A question regarding amplifiers.

[Laura Palmer]

I've listened to the RTi12s on a HK635 now, but I'm wondering what exactly is gained with an amplifier.

I understand more power = more headroom and louder volumes.

However I usually listen to my music between -25db and -35db. (So, moderately low right?)

Will an amplifier make "-25db" LOUDER than my current "-25db", or does it mean that I can go higher (like -5db) without distortion?

Does my question make sense?

Hehe, cause I don't see myself needing louder volume than that for a while... but I'd love to know that I'll be achieving a fuller sound with more "headroom".

...even though that's a term I don't TRUELY understand yet :)

[Willow]

-25 is quite loud, if I listen to a cd @ -25 I would not be able to hear people talk.

[BlueMDPicker]

As they say, a picture is worth a thousand words. Here (http://store.tubedepot.com/whisbipo.html) is a graphic animation of head room as it relates to the waveform of a tube amplified signal -- same general principle applies to SS circuits. Click the "Launch the Bias Point Wave Simulator" link.

With a more powerful amplifier, yes, you could achieve higher SPLs before clipping occurs. Since you listen at modest levels, this doesn't seem to be much of an issue for you with the present receiver. However, there is a school of thought that extra head room provides a more dynamic overall sound -- even at modest volume levels.

Mike

[McLoki]

Oddly enough, I would say going louder is not one of the largest reasons to get an external amplifier. (You are much better off getting a more efficient pair of speakers for sheer volume)

An external amp often supplies more current as well as more watts. The watts are what is going to give you the max volume. The current is where (imo) the real story is told for most of us. It allows better control of the speakers. It can stop and start the woofer much better allowing for a more defined bass signal. Here is an Analagy I used in an earlier thread.... (http://clubpolk.polkaudio.com/forum/showthread.php?s=&threadid=24911&highlight=baseball+bat)
In terms of loudness keep this in mind - to hear any increase in volume requires a 3db increase in volume. This requires double the number of "watts". To make something twice as loud requres a 10db increase in volume and that requires a 10x increase in "watts".

Amplifiers typically can produce more current (amps) than a reciever. This will assist in driving speakers with a lower ohm rating (like polks LSi or SDA lines) as well as driving woofers. (the woofer requires much more power than a tweeter due to the fact that it takes more power to move the speaker cone (and air) than it does to vibrate the tweeter. (This can make many speakers sound better but makes the largest impact on speakers with arrays of woofers or large woofers. (many SDA's, RTi12's etc.)

An example of this would be to take a pencil and swing it as fast as you can at something and try to stop it about 1" from the object. Then do the same thing with a baseball bat. One not only requires more strength to swing, but also to stop accurately

The fist point is volume and that can increase with an amplifier.

The second point is sound quality. (This helps explain why a speaker connected to an amplifier may sound better (more clear) at lower volumes than a speaker connected to an AVR. - The Amplifier has the power to drive the speaker cones to start and stop much more accurately.)

[cfrizz]

Hi Laura.

It's not just louder, the biggest improvement I noticed when I got my Parasound hooked up was there was far greater clarity. I started hearing small things on cd's that I have played hundreds of times before, but never heard these small things.

On Jim Croce's greatest hits, I could actually hear him changing keys on the guitar!

On the Indigo Girls: Closer To Fine, I didn't even realize that they had some backup singers helping them with the refrain until I heard it with the amp pushing my speakers!

I had to turn down the volume on my subwoofer because the woofers in my 15 yr old Polks suddenly had more oommpphh!

Voices, instruments, placement is all improved when the speakers are able to operate to their full potential.

As for volume, I used to listen to everything at around -30 this was normal. My new normal is now -38 -40. That is for cd's. If I play DVD-A or SACD's early in the morning as I did this morning it was at -50 & it was as clear as a bell!

You won't really be able to tell any of this until you get an amp Laura. I didn't know until I got mine.

Hope this helps.
Cathy

[reeltrouble1]

Bottom line is:

Seperates kick butt on receivers. Its a path many here have already taken myself included. Did not take long for your upgradites to start putting thoughts into your head!!!

The I "wonder" how this would sound in my system. Makes the hobby fun though.

RT1

[Laura Palmer]

I think I'll see if there's a place in town that would let me borrow an amp for a few days. Maybe a NAD 272.

[2+2]

Laura, keep this in mind as well....your HK has a pretty good amp section with high current capacity...something like 45amps....If you are using 2ch only, you are pushing more watts as well...I just mention this to point out your milage in adding an amp may vary from the testimonials here. Also, b/c HKs have very good amps, if you go higher, make sure its a big step up....otherwise, you may not even notice much of a difference...

[unc2701]

Where do you live? If you're in NC, local to RTP through Winston, I'd be happy to let you borrow an old Adcom 555 for a week or so...

I doubt anyone is going to want to ship you one, but I'm sure plenty of polkies will let you listen and/or borrow one if you're local.

[Laura Palmer]

A very generous offer, thank you.

However, I just found out that there is a place in town that can lend me an amplifier for a couple of days, so that way I can see how it would affect my system and whether it's worth the upgrade price.

[heiney9]

Originally posted by 2+2
Laura, keep this in mind as well....your HK has a pretty good amp section with high current capacity...something like 45amps....If you are using 2ch only, you are pushing more watts as well...I just mention this to point out your milage in adding an amp may vary from the testimonials here. Also, b/c HKs have very good amps, if you go higher, make sure its a big step up....otherwise, you may not even notice much of a difference...

Jesus if that receiver actually has a peak output of 45 amps in 2-channel mode then there is no way in hell your going to notice much difference with a seperate amp. I will say I haven't seen the spec's for too many H/K products, but 45 amps for a receiver is alot a juice...... I doubt my Adcom amp could push that kind of amperage. You may want to re-visit the spec sheet :D

H9

[organ]

No comparison! I'd take seperates rated at 50w/ch over a HT receiver rated at 150w/ch. When it comes to 2ch music, seperates rule. It's not just increased bass and better clarity that you'll be getting. Music will sound more lifelike and real. One thing you'll notice after living with seperates for a while and going back to receivers is that receivers are 'noisy' and 'grainy'. Seperates have a darker background.

Try to borrow a pre amp along with the amp from your dealer. If you're planning to use the receiver as a pre, the amp will amplify the receiver's sound signature from its pre section. You end up getting more of the same sound. Pre amps have a big impact on sound qualiity.

Good luck. Let us know how things go.

Maurice

[2+2]

I stand corrected...her HK puts out 90w/ch in stereo mode (75w all channels in surround mode) and handles 50Amps....IMO, HKs sound great...

[shiu]

Just want to make two points:

Watts and Currents

Using the same speakers, an amp that outputs the same watts as an AVR (on per channel basis) is going to output the same current. I don't know how you can have watts without current or vice versa, unless we are talking about instantaneous values.

On instantaneous basis, it is likely that an amp that has the same output power rating as an AVR can deliver higher current, because power amps generally have large power supply capacitors that help provide high instantaneous currents. Again, the keyword here is "instantaneous", not continuous.

The applicable formulae are:

Power=VoltXCurrentXpower factor, or
Power=CurrentXCurrent (square)Xresistance (the resistive component of impedance). So power is always tie to current.

The current capability of the AVR635

I think the HKAVR635 can do 50A but it is an instantaneous (extremely short duration) rating, and is more of a power supply rating. Since the power supply delivers power/current to 7 channels, it is possible that each channel(amplifiers) can handle approximately 1/7, or a little more, of the total current. I could be wrong on this, it is just an educated guess

I am using a GFA-555 with my 3805 and I do not hear any huge improvements. My guess is that an amp will improve the sound quality if you have those power hungry RTi12 speakers.

[heiney9]

Originally posted by shiu
Just want to make two points:

Watts and Currents

Using the same speakers, an amp that outputs the same watts as an AVR (on per channel basis) is going to output the same current. I don't know how you can have watts without current or vice versa, unless we are talking about instantaneous values.

On instantaneous basis, it is likely that an amp that has the same output power rating as an AVR can deliver higher current, because power amps generally have large power supply capacitors that help provide high instantaneous currents. Again, the keyword here is "instantaneous", not continuous.

The applicable formulae are:

Power=VoltXCurrentXpower factor, or
Power=CurrentXCurrent (square)Xresistance (the resistive component of impedance). So power is always tie to current.

The current capability of the AVR635

I think the HKAVR635 can do 50A but it is an instantaneous (extremely short duration) rating, and is more of a power supply rating. Since the power supply delivers power/current to 7 channels, it is possible that each channel(amplifiers) can handle approximately 1/7, or a little more, of the total current. I could be wrong on this, it is just an educated guess

This whole "electronics " thing is very complicated and I'm far too removed from my 4 years of electronics classes to get into detail.

Your 1st paragraph is incorrect. Just because you have watts doesn't mean you have current. Current is a product of voltage, if I remember correctly. As far as the 50A instantaneous current, it's duration is so short it's not worth mentioning, and in this case has no effect on real world listening. And as a rule of thumb AVR rec are not capable of producing the kind of current for any usable amount of time over that an amp . The 50A current measurement you talk about is meaningless in the real world. Quality and type of power supply has a huge influence on current, as does size and quality of filter caps.

Please don't take me the wrong way, H/K is good stuff but it's just not capable of producing the kind of current or sound seperates do. IC's (integreted circuits) are perfect examples of output devices that can produce many watts but relatively little current compared to discrete output components with no current limiting circuits. See, many AVR' s and some amps have to protect against current output overload and design circiuts/relays that limit current to save the output transistors and power supplies. That right there can/does affect the sound quality. Almost all common AVR's incorporate some type of current limiting because of all that's going on inside the unit, output-wise. This is one of the reasons it's hard to find and AVR that sounds as good as seperates. There HAS to be some compromises along the way.

There are many other factors like direct coupling and minimum amount of output stages. Class A output, primary and secondary windings, discrete output stages, mulit regualted power supplies. It's very hard to incorporate all these design features plus all the audio/video/remote/5.1/Dolby/DTS...etc into one unit. There are very few, maybe a handful fo AVR's that can match the quallity of good seperates. Yes, you will most likely pay more, but you get more also.

[heiney9]

Shiu, perhaps if you had a dedicated pre-amp to go with your GFA-555 you would notice a difference. We all hear things differently. IMO and in my experience you should hear a very noticeable diff using the GFA-555 in place of the 3805's output section.

I recently bought an older Nakamichi receiver and ran it in place of my seperates for a few days. There was a night and day diff between the two. On it's own the Nak would have sounded very good, but against the seperates it just didn't cut it. And the Nak is designed to be more like seperates with discrete output stages, no common ground connections, large caps and a decent sized transformer, class A biased high current and Stasis designed output section. A damn nice sounding rec, but still not as goods as seperates. I was slightly disappointed until I realized it just reinforced what I already knew, seperates are hard to beat.

H9

[ezc]

Laura,
More power means you can play it louder before clipping but you should also have higher resolution in the lower volume range also. I have always looked for amps for my mains which has 150-200 watts per chanel but was never happy with the sound. I just purchased a BAT VK60 & found the sound I was looking for. The Amp has just 60 watts per chanel & sounds better than any SS amp I have tried in my system. I dont listen at loud vol. but even at lower to moderate levels the sound is much more full.

[organ]

ezc,
That's exactly what I was trying to point out on my previous post. Just because an amp is 200w/ch, it doesn't mean it's going to sound better than a good quality 100w/ch. Hell, I've got 12w/ch and I've never maxed it out.

Maurice

[gregure]

So what to take away from all this?
Good, high current amp equals more refined, detailed, open and often warmer sound w/ a better soundstage, and deeper bass. All in addition to being able to play it louder w/o distortion.

And don't let watts fool you. I've heard it said that the electronics industry is an industry based on standards, all operating under the standard that there are no standards. What does that mean?

That all of these specifications are uniform across the board, but each manufacturer employs different ways of measuring them, making them almost always unreliable. For instance, a $200 receiver claims to have the same 100 wpc as a $1500 receiver, yet I think you can guess which sounds better. Why? Because the $200 receiver measured 100 watts at peak power, one channel driven. Whereas the $1500 receiver was measured w/ all channels driven, and 100 watts was the continuous output into all channels. So the cheap receiver has the capability of running 100 watts per channel, at peak volume when running music out of one speaker. All of this means that the current is higher in the more expensive amp, and they obviously measured the watts in a more truthful or realistic way.
Agreed, a 200wpc amp can sound worse than a better 100wpc amp, as it is truly all about the current.
I don't pretend to believe that my B&K receiver sounds better than good separates, it doesn't. But it certainly comes closer than most other receivers, as it has a nice high current amp, capable of 150 continuous wpc, all channels driven. One just has to know which amps are the nice high current ones. In the lower price bracket, B&K, Adcom, Rotel and NAD would be examples of good amps with lots of current. On the higher end: McIntosh, Primare, Lexicon, Krell, Anthem, Plinius, and Conrad Johnson. Happy listening.

[shiu]

Originally posted by heiney9
Your 1st paragraph is incorrect. Just because you have watts doesn't mean you have current. Current is a product of voltage, if I remember correctly. [/B]

Heiney9, I think you might have misunderstood what I was saying. Watts doesn't mean current, sure, but I did qualify my point by saying, "using the same speakers................." With the same speakers, i.e. the same impedance characteristics, if you apply any of the power formula, ohms law etc., and at a certain frequency, you will see that if the speaker draws say 1A, it will consume say X watt, if it draws 2A, then it will consume 4X watts(Power proportional to the square of current)at that same freq, what ever X is. I also did mention that if we are talking about instantaneous values, then what I mentioned would not apply, because other factors such as blocking capacitors will have a major effect. To get into details, it does get complicated. Somehow I know I shouldn't have started this.

By the way, I do have a GFP-565 pre-amp as well for music, haven't figured out how to use it for H.T. yet. Any idea?

[shiu]

Laura, most people here seem to think adding an amp to your 635 will get you sound quality improvements. I thought I should mention another advantage is that it would take those RTi heavy load off the AVR, and allow it to run cooler, therefore last longer.

I have inefficient floor standing speakers, and the main reason I use the GFA-555 to drive the front channels is to save my 3805, even though I could not hear the expected "huge improvements".

[unc2701]

Originally posted by gregure
In the lower price bracket, B&K, Adcom, Rotel and NAD would be examples of good amps with lots of current. On the higher end: McIntosh, Primare, Lexicon, Krell, Anthem, Plinius, and Conrad Johnson. Happy listening. [/B]

Lexicon is Bryston w/o the 20 year warranty... or at least they used to be- they just licensed bryston amps & put a lexicon faceplate on them. Point being, if you hear a lexicon & like it, buy a bryston instead.

[heiney9]

Actually Shiu this is a fun discussion. This is what I like about this forum. Just bouncing ideas, opinions and experiences around. I do agree with you about the application of Ohm’s law. Unfortunately it’s one of those measuring of variables with everything else being constant situations; which never mimic real world application. And yes, it does get very complicated, as other variables are introduced/changed. My only point being that wattage doesn’t equal current, it’s much more complicated than that and I know you realize that. Using Ohm’s law you can calculate any variable, much like you can calculate the horsepower of a combustion engine. It’s the application of the results of your calculations that result in the outcome; good or bad. Every audio company/engineer has a different goal when they build a specific product. There are also many different ways to measure/test to get a desired outcome that looks good on paper.

As far as using your GFP-565 for HT I’ll have to check into that. If it has an external processor loop your set.

Good discussion BTW

H9

[Laura Palmer]

Very interesting. I'm learning so much.

I'm also learning however that technical specifications don't tell you anything and that the only true way to find out is to test it on your own equipment and hear the difference yourself.

What do you mean by "inefficient speakers" though? How do you gauge how efficient your floor speakers are?

It seems that since my Harman Kardon is quite good, that I'd probably need a REALLY nice amp to hear that big sound difference. Maybe a solid 250wpc amp...or an Outlaw.

[dorokusai]

Don't be a slave to specifications, just be educated about what they mean.

Manufacturers typically set specs at different distortion ratings, all of which are not audible to all but people with bat ears.

Inefficient typically means anything <90db. If you have good power in the first place, it will never matter.

UNC - That's some funny stuff....and I totally agree :D I actually don't think the two companies have much in common anymore. I've popped the tops on a few in the past year, and their nothing alike internally.

[shiu]

I consider my Energy V2.3i inefficient because it has a sensitivity of only 87 dB. At 90 dB, the RTi12 is not bad. The problem is that it has 6 drivers, 3 of them are 7" bass drivers. As you already know, your 635 can do a decent job on them, anything less powerful (e.g. the 435) will play them loud, but will not be able to make them sound their best.

The 635 may have to work hard, and get pretty warm.

[aaharvel]

i have a H/K avr 235 and just upgraded to Adcom amplifier sections.

Adcom 5300 (front L&R channel)
Adcom 7300 (Center, Sides & Rears)

honestly- using the H/K as just a pre-pro (compared to before as an all in one receiver) i can tell absolutely NO difference in the volume at -35 db or at any -db. setting. None.

BUT- since adding the two Adcoms, it does sound better, not by a wide margin and certainly the average joe couldn't tell- but for anyone interested in this shizzle like myself- i can tell a difference-Although the difference is far from huge- It was still worth the $400 to upgrade.

hope this helps.

[dcarlson]

Don't forget about using quality interconnects when you add an amp.

[heiney9]

Originally posted by aaharvel
i have a H/K avr 235 and just upgraded to Adcom amplifier sections.

Adcom 5300 (front L&R channel)
Adcom 7300 (Center, Sides & Rears)

honestly- using the H/K as just a pre-pro (compared to before as an all in one receiver) i can tell absolutely NO difference in the volume at -35 db or at any -db. setting. None.

BUT- since adding the two Adcoms, it does sound better, not by a wide margin and certainly the average joe couldn't tell- but for anyone interested in this shizzle like myself- i can tell a difference-Although the difference is far from huge- It was still worth the $400 to upgrade.

hope this helps.

Glad this set-up is working to your satisfaction. For those of you who are only getting a small improvement with external amps hooked to your AVR( no matter what brand) I suggest a high quality stand alone pre-amp. I would bet the the AVR pre-amp section maybe the limiting factor. I know using the AVR for a pre allows you to achieve HT settings on a budget. But honestly, adding beefy external amps like some have, should yield a bigger difference that what has been mentioned. Other factors such as cableing, source, speakers, room set-up not withstanding. Just my opinion.

H9

[gregure]

As far as efficiency goes, in practical terms, an efficient speaker is one that does not take a lot of current, or watts if you prefer, to make them sound great. As opposed to inefficient speakers, that require a lot of power to make them sing properly. Efficient speakers like Boston/Polk towers sound pretty good on a lot of recievers, even at lower ratings, because it doesn't take a lot of power to make them sound decent. However, adding more power will improve sound quality even on more efficient speakers.
Inefficient speakers, such as 4 Ohms like LSi or Vienna Acoustics, need a lot of power or they sound constricted and dry.

[2+2]

I suggest a high quality stand alone pre-amp. I would bet the the AVR pre-amp section maybe the limiting factor.

Well, I am toying with a high quality pre-amp instead of my HK 230 as preamp and that was what I was hoping for. Unfortunately, I am finding that things are not that simple, and I am not getting the results hoped for....

The more I play with this audio stuff including amps, cables etc., I am finding that it is more about synergy between the components and less about the quality (or expense) of any given component or even all the components.....things are somewhat unpredictable.....

[shiu]

Originally posted by heiney9
As far as using your GFP-565 for HT I’ll have to check into that. If it has an external processor loop your set.
H9

H9, my 565 has a "processor in" button on the front panel, so it probably has the loop that you were referring to. I am going to dig out the manual this weekend.

Thanks,
Shiu

[W WALDECKER]

hi laura . i am somewhat new to this website but i have been around audio for quite some time. the main reason for seperate amplifiers and preamplifiers is to try to avoid interaction between the electronic circuit.s in the different stages of amplification. and using monoblocks allows another degree of seperation by totally isolating the right and left channels from each other. when everything is jammed into one unit the internal electronics can bleed unwanted interference into the other circuit.s that are also packed into the same unit. in laymans terms the wires talk to each other and that can lead to distortion. the more seperation you have in a system the cleaner the sound! if you are looking at seperate amplification i would talk to klaus bunge at odyssey audio he will recommend equiptment based on your system and needs and he might have b-stock items with a twenty year warranty for a lot less money. check out the reviews at audioreview on the khartago and stratos amplifiers i think odyssey has the best cost vs performance in high end audio. good luck p.s on the website for international audio video review they rate the odyssey stratos at class 1b along with the sim moon w 5 and jeff rowland model 9. krell and mark levinson only rate at class 3 this website accepts no advertising and tells it like it is. when it comes to reviews they pull no punches and the odyssey rated very highly. and a bryston while good cant even play in the same yard as the odyssey. also check out the tempest pre amp... odyssey is all about synergy i use the same wire for my speakers and ic.s that is hardwired into my monoblocks and preamp. again good luck

[heiney9]

Here are a couple of links that help explain amplifier basics. Read for fun or to gain a better understanding. The explanations aren't too technical. However, for some it may cause more questions than it answers. I found both articles very interesting.


http://www.rocketroberts.com/techart/powerart_a.htm

http://www.rocketroberts.com/techart/amp.htm

These articles may not answer specific ?'s but the read is interesting anyways

Enjoy

H9