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what to expect with a 2.0v rms difference

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kirstenj

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Post Mon Sep 02, 2013 2:16 am

what to expect with a 2.0v rms difference

I stumbled on this article (http://www.audioholics.com/audio-amplif ... ltage-gain) when looking for advice on setting the impedance on my pre-amp. I found the answer to that out elsewhere, but got curious about how my pre-amp and amp matched up. I followed the formulas and came up with the Sunfire 300x2 wanting no less than 4.8v rms, but the Yamaha RX-A1010 pre-amp delivering only 2.8 via the pre-outs. With this 2.0 difference, does this equate to only being able to drive the Sunfire 300x2 at around 58% of it's max output? The volume from this setup is more than enough in our small house, so I'm asking this purely out of curiosity and wanting to learn.
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TNRabbit

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Post Mon Sep 02, 2013 7:18 am

Re: what to expect with a 2.0v rms difference

Yes, it basically means you won't realize it's full potential. Possibly a slightly higher noise floor.
TNRabbit
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From FrankieD's lips to your ears: Sunfire - a quiet box of endless power.

Sunfire TG-IV/400~7 Amp
Carver SD/A-360 CDP
Benchmark DAC-1
Sony SACD/DVD-A
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Sub: Klipsch RT-12d
Center: Sunfire CRS-3c
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OconeeOrange wrote:"Gary likes to play it 'loud' as do I. His system begs you turn it up until you die"

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mbskeam

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Post Mon Sep 02, 2013 9:41 am

Re: what to expect with a 2.0v rms difference

if you look in the upper right corner your answer is there.
Attachments
sunfireamp.jpg
Mbskeam


#1 BLACK BEAUTY's made by the man, the myth, the legend Bob Carver
CARVER: TFM-75, TFM-45(3), SD/A-490T
SUNFIRE: Tube pre
2 sets of ALS'3, set of SILVERS, set of PLATS
AUDIOCONTROL: phase coupled activator
KENWOOD: BASIC M2a (2)

“Youth ages, immaturity is outgrown, ignorance can be educated, and drunkenness sobered, but stupid lasts forever.”
― Aristophanes

The only thing I'll feel......will be the RECOIL
Necronomicon Ex-Mortis....... Klaatu Barada Nikkto
"We should seek the greatest value of our action"
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kirstenj

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Post Tue Sep 03, 2013 12:45 am

Re: what to expect with a 2.0v rms difference

Thanks Gary.

Re the manual: Not sure how input sensitivity alone would answer my question as to what to expect :-k . I did reference the manual (sensitivity etc), to input into the formulas in the article.
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TNRabbit

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Post Tue Sep 03, 2013 4:47 am

Re: what to expect with a 2.0v rms difference

How did you come up with the Sunfire needing 4.8 v minimum?

The manual states it will reach it's rated power with 1.64 v input...?
TNRabbit
Image

From FrankieD's lips to your ears: Sunfire - a quiet box of endless power.

Sunfire TG-IV/400~7 Amp
Carver SD/A-360 CDP
Benchmark DAC-1
Sony SACD/DVD-A
Active bi-amp: Ashly XR-1001 & 2 Rane PEQ-15s
Main: HotRodded AL-IIIs
Sub: Klipsch RT-12d
Center: Sunfire CRS-3c
Surround: Sunfire CRS-3 (x 2)

OconeeOrange wrote:"Gary likes to play it 'loud' as do I. His system begs you turn it up until you die"

RIP WIlliam B. Dibble, 1948-2012. I'll miss you my friend.
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radioeng2

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Post Tue Sep 03, 2013 8:55 am

Re: what to expect with a 2.0v rms difference

You cannot change the output impedance of the preamp line out, so I'm not sure what that was talking about.

The idea of our equipment interfacing is what is known as voltage transfer. The general idea is that as long as there is a 10:1 ratio, you're not going to appreciably change the freq response from anything at the load end. ie....anything less than 1K output impedance into anything lighter than 10K input load and you're golden. So again, just remember the 10:1 ratio for interfacing.

So the desired, for normal voltage transfer, is low output impedance and reasonably high input impedance. Technically, lets say you've got a very nice low output impedance and several devices with really high input loads. Like 50K or higher. That means you can safely do a Y splitter and not have loading effects. The warning being that you are sharing ground currents and noise.

The reason for greater voltage output capability in a preamp is so you have extra gain available for low input level sources. Greater gain though pays the penalty of increased noise floor. So reasonable extra gain is prudent.

There is no advantage I can think of to applying more voltage to the amp input than it takes to drive it to full output. With these high power amps, I can't image most can reach that level before the speaker would give it up. Ribbons are generally the most power hungry.

Well matched preamp gain and amp gain is worthy target. When you have enough gain to get a slightly low level source to the max speaker output level you'd ever want, and the preamp gain is all the way up at that point, then you've maximized signal to noise. If you're at the full output you can stand and aren't all that far up on the preamp gain, then you're thowing away resolution.

Be careful believing anything at all from that website. They are stuck in the numbers and graphs of low fi reproduction and don't know yet that there is greater fidelity available that the numbers game doesn't show. Simpifying the technical too far and you're missing out. And that's a shame.

Mark
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mbskeam

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Post Tue Sep 03, 2013 3:03 pm

Re: what to expect with a 2.0v rms difference

I bet your vol knob will be at 11:00 for loud....
and 2:00 for party timeeeee.... \:D/ \:D/
Mbskeam


#1 BLACK BEAUTY's made by the man, the myth, the legend Bob Carver
CARVER: TFM-75, TFM-45(3), SD/A-490T
SUNFIRE: Tube pre
2 sets of ALS'3, set of SILVERS, set of PLATS
AUDIOCONTROL: phase coupled activator
KENWOOD: BASIC M2a (2)

“Youth ages, immaturity is outgrown, ignorance can be educated, and drunkenness sobered, but stupid lasts forever.”
― Aristophanes

The only thing I'll feel......will be the RECOIL
Necronomicon Ex-Mortis....... Klaatu Barada Nikkto
"We should seek the greatest value of our action"
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kirstenj

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Joined: Sat Aug 20, 2011 6:08 pm

Location: Edmonds, WA

Post Tue Sep 03, 2013 4:36 pm

Re: what to expect with a 2.0v rms difference

I'd plugged in numbers to those formulas and came up with the numbers. New formula (10:1) is easier. My Yamaha Rx-A1010 has output impedance of 1.2k, and the Sunfire input impedance 24k, so it looks like I'm twice what I need and "am golden" ;-)

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