with preouts.  Some mfr's flagship pre/pros have the same guts(minus amps) as their flagship AVR's.

 

Bill 

 

 

as i see marantz has 7702 which is about the same price as their flagship avr sr7010... so they would have similar internals? then wouldn't that make the avr as better option? even if you don't use the amps? or the dac would perform better in a preamp due to lower noise floor equaling more detail in sound? my audio knowledge is limited to mostly headphone audiophile world, and all my assumptions are based on that... an external dac is better due to lesser noise etc...

Edited by Destiny
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researching more and more gets a little confusing at times... i didn't know of an issue before that i think i must understand before investing into the equipment that i want to buy...

 

the issue i am wondering about is that with pre outs you need adequate output voltage to the amplifier to get the full potential of the amplifier... e.g the gfa 7805 has input sensitivity of about 1.61Vrms and 29.6db gain etc... so does that mean the the pre should have an output of 1.61vrms as well for full potential? i have heard, or rather read, that normal avrs have very low output like 1vrms... so a dedicated pre pro like the marantz av7702 or the yamaha cx a5100 a better choice or only cheap avrs have this much low output voltage? if i rather use a marantz sr6009 for a pre pro, is that good enough(don't know its output figures on preouts)? this is confusing me... what preout voltage would i need and ofcourse how?

Edited by Destiny
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Adequate voltage is not a problem 99% of the time when using an amp with a avr or preamp.  Once you start using pro amps, this change.

 

not that i need a lot of power the headroom would be lost won't it? e.g using this article

http://www.audioholics.com/audio-amplifier/amplifier-voltage-gain

 

i concluded(correctly hopefully) that the amp adcom gfa 7805,rated at 300w into 8ohms per channel and 29.6db gain with 1.61vrms input sensitivity, would only give me about 164W into 8ohms max when feeded with 1.2v rms input.... if so then spending for an external amp might be a waste considering that is pretty close to what a receiver like denon 4520(according to soundandvision.com)... so this is worrying isn't it? spending twice the money for really no reason at all? confused

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the amp adcom gfa 7805,rated at 300w into 8ohms per channel and 29.6db gain with 1.61vrms input sensitivity, would only give me about 164W into 8ohms max when feeded with 1.2v rms input

Ok....let's see....

 

RF-7ii have a 101db sensitivity.
Double the power = a 3db gain in volume

 

1 watt = 101db

2 watt = 104db

4 watt = 107db

8 watt = 110db

16 watt = 113db

32 watt = 116db

64 watt = 119db

128 watt = 121

 

Hearing_Loss_Danger_Chart_in_Decibels_pj

 

 

 

Looks like you will be able to enjoy about 8 seconds of that amp cranked wide open before you lose your hearing.  I somehow "think" that Adcom would power your RF-7ii's just fine.  :)

 

if so then spending for an external amp might be a waste considering that is pretty close to what a receiver like denon 4520(according to soundandvision.com)

Keep in mind, a quality power amp will have a much easier time driving a set of speakers, especially when you get above 5 speakers.  With a receiver, as you ad more speakers, you get less power from your amp.  With power amps, you have the same watts / ch even when adding more speakers.

 

so this is worrying isn't it?

Yes...but you are wise in doing as much research as you can.  Then and only then will you be able to make the best decision for you and for your setup.

 

spending twice the money for really no reason at all? confused

I wouldn't say it's for no reason at all.  Truth is....do any of us "need" an amp?  No.  Are there benefits of adding an external power amp?  Absolutely.  Are they night and day difference from your receiver?  No.  Is this all confusing?  Yes.  :lol::D:P;)

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the amp adcom gfa 7805,rated at 300w into 8ohms per channel and 29.6db gain with 1.61vrms input sensitivity, would only give me about 164W into 8ohms max when feeded with 1.2v rms input

Ok....let's see....

 

RF-7ii have a 101db sensitivity.

Double the power = a 3db gain in volume

 

1 watt = 101db

2 watt = 104db

4 watt = 107db

8 watt = 110db

16 watt = 113db

32 watt = 116db

64 watt = 119db

128 watt = 121

 

Hearing_Loss_Danger_Chart_in_Decibels_pj

 

 

 

Looks like you will be able to enjoy about 8 seconds of that amp cranked wide open before you lose your hearing.  I somehow "think" that Adcom would power your RF-7ii's just fine.  :)

 

 

 

if so then spending for an external amp might be a waste considering that is pretty close to what a receiver like denon 4520(according to soundandvision.com)

Keep in mind, a quality power amp will have a much easier time driving a set of speakers, especially when you get above 5 speakers.  With a receiver, as you ad more speakers, you get less power from your amp.  With power amps, you have the same watts / ch even when adding more speakers.

 

 

 

so this is worrying isn't it?

Yes...but you are wise in doing as much research as you can.  Then and only then will you be able to make the best decision for you and for your setup.

 

 

 

spending twice the money for really no reason at all? confused

I wouldn't say it's for no reason at all.  Truth is....do any of us "need" an amp?  No.  Are there benefits of adding an external power amp?  Absolutely.  Are they night and day difference from your receiver?  No.  Is this all confusing?  Yes.  :lol::D:P;)

 

 

 

i know that i won't be able to ever hear that loud... though some people say that the rf 7ii is not as efficient as klipsch labels them... i am actually only concerned about the bottom end, which ain't no concern with a separate amp but there is that itch that i should at least have the full capability under the belt, even though i may only crank it up full once in my lifetime...  it is not actually research, i just am reading up before i have to buy them, as i still am about a week away from getting the money :P ... and why don't the avr/ avp makers tell these things in their specs. I have been trying to find the pre out voltages for the rca outputs of these two yamaha and marantz processors on their site and other forums but there are no proper figures... ah, i just don't want that extra 140 watt capability going to waste even though that will be less than 3db difference...

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i know that i won't be able to ever hear that loud... though some people say that the rf 7ii is not as efficient as klipsch labels them

In reality, if you measure them like everybody else does, the efficiency is more like 96, which is still very high compared to your usual consumer grade speakers. The pro and cinema lines are accurate but the consumer stuff is measured differently, in-room or something, I'm not sure. Efficiency is usually up 4-5 db and bass response is more extended. Same thing with THX, claimed 97 db I think but it's more like 92. Seems like Sound and Vision tested both of these. Here's an example:

http://www.soundandvision.com/content/klipsch-thx-ultra2-speaker-system-ht-labs-measures#x3irvYuH2BY84CaS.97

 

i am actually only concerned about the bottom end, which ain't no concern with a separate amp

Like you said it's probably not a concern to you with an external amp, but the biggest issue with RF-7ii's on the bottom end is that there's a big impedance dip in the lower midbass / upper sub area, somewhere around 70 hz. Drops down to like 3 ohms or something. You can hear my Marantz receiver choke on kick drums coupled with bass guitar at higher volumes because of this. For a fat bottom end at high volume these things really need a high current 4 ohm stable external amp.

 

i just don't want that extra 140 watt capability going to waste even though that will be less than 3db difference...

Unused headroom isn't exactly a bad thing. :)

Edited by MetropolisLakeOutfitters
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I read page one and then jumped to page 6...welcome to the forum Destiny and although I have no experience with the AVR-4520ci, I have the previous model the AVR4311ci and have had it for almost 2 years and prior to that I had the Denon 4806 and 4802r. As others mention if you are going to cross the RF-7IIs to a sub I would get the Denon (It's discontinued so you should get a good price--that's what I did when I purchased my latest unit) and use the money you saved to purchase source material or spend it on something else.

 

Fwiw, I've had my speakers listed below for almost 15 years and listen to loud multichannel music nightly--Last night was Robert Plant and the Band of Joy Bluray and the volume was at -4 on the MV after Audyssey calibration, which is also a plus...My 2 cents.

Edited by Zen Traveler
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RF-7ii have a 101db sensitivity.

Double the power = a 3db gain in volume

 

1 watt = 101db

2 watt = 104db

4 watt = 107db

8 watt = 110db

16 watt = 113db

32 watt = 116db

64 watt = 119db

128 watt = 121

Complicating this is that the distance from the speakers can make them drop quite a bit. The difference between 3 feet and 12 feet can cut what you actually hear by about 12 decibels.

http://www.globalrph.com/master_speaker.htm

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In reality, if you measure them like everybody else does, the efficiency is more like 96, which is still very high compared to your usual consumer grade speakers. The pro and cinema lines are accurate but the consumer stuff is measured differently, in-room or something, I'm not sure. Efficiency is usually up 4-5 db and bass response is more extended. Same thing with THX, claimed 97 db I think but it's more like 92. Seems like Sound and Vision tested both of these. Here's an example:

http://www.soundandvision.com/content/klipsch-thx-ultra2-speaker-system-ht-labs-measures#x3irvYuH2BY84CaS.97

Like you said it's probably not a concern to you with an external amp, but the biggest issue with RF-7ii's on the bottom end is that there's a big impedance dip in the lower midbass / upper sub area, somewhere around 70 hz. Drops down to like 3 ohms or something. You can hear my Marantz receiver choke on kick drums coupled with bass guitar at higher volumes because of this. For a fat bottom end at high volume these things really need a high current 4 ohm stable external amp.

 

Unused headroom isn't exactly a bad thing. :)

 

this is exactly what i am thinking. I want that extra headroom which i will have due to higher pre out voltage as the amp can go to 450W to 4 ohms also. Bottom end is the main reason i am not going with a receiver even as good as denon 4520 which can give those 160W to the channels i want to drive. An external amp would be much much better with impedance dips.

I read page one and then jumped to page 6...welcome to the forum Destiny and although I have no experience with the AVR-4520ci, I have the previous model the AVR4311ci and have had it for almost 2 years and prior to that I had the Denon 4806 and 4802r. As others mention if you are going to cross the RF-7IIs to a sub I would get the Denon (It's discontinued so you should get a good price--that's what I did when I purchased my latest unit) and use the money you saved to purchase source material or spend it on something else.

 

Fwiw, I've had my speakers listed below for almost 15 years and listen to loud multichannel music nightly--Last night was Robert Plant and the Band of Joy Bluray and the volume was at -4 on the MV after Audyssey calibration, which is also a plus...My 2 cents.

I have some budget flexibility which is why i am trying to get better parts right now. I am not sure about how good a receiver would handle the impedance dips below 4 ohms, as i will push them for bass. I don't have a proper home theater room right now but i want to buy the equipment first and then build a room around it.

 

 

RF-7ii have a 101db sensitivity.

Double the power = a 3db gain in volume

 

1 watt = 101db

2 watt = 104db

4 watt = 107db

8 watt = 110db

16 watt = 113db

32 watt = 116db

64 watt = 119db

128 watt = 121

Complicating this is that the distance from the speakers can make them drop quite a bit. The difference between 3 feet and 12 feet can cut what you actually hear by about 12 decibels.

http://www.globalrph.com/master_speaker.htm

 

 

i will only be 2 meters away though... i like the "in your face" blown away effect...

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I have some budget flexibility which is why i am trying to get better parts right now. I am not sure about how good a receiver would handle the impedance dips below 4 ohms, as i will push them for bass.

 

Fwiw, the AVR-4520 ci is rated to drive 4 Ohm speakers and if you are not going to be running a sub and at loud volume I can't argue against going separates--That said, if you are eventually going into Home Theater I still think investing in a sub, setting a crossover and using that AVR would be a better bang for your buck. Regardless, good luck!

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i will only be 2 meters away though... i like the "in your face" blown away effect...

Every time I see your username, this scene replays in my mind. :)

 

 

i am a sci fi fan and my username and avatar is basically from stargate universe series... the universe exploration ship aka destiny... great movie though and great scene

 

and can anyone tell me what is voltage trigger on these avrs? trying to find pre out voltage mostly led to this subject...

Edited by Destiny
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and can anyone tell me what is voltage trigger on these avrs? trying to find pre out voltage mostly led to this subject...

That's talking about the trigger that it uses to turn other stuff on with. Turn on the AVR and it powers up a 12v trigger that you can tap in to with a mono 1/8" jack. You can automatically turn on amps, surge protectors, do stuff with automation, etc. I'm assuming this is what you're asking at least.

Edited by MetropolisLakeOutfitters
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though some people say that the rf 7ii is not as efficient as klipsch labels them

I have heard that as well.  I do know they are much louder than the B&W's that I've owned.

 

i am actually only concerned about the bottom end

Dedicated amp will help with that, even at low volumes (I've owned 4 power amps)

 

but there is that itch that i should at least have the full capability under the belt

There it is.....that's your answer.  Honestly, if you have that itch now, you will likely have it later if you don't buy an amp.  If you are like me, the "What if" will always be in the back of your mind.

 

it is not actually research, i just am reading up before i have to buy them

Isn't that research?

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