Generic amp question

[kippyieh]

Just curious, all things being equal, does the amount of 'hum' emmitted from a set of speakers (with the amp or reciever at full volume, no input) indicative of the quality of the amp/reciever?

[Ray Garrison]

"...all things being equal..." is the problem here. If you take, say, a receiver, set the input selector to (a) an input that has a component attached to but not turned on, or ( an input that does not have a component attached to it, or © an input that has a component attached and turned on but not playing anything (like a CD player in PAUSE or STOP mode) and then turn the volume all the way up, you will likely get three different levels of hiss or humm from your speakers. Which is higher and which is lower will depend upon a lot of factors regarding the design and engineering of the receiver, particularly how the inputs are buffered and grounded.

Set that aside for a moment. If you take two 100 watt / channel receivers, connect a CD player to them, turn on the CD player and don't put in a disc, then turn the volume all the way up on each receiver, you will likely find two different levels of hiss. Does this mean that the "quieter" unit is "better"? Well, uh, no... not necessarily. There are a LOT of other factors.

I don't have the time right now to go into this in too much detail - perhaps someone else can - but just a few things to think about:

Gain of receivers preamp and driver circuits

Noise of preamp / driver vs noise of power amp sections

If the quieter receiver has lower ultimate current output capability, it will sound worse when driven harder or into lower impedence loads

If the quieter receiver has higher voltage gain and the speakers have high impedence (say 15 ohms) it may sound much better

Noise is no indicator of harmonic distortion, intermodulation distortion, transient intermodulation distortion, slew rate, phase distortion, EMI or RFI suppression, crossover distortion, or a bunch of other things...

[kippyieh]

Lets say that everything is equal. Like the speaker/receiver connection at Ultimate Electronics, I select my Klipsch speakers, keep the same cd player as an input device (or none at all for that matter) and just switch the between th same price range-same wattage reciever/amp combo devices and turn the volume up till I hear the hum/hiss; will the better receiver remain quiter longer? Granted, the volume control knobs are all incremented differently; but shouldn't max volume setting = max wattage = same wattage? Or am I like out in left field here? What does it mean if anything?

BTW, does anyone know anything about Consumer Reports testing procedures? Do they rate recievers according to accurate reproduction of electronic signal; leaving the subjective 'ear' at home? That is the way it sounded, but I wasn't sure.

[dougdrake]

kippy - I think what Ray is saying is that the noise/hum issue by itself is not necessarily a good yardstick because there are things that the noisier amp may do better than the less noisy amp, which might make it the better amp. For example, if the power supply in the less noisy amp is low current, then it will clip and falter sooner than the noiser amp with a high current power supply when demands are placed on it. Some would consider the high current amp to be the better unit. All it means is that one receiver is noisier than another with no signal in it.

Personally, I completely ignore Consumer Reports for anything but car/appliance repair histories and who makes the best space heater. Not very subjective information there. Audio, OTOH, doesn't fit well in their if-you-can't-measure-it-we-can't-evaluate-it mindset, IMO.

DD

[kippyieh]

I am getting a little confused, is there really such a thing as an objective criteria with which to judge a HT system? Are there no measurable quantities? Is it really nothing more than brand preference? What is the objective good when it comes to a sound system?

Let me relate my recent endeavors. I was all set to buy a HtiB from Sony, Sony being the brand I was the most familiar with in personal electronics. Found several on eBay for under a thousand dollars, some looked nicer than others, so I decided to head to the nearest electronics store and attempt to listen to them.

Best Buy had several of the ones I was interested in, but none of them were set up correctly, all the speakers were hunched up on top of their respective consoles. The smaller units had more visual appeal, but I really had a hard time judging sound differences. I proceeded to ask the nearest salesman which systems were supposed to sound better. He said that bigger speakers move more air thus more potential for good sound. It didnt get much more complicated then that, but it made sense.

I went home and started doing some research on the net and ran across cnet.com, ecoustics.com and audioreview.com. I promptly looked in the forum where I found the Onk HTS 600 (or something like that) to be all the rage. Nothing better for the buck. I was convinced that Onk made a good product and that separate components were the way to go. I headed to the nearest Ultimate Electronics to give it a look see. They did not carry Onk, but had this great Denon/Klipsch (I think it was the Synergy setup) for under $1500.00. Well I was still partial to the Onk components (dont ask me why) but I was sold on the Klipsch speakers. Went back and did some more research and found out about the Reference series. After much straining of the head muscle, I purchased an Onk DVD and receiver and the Klipsch R-3s.

Now I run into this great forum, and I ponder upgrading the entire system and it is not even 2 weeks old.

It seems like I have had no guiding principals except the general consensus of the time, and I wonder what I have ended up with; sure it sounds great; much, MUCH better then my old system, but could it sound better? What is better? Do I upgrade the amp? Upgrade the speakers? I mean which do I work with? Stick with Klipsch? Why? Because I like the way they bronze the logo? Stick with Onk? Why? Because their $500 system was a good bang for the buck? Sure, we have various options on different brands of receivers, which may make things a little easier in this area, but all the receivers sound different on different speakers? So which comes first, the nice-looking-option-packed receiver and then speakers to match (whatever that means sounds the best) or should I remain loyal to the bronze logo and pick a receiver to match? I mean, what does it mean to sound good? Cannot ears (like the sense of smell), be conditioned to think that a whole host of things sound good? Am I striving to re-capture the intention of the original artist? Is this even possible without having the same amp and speakers he/she used when producing the original mix? (Isnt that the whole purpose of THX?) Should I be looking for un-adulterated signal processing in an amp? (Is this measurable? In amps or speakers?) Or should I be looking for the amp that conditions the signal and then find speakers that compensate? Where do you guys start anyways?

Peace

[dougdrake]

Kippy - So many questions, so little time (LOL)! All good ones, though.

Were it me, I'd get the best speakers I could possibly afford. Best, of course, meaning what sounded best to MY ears in MY home. That will give the best bang for the buck spent. Then, I'd back into the best receiver or amp/preamp combo I could swing. Then, the best source for the primary type of use I intend to make of the system (2-channel stereo, multi-channel music, HT, etc...).

Keep in mind that buying the best speakers you can afford may expose weaknesses in your current source components. So, you either have to be prepared to live with that until you upgrade the sources, or maybe step back a bit on the speaker budget and allocate some of that to source components, if you can't swing the whole enchilada at once.

The R-3 series is a great set of speakers. No particular reason to change unless you are burning to upgrade and have the cash to do it. Just remember, the upgrade path will never end. So, you have to be happy where you are, keeping an eye to the future (kind of like life).

This is why I'm a fan of buying used speakers -- let someone else take the depreciation hit, and I can usually sell for about what I paid for them. Same for electronics, but they depreciate far faster.

DD

[HDBRbuilder]

Kippy,

No matter how you look at it...cranking the volume of any amp/integrated amp/receiver all the way up, with NO CONNECTION to any speaker source is gonna RUIN the amp...it doesn't matter WHO MAKES IT or if it is tube or solid state...you are just frying capacitors when you do it!! It will also NOT tell you anything about the amplifier section except maybe that it can withstand this kind of abuse for a short period. And if you do this and some signal accidentlally gets into the amplifier section, then you may well blow the amp up!! If you are looking to find out what kind of backround noise an amplifier section produces...you have to try it out on the speakers you intend to use...that is the ONLY way you can find that out...and even then it may well be the sources going into the amp instead of the amp itself which are providing the backround noises. Either way...when testing an amp to do this..you NEVER crank it all the way up in volume!! doing so will drive the amp into clipping well before you get it turned all the way up, and will often blow a speaker component and/or the amp section itself. The general rule of thumb is to never go past HALF the distance a volume control has in its adjustment...because once you exceed that distance, you will likely be driving the amp into clipping soon! With highly efficient speakers, such as the heritage models...if you drive the amp too far, you will be deaf shortly anyway!! LOL! Specs for equipment are good to know, but the actual performance of equipment often belies the stated specs for it...so keep that in mind. there are many pieces of equipment out there that have virtually identical given specs, but which are a world apart in ACTUAL performance!! And keep this in mind too: Just because it is new and costs alot, doesn't mean that it will outperform something much older and far less expensive to purchase!! This last fact is proven daily on here!!

[kippyieh]

I meant to imply that the hum was coming from the set of speakers I had chosen, which happened to be the RF-3's. There was an input selected, the one generally used for demos (it had all the cds in it), but it was not playing. Without the salesman around, I was actually trying to figure out if I had punched the right buttons into the little demo board to try out the RF-3's vs. the RF-5's. I was slowly turning the Denon up - thinking that I did not have it turned up enough to hear, and maxed it out, somewhere before max I heard the hum. On the way home I began wondering if the hum was indicative of the quality of the amp.

What is actual performance? How do you measure it? If you have an accurate comprenhension of the input signal, can you measure the signal coming out of the amp and compare it to what you know you sent in? Can the perfect amplification of a signal be modeled? Or is it all in the ear?

[JohnA]

Kippyieh,

Yes your ears will get conditioned to a sound just like your nose will no longer smell ammonia after a while.

I, in fact, expect the entire audio chain to relay the source as unadulterated as possible and choose my components with that goal in mind, after I filter out the ones I am unwilling to pay for. I DO NOT want any "conditioning" of any sound from any component. If the recording sucks, so be it. Toss it and get another. You cannot recapture the the "intention of the original artist" in a different room with different gear. Don't try. Try for the least degradation you are willing to afford.

Doug is a friend and gives good advice. The components that transform the audio from one form to another are usually the most important. Start with speakers.

All components have specs and they can be used to select one over another. Beware of the gear with the "best" specs. The measures required to achieve great specs often makes for a lousy sounding component. Amplifier harmonic distortion is a good example. It can be reduced to detection limits, but if you do, the amp will have other forms of distortion caused by the huge amounts of corrective feedback needed to lower the distortion. Feedback is putting the output signal back into the circuit at the beginning in a way that cuts distortion. There is an inevitable time delay from the putting output back into the input after the signal has already gone through the amp. It can never be perfect.

Look for an amp that has a distortion no lower than 0.05% and no higher than 0.5%.

Other specs to look for are a damping factor greater than 80, but over 400 is not necessary.

Power should be calculated based on your speakers and room size. No Klipsch I know of can make use of more than 100 watts (100 will hurt). Even with your R?-3s, the first watt is the most important. Try to get an amp that is made to operate in Class A up to a watt. This is esoteric and it's called "biased to run in Class A up to x watts", but it's a way to get an amp that is cleaner in the first watt. All modern solid state amps run in Class A down low and Class B higher. It's called Class AB and it's very efficient.

Noise and hum will be specified, but again, don't go for an amp rated at 120 dB signal to noise ratio, too much feedback. 90 to 100 dB is probably good enough.

Lots of amps are called "High Current" these days. There is no standard for what that means. It's supposed to imply the the power supply and cooling is big. IMHO, "high current" should mean an amp can put out twice its 8 ohm rating into 4 ohms, like theory predicts. In practice, 1.5 times into 4 ohms is likely all you will see. In your price range, ignore "high current".

CD and DVD players will all have specs that look much the same. You'll just have to listen to them. Burr-Brown DACs are good ones to have. Others are probably as good, just stay away from $100 DVD players.

THX is a set of standards and it costs $$$$$ to get a product certified, mostly for the royalty fees. Non-THX gear is often better.

Finally, regardless of any of the above, listen to all of the components with your speakers in your room. Make sure it sounds good there. Have an agreement that you can return the component if you don't like it at home.

[kippyieh]

Sorry to Doug, I had no intention of sounding like I was jumping on him, it is the sound of desperation you hear

So the specs do matter; but receivers with the same specs may sound differently, correct? What is not listed in the specs that makes them sound differently?

It seems like THX does matter then to a degree, but I am unfamiliar with how they obtain the measurements; is it a measurement or x-number of dollars that does the deal?

Sorry to beg back to the perfect amplification model, but does it exist?

Thanks for the patience.

[JohnA]

Different amplifiers with similar specs can sound different. The difference nowdays is pretty small, though. The things that make one amp sound different from another usually can't be measured, yet.

A THX certicied part is usually very well made, but it is more a certification process with expensive royalties required to display the symbol and claim the certification. In many cases a non-THX component will be a superior product.

[dougdrake]

Hey Kippy - I don't think you were jumping on me, and I don't think John thought so either. I think he was just commenting on my advice

The analogy I think of is ice cream. You can take two premium brands of vanilla flavor, and their ingredients list could read the same, yet taste very different. Why? Probably the quality/source of the ingredients -- vanilla beans from the upper regions of the whosiwatsus mountains that were fed with rainwater hand dripped on them by a vestal virgin. Or that they were transported one at a time, completely by hand, by Tibetan monks wearing sandals. Anyhow, that's the stuff that can't be measured by might well affect the taste.

Hard for us engineering types to deal with, but just lend an ear and enjoy!

DD