When to Add External Amplification to an A/V Receiver

[AcuDefTechGuy]

... and well you should be

- Rich

Yeah, we can debate for days on end, but you just got to buy what you got to buy.

If you feel the need to buy an amp, nothing is going to stop you. I suppose some people may be looking for moral support.

I always say that if you have the money and the itch, just buy the amp like the 180-300WPC amps from ATI or Parasound. If you have more money, then buy McIntosh, Bryston, etc. Numbers aren't everything for sure.

 

[alienmuppet]

Your statement is only correct for DC signals. When music is playing an amplifier is simultaneously acting on many thousands of signals at different frequencies and phasing. Also, amplifier distortion can be dependent on frequency, power level, and how many different frequencies the amplifier is working on at once.

Over time yes, but in a single instance it is still just a single voltage level. 1 microsecond later it might be another voltage level yes, but I'm not sure why that matters. I don't think electronic components have a memory of that previous microsecond (baring the power drain on capacitors).

No matter how complex the music, at any one moment in time there is one value. You can prove this with music in the digital realm. One sample has one value between 0 and 65535 (when 16 bit at least).

All an amplifier is doing is taking the voltage for that one moment, and boosting it to the appropriate relative level.

There could well be something I'm missing here, but I just cannot see what.

 

[PENG]

Testing in a lab can be more strenuous than testing in a lab, except when it is not. For example, for speakers that dip below 4 ohms. If heat is an issue, the duration of a 4 ohm test matters as well. A few minutes may not be indicative of a 4 ohm speaker listening for an extended period of time.

Here is a real world example:
There Revel Salons are rated with a nominal impedance of 6 ohms.
The A51 amp has been measured by many sites including AH at 400 watts RMS 20-20kHz 2 channels driven.

I was able to put the A51 (on an open shelf) into thermal overload in 15 minutes driving my Revels with 2 channel musical at near reference levels (-5 on the Marantz Pure Direct, but I am uncertain of the DB level). There was no discernable clipping.
To be fair, I was doing this at the bequest of a friend that was having some trouble with midrange distortion at high volume level on his speakers. This is not a listening level that is normal for me. The album was Alison Krauss "Paper Airplane" which is has good bass content but not bass heavy).

In reality, the Revel Salons dip below 4 ohms and they have some difficult phase angles.
Damn reality.

- Rich

Just to add my two cents, that album appears to be quite compressed, with DR of probably only a few dB so it is like stressing your A51 (thermally speaking) with sine waves, well obviously I am exaggerating now..

 

[PENG]

Over time yes, but in a single instance it is still just a single voltage level. 1 microsecond later it might be another voltage level yes, but I'm not sure why that matters. I don't think electronic components have a memory of that previous microsecond (baring the power drain on capacitors).

No matter how complex the music, at any one moment in time there is one value. You can prove this with music in the digital realm. One sample has one value between 0 and 65535 (when 16 bit at least).

All an amplifier is doing is taking the voltage for that one moment, and boosting it to the appropriate relative level.

There could well be something I'm missing here, but I just cannot see what.

In terms of moment by moment, I have to agree with you on this. I would go further to say that the complex music wave shouldn not cause any adverse/audible effect to well designed amplifiers. Even boom box, cheap headphone amps could sound quite nice to most people except us crazy audiophiles. To me, sonic signatures of amps used well within their output limits are mainly determined by its distortion characteristics and that would have little to do with the complexity of the music waveforms.

 

[PENG]

What courses in college cover this?

Was it engineering physics II?

Yeah, how does an amp know if the signal is complex waveforms?

When they test amps, they use continuous testing, which they label as "RMS"? In real life, amps don't really see RMS continuous signals like they do in testing?

So I would think that the amp testing is a lot more severe than most real life situations.

Advanced engineering mathmatics, Mathematical analysis, Fourier analysis, Electrical power and machines, Applied electromagnetism, Electronic devices & circuits, Communication systems, Digital circuits & microprocessors etc., I can PM you a list of my textbooks for self studies, or just go to the library.

 

[gene]

If not even an $11k Pass Labs can drive your speakers properly then isn't that a testament to poor loudspeaker engineering? Plenty of speakers do not need $11k of amplification to be driven well. Well, unless you feel price and performance is a linear function, but I don't agree with that.

Or it's a testament to having a speaker that can deliver TRUE Fullrange sound with NO compression at output levels that can exceed even the most demanding listening environment. Until you hear a speaker like this, you just won't get it. It's like trying to explain the driving experience of a Porsche 918 Spyder to someone who has only driven Hyundai cars their whole life.

Look, I don't think it is unreasonable to assume that typical people a) don't sit very far away from their speakers (more than 5 meters), and don't crave ridiculous SPL (105 dB+) in their homes. I'm not talking about the small subset of people who enjoy trying to recreate a live concert in their rooms, but the everyday, ordinary guy who enjoys listening to music.

You don't need bucket loads of power to handle the kinds of SPL that the average guy enjoys (75-95 dB), and the typical guy probably won't own speakers that have impedance dips down to 1 ohm with weird phase angles. Contrary to popular belief, speakers today don't all require a big stonking power amp in order to sound decent.

Most speakers in the price range of the average listener you are describing don't offer true fullrange sound free of compression. In these cases, an AV Receiver will typically be fine for them hence why our point system makes a lot of sense. People can still try a separate amp but if they don't hear the benefit, then by all means they can stick with the amps in their receivers.

Now sure, I'm generalising here, but the above seems reasonable to me. Yes, you may need a bucket load of power to drive your speakers with rerouted LFE, which is not a typical scenario. It is atypical. How many people will not use a subwoofer to handle the LFE? I imagine not many. That's another generalisation, but a reasonable one to expect given the popularity of subwoofers.

If you ask me, most people today use subwoofers for handling LFE and rerouted bass information. Again, another generalisation, but am I wrong?

You didn't read my review so you missed the reasons why I run my speakers this way.

Status Acoustics Titus 8T Floorstanding Speaker System Review | Audioholics

Even for 2CH audio running with no LFE, a good solid amp makes the world of difference over a simple mid level AV receiver amplification. I know this is something you don't want to believe and I don't really care to convince you otherwise. The Pass Labs amp did great for normal 2CH but it couldn't keep up with the LFE Blu-ray stuff b/c the power supply wasn't big enough. The XPR-1s did a better job under these type of load conditions. Now if I was using an Infinity P363 speaker, a receiver amp would have been fine in ALL listening scenarios but of course I wouldn't be getting even remotely as good sound at ANY listening level that my reference speakers are able to reproduce

 

[AcuDefTechGuy]

Advanced engineering mathmatics, Mathematical analysis, Fourier analysis, Electrical power and machines, Applied electromagnetism, Electronic devices & circuits, Communication systems, Digital circuits & microprocessors etc., I can PM you a list of my textbooks for self studies, or just go to the library.

No thanks. Glad I changed my major.

I took Engineering Mathematics (I) before changing my major so I guess this electrical stuff was covered afterwards.

 

[PENG]

No thanks. Glad I changed my major.

I took Engineering Mathematics (I) before changing my major so I guess this electrical stuff was covered afterwards.

It might be possible that Fouier, Laplace transforms, Vector calculus etc., were in the Advanced engineering math level, probably in the second or 3rd year in the engineering discipline. I think we better stop talking math and science, this is an amp thread.

 

[RichB]

Just to add my two cents, that album appears to be quite compressed, with DR of probably only a few dB so it is like stressing your A51 (thermally speaking) with sine waves, well obviously I am exaggerating now..

To be fair the Alison:

Here are the DR ratings from HDTracks:

Album details - Dynamic Range Database

DR Peak RMS Duration Track
--------------------------------------------------------------------------------
DR9 -0.30 dB -13.10 dB 3:37 01-Paper Airplane
DR11 -0.30 dB -13.76 dB 3:07 02-Dust Bowl Children
DR9 -0.30 dB -12.50 dB 3:56 03-Lie Awake
DR10 -0.30 dB -12.17 dB 3:52 04-Lay My Burden Down
DR9 -0.30 dB -11.22 dB 4:04 05-My Love Follows You Where You Go
DR11 -0.30 dB -14.21 dB 5:20 06-Dimming Of The Day
DR10 -0.30 dB -11.18 dB 3:36 07-On The Outside Looking In
DR10 -0.30 dB -12.25 dB 2:54 08-Miles To Go
DR9 -0.30 dB -11.77 dB 4:43 09-Sinking Stone
DR10 -0.30 dB -11.86 dB 4:04 10-Bonita And Bill Butler
DR9 -0.30 dB -11.69 dB 4:12 11-My Opening Farewell
--------------------------------------------------------------------------------

The offending track "Lie Awake" is DR9.

Also, the J River DR ratings exactly match these published values allegedly from "HDTracks"

- Rich

 

[PENG]

To be fair the Alison:

Here are the DR rating from HDTracks:

Album details - Dynamic Range Database

DR Peak RMS Duration Track
--------------------------------------------------------------------------------
DR9 -0.30 dB -13.10 dB 3:37 01-Paper Airplane
DR11 -0.30 dB -13.76 dB 3:07 02-Dust Bowl Children
DR9 -0.30 dB -12.50 dB 3:56 03-Lie Awake
DR10 -0.30 dB -12.17 dB 3:52 04-Lay My Burden Down
DR9 -0.30 dB -11.22 dB 4:04 05-My Love Follows You Where You Go
DR11 -0.30 dB -14.21 dB 5:20 06-Dimming Of The Day
DR10 -0.30 dB -11.18 dB 3:36 07-On The Outside Looking In
DR10 -0.30 dB -12.25 dB 2:54 08-Miles To Go
DR9 -0.30 dB -11.77 dB 4:43 09-Sinking Stone
DR10 -0.30 dB -11.86 dB 4:04 10-Bonita And Bill Butler
DR9 -0.30 dB -11.69 dB 4:12 11-My Opening Farewell
--------------------------------------------------------------------------------

The offending track "Lie Awake" is DR9.

Also, the J River DR ratings exactly match these published values allegedly from "HDTracks"

- Rich

Yes I see that it is DR9, but 90% of the time it is more like DR4 or 6 at the most. Problem is, by definition if it hits DR9 for a couple of second then it is. If you compare it with the Patricia Barber album, Smash, pick one that is also around DR9 and compare it with Allison's and you will know what I mean. It is like comparing peaks to RMS.

 

[RichB]

Yes I see that it is DR9, but 90% of the time it is more like DR4 or 6 at the most. Problem is, by definition if it hit DR9 for a couple of second then it is..

That makes me wonder about Adele which has many DR7 tracks (not to mention the terrible Mic'ing)

- Rich

 

[PENG]

That makes me wonder about Adele which has many DR7 tracks (not to mention the terrible Mic'ing)

- Rich

The Mic'ing is my pet peeve, but everyone seems to tell me it is the raspiness of her voice. I don't think so because I know the difference between her raspiness and distortion. I actually like her raspy voice. Well I have given up on that one because on one else heard it.

Some or Adele's tracks are compressed too regardless of the DR rating, but some are quite dynamic.

 

[PENG]

Rich:

This article does touch on what I was trying to say high DR number does not mean it is not compressed.

'Dynamic Range' & The Loudness War

I can assure you that if you play the Patricia Barber's Smash album at the same volume level, your A51 will not shutdown on you.

 

[AcuDefTechGuy]

Let's start a poll to see how many people DON'T own at least one external amp, regardless of what they believe.

Back when I started this hobby, I owned external amps right off the bat - 2 Acurus 200X3 amps. Never been without an amp.

So most likely when an audiophile asks, "When should I get an amp?", the answer is, "It's not When, but Which amp."

 

[PENG]

Let's start a poll to see how many people DON'T own at least one external amp, regardless of what they believe.

How long are you willing to wait to get an honest answer in an affirmative (to your exact question) fashion? You could be 100 years old by then.

 

[AcuDefTechGuy]

How long are you willing to wait to get an honest answer in an affirmative (to your exact question) fashion? You could be 100 years old by then.

You mean guys who don't own an amp won't participate?

 

[Irvrobinson]

A lot of hypotheses.

What did I say that's a hypothesis?

 

[RichB]

Rich:

This article does touch on what I was trying to say high DR number does not mean it is not compressed.

'Dynamic Range' & The Loudness War

I can assure you that if you play the Patricia Barber's Smash album at the same volume level, your A51 will not shutdown on you.

I have played some if it, but my PC is in pieces right now do to a DOA motherboard. Hopefully, I'll be back in business later in the week.
I am not sure why music has to be compared with the 60s although I have found that many of my late 80's CD are far less compressed than disks purchased more recently.

At some point, one has to ask, does this record sound good and what makes them sound good, Lack of limiters and compressors, the style of music?

Here is something that might be fun:

Dr. Chesky’s Ultimate Headphone Test Disc’s three flavors cost $12 (16-bit/44.1kHz),$18 (24-bit/96 kHz), or $25 (24-bit/192 kHz). If you’re looking to test out some headphones, or see how good your current headphones are, this “disc” is an excellent place to start. Definitely use music you know, but get to know this music too, as it’s exceptionally well recorded.
The test tracks, some of which are jaw-droppingly cool if your headphones are good, are like icing on the cake. Or maybe it’s the music that’s the icing on the cake of test tracks? Either way, good cake, and good icing.

[video=youtube;HzRYsw-WRPk]http://www.youtube.com/watch?v=HzRYsw-WRPk[/video]

- Rich

 

[Irvrobinson]

Over time yes, but in a single instance it is still just a single voltage level. 1 microsecond later it might be another voltage level yes, but I'm not sure why that matters. I don't think electronic components have a memory of that previous microsecond (baring the power drain on capacitors).

No matter how complex the music, at any one moment in time there is one value. You can prove this with music in the digital realm. One sample has one value between 0 and 65535 (when 16 bit at least).

All an amplifier is doing is taking the voltage for that one moment, and boosting it to the appropriate relative level.

There could well be something I'm missing here, but I just cannot see what.

Just for starters, using the notion of Pulse Code Modulation, which is an algorithm for representing sine waves in the digital domain, to try to characterize analog electrical circuits is not valid. I know you have it in your head that all an amplifier does is change a current with a certain voltage level to another voltage level, but the actual way audio amplifiers driving loudspeakers work is different, and more complicated. In the analog domain all of the frequencies you hear are being transmitted simultaneously and continuously for the duration of the sound they trigger from the speaker drivers. Each one of those waveforms, and there can be many thousands of frequencies being amplified at the same time, may entail different electrical parameters, like different impedances, different phase angles (sometimes the voltage will lead the current, or vice-versa) or differing capacitance or inductance. Back EMF is a factor that varies by speaker design and by frequency. There's a myriad of issues that make understanding analog signaling more complex than just your impression of a summed voltage level at an instant. The amplifier doesn't just "see" a single voltage level, it "sees" the summation (which is a figure of speech; the calculations aren't all addition by any stretch of the term) of every different electrical characteristic at every different frequency being conducted at any particular instant.

 

[alienmuppet]

Just for starters, using the notion of Pulse Code Modulation, which is an algorithm for representing sine waves in the digital domain, to try to characterize analog electrical circuits is not valid. I know you have it in your head that all an amplifier does is change a current with a certain voltage level to another voltage level, but the actual way audio amplifiers driving loudspeakers work is different, and more complicated. In the analog domain all of the frequencies you hear are being transmitted simultaneously and continuously for the duration of the sound they trigger from the speaker drivers. Each one of those waveforms, and there can be many thousands of frequencies being amplified at the same time, may entail different electrical parameters, like different impedances, different phase angles (sometimes the voltage will lead the current, or vice-versa) or differing capacitance or inductance. Back EMF is a factor that varies by speaker design and by frequency. There's a myriad of issues that make understanding analog signaling more complex than just your impression of a summed voltage level at an instant. The amplifier doesn't just "see" a single voltage level, it "sees" the summation (which is a figure of speech; the calculations aren't all addition by any stretch of the term) of every different electrical characteristic at every different frequency being conducted at any particular instant.

Okay maybe bringing digital into it was a bad idea; it was just to express that at a single instance in time there is a single voltage level.

You say the frequencies are being transmitted simultaneously, of course they are, but what is a frequency? Isn't it just a change of level *over time*, and sending multiple frequencies IS the result of summing? You do not have 2 levels at once at 1 particular instant of time, you have the SUM of them.

If at time point T we are at the peak of a 100hz frequency, and the peak of a 200hz frequency, the resulting level will be the 2 added together - as far as I know. This is why when you mix a song in a recording studio, you have to "make room" for each instrument to sit in a mix, and how well this is done depends on the engineer.

I realise at T, T1, T2, T3 etc. the voltage will be different and therefore the components may have different characteristics, and I realise that the back EMF is a factor, probably the single biggest factor. I just can't see how a transistor or resistor cares what voltage was being passed through it previously at T-1 T-2 T-3. I *can* see how a speaker cares, and I can see how a capacitor cares because they are both effected by what happened in the past.

I'm not saying all this to be argumentative, I'm just genuinely interested in how amplifiers work and I'm thinking of making a simple one just out of interest (I've played with electronics all my life, and write firmware/software for electronic devices made by one of my clients so have access to a fair few resources). I know there are different "classes" (like A, D, AB) of amplifier which I'd also need to look into. I know at the most basic level that it is just a transistor varying the resistance to the supply based on the input level [at any one point in time ;-)]. So as the input level goes up, the transistor allows more of the supply through. I imagine there also needs to be a hefty capacitor on the supply to handle the transients.

I do realise it gets more complicated in real world amplifiers than this... If there really are differences between the sound of an amplifier, surely the best way to understand why is to understand how they work and how the designs vary. I think sometimes people over romantise them as if they are doing something magical to some mystical input signal - I'm certainly guilty of it when I see some expensive sexy looking piece of audio hardware.. "it surely must be better". I sometimes wonder if the marketing team say "make it more expensive and it'll get better status and we'll make more money".