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Post by avphile on Jan 19, 2005 10:52:38 GMT 7
Are you using separate power amps to boost the power of your receiver?
I suppose those with pre-amps in the other thread would have power amps as well. Care to share them?
What are the characteristics of power amps you value the most?
To start off, I have a couple of ACURUS power amps, one 2-channel(A250), 250watt RMS/ch and another 3-channel (A200X3), 200watt RMS/ch to power a 5.1 set-up. Then I just turn off the 3-channel amp for plain stereo listening.
Transparency, Accuracy and Clean Power are the things I look for and value in any amplifier. To explain:
Transparency - means a wide bandwidth with FLAT frequency response at its rated power - a wide sonic highway so to speak. It simply means allowing ALL the signals that went in to come out unimpeded. At least 20hz to 20khz at +-1.0db deviation from flat is adequate. My amp is rated at 10hz to 100khz at +-0.5db. Better amps have a rating of DC to 100khz +- 0.1db.
Accuracy - means nothing is added or subtracted to what went in in terms of THDs, IMs, TIMs, and other harmonic and non-harmonic distortion artifacts as well as amplification noise and many others. Ofcourse, there will always be something added or subtracted to the signals in the real world. But the lower and the less audible, the better. It often connotes the same thing as Neutrality. At its rated power, my amp has 0.06%THD and an IM and TIM of 0.005% max at 8ohms. Not the lowest figures I've seen, but good enough for me.
Noise floors or S/N ratios also speak of the level of accuracy. Good figures start at 100db and upwards, Mine is rated at 110db S/N, which would be close to most SACD and DVD-A players that have 110db S/N and above. (It doesn't really make sense to have a player rated at 110 db S/N only to be thrashed by an amp with a 90db S/N. As always, the audio chain is only as good as the poorest link.)
Some other aspects are slew rates, or the speed at which the amp can deliver a 1-volt signal, the faster the better. Most amps and receivers today have excellent slew rates and most manufacturers don't see the need to indicate this in their specs. Then, there's channel separation; no interchannel bleeding or inteference common in most jampacked receivers. 75db is the starting point, the higher the better. (That's why monoblock amps or stereo amos with monoblock construction are preferred in this area with channel separtion above 100db.) Mine is rated at 90db, good enough for me.
Lastly, much debate attends the issue of damping factor, or the amp's ability to control the speakers, especially the woofer. The higher the figure the better. Mine is 500 at 50Hz into 8 ohms. I've seen some amps with 1000 or more. An amp with good damping will certainly deliver a more musical bass line. (But since, I am using a powered sub, I think this is a province better reserved to the power amp in the sub.)
Some would define accuracy to mean the sound is identical to live instruments. Let's not kid ourselves, no home playback system will ever sound like the real thing. The most accurate ones can only approach. High Fidelity has often been misconstrued to mean sounding like the real thing. They sometimes do. But Hi-fidelity simply means fidelity to the recorded media. Not to the real thing. That's the objective of home playback - to give justice to the recorded media. OTH, capturing the real thing on any media as accurately as technology permits is the objective of the recording process. But even the finest recording effort fall short of capturing how real instruments and voices sound. Hopefully, they come up with a recorded media that is as near-to-perfect REPLICA of the real thing that, when played back at home on a transparent and accurate system, will sound precisely as it was recorded. That's the best any home playback system can achieve. And that is why audiophiles do not settle for anything less than uncompressed audiophile-grade media.
Clean Power - simply means unclipped sufficient power reserves to allow the dynamics of musical signal to come through with accuracy and transparency at my preferred listening levels. High Current amplifiers allow instantaneous current to support dynamic musical signals. They're fine, definitely a lot better than amps with poor dynamic headroom. But only if you listen at or close to their maximum rated power. So an amp with typically 3db dynamic headroom means you can listen at the maximum rated power and still enjoy twice the power instaneously. But we hardly listen at close to the maximum rated power of an amp, do we? And even then, those high current amps will still be taxed to clipping if pushed to their limits. Yoy can only extract so much current.
For me continuous RMS rating matters more. If I only listen at a 25-watt RMS per channel level continuously, having a 50 watt RMS amplifer is good enough for the dynamic headroom I can reasonably expect. Power reserves should be at least twice that of your maximum continuous listening level. It's much safer that way. In power amps, I don't mind erring on the side of plenty. ;D So I will never really use all that 250 watts RMS that I have, knowing that my listening comfort is only around the 30-40 watt level ( I measured 15-17 volts RMS at my 8-ohm speaker terminal). But I get all the power reserves I will ever need. That's more than 10db headroom. (My Acurus only has a 1.5db dynamic headroom at rated power into 4 ohms. Poor dynamics at the 250-watt RMS level.)
So there, my thoughts on power amps. Your turn.
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ppp383
Audionut
audiophile - Sa Audio Maphile
Posts: 92
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Post by ppp383 on Jan 19, 2005 22:33:22 GMT 7
Whewwww..... nalito ako, when the going gets tough, the tough gets going....
Just wanna say I have a borrowed Rotel RB-03, he....he....
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Post by Octaver on Jan 20, 2005 16:35:55 GMT 7
Sir AV Phile,
What is the advantage of Class A Amp design? Why most why is it most audiophile grade amp are class A design either SS ot Tube?
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Post by avphile on Jan 21, 2005 9:15:59 GMT 7
Because Class A is simple and straightforward. No crossover distortions inherent in class B.
But Class As are not powerful. And a real electricity eater, just around 20% efficient.
For audiophiles who like comfortable listening levels in a typical room, 2 watts to 10 watts RMS are all that matters. Class A amps will do that perfectly. And they don't mind wasting electricity for what little they get.
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Post by wanderlust on Jan 31, 2005 13:03:46 GMT 7
have just bought a surplus diatone da-a610 power amp, havent actually used it pa, but im hearing good reviews from master jo.... the units with him for replacment of the binding post, rca cable and a little spa
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Post by punk kid on Feb 7, 2005 7:58:43 GMT 7
have just bought a surplus diatone da-a610 power amp, havent actually used it pa, but im hearing good reviews from master jo.... the units with him for replacment of the binding post, rca cable and a little spa master.... musta na tong power amp mo? ok ba tunog?
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Post by JojoD818 on Feb 7, 2005 17:43:58 GMT 7
Octaver, guys,
My DIY Leach amp is a full-symmetrical class AB power amp. However, when I built it is was (as usual) overkill in the psu and heatsink (thermal) department. I was then adviced by some diy friends to why not try to bias it in semi class A and find out if the heatsinks can handle the heat and if the psu won't collapse. Since I am using the most latest output devices known for their high SOA, to my surprise, increasing the bias to force the amp into class A is really a great sounding adventure.
So now, my Leach amp runs the first 8 watts in class A, and the rest is history. ;D
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Post by wanderlust on Feb 8, 2005 10:32:11 GMT 7
Octaver, guys, My DIY Leach amp is a full-symmetrical class AB power amp. However, when I built it is was (as usual) overkill in the psu and heatsink (thermal) department. I was then adviced by some diy friends to why not try to bias it in semi class A and find out if the heatsinks can handle the heat and if the psu won't collapse. Since I am using the most latest output devices known for their high SOA, to my surprise, increasing the bias to force the amp into class A is really a great sounding adventure. So now, my Leach amp runs the first 8 watts in class A, and the rest is history. ;D ok to sir ah, pa-audition ;D
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Post by bogsle on Feb 13, 2005 19:15:35 GMT 7
Are you using separate power amps to boost the power of your receiver? I suppose those with pre-amps in the other thread would have power amps as well. Care to share them? What are the characteristics of power amps you value the most? To start off, I have a couple of ACURUS power amps, one 2-channel(A250), 250watt RMS/ch and another 3-channel (A200X3), 200watt RMS/ch to power a 5.1 set-up. Then I just turn off the 3-channel amp for plain stereo listening. Transparency, Accuracy and Clean Power are the things I look for and value in any amplifier. To explain: Transparency - means a wide bandwidth with FLAT frequency response at its rated power - a wide sonic highway so to speak. It simply means allowing ALL the signals that went in to come out unimpeded. At least 20hz to 20khz at +-1.0db deviation from flat is adequate. My amp is rated at 10hz to 100khz at +-0.5db. Better amps have a rating of DC to 100khz +- 0.1db. Accuracy - means nothing is added or subtracted to what went in in terms of THDs, IMs, TIMs, and other harmonic and non-harmonic distortion artifacts as well as amplification noise and many others. Ofcourse, there will always be something added or subtracted to the signals in the real world. But the lower and the less audible, the better. It often connotes the same thing as Neutrality. At its rated power, my amp has 0.06%THD and an IM and TIM of 0.005% max at 8ohms. Not the lowest figures I've seen, but good enough for me. Noise floors or S/N ratios also speak of the level of accuracy. Good figures start at 100db and upwards, Mine is rated at 110db S/N, which would be close to most SACD and DVD-A players that have 110db S/N and above. (It doesn't really make sense to have a player rated at 110 db S/N only to be thrashed by an amp with a 90db S/N. As always, the audio chain is only as good as the poorest link.) Some other aspects are slew rates, or the speed at which the amp can deliver a 1-volt signal, the faster the better. Most amps and receivers today have excellent slew rates and most manufacturers don't see the need to indicate this in their specs. Then, there's channel separation; no interchannel bleeding or inteference common in most jampacked receivers. 75db is the starting point, the higher the better. (That's why monoblock amps or stereo amos with monoblock construction are preferred in this area with channel separtion above 100db.) Mine is rated at 90db, good enough for me. Lastly, much debate attends the issue of damping factor, or the amp's ability to control the speakers, especially the woofer. The higher the figure the better. Mine is 500 at 50Hz into 8 ohms. I've seen some amps with 1000 or more. An amp with good damping will certainly deliver a more musical bass line. (But since, I am using a powered sub, I think this is a province better reserved to the power amp in the sub.) Some would define accuracy to mean the sound is identical to live instruments. Let's not kid ourselves, no home playback system will ever sound like the real thing. The most accurate ones can only approach. High Fidelity has often been misconstrued to mean sounding like the real thing. They sometimes do. But Hi-fidelity simply means fidelity to the recorded media. Not to the real thing. That's the objective of home playback - to give justice to the recorded media. OTH, capturing the real thing on any media as accurately as technology permits is the objective of the recording process. But even the finest recording effort fall short of capturing how real instruments and voices sound. Hopefully, they come up with a recorded media that is as near-to-perfect REPLICA of the real thing that, when played back at home on a transparent and accurate system, will sound precisely as it was recorded. That's the best any home playback system can achieve. And that is why audiophiles do not settle for anything less than uncompressed audiophile-grade media. Clean Power - simply means unclipped sufficient power reserves to allow the dynamics of musical signal to come through with accuracy and transparency at my preferred listening levels. High Current amplifiers allow instantaneous current to support dynamic musical signals. They're fine, definitely a lot better than amps with poor dynamic headroom. But only if you listen at or close to their maximum rated power. So an amp with typically 3db dynamic headroom means you can listen at the maximum rated power and still enjoy twice the power instaneously. But we hardly listen at close to the maximum rated power of an amp, do we? And even then, those high current amps will still be taxed to clipping if pushed to their limits. Yoy can only extract so much current. For me continuous RMS rating matters more. If I only listen at a 25-watt RMS per channel level continuously, having a 50 watt RMS amplifer is good enough for the dynamic headroom I can reasonably expect. Power reserves should be at least twice that of your maximum continuous listening level. It's much safer that way. In power amps, I don't mind erring on the side of plenty. ;D So I will never really use all that 250 watts RMS that I have, knowing that my listening comfort is only around the 30-40 watt level ( I measured 15-17 volts RMS at my 8-ohm speaker terminal). But I get all the power reserves I will ever need. That's more than 10db headroom. (My Acurus only has a 1.5db dynamic headroom at rated power into 4 ohms. Poor dynamics at the 250-watt RMS level.) So there, my thoughts on power amps. Your turn. Nice features learned about power amps. But would a 70 watt power amp sound much better than a 100 watt integrated amp? What would be the advantage of separating the power amp from its sound processor? Regards,
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Post by wanderlust on Feb 15, 2005 13:30:31 GMT 7
this might not apply to all and maybe this is just me, but lately i have chnged amps, from a 170 watter (wpc)intergrates to a 60 watter (wpc) power amp, using essentially the same configuration: source---->tube pre-amp------> amp (same speaker also). i find the power amp more compatible (well, at least with my preferred set-up) than the intergrated, its more tube sounding.
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Post by avphile on Feb 16, 2005 10:58:16 GMT 7
Nice features learned about power amps. But would a 70 watt power amp sound much better than a 100 watt integrated amp? What would be the advantage of separating the power amp from its sound processor? Regards, You have to DOUBLE the power to perceive any difference. Twice the power is only 3db increase, just barely perceptible. And anything louder is always perceived to be be better at the start. That's just how human hearing works. It's often difficult to say whether your older integrated is a true 100wpc or is more hyped up. A lot of my colleagues wonder why their new NAD rated at just 60wpc sounds fuller and more dynamic than their replaced Yamaha rated at 120wpc. That's because their former gear is NOT rated conservatively, using DIN standards into 4 ohms at 1khz, while the NAD was rated conservatively at 8ohms into FULL 20hz-20khz bandwidth. OFten, comparing apples to apples is difficult, if not misleading. With everything else equal, about the only difference using separate power amps from integrateds or receivers is power supply isolation and dedication. Power amps, especially in the 150watts ++ range, really require large power transformers and caps in order to deliver their current. Such monstrosities tend to leak EMI interference on the more sensitive preamps and processors if not properly isolated within a box or chassis. Not to mention that they do vibrate more during operation. Also, having a dedicated power supply for the amps mean you can put in more humongous power transformers and caps the better to provide sufficient current to the amps. There's no reason why this can't be done in integrateds and receivers, since preamps and processors eat no more than 50watts. But it can get a bit cramped when you put all these in just one box. The chances of interference leaking unwanted HUM into the the more sensitive preamp circuits is higher with integrated and receivers than if you rellocated the power amps in a separate box. But for moderate power requirements below 150 watts per channel, many integrated and receivers do a good job, even if the space is cramped. And, it's always more convenient to have separate power and pre/pros. There's always a greater likelihood that preamps and processors get upgraded or repaired more often than power amps. I would hate, for instance, to pull out a 75lb Yamaha z9 receiver out of the rack just to repair a faulty DSP switch or volume control. ;D While doing so for an Adcom or Rotel pre/pro would be a breeze. ;D
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ppp383
Audionut
audiophile - Sa Audio Maphile
Posts: 92
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Post by ppp383 on Feb 16, 2005 13:18:31 GMT 7
Because Class A is simple and straightforward. No crossover distortions inherent in class B. But Class As are not powerful. And a real electricity eater, just around 20% efficient. For audiophiles who like comfortable listening levels in a typical room, 2 watts to 10 watts RMS are all that matters. Class A amps will do that perfectly. And they don't mind wasting electricity for what little they get. I have seen amp which says "class AA" on their front plate most especially those Technics amps, what's this all about, is this new technology? what the difference between this technology? Nagtatanong lang po?
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Post by Octaver on Feb 16, 2005 15:35:35 GMT 7
That's because their former gear is NOT rated conservatively, using DIN standards into 4 ohms at 1khz, while the NAD was rated conservatively at 8ohms into FULL 20hz-20khz bandwidth. OFten, comparing apples to apples is difficult, if not misleading. Sir avphile, i'm just wondering why some amplifiers (commonly to Tube amps) are rated 10hz - 60khz or higher than usual 20hz - 20khz? are this correct or attainable? Thanks?
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s2kov
Critical Listener
Posts: 353
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Post by s2kov on Feb 16, 2005 16:45:55 GMT 7
For the amp, it's still possible if they can totally eliminate gain slope for that region. Also, consider the frequency range of the whole chain from source to speaker, otherwise, the amp is useless having that frequency range. Sir avphile, i'm just wondering why some amplifiers (commonly to Tube amps) are rated 10hz - 60khz or higher than usual 20hz - 20khz? are this correct or attainable? Thanks?
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Post by Octaver on Feb 17, 2005 7:44:26 GMT 7
For the amp, it's still possible if they can totally eliminate gain slope for that region. Also, consider the frequency range of the whole chain from source to speaker, otherwise, the amp is useless having that frequency range. From what I know only SACD can achieved highs higher than 20khz a ribbon tweeter is a must (isn't it beyond human audible recognition?) A good(huge) subwoofer possibly can do 10hz to 2hz? (this is for SPL (sound pressure level)). Amplifier is just one of the component of our sound system, so Speakers & Source are still the number one factor how our system sings?
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Post by bogsle on Feb 22, 2005 9:29:23 GMT 7
And, it's always more convenient to have separate power and pre/pros. There's always a greater likelihood that preamps and processors get upgraded or repaired more often than power amps. I would hate, for instance, to pull out a 75lb Yamaha z9 receiver out of the rack just to repair a faulty DSP switch or volume control. ;D While doing so for an Adcom or Rotel pre/pro would be a breeze. ;D Thank you very much.
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Post by avphile on Feb 22, 2005 13:49:17 GMT 7
Sir avphile, i'm just wondering why some amplifiers (commonly to Tube amps) are rated 10hz - 60khz or higher than usual 20hz - 20khz? are this correct or attainable? Thanks? I've come across SS amplifiers rated from DC or 0hz to 100khz in the past. Nothing new there. The higher the bandwidth, the better. Bandwidth can be compared to a road or highway, the wider it is the better. This just indicates what freqeuncies the amp can handle. It does not indicte the LINEARITY or linear regions of the bandwith which is more importanct to human hearing. Thus, they also specific the 20hz - 20khz +/- 1db where the response is more or less linear as indicated by the +/- db variation from a straight line response. Human hearing is bandwidth-limited to just 20khz. The older you are the less bandwidth. In general people aged 30+ can only hear up to 17khz or so. 40+ up to 15khz. Exceptions abound but very few.
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Post by avphile on Feb 22, 2005 14:13:26 GMT 7
Amplifier is just one of the component of our sound system, so Speakers & Source are still the number one factor how our system sings? The system is one long chain that is only as great as the weakest link. Not a single link is more important than another. That links starts with the recording media, the CDs, LPs, SACDs, tapes, etc. and ends with the room accoustics - just immediately before reaching the ears. In between you have the players, preamps, processors, amps and speakers that must pass the recorded signal as transparently and neutrally as possible without adding to or subtracting from the signal - called sonic coloration. I'd say 50% of the sound that reaches our ear comes from the source and the hardware. The other 50% comes from room accoustics that color the sound that reaches the ears. Having said that, there is, however such as thing as the order of priority when creating a sound system. Some say you start with speakers. Others say you start with the amps. Or even the player. Others say you start first by creating an audio room that is as neutral and transparent as possible, complete with bass traps, diffusers and absorbers. Each have their merits. I personally would prefer to start with the room accoustics. But that should come while still constructing the house. But after that or not being able to afford that, I consider the matching of speakers and amplifiers as the next order of priority. Not one or the other. I have to buy both at the same time. I have to make sure that they go together well. Next comes the pre/pros then the players. But that's just me.
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Post by bogsle on May 2, 2005 14:46:51 GMT 7
Question: I have a Rotel RA-02 Integrated Amp. If I get a Rotel RB-03 power amp, can I use the two in a bi-amp setup? The configuration will be the ff:- The RA-02 with RMS 40 watts/ch will be connected to the HF.
- The RB-03 with RMS 70 watts/ch will be connected to the LF.
Will this setup be ok? Will I be damaging my speakers or any equipment for that matter? BTW my speakers is a pair of AE EVO1s @ 8ohms, 89Db, and 120 watts max input. Please give me some recommendations. Thank you very much for the help. Regards, Bogsle
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Post by JojoD818 on May 2, 2005 18:04:23 GMT 7
Bogsle,
Will you be using an active crossover for that or the passive crossover built inside the speaker?
JojoD
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