|   Good AMP - vs - Bad AMP | ne1scott
Nov 3, 2003 8:56 PM | | From what I have been hearing and reading, the home audio world is devoid of any real comparable standards that can be counted on to tell the difference between a good amp and a bad amp. The only thing that seems to ring true, is that if it costs ALOT more...it's probably better. Duh !!!
If I want a good sounding amp that has kick ass power then what exactly do I look for ? Watts RMS from 20-20k ? Weight ? transformer/cap type ? brand name ? cost ?
I see the Audiosource AMP3 and the Alesis RA500 weigh only about 30 lbs and are rated 150Wx2 @8 ohms. I assume that Parasound, Harmon Kardon, Rotel, Adcom, and others have about the same weight for the same give power output. Is this the new norm ? If so, what was sacrificed ?
Why then is my friends 6 year old Adcom AMP rated at only 100Wx2 @8 Ohms yet it weighs 80 lbs ? It has the performance I am looking for. How can these new lightweight amps compete ?
I really want to buy something NEW so that I will have a full warranty. I need at least 100 Watts or more. |
| Good amps wear white hats, bad amps wear black hats | skeptic
Nov 4, 2003 5:24 AM | | The heart and soul of ANY power amplifier is its power supply. You can't have a good amplifier without a good power supply. And the heart and soul of a good power supply is the power transformer. You can't build them on the cheap or fake them with small light weight immitations. Lots of filtering from large capacitors is also a requirement. It's harder to tell what kind of regulation they have without a schematic and knowledge of electrical circuits or detailed specifications. As for circuit topologies for the signal itself, arguements vary all over the place as to whose is best. For solid state amps, look for large heat sinks required to efficiently dissipate lots of heat. Even fans may be present. For tube amplifiers, look for large heavy output transformers and large output tubes. For fans of small low powerered SET amps, you're on your own. Finally, listen to the amplifier with a variety of loudspeakers of different efficiences and complexities of crossover networks to see how they take up the challenge of difficult loads. Listen to music at low volume through very efficient speakers to see if you hear crossover notch distortion. Listen to them playing loudly with low efficiency speakers to see how well they handle peak power demandss and even how they recover from momentary overloads.
When small lightweight amplifiers cost a lot of money, the manufacturer will usually tell you he is a design genius who knows something nobody else knows and implies that you should pay a lot for this knowledge. He may also stress difficult to get custom or high quality parts. (He won't tell you that he is an inefficient manufacturer who has no economy of scale--see my posting on amplifier costs.) If it is light weight and small but boasts a lot of power, it may have a cheap and poor quality switching mode power supply. Learn to read and understand specifications and independent test reports. If you can take it apart to see the inside, examine the quality of manufacture. Look for neat open wiring and glass epoxy circuit boards as a good sign. Look for plenty of clearance between parts and high quality soldering too. It's your money. The more you know, the more wisely you can spend it. |
| What about digital amps, such as TacT, PS Audio? | Feanor
Nov 5, 2003 2:02 PM | | The large and heavy power supply rule doesn't apply to them, as I hear.
(Just had the caps in my old Phase Linear 400 upgraded from 5900 uFd to 22,000 -- they had to be installed in an outboard box! I think the result is an improvement: not entirely sure though, the tech had my amp for 8 weeks so I can't precisely remember what it sounded like before. Duhh!) |
| What about digital amps, such as TacT, PS Audio? | skeptic
Nov 6, 2003 4:44 PM | | Don't know about digital amps. That is a new and rare animal. But one way or another, they have to deliver current to a loudspeaker.
Anyway, insofar as analog amps are concerned the large capacitors do at least two things; first they filter out 60 hz hum so the larger the capacitors, the lower the residual hum lever. Second they act as a charge reservoir to supply large amounts of current for short bursts until they are depleted. |
| Do different caps affect sound? If they do, why? | topspeed
Nov 7, 2003 11:53 AM | | Hey Skep,
I've got paper in oil(?) caps in my amp and have heard from another owner that switching to Black Gate electrolyctic(sp?) caps improves the sound by adding more detail. Outside of the additional capacity that the larger caps would have for transients, should switching them out make a difference? Why? This is all latin to me so I may not have even got the type of caps right, sorry?
BTW, I thought you'd appreciate this: My dad used to build Dynaco tube amps (I told you they were Hafler before, sorry my bad) and my sister e-bay'd them last year for practically nothing. AAUUUUUUGHHHH! |
| Do different caps affect sound? If they do, why? | skeptic
Nov 11, 2003 4:25 AM | | Frankly, to be perfectly honest....I don't know. People claim to hear things that would seem impossible. My guess is that if they are the same size, it wouldn't matter. As I said, larger capacitors in the power supply will give better 60 hz hum filtering and more reserve for short bursts of heavy current demand. That could make a difference depending on listening circumstances. As to the fact that they are made of different diaelectric materials, I can't see why minor differences in the small circuit model of their parasitic components would have much effect. But if you try them, let us know what you think.
Too bad about the Dynaco amps going so cheaply... I mean, how did I miss them? |
| 60hz hum? | topspeed
Nov 11, 2003 1:06 PM | | "will give better 60 hz hum filtering"
Is there an inherent hum at 60hz with all amps? What is this? The Black Gates are quite a bit larger than the stock ones so they will definitely have more reserve, although I'd imagine you'd have to really be pushing to make it worth while. Thanks for the info as always. |
| 60hz hum? | skeptic
Nov 12, 2003 4:46 AM | | Unless your equipment is powered from a battery, it gets power from the utility company at 60 hz ac. The first thing that happens to it after it gets past the on off switch and fuse is to be converted to dc, hopefully with as little ac ripple as possible. How is this done? A transformer changes it to the correct voltage, diodes whether solid state or tube rectify it to dc and large capacitors filter it. They do this by providing storage for charge. In fact they were once also referred to as bathtubs because they are charge reservoirs. Without the large electrolytic capacitors in the power supply, your dc voltage would look like ac except every negative going half cycle would appear as its mirror image on the plus side. The larger the capacitors, the better the filtering. The process can never be perfect. Residual hum shows up as a ripple on an oscilloscope. These dc voltages are used to bias the tubes or transistors. This ripple is superimposed on the signal and is part of what is measured and specified by "hum and noise." Obviously the lower the better. So one way to judge an amplifier without even hearing it is to look for large power supply capacitors. (Large transformer too but that's another story.) |
| re: Good AMP - vs - Bad AMP | topspeed
Nov 4, 2003 8:47 AM | | In addition to what Skeptic said, which is great advice, weight is one of the more naive ways to determine quality in an amp. While certain items such as quality power supplies are of course necessary (and necessarily heavy) there is very little correlation between the overall weight of an amp and it's abilities. New technology such as digital amps jettison heavy heat sinks and fins because they are so efficient, they simply don't need them. In fact, I remember reading an article where a reviewer popped the lid on an amp and found a 1/4" steel plate underneath the lid to add weight to the chassis. Of course the manufacturer said the plate was there to stabilize the amp. Uh, yeah...right. You're not alone in this weight=quality mindset. A noted reviewer even admitted recently that while he loved the sound of a particular amp that was small in stature, he missed seeing his monster reference mono blocks on the amp stand. Obviously, ego can be a factor with even supposedly unbiased reviewers. Hey, at least he was honest enough to admit his bias.
Personally, I'd be more concerned with current than watts. Watts are for headroom and bragging rights, current is where it's at. Don't forget, it takes twice as many watts to make a 3dB increase (which isn't very much). The proper amp will depend a lot on what type of speakers you're driving. Challenging speakers such as planers and 'stats that dip into 1 or 2 ohm loads at times will absolutely devour amps that can't provide enough current. I don't care if it's a 250w, 100lb beast, if it doesn't have the juice, it's a poor match with those speaks. System matching is very important so try to play with a lot of different amps within your budget and if possible, try them with your speakers in particular. There's no substitute for leg work, so get out there and enjoy the process.
Have fun! |
| re: Good AMP - vs - Bad AMP | RGA
Nov 4, 2003 11:13 AM | | Well hey if we're going to go by a watt to weight ratio most tubes amp kick butt. The ASL AQ1003DT is less than half the size of the amps you mention is only 30 watts and weighs over 30lbs...and a measily $800.00.
Bigg ass tranformers which weigh a ton with highish quality parts for the money. It prefers an 8 ohm speaker of which 90% of speakers are. SO if you choose a 4ohm or tougher speaker I would reckon you'll need to spend 10 times the money to get an amplifier that will sound AS GOOD and also drive the inneficient speaker.
Designing inneficient speakers is a way for the manufacturer to have an excuse "Well our speaker would sound better if you bought a better amp". SO then you end up in a long audio hell of upgrading your gear all the time when in fact your speaker was a dog all along.
You don't buy based off a weight...though it's not a bad indicator. Lifting some of those recievers I'm amazed they even have an amp inside them. |
| re: Good AMP - vs - Bad AMP | ne1scott
Nov 4, 2003 1:17 PM | | So...barring tube amps from the discussion due to price....What brands of amplifiers in the $300 to $500 street price range do you think would most meet my 4 Ohm 87db sensitivity needs ?
Has anyone tested the Alesis RA500 ? It's the one that seems the best from reading the specs. The Audiosource AMP THREE has gotten rave reviews from consumers. What about the Rotel 1070/1080, PArasound HCA-1000, Harmon Kardon PA2000 ?
I don't want to spend weeks listening to different setups since my speakers are different than anything in any store. I just want to make sure I have something that will be happy living life at 4 ohms or lower and will have plenty of power reserves. (I am going to a second custom shop)
Someday I'll be able to afford audiphile equipment. Today is not the day.....tomorrow doesn't look good either.... |
| re: Good AMP - vs - Bad AMP | RGA
Nov 4, 2003 6:39 PM | | Generally speaking you're always safe with a Rotel Power amp. For the money they don't exhibit any bad habits. Many consider them less transparent that Bryston...but at the same time more musically involving...that's what some people say not me. However, for the money, their build is excellent, they offer a lot of power, and sound very good. They also have a reputable name, been around along time, etc which are things you need to be aware of.
Lots of fly by nights - Rotel has been consistantly solid for decades. Alesis 500 - I've never heard of it...might be good who knows? |
| re: Good AMP - vs - Bad AMP | topspeed
Nov 6, 2003 10:29 AM | | Well Scott, you may not want to drag your speakers around from shop to shop but that's what you should probably do if they won't let you demo amps in your own set-up. Is it a pain in the ass? Yes. But if you blowing $500 buck on something that will give you years of enjoyment, the effort is worth it. BTW, I don't worry about "audiophile equipment" because most of it is hideously overpriced and bring questionable advantages to the table. I'd much rather have a giant killer in my rack than the giant itself. For many, ego is unfortunately a major part of this hobby.
Of the amps mentioned I agree with RGA in that Rotel is very reputable. You don't like used so that definitely limits you so check into Outlaw too.
Have fun! |
| I like them to be heavy | jbangelfish
Nov 4, 2003 1:51 PM | | My Parasound amps weigh about 65 or 70 lbs each and I like that. They have a quality look and they're a bitch to move around. I also have an old Accuphase integrated amp that is very heavy and a Crown DC300A that is quite heavy. While weight isn't everything, I've never heard a lightweight amp or receiver that I liked. Had some (Sony ES, Yamaha, Onkyo and others) and they did not impress me as having quality build or sound. There could be some new products that would impress me very much, I just haven't heard any.
I also like the distortion specs to be very low (measured in thousanths)and never to exceed .5 at the rated output. If it stays in this range, it should never produce audible distortion. The best frequency range that I can find, the old Crown gives 0 to 100k as it's range. I tend not to trust anything that claims 20 to 20,000 as this is sort of a standard rating for inferior equipment. While some may be exactly that, it's not a particularly good spec anyway unless you were talking about a speaker and many speakers claimed this range but either did it poorly or not at all.
I don't know why you'd want to buy new equipment when it will cost 3 to 4 times the money or more than if you bought equipment that is anywhere from 1 year to 20 or 30 years old. The point to this is that a waranty is usually 1 to 5 years with some going to 10 or even 20 but it's rare and quite expensive. 10 year old bryston 4b's sell for less than half their original price and still under waranty. My Parasound amps are nearly 20 years old and still work like new. I bought 2 of them for $750 each and they were near 2k each new. My Crown, which I bought new in 1975, is nearly 30 and has been repaired once for $125 (last year). They sold for around $1400 in the mid 70's. They still show up for $200 to $300 but they are getting old and nobody knows how long they will last yet.
Anyway, some of my thoughts,
Bill |
| Agree, buying used would make more sence | Geoffcin
Nov 7, 2003 3:49 PM | | If you want a quality amp that deliver the goods and not break the bank. I am amazed at how many great amps are to be found for a song on Ebay, and AudiogoN. I would definitely look into one for your current loving speakers. |
| Hey Geoff | topspeed
Nov 10, 2003 1:08 PM | | How's that HCA2 working with your 3.6's? I'm waiting for your review! |
| re: Good AMP - vs - Bad AMP | poneal
Nov 4, 2003 2:15 PM | | Ya its a jungle out there. I found a manual on the Audiosource AMP THREE and it didn't list curent capacity or whether the watts was continuous from 20-20,000. I'm definitely not an engineer or such but it seems to me that the more current the better equipped the amp is to power speakers. Out of the amps i have bought (which last me from anywhere between 15-20 years) Harman Kardon has been the best. The others were kenwood and pioneer. |
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