| samsagaz |
Hey guys, i want to upgrade my HT, its just an 5.1 channels. I want to sold the Receiver and want to use dedicated amps for each channel, i want to get at least 200Watts per channel. i really want to know if buiding and classD amp will get nice sound, (comparable with comercial ones like Rotel RMB-1095)?
I want to drive a pair of Polk LSI Series Speakers. |
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| fokker |
| Class D used to ultra low-end, and with the advances of technology they are becoming more mainstream. |
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| classd4sure |
| Rowland doesn't even use decent modules :) |
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| phn |
| Asking if it's "high-end" is the same thing as asking if it's expensive. Class D's not. But it can sound pretty good, or expensive if you like. |
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| samsagaz |
mm i understand, but will be better to use an A/B or Class D amp?
or is not possible to get an answer like that?
i know that class D is great for high power amps like 1000w+ for subwoofers or stuff like that, but dont know for mid and hig frequencies. |
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| classd4sure |
There's no clear answer to that I don't think.
In terms of efficiency there's a clear answer. In terms of performance, probably in either case it depends on the amp itself and how well it's been implemented. Better amps cost more money, period, so how much you're willing to spend to get to your expectations is the deciding factor, unless it's the ultimate in power you're after.... what do you want?
Do you expect to cram 7 amps in a single case because it takes up less room... then you compromised performance in a big way, but also saved a good deal of money.
Is the ultimate in performance all you want, cost no objective? Full monoblock, or multi amped active speakers even better. That's about the ultimate you can get and I would sure as hell do it with D amps tweets and all.
Could you maybe buy a better commercial class a/b receiver for the same price as a commercial class d receiver? Very likely! |
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| planet10 |
One thing to keep in mind is that it seems, as a generalization, that quantity of power is inversely proportional to quality....
There are certainly small class D amps that seem to be of comparable quality to the better of Class A SS & tube amps (not from personal experience yet -- i have a set of Brian West's 10W modules on the way)
dave |
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| classd4sure |
True, yet the quality of that power in a good D amp is maintained at low levels, and the ability for much greater power/cost is unmatched. Having higher power ability does not mean that you have to give up quality at normal listening levels. You might find that sort of argument made by someone who makes a bad amp though.
For example I've heard Nuforce people say that it only sounds good at low power, therefore, the amps must be low power and speakers must be efficient.
They've failed in their meager attempts at addressing EMI though, so obviously quality goes to hell when the current starts to flow.
It not usually a good idea to over generalize things. The whole point to a good D amp is to attain higher levels of clean power than was possible before, or at least affordable. |
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| BWRX |
One very important ingredient of a really good amp is the power supply. Because class d amps are much more efficient than other topologies you don't need a huge beefy power supply to get great performance. Conversely, a really good power supply makes them sound that much better!
What's amazing is that class d amps get more efficient as the power output increases. That is in stark contrast to class a and ab where power output peaks and then starts decreasing.
My little modules are good for about 7Wrms into 8ohms and about 13Wrms into 4 ohms and nothing on the board even gets warm when putting out maximum power into 8 ohms. Other higher power class d amps perform similarly in terms of heat dissipation. |
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| fokker |
| quote: | Originally posted by BWRX
Because class d amps are much more efficient than other topologies you don't need a huge beefy power supply to get great performance. |
I think it is just the opposite: because most of class D amps have very bad PSRR, they need much beefier power supply to work. You can check out how TI proposed to control volume on its Class D chip set by changing power supply voltage.
One exception to that is the amps with feedback, aka the UCD. |
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| raintalk |
| quote: | Originally posted by BWRX
...
What's amazing is that class d amps get more efficient as the power output increases. That is in stark contrast to class a and ab where power output peaks and then starts decreasing.
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Hmmm - as I understand it, class-d reaches maximum efficiency very low in power curve. In other words, for a 100w class-d it is as efficient at 10W as it is at 100w - which would be like 90%
Class-ab doesn't reach it's maximum efficiency until its approaching full power. At 10w it'd be like 25% efficient, reaching 90% at full power. |
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| classd4sure |
As far as efficiency Vs output in a D amp it will be affected by type of modulation .... self oscillating amps would get more efficient at higher output though, because they usually aren't fixed frequency and it slows with increased power output.
An amp really should have feedback. As far as I know, there hasnt' been a good amp designed without it yet. TI speaks in terms of marketing their products as does Zetex and all the others. I find it best when looking for an example to follow to look up to those who've actually achieved their design objectives and had success in the market, rather than with marketing. |
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| samsagaz |
well, so what do you guys recommend me? my budget are 2000u$s, i need at least 5 channels i was thinking abt rotel 1095 (200wx5). i will use an Rotel RSP-1068 as processor. Maybe building my own Amp will give me an nice looking system, (coz i can made custom boxes for each amp), but what abt quality? :D
i really want to move away from receivers, i just want to build an good system and easy to improve/upgrade.
im tyred abt selling all my receivers year/year, i used sony, and yamaha, but this time i want to have all the pieces separated (amps, pre....) |
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| classd4sure |
| get out of the commercial junk and start researching DIY class d amplifiers :) |
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| planet10 |
| quote: | Originally posted by classd4sure
An amp really should have feedback. As far as I know, there hasnt' been a good amp designed without it yet. |
Maybe Class D amps... i know more than a few really good no feedback amps (well there is degenerative feedback across the cathode R in most cases)
dave |
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| classd4sure |
Yah, class D. It's possible to make it without it, but to do it well I think is counter productive in every aspect, just for the sake of making the "true digital" claim :confused:
Hey I hope you have fun testing those modules that are on the way. |
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| planet10 |
| quote: | Originally posted by classd4sure
Hey I hope you have fun testing those modules that are on the way. |
Me too... i need to start getting the power supply and a case togther (i'm using 4 x 13 V 110VA trafos with LM328 regs -- should put me into the overkill zone on the PS)
dave |
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| BWRX |
| quote: | Originally posted by fokker
I think it is just the opposite: because most of class D amps have very bad PSRR, they need much beefier power supply to work.
One exception to that is the amps with feedback, aka the UCD. |
I worded my other sentence poorly. It would have been better to say class d amps don't need as beefy of a supply as similar power class a and ab amps do because they're much more efficient.
Any amp, whether it be with a high or low PSRR will benefit from a more stable, quiet supply. Amps with low PSRRs will just benefit more. Feedback definitely improves that figure and reduces output impedance at the same time.
| quote: | Originally posted by raintalk
Hmmm - as I understand it, class-d reaches maximum efficiency very low in power curve. In other words, for a 100w class-d it is as efficient at 10W as it is at 100w - which would be like 90%
Class-ab doesn't reach it's maximum efficiency until its approaching full power. At 10w it'd be like 25% efficient, reaching 90% at full power. |
Like Chris said, it depends on the type of class d, but most do not reach peak efficiency until they're near maximum output power. The efficiency curve usually looks like a logarithmic function, which means they reach high levels of efficiency fairly quickly and then it continues to increase slowly.
Class B has a theoretical maximum efficiency of 78.5%. Class D has a theoretical maximum efficiency of 100%. Class AB will obviously be lower than B.
| quote: | Originally posted by planet10
(i'm using 4 x 13 V 110VA trafos with LM328 regs -- should put me into the overkill zone on the PS) |
That's what I like to hear :) |
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| raintalk |
You're splitting wires. :D
Class-ab increase in efficiency as the power output rises. I couldn't find any documented humps.
Yeah sure, Class-d does jump up in the power curve quickly, and slightly rise - but it's mostly flat.
Seeing as music isn't always played at full output, and you need some headroom. Class-d is more efficiency for normal listening levels. No matter which class-d it is. |
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| classd4sure |
Headroom? Need? I take headroom specifications as the surest sign of a weak supply that'll sag far too much to be considered "high end" as soon as you work it a little.
Classd is clearly the most efficient period, some more than others, and the point was depending on the exact method used, it will effect the efficiency curve slightly, but they're all fairly comparable.
Saying the curve is mostly flat though isn't such a good argument when you consider manufacturers rave about just a few percent higher efficiency than the next guy. It's a pretty big deal in that sense.. and the fact is while being mostly flat, it is typically highest towards peak output.
In it's most inefficient state though, it will still outdo a class B amp. While graphs may show it hitting 0 efficiency with 0 power output, that's too idealized. Fact is power in just becomes idle current consumed, and most of that doesnt' get consumed, but returned to the supply. Though, it switches faster, so there's some extra switching loss to be seen. It's easily handled most often with just the case as heatsink.
If efficiency were truly ever to hit 0 with it, "idle" would obviously become an illegal mode of operation.... it'd have to shut down as soon as no signal was present. As it is, it just warms up a little bit more. |
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| Pafi |
| quote: | | Class-d is more efficiency for normal listening levels. No matter which class-d it is. |
I have to disagree. ClassD needs additional power supply for modulator and gate driver, which can be as high as 50...90 mA. In many amps this is linearly stabilized from main supply, so there can be already ~10 W idle loss without any power device. Switching loss adds some watts further. A ClassAB can easily operate with 10 mA idle current. If I listen to music while I reading a book, with my unefficient speakers average power output doesn't exceed 40 mW. This means about 100 mA current, so 6W power consumption at 60V supply + 10mA*2*60V=1,2W idle loss. At average home use tipical ClassD is hot, ClassAB is cool. I would be very happy, if this wasn't true, but it is.
ClassD can be more efficient, if we supply it with 3 small sources plus two main voltage, but it requires many connections, and a logic circuit to disable output when any of these is not present. I do it this way in my bigger amps, but it doesn't worth the efforts in small (<800W) amps.
| quote: | | While graphs may show it hitting 0 efficiency with 0 power output, that's too idealized. |
What do you mean? efficiency=power output/power input. 0/positive is definitely 0!
| quote: | | If efficiency were truly ever to hit 0 with it, "idle" would obviously become an illegal mode of operation... |
Power input is almost constant at very low output power, so efficiency is directly proportional to output power. This doesn't mean any inhibition on signal. |
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| classd4sure |
Not sure what you mean by inhibition on signal, but as per the equation power output is not 0, it's just too textbook.
If you have a systen capable of sustaining 1kW, where all of a suddent for whatever reason it suddenly drops to 0% efficiency, that means it's wasting the entire 1kW.... that'd be one damn hot class d amp at idle dont' you think?
So I guess I look at it more as power used (including all losses + what's delivered to load)/power available.
Graph that and I think the graph will look a little different towards idle, and probably alot more realistic, since there's no way a class d amp idle is cooking off all it's available power as heat. |
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| Ouroboros |
| But you're looking at efficiency the wrong way. Pafi is quite right. If a 200W (say) amplifier uses 6W as 'housekeeping' power, then if it is outputting only 100mW, then it is consuming 6.1W. This is a very low efficiency indeed. Not quite 0 but not far off! At an output of 100W it is consuming 106W which is a very high efficiency. |
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| classd4sure |
| I know I know.... it's not the conventional way to look at it, non the less... if a 1000 watt amp hits zero efficiency it ought to be cooking off 1000W as wasted heat correct? But it doesn't does it. |
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| Pafi |
| quote: | | I know I know.... it's not the conventional way to look at it, non the less... if a 1000 watt amp hits zero efficiency it ought to be cooking off 1000W as wasted heat correct? |
Absolutely not! Nobody told that a 1 kW amp have to consumpt 1 kW all the time! (It's true only for classA.) Power input can be as low as you want, eg. 1W, but if you divide 0W by 1W, you still get 0%.
Are you joking? You know much more then this! |
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| ghemink |
| quote: | Originally posted by Pafi
Absolutely not! Nobody told that a 1 kW amp have to consumpt 1 kW all the time! (It's true only for classA.) Power input can be as low as you want, eg. 1W, but if you divide 0W by 1W, you still get 0%.
Are you joking? You know much more then this! |
All this talk about power consumption. Try an UCD180, stays very cool and sounds incredible. If you ask me, easily beats commercial amps that cost 10x more.
Gertjan |
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| fokker |
the fact that jeff rowland, audio research or halco have hi-end products in this space does not negect the fact that class D started its life at the bottom end, mostly as subwoofer amps or computer / pda / cell phone audio amps where full-band fedility wasn't required.
recent advances in dsp and switchers and topologies made it more appealing to full-band and hi-fi applications that we are interested.
Conceptually, Class A is the most natural way of amplifying a signal: the output device is fully on.
Class D is NOT very natural in that it is trying to approximate a continueous sine wave by switching the output devices very fast.
Class B is somewhere in between: it is switching (aka Class D) from positive half to negative half. However, within the halfs, it is Class A. |
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| classd4sure |
| Better mosfets is what did it, not DSP's or anything else |
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| raintalk |
| quote: | Originally posted by classd4sure
Headroom? Need? I take headroom specifications as the surest sign of a weak supply that'll sag far too much to be considered "high end" as soon as you work it a little.
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I guess I don't pay attention to "headroom" specs. I tend to buy amps modules with more power than I'll probably use, and use a bigger power supply - creating my own headroom spec. And I at least think that I'm being more green over running class-ab (which I'd also buy more power and use a bigger xformer) |
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| sx881663 |
You must bear in mind that efficiency ratings are for max power out. At low level and idle the situation reverses with typical class A/B using less power. Note I did say typical not some unit that runs class A to several 10’s of watts. This difference can easily be a 10:1 advantage for the A/B amp. Nothing new here Bruno already addressed this issue in one of the early threads for the UcD’s, unfortunately not much can be done about it yet. It will have to wait for better parts.
Roger |
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| BWRX |
I guess it depends on what amplifier you would be talking about but just by looking at a published efficiency vs output power curve I found here (go down to figure 6 http://www.bashaudio.com/technologies.htm) you can obviously see that class d would still have better efficiency even at low power.
Here's some more good reading.
http://www.audiodesignline.com/howt...audio/189602183
Class ab amps aren't used in low power battery powered applications because they usually dissipate more power than class d; even at idle. |
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| samsagaz |
so if i dont care abt battery the A/B will be an better choice, right?
I found some cheap chinese PRO amplifier with nice specs and high power, but really dont know if they are good, btw, i can found wich output trnsistors it use, this can help me to found if are good amps? |
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| planet10 |
| quote: | Originally posted by samsagaz
so if i dont care abt battery the A/B will be an better choice, right? |
No
| quote: | | I found some cheap chinese PRO amplifier with nice specs and high power, but really dont know if they are good, btw, i can found wich output trnsistors it use, this can help me to found if are good amps? |
My guess is that you'd likely be way better off with even chip-amps. Pro amps aren't built for their sonics, but to be reliable. Being cheap doesn't help & commonly published specs are largely meaningless.
dave |
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| Pafi |
| quote: | | I guess it depends on what amplifier you would be talking about but just by looking at a published efficiency vs output power curve I found here (go down to figure 6 http://www.bashaudio.com/technologies.htm) you can obviously see that class d would still have better efficiency even at low power. |
Actually I don't see low power specification here. These test were made with full drive, and that curve can't be read at 100 mW. And if it were as you said, still you can't generalize. There are many ClassD wich dissipates more then a comparable ClassAB at room volume. (These amps are tipically very big.)
| quote: | | so if i dont care abt battery the A/B will be an better choice, right? |
It depends on your requirements. Power output, cooling, etc...
Do you want to build it completely, or you want to buy modules? If you can buy, UcD180s are very good (however a litle bit expensive). If you want to build, then forget about discrete ClassD, unless you have oscilloscope and many experience. |
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| samsagaz |
| quote: | Originally posted by Pafi
Actually I don't see low power specification here. These test were made with full drive, and that curve can't be read at 100 mW. And if it were as you said, still you can't generalize. There are many ClassD wich dissipates more then a comparable ClassAB at room volume. (These amps are tipically very big.)
It depends on your requirements. Power output, cooling, etc...
Do you want to build it completely, or you want to buy modules? If you can buy, UcD180s are very good (however a litle bit expensive). If you want to build, then forget about discrete ClassD, unless you have oscilloscope and many experience. |
well, i have an osc but not too much experience so will be hard do it 100%myself, btw, i was thinking in modules.
I really want to spend the same money that i will use for an commercial unit but do it myself. I really cant use Class A because i want at least 200W per channel. So need to use A/B or D. I think that D is easy to build (with the kits), but i dont care abt it, i want nice sound, with specs similar to commercial ones.
i need at least 5 channels (can use diferent case for each one). maybe can build 7 channels to byamp the front stage.
The speakers that i will use will be a pair of Polk LSi 15 (at least to start, later i can do it myself other colums, i have 3 Ribbon Tweeters, but cant spend money in woofers now, i want to purchase the LSi and some processor (DTS, DD...).
About the power, i need to build an nice amp, i dont want to change it in a few years, i want to use it for looooonnggg time, i want to upgra processor, maybe speakers but not amps :)
Thanks for all your help guys. |
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| fokker |
there may be a distinction between how power is dissipated in a class A/B amp vs. a Class D amp.
In a class A/B amp, the dissipation takes place mostly in the output devices. because they are essentially voltage-controlled variable resistors.
You can view a class D amp as a capacitor being alternately connected to either the positive rail or the negative rail, through an inductor whose sole purpose is to limit the current charging up or discharging the capacitor. It is the charging and discharging that consumes energy, but in the power supply, not in the output devices.
The amount of the current I guess depends on the size of the inductor / capacitor, rail voltage and oscillation frequency: the larger the inductor, or the smaller the capacitor, or the lower the rail voltage, or the faster the frequency, the lower the current. |
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| fokker |
the way I view it is that the capacitor is like a bucket and the inductor is like a valve. It gets filled up by the positive rail, and the valve controls how fast the bucket gets filled up. and then the bucket empties itself to the negative rail, through the valve again.
The capacitor is essentially shorting the positive rail to the negative rail, indirectly and alternately. |
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| BWRX |
| quote: | Originally posted by Pafi
Actually I don't see low power specification here. These test were made with full drive, and that curve can't be read at 100 mW. And if it were as you said, still you can't generalize. There are many ClassD wich dissipates more then a comparable ClassAB at room volume. (These amps are tipically very big.) |
What do you mean you don't see low power specs? You can read the graph down to about 1W, where their efficiencies are about equal. Why would you bother calculating efficiency below a watt for a power amp? The most power that will be wasted below 1W output will clearly be less than a watt.
For most speaker systems today, I would consider "room volume" to be at least 1W output for lower listening levels. Maybe more like 2-4W for more reasonable/adequate listening levels.
Another way to think about class d operation is just a high power PWM signal being fed to a low pass filter. |
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| classd4sure |
| quote: | Originally posted by samsagaz
well, i have an osc but not too much experience so will be hard do it 100%myself, btw, i was thinking in modules.
I really want to spend the same money that i will use for an commercial unit but do it myself. I really cant use Class A because i want at least 200W per channel. So need to use A/B or D. I think that D is easy to build (with the kits), but i dont care abt it, i want nice sound, with specs similar to commercial ones.
i need at least 5 channels (can use diferent case for each one). maybe can build 7 channels to byamp the front stage.
The speakers that i will use will be a pair of Polk LSi 15 (at least to start, later i can do it myself other colums, i have 3 Ribbon Tweeters, but cant spend money in woofers now, i want to purchase the LSi and some processor (DTS, DD...).
About the power, i need to build an nice amp, i dont want to change it in a few years, i want to use it for looooonnggg time, i want to upgra processor, maybe speakers but not amps :)
Thanks for all your help guys. |
It sounds like you're for a full mono class d type system, and I can recommend UCD wholeheartedly.
You can easily build yourself an amp that will last a lifetime, but I'd recommend you start slowly to gain some experience in implementing them before going all out. This will also give you an intro to their sound and you'll know what to expect from them.
Even if it takes two years to learn all the tricks and get it done right, when they're done they're done and will last a loooong time.
The other upside to doing it this way makes it easier to reconfigure your system or add this or that at anytime down the line which you can never really do with commercial junk.
I'd seriously consider the DIY way :) |
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| planet10 |
| quote: | Originally posted by BWRX
For most speaker systems today, I would consider "room volume" to be at least 1W output for lower listening levels. Maybe more like 2-4W for more reasonable/adequate listening levels. |
Inefficient speakers? Really big room?
dave |
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| BWRX |
| I was thinking around 89dB at 1W/1m in a small to medium size room. |
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| planet10 |
| quote: | Originally posted by BWRX
I was thinking around 89dB at 1W/1m in a small to medium size room. |
Unless you listen really loud your estimate is probably an order of magnitude high.
dave |
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| samsagaz |
| the room is 13x23ft |
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| BWRX |
| quote: | Originally posted by planet10
Unless you listen really loud your estimate is probably an order of magnitude high. |
1-2W with 89dB at 1W/1m speakers while sitting about 2 meters away produces good listening levels in an 11' x 12' (approximately) room. Listening at lower levels is nice for some things but I like it a bit louder when listening critically or just really feeling the music :sing:
| quote: | Originally posted by samsagaz
the room is 13x23ft |
I would consider that to be a medium sized room. |
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| samsagaz |
| i will be seated at like 3, 3.5 mts and for movies and some music (like salsa) i really like louder :D |
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| raintalk |
I rarely ever see speaker efficiency measure across the frequency spectrum. It's usually 1khz. You need more power at say 40hz to make it sound even at low volumes where your ears are more sensitive to midrange.
Come on folks, take out your scopes and meters and do some real world measurements. |
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| ghemink |
| quote: | Originally posted by fokker
the fact that jeff rowland, audio research or halco have hi-end products in this space does not negect the fact that class D started its life at the bottom end, mostly as subwoofer amps or computer / pda / cell phone audio amps where full-band fedility wasn't required.
recent advances in dsp and switchers and topologies made it more appealing to full-band and hi-fi applications that we are interested.
Conceptually, Class A is the most natural way of amplifying a signal: the output device is fully on.
Class D is NOT very natural in that it is trying to approximate a continueous sine wave by switching the output devices very fast.
Class B is somewhere in between: it is switching (aka Class D) from positive half to negative half. However, within the halfs, it is Class A. |
As an engineer, you may think along the above lines (that Class D "must" be worse), however, if you listen to recent Class D amps you will probably be quickly convinced that we are talking high-end and I find them better than expensive AB amps. Have you listened to any recent Class D amps?
Gertjan |
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| fokker |
| quote: | Originally posted by ghemink
that Class D "must" be worse
Gertjan |
I do not believe I said anywhere that Class D must be worse. I said that Class D was historically ultra-low-end. I don't believe that is without fact. |
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| classd4sure |
| quote: | Originally posted by fokker
I do not believe I said anywhere that Class D must be worse. I said that Class D was historically ultra-low-end. I don't believe that is without fact. |
Only in practice, in theory they've always been superior, well, since the theory came to be.
You can't seriously shame the technology as a whole simply because the components of the day weren't up to snuff to properly realize the theory.
How many thousands of years did the wheel exist before a decent racing tire came along?
Quite often we're given new technology to contend with that promises to be the next best thing, all the early adopters dive right in and I think more often than not regret it. Sometimes that technology is even pushed out the door with the next greatest thing before it even became optimal..... laser disc for instance.
High end class D has been here for a good five years now and it's only going to get better from here. Just ask Bryston :)
Although, it may take another decade or two before the class d you see appearing in commercial scrap is up to par with mid fi A/B standards.. you can't build a race car by nickle and diming everything either right. |
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| Pafi |
| quote: | | What do you mean you don't see low power specs? You can read the graph down to about 1W, |
Just read what I wrote! Max. 100 mW.
| quote: | | where their efficiencies are about equal. Why would you bother calculating efficiency below a watt for a power amp? The most power that will be wasted below 1W output will clearly be less than a watt. |
Of course not. On figure6 you can see definitely less then 50% efficiency at 1W output, so wasted power must be higher then 1W. On figure5 you can see ~2W loss at 0W output power, while loss of ClassB (red curve) reaches near zero! Don't guestimate, when you have relevant data!
| quote: | | For most speaker systems today, I would consider "room volume" to be at least 1W output for lower listening levels. Maybe more like 2-4W for more reasonable/adequate listening levels. |
I have measured the voltage on my speakers at a comfortable volume: ~20 mV. Yes, that's true! Little more than 100 uW/speaker.
Just think! 1W on a 86dB sensitivity speaker means 86dB volume (assuming 1 meter distance)! Volume of human speaking is ~50 dB, 1/4000th power of the above mentioned!
My relatives would immediately shout at me, if I listened this high (86 dB) volume! My student has just left. He asked me to turn off that 400 uW music, because it disturbed him!!!
Human hearing, and logarithmic scale are very strange things... |
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| ghemink |
| quote: | Originally posted by fokker
I do not believe I said anywhere that Class D must be worse. I said that Class D was historically ultra-low-end. I don't believe that is without fact. |
OK, you did not say that, I thought you implied it. Anyway, my question whether you ever have heard a recent Class D amp still stands. If you have heard one, what was your impression? My opinion is that they easily beat high-end Class AB amps. Would be interested what your experience is.
I have to admit that I had not expected that Class D would sound that good. I have an Accuphase E407 amp (I guess everyone knows that by now:-)) and for experimental purposes I bought a cheapo 4 channel Marantz Tripath based amp about 2 years ago. When I had a brief listen to that amp in an audio shop I was already a bit surprised about how good that cheapo amp sound was. Then at home hooked it up and immediately knew that this was different, very clean sound, can play very loud without sounding loud (I guess a sign of low distortion at high power levels), very good imaging etc, all the good stuff you often hear people say about Class D. From that moment on I was hooked to Class D. I`m now using UcD based amps as these are very good problemfree modules. They are extremely low noise (much lower noise than the Tripath based Marantz) and are therefore very good in an active setup (3 amps per speaker). I have the tweeters directly connected to the amps (UcD180) and have in that 2 year that I have them never blown a tweeter.
That`s enough from my side, would like to know your personal experience with class D, not from an electronics point of view but from a sound point of view.
Best regards
Gertjan |
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| Pafi |
| quote: | | i was thinking in modules. [...] i want at least 200W per channel. |
Then UcD180 modules are perfect for you. |
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| BWRX |
| quote: | Originally posted by Pafi
Of course not. On figure6 you can see definitely less then 50% efficiency at 1W output, so wasted power must be higher then 1W. On figure5 you can see ~2W loss at 0W output power, while loss of ClassB (red curve) reaches near zero! Don't guestimate, when you have relevant data! |
My point was that there's no need to be concerned with efficiency at 100mW or less with a power amplifier. Class d is less than 50% efficient at 1W but class ab is even worse.
In the attachment is a portion of the efficiency vs power output graph from my previous link. The visible tick mark on the x axis is 2.5W output, the next line I added is about 1.125W output, and the next is about 0.5625W output. At 1.125W the class d amp is about 25% efficient while the class ab is around 7% efficient. Around 0.5626W both amps are clearly under 5% efficient and the power dissipation mainly depends on idle losses in the amplifier.
| quote: | Originally posted by Pafi
I have measured the voltage on my speakers at a comfortable volume: ~20 mV. Yes, that's true! Little more than 100 uW/speaker.
Just think! 1W on a 86dB sensitivity speaker means 86dB volume (assuming 1 meter distance)! Volume of human speaking is ~50 dB, 1/4000th power of the above mentioned!
My relatives would immediately shout at me, if I listened this high (86 dB) volume! My student has just left. He asked me to turn off that 400 uW music, because it disturbed him!!!
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I have measured about a couple volts rms at the output of my amps at more realistic listening levels. I told you I sit about a couple meters away so you obviously more power to get louder. Surely you've been to concerts where the level is a lot higher than 86dB? 86dB is fine for low level listening but I know I like to blast it once in a while - who doesn't, right? :) Regardless, class d is more efficient than class ab where it counts. The fact that the good class d amps sound really good is certainly nice as well. |
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| Pafi |
| quote: | | My point was that there's no need to be concerned with efficiency at 100mW or less with a power amplifier. |
Then don't say untrue things about an amp, only say that you just can't hear the sound what is the highest room volume for me!
| quote: | | I have measured about a couple volts rms at the output of my amps at more realistic listening levels. |
| quote: | | 86dB is fine for low level listening |
86 dB=low level? :eek: Then consult with your doctor about your ears! More then 80 dB can cause health problems if you are exposed to this for a long time!
Check this out:
http://www.nonoise.org/library/levels74/levels74.htm
This tells e.g.: "Stereo music: 50-70 dB" (Page 15, table2.)
"PREPARED BY
THE U.S. ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF NOISE ABATEMENT AND CONTROL"
When I measure 3-4 V, then I start to feel bass, not only hear. I sit less then 1 m from speakers, but they are absolutely not efficient (~82 dB).
Sometimes I like storm-like bass for fun also! When I drived 6 pcs of Eminence Kappa pro 18s in band-pass boxes, in a 6*8 meter closed room with my bridged, +/-63V supplied amp module (~ 10 kW peak power), then sound pressure rumpled my hair in a point of the room, but this is not listening to music at all!
| quote: | | Surely you've been to concerts where the level is a lot higher than 86dB? |
Yes, I have some, but you seems to have been too many times! |
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| BWRX |
| quote: | Originally posted by Pafi
Then don't say untrue things about an amp, only say that you just can't hear the sound what is the highest room volume for me! |
What did I say that was untrue???
I can certainly hear low level sounds and like to listen to background music below 50dB SPL, but when I want to really listen I like to have more realistic sound levels. 90dB or more is not uncommon there.
| quote: | Originally posted by Pafi
86 dB=low level? :eek: Then consult with your doctor about your ears! More then 80 dB can cause health problems if you are exposed to this for a long time! |
I overstated myself there :) You are right that 86dB is not low level. The most I listen at higher levels is for the majority of the tracks on a CD. So probably about 30 to 60 mins.
| quote: | Originally posted by Pafi
Yes, I have some, but you seems to have been too many times! |
My upper hearing limit is 17kHz so chances are I have damaged my hearing a bit but I really haven't been to too many really loud concerts. I never go in really loud night clubs either. I can't stand it when you can't talk to the person right next to you and everything reeks of smoke :dead: |
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| Pafi |
| quote: | | What did I say that was untrue??? |
This: "The most power that will be wasted below 1W output will clearly be less than a watt."
| quote: | | but when I want to really listen I like to have more realistic sound levels. |
I think we just talk about different things. What you talk about is more similar to a concert, when you want to hear _only_ the music. I meant music as background, while I can do other things in same time (exept talking). I think this is more typical. |
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| classd4sure |
| Background music? Hm, no need to get vulgar. |
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| fokker |
| quote: | Originally posted by ghemink
If you have heard one, what was your impression? Gertjan |
the answer to your question is a decidedly yes. I have heard quite a few digital amps lately, T/SuperT, HK DPR1K, UCD, Panasonic XR, and a few in my computers/pda/cell phones, to name a few. not to mention a NuForce Ref9.
Sound quality wise, they are on par with a decent SS amp, and I would consider them a notch below my HK630 but in all honesty I would be hard pressed to tell them apart in a DBT.
In my view, they are grossly overhyped, in terms of sound quality.
That is not to say that they are bad amps. They are just indistinguishable from a good analog amp. |
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| fokker |
| quote: | Originally posted by classd4sure
Only in practice, in theory they've always been superior, well, since the theory came to be. |
I don't know why in theory they are superior but Class D, no matter how beautiful it is in theory or in its current state of affairs, started low. |
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| BWRX |
| quote: | Originally posted by Pafi
This: "The most power that will be wasted below 1W output will clearly be less than a watt." |
Yes, you're right Pafi, that is not a correct statement. I don't know what I was thinking about.
From the graph at 1.125W output the class d amp is about 25% efficient. So it's input power would be 4.5W and the other 3.375W would be wasted as heat.
The class ab amp is about 7% efficient. That means it's input power would be about 16W, so 14.875W would be wasted as heat.
Below that output power I can't easily see what the efficiency would be but it's pretty close between the two. |
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| classd4sure |
| So I guess there's little use for a headphone class D amp then |
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| BWRX |
| In terms of efficiency class d probably wouldn't be any better for a headphone amp. In terms of sound, that is yet to be determined. |
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| Pafi |
| quote: | | So I guess there's little use for a headphone class D amp then |
Not neccessary. My arguments implies only that a 80W ClassAB can be more efficient as headphone amp then a 80W classD. But a 2W ClassD is probably more efficient at 100 mW then a 2W ClassAB! This really can be seen on the other link of BWRX. |
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| ghemink |
| quote: | Originally posted by samsagaz
Hey guys, i want to upgrade my HT, its just an 5.1 channels. I want to sold the Receiver and want to use dedicated amps for each channel, i want to get at least 200Watts per channel. i really want to know if buiding and classD amp will get nice sound, (comparable with comercial ones like Rotel RMB-1095)?
I want to drive a pair of Polk LSI Series Speakers. |
The poor guy (samsagaz) started this thread with a simple question (see above). Most of the thread now comes down to in my opinion irrellevant quarreling about mA`s quiescent current. He just wanted to know whether a 200W Class D will give a nice sound. Personally I think it will blow away the above mentioned conventional amp, however, anybody heard that Rotel AMP? So I would say go for Class D and you won`t regret it.
Best regards
Gertjan |
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| samsagaz |
ok i will purchase an ClassD kit and some ClassAB Kits and will compare the results :)
Thanks for all your words |
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| BWRX |
Well there you go. Getting both and listening for yourself really is the best way to find out anyway :up:
Have fun building sam :) |
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| classd4sure |
C'mon, you know you can't have a "class d highend??" thread without all kinds of fighting :)
I can also highly recommend the UcD180 modules. They're about as bulletproof as it gets and absolutely qualify as high end in my book.
I don't think you'd regret em one bit. It is a good idea to get a few and experiment with for awhile before planning your entire system though. |
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