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Topic: Simple stereo amplifier? (Read 20012 times) previous topic - next topic
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Simple stereo amplifier?

I'm looking for a stereo amplifier that will drive speakers rated at 6 ohms 40-250W.  Input would be at least two line inputs (audio out from old TV and the like).

Any specific recommendations?

Is there likely to be an audible difference between 0.02% THD and 0.2% THD?

Do these specs seem appropriate for the speakers?
Minimum RMS Output Power (8 ohms, 20 Hz-20 kHz): 100 W + 100 W (0.2% THD)
Dynamic Power / Channel (8 / 6 / 4 / 2) ohms: 125 / 150 / 165 / 180 W

Anything else I should be looking for?

Simple stereo amplifier?

Reply #1 –
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Is there likely to be an audible difference between 0.02% THD and 0.2% THD?
No.    It's unlikely that you'll hear any distortion from any modern amplifier unless it's overdriven.


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I'm looking for a stereo amplifier that will drive speakers rated at 6 ohms 40-250W.
I'm not sure what that means.    If the speakers can handle  250 Watts of normal program material, I don't know what the 40W means.

Amplifiers are rated for minimum impedance...  An amp that works with 4-Ohm or 6-Ohm speakers will also work with 8-Ohm speakers.    However since you get more current with lower impedance, many amplifiers will put-out more power (more Watts) at with lower impedance speakers.

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RMS Output Power (8 ohms, 20 Hz-20 kHz): 100 W + 100 W (0.2% THD)
Dynamic Power / Channel (8 / 6 / 4 / 2) ohms: 125 / 150 / 165 / 180 W
For "normal home listening", 100W is usually way more than enough.  But, the amount of power you need is almost impossible to predict.  It depends on the sensitivity/efficiency of the speakers, how loud you listen, and the size of your listening room.  If your speakers are 6-Ohms, only the 6-Ohm power ratings are relevant.  I'd probably ignore the "dynamic" power ratings.

If you want to "rattle the walls" and feel the bass, you may benefit from more power (if your woofers/subwoofers are capable of that kind of bass).

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Anything else I should be looking for?
As far as electrical specs, power and the ability to drive 6-Ohm speakers is the only thing I'd worry about. 

Beyond that, you can consider the manufacturer's reputation (do you believe the power rating?) overall quality, any features you want like gain controls, power or clipping indicators, appearance, etc.    Some high power amps have cooling fans, which some listeners don't like because of the noise. 



Simple stereo amplifier?

Reply #2 –
Quote from: DVDdoug on
Quote
I'm looking for a stereo amplifier that will drive speakers rated at 6 ohms 40-250W.
I'm not sure what that means.    If the speakers can handle  250 Watts of normal program material, I don't know what the 40W means.

I can't find official specs, as the speakers are rather old and no longer made, but here are two rather similar versions:

Sensitivity 87 dB @ 1 watt-meter
Impedance 6 ohms
Recommended power 40-250 watts

Sensitivity: 87dB/2.83V/m.
Nominal impedance: 6 ohms.
Minimum amplifier power: 40–250W.

The speakers are Thiel CS2.

I'm not looking for heavy bass or to rattle walls.

Any manufacturers you'd recommend or recommend against? Any views on brands such as Yamaha and Sony?

Simple stereo amplifier?

Reply #3 –
Quote from: richard123 on
I'm looking for a stereo amplifier that will drive speakers rated at 6 ohms 40-250W.  Input would be at least two line inputs (audio out from old TV and the like).


All of the integrated amps and receivers I know of have much less than 250 wpc,

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Any specific recommendations?


Rethink your application. 120 wpc works for most people, speakers, and rooms.

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Is there likely to be an audible difference between 0.02% THD and 0.2% THD?


More to the point, is that really an issue?

The given distortion is just specsmanship. Most good SS amps have 0.02% or less  THD right up to clipping. Distortion rises pretty qucikly after clipping, so the 0.2% spec is probably taken while the amp is clipping. It might be a matter of backing the power off an insignificant amount to reduce its distortion below 0.02%.

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Do these specs seem appropriate for the speakers?
Minimum RMS Output Power (8 ohms, 20 Hz-20 kHz): 100 W + 100 W (0.2% THD)
Dynamic Power / Channel (8 / 6 / 4 / 2) ohms: 125 / 150 / 165 / 180 W


The  major but hidden agenda item is your preference for loudness, given in dB SPL.

In general your best price/performance is obtained from an AVR (multichannel receiver) even if you don't use more than 2 of its channels.  This is due to the economies of scale and tight competition.

Simple stereo amplifier?

Reply #4 –
Since nobody has mentioned it: listen before you buy.  Placebos not withstanding, if you listen to it and you don't like it then it can't be a good idea to buy it whatever the specs say.  Ideally you would want to listen with your actual speakers in your actual situation, but I guess nothing is perfect in the real world.  Still, given the amount I imagine you're going to spend, it is worth a little effort to get close.

Simple stereo amplifier?

Reply #5 –
Quote from: lithopsian on
Since nobody has mentioned it: listen before you buy.  Placebos not withstanding, if you listen to it and you don't like it then it can't be a good idea to buy it whatever the specs say.  Ideally you would want to listen with your actual speakers in your actual situation, but I guess nothing is perfect in the real world.  Still, given the amount I imagine you're going to spend, it is worth a little effort to get close.

Based on what I've read here, including the helpful comments in this thread, there's little if any audible difference between modern amps so long as they have adequate power.

I'm not looking to spend much.

Simple stereo amplifier?

Reply #7 –
Quote from: richard123 on
I'm looking for a stereo amplifier that will drive speakers rated at 6 ohms 40-250W.  Input would be at least two line inputs (audio out from old TV and the like).

Any specific recommendations?

A good amp available for very reasonable price is the Yamaha AS500. Well built with a 85 wpc output. The latest version is the 501 with a built in DAC, so the 500 may be marked down now and be a very good buy. Only con perhaps is the weight and the size/footprint.
Just one good solution out of many in the market these days.

Simple stereo amplifier?

Reply #9 –
Only because I have no idea about AVRs of any kind. I looked it up just now and was taken aback to see how cheap it is. If it would do as well as the AS500 for the application, it is the better buy.

Simple stereo amplifier?

Reply #10 –
Quote
I'm looking for a stereo amplifier that will drive speakers rated at 6 ohms 40-250W. Input would be at least two line inputs (audio out from old TV and the like).

Any specific recommendations?

Is there likely to be an audible difference between 0.02% THD and 0.2% THD?


Higher rated power sounding better usually is linked to it having lower distortion at the actual power levels listened to. Have a look at the THD vs Power graphs on Stereophile to check this. A 100W amplifier may be rated at 100W but at e.g. 1% THD, while a 200W amplifier may have just 0.1% THD at the same 100W output load.

Unfortunately power ratings are the Wild West, just like frequency responses and weighing filters. Anybody can claim anything, and it's up to the consumer to make sense of the testing conditions. Some manufacturers rate at 10% THD or frequency response at -10dB, while others may use 1% THD and -1dB for example.
We are beyond the days of PMPO mostly, thank goodness, so now there are ways to tweak RMS values.

Simple stereo amplifier?

Reply #11 –
Quote from: lithopsian on
Since nobody has mentioned it: listen before you buy.  Placebos not withstanding, if you listen to it and you don't like it then it can't be a good idea to buy it whatever the specs say.  Ideally you would want to listen with your actual speakers in your actual situation, but I guess nothing is perfect in the real world.  Still, given the amount I imagine you're going to spend, it is worth a little effort to get close.


Looks to me like just another rendition of the placebophile dictum that all amplifiers sound different. Where is TOS 8 when you need it? ;-)

If someone says that you need to operate a piece of equipment to make sure that its controls and functions work for your situation, than of course that's hard to argue with to a certain degree. However, all amps have inputs and outputs and a level control, and after that the variations go downhill pretty fast.  You might have to look at a real piece of equipment to determine whether you want silver face or black face or like the colors and fonts of the text displays, but...

Simple stereo amplifier?

Reply #12 –
Quote from: Yahzi on
Quote
I'm looking for a stereo amplifier that will drive speakers rated at 6 ohms 40-250W. Input would be at least two line inputs (audio out from old TV and the like).

Any specific recommendations?

Is there likely to be an audible difference between 0.02% THD and 0.2% THD?


Higher rated power sounding better usually is linked to it having lower distortion at the actual power levels listened to. Have a look at the THD vs Power graphs on Stereophile to check this. A 100W amplifier may be rated at 100W but at e.g. 1% THD, while a 200W amplifier may have just 0.1% THD at the same 100W output load.


Misses two important points:

(1) There is no necessary relationship between THD well below clipping (which is where most equipment operates most of the time) and maximum power output.  Look at data from the source you cited:

(example A) http://www.stereophile.com/content/pass-la...er-measurements



Fig.4 Pass Labs XA60.5, distortion (%) vs 1kHz continuous output power into 8 ohms.

(example B)

http://www.stereophile.com/content/rotel-r...er-measurements

[

Fig.8 Rotel RB960BX, distortion (%) vs 1kHz continuous output power into (from bottom to top): 8, 4, 2 ohms.
Fig.1 Goldmund Mimesis 8, distortion vs output power into (from bottom to top at 10W): 8 ohms, 4 ohms, and 2 ohms.

Now, you have to look at these tests sensibly, which means that any amount of THD that is well below 0.1% (e.g. 0.05% or less) is perceptually the same - always inaudible no matter what.

Both amps therefore have the same amount of distortion if they are not clipping. Clipping is indicated by the sharp rise in THD above about 100 watts for the Pass and 60 watts for the Rotel.  Interestingly enough the Pass actually rises above 0.1 %THD before it starts clipping, but the range of power where this happens is not perceptually significant.

Simple stereo amplifier?

Reply #13 –
Quote
There is no necessary relationship between THD well below clipping (which is where most equipment operates most of the time) and maximum power output. Look at data from the source you cited:


So you are saying that THD does not follow output power below clipping?

So if the power output rises, the distortion won't rise linearly? But I see in the graph that the distortion started to rise steadily on the Pass Labs after 3 watts or so, all the way up to 100 watts, until it skyrocketed.

That tells me that distortion is increasing with output.

Can you explain that?

Simple stereo amplifier?

Reply #14 –
Quote from: KumarK on
Quote from: richard123 on
I'm looking for a stereo amplifier that will drive speakers rated at 6 ohms 40-250W.  Input would be at least two line inputs (audio out from old TV and the like).

Any specific recommendations?

A good amp available for very reasonable price is the Yamaha AS500. Well built with a 85 wpc output. The latest version is the 501 with a built in DAC, so the 500 may be marked down now and be a very good buy. Only con perhaps is the weight and the size/footprint.
Just one good solution out of many in the market these days.

Yes. Always a good idea to take a look at something that has just been replaced by a newer model. Dealers will want to get rid of them and are likely to do you a good deal. Richer Sounds built an empire out of such practices.

Simple stereo amplifier?

Reply #15 –
Quote from: Yahzi on
But I see in the graph that the distortion started to rise steadily on the Pass Labs after 3 watts or so, all the way up to 100 watts, until it skyrocketed.
The scale on the graph is logarithmic.
Ignoring how the ear behaves at different SPL levels, at what level do you believe THD becomes audible with a 1k test tone?  How about replacing that test tone with real content?

Simple stereo amplifier?

Reply #16 –
Quote
The scale on the graph is logarithmic.


But the power and distortion increased in a linear fashion past 3 watts. I thought it was said that distortion and maximum output had no relationship. The graph proves otherwise.

Simple stereo amplifier?

Reply #17 –
Quote from: Yahzi on
Quote
There is no necessary relationship between THD well below clipping (which is where most equipment operates most of the time) and maximum power output. Look at data from the source you cited:


So you are saying that THD does not follow output power below clipping?


It may or it may not.

There are no absolute rules.

There will be examples and counter examples.

There are conflicting influences. For example, really powerful amplifiers tend to have more THD+N at low power levels simply because they have to have more gain to reach full power with a standard input signal (+4 dBm). Talk to the people who make the mistake of hooking really powerful amps to really efficient speakers and then sit close to them in a quiet room.

But big picture, the discussion is going off topic. What is the global relevance of lower measured distortion? Beyond a certain readily obtainable point, lower measured distortion means nothing related to sound quality. I said as much in my post. Don't you believe it?


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So if the power output rises, the distortion won't rise linearly?



The mistake above is making it all about how distortion rises not to mention yet another repetition of placebophile obsession with measurements uber alles.  The starting point also matters.  Take 100 milliwatts or 1 watt as your starting point. Right away the discussion gets derailed, because everybody measures THD+N, and at those levels, the noise often dominates the measurement.  Therefore the curve in print is never monotonic.

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But I see in the graph that the distortion started to rise steadily on the Pass Labs after 3 watts or so, all the way up to 100 watts, until it skyrocketed.


What's wrong with staying on topic and talking only about audible distortion? Amp measurements can go all over H&!!'$ half acre and as long as they remain below readily obtainable levels, they mean nothing related to SQ.

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That tells me that distortion is increasing with output.


It tells you what you want to hear, it seems.


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Can you explain that?


It's just a limited sample of data, and data that is largely irrelevant to SQ unless you make some of the mistakes mentioned above. 

The fact that none of the curves are truly monotonic destroys the claim that more powerful amps always have lower measured distortion as the ragazines measure it.

Simple stereo amplifier?

Reply #18 –
Quote from: Yahzi on
Quote
The scale on the graph is logarithmic.


But the power and distortion increased in a linear fashion past 3 watts. I thought it was said that distortion and maximum output had no relationship.


Reading comprehension seems to be a lost art. I said that there was no necessary relationship.

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The graph proves otherwise.


Cherry-picked data alert!

I like this curve: ;-)

http://www.soundandvision.com/content/yama...t-labs-measures



(1) The amp is deadly cheap.

(2) Contrary to placebophile dictum, it does not use a discrete output stage.

(3) I own one.

Simple stereo amplifier?

Reply #19 –
Quote
The fact that none of the curves are truly monotonic destroys the claim that more powerful amps always have lower measured distortion as the ragazines measure it.


Sorry English is not my first language. What does monotonic mean? I don't understand the context.

Simple stereo amplifier?

Reply #20 –
Quote from: Yahzi on
Quote
The fact that none of the curves are truly monotonic destroys the claim that more powerful amps always have lower measured distortion as the ragazines measure it.


Sorry English is not my first language. What does monotonic mean? I don't understand the context.


Monotonic means steadily increasing or steadily decreasing.

The basic concept we are struggling with here is the idea that amplifier distortion is always steadily increasing with increasing power.

Reality is that all of the plots we've discussion are neither entirely steadily increasing nor steadily decreasing but instead have regions where they increase and regions where they decrease.

Furthermore, if we pick some standard low power level, such as 100 milliwatts or 1 watt, the distortion at this point varies from amp to amp.  This is significant because a great deal of listening is performed at levels below 1 watt.

Simple stereo amplifier?

Reply #21 –
Quote from: Arnold B. Krueger on
Quote from: Yahzi on
Quote
The fact that none of the curves are truly monotonic destroys the claim that more powerful amps always have lower measured distortion as the ragazines measure it.


Sorry English is not my first language. What does monotonic mean? I don't understand the context.


Monotonic means steadily increasing or steadily decreasing.

The basic concept we are struggling with here is the idea that amplifier distortion is always steadily increasing with increasing power.

Reality is that all of the plots we've discussion are neither entirely steadily increasing nor steadily decreasing but instead have regions where they increase and regions where they decrease.

Furthermore, if we pick some standard low power level, such as 100 milliwatts or 1 watt, the distortion at this point varies from amp to amp.  This is significant because a great deal of listening is performed at levels below 1 watt.


Do the power levels have regions where they increase or decrease because of how the measurements are done, or is this just a function of how amps operate in general?

Why do distortion levels fluctuate like this? I don't understand. One minute it's lower at a lower power level, then it's higher.

What I also don't know is if the amp measurement test is representative of how amps are used in the home. They use 1 kHz tones. We use music. But music can have frequencies that are full-range, so wouldn't that put a whole lot more strain on average on amps and speakers than just a 1 kHz tone?

Simple stereo amplifier?

Reply #22 –
Quote
Furthermore, if we pick some standard low power level, such as 100 milliwatts or 1 watt, the distortion at this point varies from amp to amp. This is significant because a great deal of listening is performed at levels below 1 watt.


Is 0.1% audible? I saw the Yamaha receiver you posted has 0.1% THD+N at 1W. Or is it just a general rule that amps at 1W produce distortion too soft to hear regardless?

The only thing I'm curious about is that 0.1% seems low, but then it's only handling a single frequency. I can't imagine how it would be easier for the amp to handle a burst of energy at many different frequencies, especially frequencies well below 100 Hz.

Simple stereo amplifier?

Reply #23 –
Quote from: Yahzi on
Do the power levels have regions where they increase or decrease because of how the measurements are done, or is this just a function of how amps operate in general?


It can be either.

The general initially decreasing followed by increasing at a low slope, followed by increasing at a high slope pattern is partially a consequence of the common questionable practice of measuring THD+N.

the initial region of decrease may be due to noise, or it may be due to low-level nonlinearity.  If the measurement were of just THD then this area of ambiguity would disappear.

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Why do distortion levels fluctuate like this? I don't understand. One minute it's lower at a lower power level, then it's higher.



Different measurement practices produce different results.

Different amplifiers produce different results.

Quote
What I also don't know is if the amp measurement test is representative of how amps are used in the home. They use 1 kHz tones. We use music. But music can have frequencies that are full-range, so wouldn't that put a whole lot more strain on average on amps and speakers than just a 1 kHz tone?



Most SS amps are equally comfortable amplifying any frequency from 60 Hz to 12 KHz, and that will suffice in a great many cases.

Most power amps are used at far lower power levels than their maximum, and that means that they will probably operate more cleanly than they do at or near full output.

Finally, music generally has dynamics that are easier for just about any power amp to amplify than pure sine waves.

In general the tests that are commonly used put far more stress on the amp than actual use by far, even if they don't go up to clipping or down to 20 Hz or up to 20 KHz.

Simple stereo amplifier?

Reply #24 –
Quote from: Yahzi on
Quote
Furthermore, if we pick some standard low power level, such as 100 milliwatts or 1 watt, the distortion at this point varies from amp to amp. This is significant because a great deal of listening is performed at levels below 1 watt.


Is 0.1% audible?


Generally no.

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I saw the Yamaha receiver you posted has 0.1% THD+N at 1W.



More likely the noise is 60 dB down.\

But we don't know for sure because THD+N conflates noise and distortion which is really pretty misleading if not stupid.


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Or is it just a general rule that amps at 1W produce distortion too soft to hear regardless?


Most amps are audibly clean at 1W.

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The only thing I'm curious about is that 0.1% seems low, but then it's only handling a single frequency. I can't imagine how it would be easier for the amp to handle a burst of energy at many different frequencies, especially frequencies well below 100 Hz.



Actually, handling energy at a few or even many frequencies simultaneously below clipping is far easier than handling a sine wave because any multitone has a higher crest factor than a pure sine wave.