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Posted By: PaulCanada Pre-Amps and Amps questions. - 10/30/12 02:56 PM
Hi Everyone:

I have a couple of questions about pre-amps and amps that I hope someone will answer.

I have a Denon avr3311ci, M80s, vp180, qs8s, and a crappy sony sub from and old HTIB.

My questions are what is the purpose of a pre-amp?
2) will an external amp make my speakers sound better?
3) if I were to buy an external amp what would I buy a mono, stereo, etc?

I have looked at this and other forums and there is lots of information, however I have not found a simple dumbed down answer. any information will be greatly apreciated.

Paul
Posted By: Ken.C Re: Pre-Amps and Amps questions. - 10/30/12 03:17 PM
1. A pre-amp generally does the processing and selection of inputs. You can consider it to be equivalent to a receiver without a tuner and the final amplification stage.
2. A good sub is far more likely to make your system sound better.
3. You would buy an amp with the number of channels you would like, or multiples thereof (in other words, 5 mono amps for your existing speakers, or 2 stereo and one mono, or a 5 channel, or a 7 channel...)
Posted By: Boltron Re: Pre-Amps and Amps questions. - 10/30/12 05:24 PM
The preamp takes all your audio sources like Blu-ray, MP3 player, TV etc… and:
- Does the switching i.e. selects the input you want to watch, say TV.
- May do Digital to Analogue conversion
- Does equalization (bass, treble, room equalization etc…)
- Handles the volume control
- Does any channel mixing (eg. Stereo to DTS Neo 6)
- Adjusts the voltage of all the inputs to an appropriate level
- Finally, send the audio signal to the Power Amp

The Power Amp is what amplifies the audio signal and drives the speakers. Most AVRs have built in power amps and can typically drive 5 channels (L,R,C,SL,SR). This is convenient because one unit does it all. However there is a tradeoff.

While AVRs may state that they can output 5.1 at 100 watts per channel for example, they cannot actually output 100 watts simultaneously to all 5 channels at the same time. My Denon 4311CI claims 140W to 7 channels but read the fine print and you will find it can only drive two channels simultaneously at that power. The AVR power supply simply does not have the capacity to do so. If you are like me and like your explosions loud, you may be disappointed.

In addition, if you drive you AVR beyond its capacity (which is easy to do) it may go into clipping which is very bad for your speakers and will ultimately damage them.

So what to do if you want louder explosions? You go with external amps. I use a 3 channel ADA1000 to drive my M80s and VP150. My Denon just needs to drive my two surrounds and two rears. It all sounds pretty awesome.

The catch with using external amps however is that you're AVR must have Pre-Amp outs.

I hope this helps clear things up a bit.
Posted By: Ken.C Re: Pre-Amps and Amps questions. - 10/30/12 05:27 PM
I still say that his money will be better spent now on a (much) better sub than an amp. That way you'll definitely get better explosions.
Posted By: MarkSJohnson Re: Pre-Amps and Amps questions. - 10/30/12 05:40 PM
+1
Posted By: Kruncher Re: Pre-Amps and Amps questions. - 10/30/12 05:50 PM
Originally Posted By: Ken.C
I still say that his money will be better spent now on a (much) better sub than an amp. That way you'll definitely get better explosions.


Absolutely. That made a vast improvement for me in the overall sound and "enjoyability".

As JohnK always says, unused headroom is exactly that: a waste of all resources. You know that he'll chime in later.

I'd also say that your room size may play a factor here. I've got under 2K cubic feet in my room and my Onkyo receiver is plenty loud enough thank you. Large rooms - I mean huge here - are obviously different animals, and would need more assistance/power. Simple physics.

I really don't understand some of the folks here who have small rooms and seem to want to continually jeopardize their hearing. Mine's at risk from health treatments and I've been suffering with tinnitus for a over year now because of a single treatment of a drug last summer. It's really very uncomfortable. Be reasonable and protect your hearing. </dismounts soapbox>
Posted By: tomtuttle Re: Pre-Amps and Amps questions. - 10/30/12 06:56 PM
+n to what our other friends said.

If you want your "system to sound better", before spending money on an amp, I would:

-Get a new sub
-Experiment with speaker placement
-Experiment with wall coverings or sound treatment

I don't know how loud you are listening, how big your room is, or what content you're consuming. It's unlikely that the amplifier section of your receiver is the weak link in your system, or that buying a new amp is going to make the biggest difference for the money.

I bought a 3-channel amp for the L/C/R channels because it made me happy. I'm pretty sure it did NOT make an audible difference for the overwhelming majority of things I watch/listen to. But I'm still glad I did it.
Posted By: Murph Re: Pre-Amps and Amps questions. - 10/30/12 07:00 PM
Buying new electronics is always fun, but I agree with the above. Unless you need to fill an abnormally large sized area, there is a lot of other fun stuff to be had that will prove a better bang for the buck.
Posted By: fredk Re: Pre-Amps and Amps questions. - 10/30/12 10:51 PM
Originally Posted By: tomtuttle
+n to what our other friends said.

Friends don't let friends buy preamps when they could buy a really big sub to annoy the neighbours with? grin

Most rooms will do fine with a receiver rated at 90-100 wpc (two channels driven).

Most of the time, you are going to be using less than 20 watts to enjoy your system at a reasonable listening volume.

The exception is when your system is in a very large room AND you are listening from further away. In most cases, I expect that the listener is going to be in the range of 10-12 feet from their speakers.

Get a better sub so you can really enjoy the deep rumble in all those awesome action movies.
Posted By: dakkon Re: Pre-Amps and Amps questions. - 10/30/12 11:14 PM
Originally Posted By: PaulCanada


My questions are what is the purpose of a pre-amp?
2) will an external amp make my speakers sound better?
3) if I were to buy an external amp what would I buy a mono, stereo, etc?

Paul


2) no, it won't... amps "Should" simply amplifier the input signal. However, is another topic all together.. The simple answer is no....

3) in my system i have 3 amps. 2 stereo amps, and a three channel amp.

My small my stereo amp is rated to 500W @4ohms, as is my three channel amp. My second stereo amp is rated for 1,200W @ 2ohms...

My "small" stereo amp/three channel amp weigh about 50-60lbs.. my "large" stereo amp weights about 110lbs...

I am sure JohnK will chime in here, me and him have polar opposite opinions to your question.

I have the amps i have for 2 reasons.. one, because my previous 5 channel amp was being driven into the clipping region on a couple channels (indicated by the clipping lights lighting up like a Christmas tree), so i bought bigger amps... The other reason, because i wanted a big amp, and i could afford it, so why not... Right?
Posted By: chesseroo Re: Pre-Amps and Amps questions. - 10/30/12 11:57 PM
JohnK seems to be doing alot of "chiming" based on a few reads in this thread.

So i googled "john chime" and some of the top images were:





It was a slow day.
Posted By: JohnK Re: Pre-Amps and Amps questions. - 10/31/12 01:57 AM
Paul, there are two stages of amplification that take place, regardless of whether a receiver or a separate pre-amplifier plus amplifier are being used. The pre-amplifier first increases the voltage coming in from the player or other source component about 4-5 times; the amplifier then increases this voltage about 25-30 times more, so the net result is an increase of about 100-150 times, which is enough voltage to drive speakers to very loud levels.

The pre-amplifier section of the receiver or separate unit also controls the various functions which other replies have listed. The volume, for example, is controlled by a variable resistor which varies the amount of the incoming voltage which is subject to the fixed 100 or so times "gain" mentioned above from almost 100% to almost none.

A separate amplifier can't improve the sound unless what you have is inadequate for the volume levels needed. Your 3311 is rated at 125 watts per channel, and this is the one area of audio that can be relied on as accurate, since it's subject to legal regulations of the FTC. Your 3311 can drive your speakers to beyond safe(to your hearing)listening levels, and more isn't needed. As Kruncher quoted me above, unused headroom is simply that: unused.


Your equipment, with one exception, is excellent, and it's agreed that a quality sub is what will improve your listening experience.
Posted By: brwsaw Re: Pre-Amps and Amps questions. - 10/31/12 04:00 AM
Originally Posted By: dakkon
Originally Posted By: PaulCanada


My questions are what is the purpose of a pre-amp?
2) will an external amp make my speakers sound better?
3) if I were to buy an external amp what would I buy a mono, stereo, etc?

Paul


2) no, it won't... amps "Should" simply amplifier the input signal. However, is another topic all together.. The simple answer is no....

3) in my system i have 3 amps. 2 stereo amps, and a three channel amp.

My small my stereo amp is rated to 500W @4ohms, as is my three channel amp. My second stereo amp is rated for 1,200W @ 2ohms...

My "small" stereo amp/three channel amp weigh about 50-60lbs.. my "large" stereo amp weights about 110lbs...

I am sure JohnK will chime in here, me and him have polar opposite opinions to your question.

I have the amps i have for 2 reasons.. one, because my previous 5 channel amp was being driven into the clipping region on a couple channels (indicated by the clipping lights lighting up like a Christmas tree), so i bought bigger amps... The other reason, because i wanted a big amp, and i could afford it, so why not... Right?


What amp visually confirms clipping?
Posted By: J. B. Re: Pre-Amps and Amps questions. - 10/31/12 09:28 AM
brwsaw, the great majority of pro amps have clipping indicators along with a few audiophile amps.
Posted By: brwsaw Re: Pre-Amps and Amps questions. - 10/31/12 03:14 PM
The search begins.
Posted By: dakkon Re: Pre-Amps and Amps questions. - 10/31/12 06:02 PM
Originally Posted By: brwsaw
What amp visually confirms clipping?


The amp i was referring to is a Marantz MM9000 135W @ 5 channels. It has an LED for each channel to indicate if that channel is clipping, so you can see which channel is clipping...
Posted By: Cohesion Re: Pre-Amps and Amps questions. - 10/31/12 07:06 PM
Originally Posted By: JohnK
Paul, there are two stages of amplification that take place, regardless of whether a receiver or a separate pre-amplifier plus amplifier are being used. The pre-amplifier first increases the voltage coming in from the player or other source component about 4-5 times; the amplifier then increases this voltage about 25-30 times more, so the net result is an increase of about 100-150 times, which is enough voltage to drive speakers to very loud levels.

The pre-amplifier section of the receiver or separate unit also controls the various functions which other replies have listed. The volume, for example, is controlled by a variable resistor which varies the amount of the incoming voltage which is subject to the fixed 100 or so times "gain" mentioned above from almost 100% to almost none.

A separate amplifier can't improve the sound unless what you have is inadequate for the volume levels needed. Your 3311 is rated at 125 watts per channel, and this is the one area of audio that can be relied on as accurate, since it's subject to legal regulations of the FTC. Your 3311 can drive your speakers to beyond safe(to your hearing)listening levels, and more isn't needed. As Kruncher quoted me above, unused headroom is simply that: unused.


Your equipment, with one exception, is excellent, and it's agreed that a quality sub is what will improve your listening experience.




With all respect to JohnK I have to go against the prevailing wisdom here and say that a new amp would likely make the biggest improvement in your listening experience. I'll explain why but it's a bit of a long story...

First of all, I was until recently in a very similar (and happy!) situation to Paul. I have a Denon AVR4802, which is a ten year old receiver also rated at 125Wpc -- a bit older than Paul's but also somewhat higher in the Denon food chain in its day. My front speakers are a pair of M80v3's and a VP180. I had no amp and it was good! The Axioms are truly a fine set of speakers!

Then I heard on the forum about the newly released LFR1100's. I had to jump on the pre-order pricing and am now the owner of a set, although I've not finished setting them up. Of course, part of the reason for that is that I now need four channels of amplification for the LFR's. I was in the process of acquiring some good Bryston amps on the used market when, wouldn't you know it, Axiom announced the new ADA amps. Of course I jumped on the pre-order pricing for that and have recently received a new four channel ADA 1500 with the idea that, if I didn't like it for driving my main speakers, I could use it for the rear channels of my HT when I eventually get a new room built in my basement and spring for a set of QS8's.

Anyway, I of course became curious: how much of a difference would the amp alone make in my existing system? I, like some of the others on this forum, didn't think there would be much difference, if any. But why not give it a try as I build up my system in preparation for the LFR's?

So I did. I took the front L & R pre outs from my 4802 and connected them to two of the inputs on the ADA1500. Then I disconnected the speaker outs from the receiver and re-connected them to the outputs of the ADA1500. Then I gave a quick listen... which became a long listen... and WOW!

There was an immediate and obvious improvement in sound, both for stereo music (from CDs) and surround sound music (the Peter Gabriel Secret World concert DVD). This improvement included much tighter, punchier bass, improved clarity, and more pronounced highs. Actually the bass was so much better I had to check if I'd accidentally changed a setting on my subwoofer but the improvement was still obvious even with my sub turned off. (It didn't seem to add too much, which I guess makes sense given that the M80's and VP180 can go quite low on their own. Note that I'd already set the 3 front channels as "large" in the receiver setup and that did make a big difference compared to "small".)

I'm quite honestly amazed at how big a difference just adding two channels of ADA1500 power to my existing system made!

I hope this posting helps.
Posted By: AdrianD Re: Pre-Amps and Amps questions. - 11/01/12 12:08 AM
Originally Posted By: cohesion
With all respect to JohnK I have to go against the prevailing wisdom here and say that a new amp would likely make the biggest improvement in your listening experience. I'll explain why but it's a bit of a long story...

I also have respectfully disagree; a good amp will make a big difference, even disregarding the raw power benefits. I have a fairly decent receiver (Yamaha RXV567) and a pair of cheap-ish monoblocks (Emotiva UPA-1).
The difference in SQ is huge. To my ears anyway.
Posted By: Cohesion Re: Pre-Amps and Amps questions. - 11/01/12 12:28 AM
Hi Adrian,

Thanks for backing me up! I actually understand that the Emotiva monoblocks are quite good. It would be interesting to compare to the ADA1500.

Actually I'm in Maple too. Perhaps we should arrange a mutual listening swap? I should have my LFRs working soon too...
Posted By: JohnK Re: Pre-Amps and Amps questions. - 11/01/12 01:42 AM
Even in Maple the amplification process has no capability to change the characteristics mentioned if other factors, especially sound level, are held constant. Amplifiers make the sound louder. That's it. No magic.
Posted By: AdrianD Re: Pre-Amps and Amps questions. - 11/01/12 02:33 AM
Originally Posted By: JohnK
Even in Maple the amplification process has no capability to change the characteristics mentioned if other factors, especially sound level, are held constant. Amplifiers make the sound louder. That's it. No magic.

I hear what you're saying John... and it's true, somewhat. It applies to ideal/perfect amps, which indeed should not alter sound in any way. I guess that's the difficulty when comparing 2 really good, hi-end amps. But unfortunately amps are not created equally; otherwise, why are we even bothering with anything more than a cheap receiver from Best Buy? grin

Originally Posted By: cohesion
Hi Adrian,

Thanks for backing me up! I actually understand that the Emotiva monoblocks are quite good. It would be interesting to compare to the ADA1500.

Actually I'm in Maple too. Perhaps we should arrange a mutual listening swap? I should have my LFRs working soon too...

I am very interested in some auditioning; it would be very exciting comparing the ADA1500 with the Emotiva stuff.
Needless to say, I want to hear the LFRs; they should be amazing.
Just say the word, and we can certainly arrange something.

John, I would be honoured to have you for some auditioning as well, a beer or a coffee, and discuss further. I am truly interested in why do you believe there is no difference in sound between amplifiers.

As it happens, not long ago I had a chance to review two amps in the same class: Emotiva XPA-5 and ATI 1504 (ATI: Amplifier Technologies Inc. makes amps for Mark Levinson, Lexicon, Cary Audio, Theta Digital, B&K, etc, owning the later two.)
You can read about my findings here:
The Emotiva Lounge - XPA-5 vs ATI 1504
Posted By: tomtuttle Re: Pre-Amps and Amps questions. - 11/01/12 04:23 AM
Can you describe your methodology?
Posted By: JohnK Re: Pre-Amps and Amps questions. - 11/01/12 06:33 AM
Adrian, I'm a long way from Maple(my reference to it was just to indicate that basic principles of audio technology of course still apply there), but your invitation is appreciated.

You appear to view this as a matter of mere personal "opinion", but on the contrary it's based on well-established principles of technology. All that amplifiers do is add more voltage so that there's enough to drive speakers to high volume levels. It would be rather amazing if simply doing this could somehow affect sound characteristics which have nothing to do with increased voltage. This applies to all amps, not just non-existent "perfect" ones. As long as the amplification is accomplished with audibly level frequency response and inaudibly low noise and distortion(achieved these days in even units of modest cost)nothing more can be done.

Of course, claims to the contrary are abundant, but when put to the(blind listening)test, they collapse for lack of support. The vintage Stereo Review blind listening tests remain unchallenged by later results(not just by stubborn disagreement)and illustrate the lack of reliability in open listening while knowing the identity of the unit involved. Note that the sometimes flowery descriptions of sound characteristics when heard openly under identical conditions before the blind sessions began disappeared when the brand labels and price tags did.

The editor of the Audio Critic summarised this basic point rather well in "Electronic Signal Paths Do Not Have a Personality!" . Failure to grasp this leads to a hopeless search for sound quality in basic amplification rather than concentrating time and money on features that matter(e.g., room EQ)and the many other variables that affect our listening enjoyment at home.
Posted By: SirQuack Re: Pre-Amps and Amps questions. - 11/01/12 02:23 PM
My caps provide a warm and powerfull punch in the gut sound over my Denon alone. smile
Posted By: MarkSJohnson Re: Pre-Amps and Amps questions. - 11/01/12 05:02 PM
MY CAPS PROVIDE A WARM AND POWERFUL PUNCH IN THE GUT SOUND OVER MY DENON ALONE.

Hmmmmm.

I dunno. Reads the same to me. grin
Posted By: CatBrat Re: Pre-Amps and Amps questions. - 11/01/12 05:33 PM
I always remembered caps as a short, high pitched pop sound.
Posted By: Murph Re: Pre-Amps and Amps questions. - 11/01/12 06:04 PM
Good One Cat,
Please press the big red button found here.
Posted By: J. B. Re: Pre-Amps and Amps questions. - 11/01/12 06:52 PM
i don't dare push it, being cautious on the net.
call me what you want!

;-)
Posted By: PaulCanada Re: Pre-Amps and Amps questions. - 11/01/12 11:40 PM
WOW! thanks for all the input!

Lots of great information provided here. I think I will add a new sub, and who knows maybe later add some amps. I dont have a big listening room and my denon can play pretty loud (hey I'm over 40 and the ears cant take it)

Thanks again for all the info

Paul
Posted By: dakkon Re: Pre-Amps and Amps questions. - 11/01/12 11:46 PM
Paul, my room is 17'X18' and is open to the rest of the house. This is part of where my extra power need was coming from... When i added a second sub, that was a significant improvement... More so than adding the extra 700W of power from the large stereo amp...
Posted By: SirQuack Re: Pre-Amps and Amps questions. - 11/01/12 11:55 PM
40's here as well, and a cranked up AVR alone is harder on the ears than one with plenty of horsepower behind it. smile
Posted By: aaaaaaaaaaaaa Re: Pre-Amps and Amps questions. - 11/10/12 03:28 AM
Not all AVRs are created equally... that is why there is a night and day difference for some and not others. A cheap best buy receiver is obviously cheaper for a reason. Transformers. (insert lazer sounds)

It has to do with the current supply rating of the secondary of the power supply transformer. Voltage is one thing, and does provide SPL. Current is also important as it provides depth, punch and clarity. Dynamics if you will. Even at low volume.

A simple way to think of it is a motor's ability to drive a mechanical load with less current vs rated current. If voltage remains constant and the load is increased current must also increase to stop the process from stalling out. If the current is not on hand, ie. the transformer is limited, then the rate of doing work will slow until the process halts. In a speaker the mechanical load is the driver itself. It's ability to quickly change motion and counter linear forces are directly related to current. Now we can understand why headroom is important.

This is why higher end power amplifier separates quote the kVa rating of their transformers. The higher the kVa rating of a transformer, the more current it can theoretically supply if voltage and frequency remains constant. Ie, the rate of work possible is much better.

This is also why subwoofers have dedicated amplifiers. It should stand to reason speakers would benefit from the same ample power treatment. Deciding what is ample is completely subjective. But it can be argued more real power is definitely a good thing, and therefore costs a premium.
Posted By: JohnK Re: Pre-Amps and Amps questions. - 11/10/12 04:45 AM
HC, Ohm's Law hasn't been repealed, and if it ever is, it'll be revealed in my AES Journal, not on an audio forum, and will probably result in a Nobel Prize in Physics.

Speakers vary widely in impedance with frequency, and at a given frequency and impedance, with a given amount of voltage from the program source, after amplification, the current is specified by Ohm's Law as I=E/R(current equals voltage divided by resistance). Whether the amplifier cost $100 or $100,000, the current has to be the same, and is specified by Dr. Ohm, not by manufacturer hype intended to entice the uninformed or misinformed.
Posted By: aaaaaaaaaaaaa Re: Pre-Amps and Amps questions. - 11/10/12 07:21 AM
Ah the ohm's law gets chucked in.

I agree totally. But ohm's law is really only pertinent for static loads purely resistive in nature (heaters/incandescent lights etc.) Once you start to account for magnetic fields, variable frequency, net reactance, efficiency(power factor), linear torque, counter torque, inrush, etc. you have to start looking at motor/transformer theory.

Stricktly speaking I=E/R is not used outside of AC\DC purely resistive circiut calculations... The "I" in this case is the "in phase" current relating to the resistive components in a circiut only. It is not what the load would draw from the source.

Resistance and impedance are not to be confused. Resistance is fixed and does not vary with input voltage or frequency. Reactance is affected by the frequency of the applied voltage, and the net inductive\capacative reactance component (leading or lagging Ohms.) Impedance is then calculated by adding resistance to reactance using trig. Since speaker drivers are a combination reactive\resistive load they require more apparent power (va) to operate than what is acutally used to drive the load mechanically (true power--W)

Speaker drivers can be seen as a motor that has a constantly changing mechanical load. The inertia created by the driver must be overcome, quickly, by a sudden inrush of current to realign magnetic fields and change the driver's motion. Inrush in a circuit usually results in a brief voltage sag-- especially when a transformer is involved (and exhibits poor voltage regulation.) This effect can be observed in your house as your lights dim slightly for a second when the microwave starts etc. Car audio is a good example of this. Large capacitors are often used to mitigate the issue.

A good amplifier is able to compensate for these demands by employing an ample transformer, with good voltage regulation and secondary current rating. They will then usually pair the transformer with a capacitor bank to help with maintaining output voltage. This all relates back to Lenz, Faraday, Henry and others that followed Ohm.

The difference and what everyone seems to ignore is that the capacity of the transformer to provide the current (VA rating) is of high importance-- and often cost.
Posted By: SirQuack Re: Pre-Amps and Amps questions. - 11/10/12 03:40 PM
oh man, here we go again.
Posted By: Boltron Re: Pre-Amps and Amps questions. - 11/10/12 03:43 PM
Ah this brings back memories. Of course Hell is correct, speakers present an inductive reactance so we shouldn't think in terms of ohms but impedance for speakers. In addition in AC circuits with reactive loads we should not think in terms of watts but VA (Volt Amps) or apparent power.

I remember many, many, many moons ago when I had a teacher make us do a lab where this little capacitor was apparently sinking something like 100 watts. The class all came up with the answer and the the prof laughed and opened our eyes to impedance.
Posted By: dakkon Re: Pre-Amps and Amps questions. - 11/11/12 01:43 AM
Originally Posted By: Hellcommute

The difference and what everyone seems to ignore is that the capacity of the transformer to provide the current (VA rating) is of high importance-- and often cost.


This is pretty much the only rating that i looked at when i was buying amps... My large stereo amp has the below spec's..

3000VA with a capacitance of 40,800µF per channel.

Considering the cost of copper nowadays... Yes, the power trasformer can be a Huge part of the overall cost.
Posted By: JohnK Re: Pre-Amps and Amps questions. - 11/11/12 02:53 AM
When a relatively simple and basic point is made briefly, there's some danger of it being inundated with a flood of terminology in response. Of course there was no suggestion that a speaker is a fixed resistor, and the varying impedance(due to capacitive and inductive reactance)with frequency was mentioned. Ohm's Law(sometimes phrased in the I=E/Z form to use Z to emphasize impedance rather than pure resistance)specifies the current in effect in a given speaker at a given frequency and voltage input. This is a fixed amount of current, dependent on the speaker, which can be neither lower nor higher, regardless of the amplifier.

This was pointed out simply because of an incorrect implication in a previous reply that the capabilities of an amplifier could change the current specified by Ohm's Law and that somehow the speaker would then work better.
Posted By: dakkon Re: Pre-Amps and Amps questions. - 11/11/12 04:15 AM
Originally Posted By: JohnK
Ohm's Law(sometimes phrased in the I=E/Z form to use Z to emphasize impedance rather than pure resistance)


John, i've never seen Ohm's law used in any AC circuite analysis.. Usually for AC circuit analyses the minimum math required is algebra, and more likely deferential calculus, due to the vector calculations required.. there are constantly changing variables of the inductance and capacitance within the circuit, Ohm's law is not sophisticated enough to do the calculations.

Here is a quick example of the differences that i am talking about, notice all of the resistances have vectors associated with them. Ohm's law has no way at all of taking angle vectors into account. it is to simple of an eqn intended to be used for a static DC circuit.

http://www.freeclassnotesonline.com/Circuit-Impedance-Analysis-Exam-1.php
Posted By: wilwom Re: Pre-Amps and Amps questions. - 11/11/12 06:40 AM
This is sooooo much fun! Pass the popcorn please.
Posted By: fredk Re: Pre-Amps and Amps questions. - 11/11/12 06:49 AM
Originally Posted By: wilwom
This is sooooo much fun! Pass the popcorn please.

It would be more fun if I knew what they were talking about, but hey, pass the popcorn please. grin
Posted By: JohnK Re: Pre-Amps and Amps questions. - 11/11/12 08:11 AM
Alex, that's curious unless maybe it's just a matter of semantics, i.e., when Ohm's Law is used in its AC form some think it shouldn't be called Ohm's Law. However, it is of universal application and a quick googling turns up numerous examples illustrating application to AC, for example here and here . Of course, this is using the Z factor rather than R to take into account varying impedance with frequency.

Certainly the calculations for impedance are more complex than for pure resistance, but the point is that once done the result is a specific current: same speaker, same frequency, same input voltage results in a fixed current which can't be changed by changing the amplifier.
Posted By: Boltron Re: Pre-Amps and Amps questions. - 11/11/12 01:39 PM
Enjoy the music, not the math.
Posted By: dakkon Re: Pre-Amps and Amps questions. - 11/11/12 03:21 PM
John, it's not a matter semantics (well it may). If an EE degree was as simple as understanding Ohms law for AC theory, then there would be a LOT more people getting EE degrees... I have several friends with EE Degrees, and Cal 3 was easy for them in comparison to Differential eqn's...

John, as you know.. You have to be careful with your sources, your second source simplifies Z to much...

I found a power point of a lecture, this professor used Z=I/V. However, i think the true take away from the lecture is that Z is not anywhere near as simple to calculate as R (which the second source above implies).. It is the same base eqn, but that is about it... When you look through the power point, you still see what i mean. The powerpoint is a little long, at 252 slides... I did not "read" the entire thing, i skimmed it to see if it was portent to our conversation... Later today I will call a buddy of mine, to get is input and will share what he has to say..

Here is the power point
http://www.personal.rdg.ac.uk/~stsgrimb/teaching/ac_circuits.pdf

Boltron, what you fail to realize, is well.... we have been here before, and will probably be here again. The biggest take away, is this is a civil academic discussion not an argument, and we all will likely learn something from each other.
Posted By: dakkon Re: Pre-Amps and Amps questions. - 11/11/12 03:40 PM
Originally Posted By: JohnK
same speaker, same frequency, same input voltage results in a fixed current which can't be changed by changing the amplifier.


John, i think this part of your statement is subjective... The subjective part of it is the design of the amp. Under ideal conditions the answer is yes. However, as we both know not all products are of the same quality. Under the statement you said above, this would be true for amps that are designed as a constant voltage source.. a good example of this not being the case is the Emotiva amps (not that i am saying emo's are bad). If you look at their ratings, as the resistance of the load is reduced by 1/2 the power does not double.. This means they do not maintain a constant voltage. With the amps i chose to buy, as the resistance reduces by 1/2 the power doubles each time; they are designed to be a constant voltage source. The large Emotiva monoblock is the only amp in their lineup that i am familiar with that doubles in power with a reduction of the load resistance.
Posted By: pmbuko Re: Pre-Amps and Amps questions. - 11/12/12 04:49 AM
Does anybody here take issue with the results of double-blind tests, the data from which show, statistically, that listeners are unable to discern any audible difference between competently designed amps of differing designs (e.g. tube, solid state, class A, B, etc.) and price points?
Posted By: dakkon Re: Pre-Amps and Amps questions. - 11/12/12 06:13 AM
no, not really... the general concensus around here is thst most solid state amps "sound" the same. i personally have never heard a tube amp, so i can not speak to that... i have solid state amps at 3 different price points, ranging from the 1,000$ area to the many many thousands of $$ area. to me, they all "sound" the same.. the big difference is the amount of power.

one thing you may notice is, me and john are discussing more the power and calculation there of, with no mention to the "sound". This is primairly because me and him both agree, and know we both agree on this point smile.

That's my take anyhow....
Posted By: Andrew Re: Pre-Amps and Amps questions. - 11/12/12 03:11 PM
My personal bent on this, after having designed, modified, and lived with numerous amplifiers over the years with differing topologies and active components, is that the question is really too complex to answer. There are too many different parameters of an amplifier that can and do change the sound. Our biggest problem is the specifications that people typically look at when trying to compare amplifiers. They are mainly meaningless, other than to quantify a measurement that is performed on a test bench with a contrived load that does not in any way resemble a loudspeaker. The interaction between amplifier and load is extremely complex, and the math involved is even more daunting because with music you are dealing with a constantly moving target.
A good example that I can thrown out there is if we were to take a fictional Class A/B amplifier and Class D amplifier, both with identical power supply capability and both rated at 100 watts into an 8 ohm load, at 1kHz with 1% THD. They both have a frequency response at 1 watt of 10Hz-30kHz. These two competently designed amplifiers should sound similar if not identical if run within their rated power. Listening to them they sound totally different beyond a certain listening level. Why would that be? Well, we have not speicified the power bandwidth of the amplifiers. Turns out the Class A/B example can deliver full power at all frequencies, but the Class D example has limited output power in the low bass and high treble. There are numerous cases, such as the one described, that CAN account for two similar amplifiers sounding different. Throw a transformer-coupled tube amplifier into the mix and now you have added non-linear frequency response to the table! smile
Posted By: Ken.C Re: Pre-Amps and Amps questions. - 11/12/12 03:27 PM
OH BURN.
Posted By: dakkon Re: Pre-Amps and Amps questions. - 11/12/12 03:52 PM
I guess the point i was trying to make, was that the math gets ridiculously hard pretty quick when dealing with an AC circuit..
Posted By: Cohesion Re: Pre-Amps and Amps questions. - 11/12/12 04:36 PM
This has been an interesting thread! With all that math being thrown about, I was about to call for an RMA on my ADA1500 because clearly the difference I thought I heard was all in my head!

Not really...

But to get back a little bit to the original question that started all this, would it be better to upgrade the OP's sub-woofer or get a new amp?

I originally based my answer on what I heard when I added an ADA 1500 to my receiver and it made a very big difference -- much more than I expected! The OP was in a similar situation to me, with M80's and a similar receiver but a 'cheapish' subwoofer.

I can say that I often like to listen to music quite loud, and this is certainly part of the difference that I heard. I checked the owner's manual for my receiver and it claims 125 Wpc @ 8 ohms for all channels, without specifying how many channels it can really drive to this level. It also claims 'Dynamic Power' up to 170 Wpc @ 8 ohms or 270 Wpc @ 4 ohms for only two channels driven. Either way, the ADA can no doubt produce much more real power when driving my M80's!

However I don't think that is the full story, as the ADA seems to sound better even at lower volume levels, though it is not so noticeable then. I do think that the difference is not only in the bass but across all frequencies.

Now let us ask a different question: How much better would an upgraded subwoofer sound? I don't know from direct experience but it does seem to depend a bit on what the system is used to listen to and how the listener likes it to sound.

I've been trying for a fairly neutral, clear sound, which I think the Axioms largely deliver regardless of amplification options. I myself don't have a very good subwoofer, so when I set it up to blend in well with my system, it probably can't go much lower than the main speakers (M80's or LFR's) can go on their own.

After all, the M80's can produce bass down to around 30 Hz or so. My sub is only rated down to 20 Hz and at that point I think it is already down by 9 db or so. The M80's themselves are probably only down by 12-15 db at 20 Hz. So assuming the M80's are being driven full range, with my sub I may only really get a slight emphasis in the bass below 30 Hz. What's down there anyway?

In terms of music, there's not much other than tubas and pipe organs that can play below 30 Hz, and even then, when do they? I guess that a better sub might be able to reproduce better, lower explosions with more rumble, but that would only help with movies (mostly action movies) and perhaps the 1812 Overture, wouldn't it?
Posted By: dakkon Re: Pre-Amps and Amps questions. - 11/12/12 05:32 PM
Originally Posted By: cohesion

In terms of music, there's not much other than tubas and pipe organs that can play below 30 Hz, and even then, when do they? I guess that a better sub might be able to reproduce better, lower explosions with more rumble, but that would only help with movies (mostly action movies) and perhaps the 1812 Overture, wouldn't it?


I noticed a significant difference when i added my second EP600. I also do a decent amount of stereo listening. John told me about a couple of pipe organ CD's.. With the Dual 600's i can tell you, there is a significant amount of sound in the lower frequencies.... So, i think there is a common mis-conception that a good subwoofer "only, or mainly" benefits action movies... There are a lot of CD's that sound MUCH better in my opinion with a couple good sub's.
Posted By: Cohesion Re: Pre-Amps and Amps questions. - 11/12/12 06:18 PM
OK, I don't have one yet but let's agree that an Axiom subwoofer like the EP600 is a very good subwoofer. Let's also agree that having two is better than one.

Having said all that, the response of the EP600 in a typical room is flat from about 17 Hz up to 100 Hz. So when you're doing your stereo listening, I don't doubt that you're getting a lot of good sound out of your EP600s. However, how much of it is actually under 30 Hz or so? In other words, how much is actually sound that you wouldn't be able to hear out of a set of M80's?
Posted By: J. B. Re: Pre-Amps and Amps questions. - 11/12/12 08:06 PM
in my own experience, having a good subwoofer that goes down very low also adds to the ambient acoustics in a recording, whether it is music or movies.
take out the sub, and the ambiance is not as good, as real sounding.
Posted By: dakkon Re: Pre-Amps and Amps questions. - 11/12/12 08:24 PM
Originally Posted By: cohesion
However, how much of it is actually under 30 Hz or so? In other words, how much is actually sound that you wouldn't be able to hear out of a set of M80's?


This is a pretty subjective question... It depends on the music. Using a pipe organ CD, like you said, the answer to that scenario would be quite significant.

I primarily listen to classical, there is a pretty good amount of material in the lower range in classical, depending on the composer. Like J.B. said, one of the big factors is the ambient sound. This is where the experience becomes more than just numbers. Sure, the M80's play down to 30hz, with that being said. There is a HUGE difference between the impact of a sub at a given frequency as compared to a pair of towers. I would say impact is the best way to describe the difference. Before my LFR's, i used a pair of M60's for many years. When i added my first 600 it was nearly night and day.. Again, the whole experience like J.B. referring to.


I guess you could liken it to a bookshelf speaker that "plays" down to say 40hz, as compared to a tower that "plays" down to 40hz.. the tower is going to have a whole lot more impact than the bookshelf.. This is where the experience becomes more than just a numbers game... Kind of like your amp experience, on a piece of paper, there "shouldn't" have been a big difference... but the real world experience can be vastly different than the numbers on a page would sugest.


I think i am starting to ramble now... So, i am going to stop with the hopes that i answered your question. If i didn't i'll be more than happy to try again!
Posted By: Cohesion Re: Pre-Amps and Amps questions. - 11/12/12 08:47 PM
Thanks for that answer!

I'd like to try one of those pipe organ CD's on my own LFR's to hear how it sounds for myself. What do you recommend?
Posted By: J. B. Re: Pre-Amps and Amps questions. - 11/12/12 08:53 PM
my former speakers, Energy 22 Pro, would go down to around 22 Hz at 75 dB SPL, but when playing loud, i would miss nearly an octave in the lows because of the box and speaker size, among other things. they could not keep up at higher power levels.

my current speakers, M80's because of box/speaker size and tuning, go lower down than the Energy when playing loud.

Frequency Response is one thing, but there is another very important thing: power response (Freq. Resp. at high power levels).

Dakkon is not the only one rambling; sometimes it's nice to be able to do that. ;-)
Posted By: J. B. Re: Pre-Amps and Amps questions. - 11/12/12 08:57 PM
Originally Posted By: cohesion
Thanks for that answer!

I'd like to try one of those pipe organ CD's on my own LFR's to hear how it sounds for myself. What do you recommend?


i would recommend Cameron Carpenter's "Revolutionary" on a hybrid SACD: http://www.amazon.com/Revolutionary-Hybr...meron+carpenter

for the price of the hybrid disc, you get a 30 min. DVD of him playing the organ, to show his style.
the sound is not as good as the SACD, the deep bass is lacking.
Posted By: dakkon Re: Pre-Amps and Amps questions. - 11/12/12 09:00 PM
Here are two. Enjoy!

http://www.amazon.com/Poulenc-Organ-Conc...words=chan+9271

http://www.amazon.com/Camille-Saint-Sa%C...ywords=cd-80274
Posted By: BlueJays1 Re: Pre-Amps and Amps questions. - 11/12/12 09:02 PM
Originally Posted By: J. B.
my former speakers, Energy 22 Pro, would go down to around 22 Hz at 75 dB SPL, but when playing loud, i would miss nearly an octave in the lows because of the box and speaker size, among other things. they could not keep up at higher power levels.

my current speakers, M80's because of box/speaker size and tuning, go lower down than the Energy when playing loud.

Frequency Response is one thing, but there is another very important thing: power response (Freq. Resp. at high power levels).

Dakkon is not the only one rambling; sometimes it's nice to be able to do that. ;-)


Exactly. 22Hz @ 75db is equivalent to the sound of a fart in the wind! Though I do believe the proper terminology is power compression rather than power response.
Posted By: exlabdriver Re: Pre-Amps and Amps questions. - 11/12/12 10:53 PM
JB:

I just ordered 'Cameron Live' CD & DVD from Amazon for $15 CAN (it's coming from California). Unfortunately no SACD available for this one.

From the reviews, this DVD is much better than the one with 'Revolutionary' that was decidedly SD in the video department. Evidently it rivals Blu Ray with upscaling...

TAM
Posted By: J. B. Re: Pre-Amps and Amps questions. - 11/13/12 02:04 AM
don't forget to tell me what you think when you've seen and heard them.
Posted By: exlabdriver Re: Pre-Amps and Amps questions. - 11/13/12 06:05 AM
JB:

I gave 'Revolutionary' a spin today. Track #2 - Bach: "Evolutionary" Toccata and Fugue in D Minor - is downright scary with its bass extension & the length of time that these notes are held.

While my M2s handled the mids & highs with ease, I thought that my little EP400 was going to cough its woofer out onto the floor; however, it made it through OK!

The dynamics of this SACD are amazing, from the softest, almost inaudible keyboard notes to the sudden blasts of the big foot pedal notes. I can't imagine what a really big system must sound like on this track...

TAM
Posted By: J. B. Re: Pre-Amps and Amps questions. - 11/13/12 11:42 AM
as i wrote a few days ago, it is a BEAST!
most impressive to listen to. it is just like you were standing
12 ft. in front of the really big pipes, with the rest of the pipes
scattered around the church.

i had a couple of people listen to that track and when finished,
they had a hard time getting up from the sofa.
if they had listened to the whole cd, they would have liquefied.

i find this cd more impressive than any sound effect in the movies i own, including the ones i like best, those in Master and Commander.

a good indicator of the quality of this recording is the fact that when you play this SACD at higher than normal vol., the sound does not degrade, it is crystal clear, but much more imposing yet.
Posted By: Cohesion Re: Pre-Amps and Amps questions. - 11/13/12 12:04 PM
OK, now to see if I have anything that will play an SACD...
Posted By: J. B. Re: Pre-Amps and Amps questions. - 11/13/12 12:26 PM
Originally Posted By: cohesion
OK, now to see if I have anything that will play an SACD...


it is an hybrid CD/SACD; you don't really need the SACD player.
unless they cut off the ULF in the CD; i haven't tried it so i can't say.
knowing Telarc, the CD should be full range.
Posted By: exlabdriver Re: Pre-Amps and Amps questions. - 11/13/12 07:12 PM
Unless one has a very robust system, I wouldn't play this one at excessive levels. Woofer damage is certainly possible if there isn't some kind of limiting involved.

I suspect that I was playing it at about an average of 85 Db. Unlike when I was far younger, once the volume gets higher than that, I have to back it down as I just don't enjoy these high levels anymore. Besides, my house & my 4 cats just can't take it either, ha!

I've heard numerous pipe organs in cathedrals & while they are impressive & powerful they don't generate these sound levels within their huge structures that we can in our smaller areas.

TAM
Posted By: J. B. Re: Pre-Amps and Amps questions. - 11/13/12 08:14 PM
I've never heard a large pipe organ;
i've heard a couple of small ones in my town, but a few dozen pipes is a different league.
Posted By: medic8r Re: Pre-Amps and Amps questions. - 11/13/12 08:21 PM
I heard that Mark played a large pipe organ in high school and college. He says it was just a phase, and then he married Joyce.
Posted By: pmbuko Re: Pre-Amps and Amps questions. - 11/14/12 01:50 PM
I'm pretty sure he said he was an organ grinder. That's quite different from a pipe organ.
Posted By: MarkSJohnson Re: Pre-Amps and Amps questions. - 11/14/12 02:14 PM
Actually, the use of the pipe organ caused me to eat Grinders.
Posted By: J. B. Re: Pre-Amps and Amps questions. - 11/14/12 03:06 PM
i had a look at your link Mark, and wonder how many people actually do what they say about subwoofers:
"In eastern Massachusetts a grinder is a toasted sub, for example the sub is toasted in a pizza oven"

i would not do that with mine, even with the promise that sound would be improved.

i suspect this is another audio myth.
i would prefer to throw a pinch of salt towards the sub for good luck (and better sound).
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