I am so loaded down with work right now that my plans to knock together a simple high current op amp booster will have to wait . It seems to me that any amp that can raise 15 V rms in bridge and drive 1 ohm is a winner .
My previous research into this said that any amp that can offer 5 watts class A and then jump into class AB ( the much criticized bad type AB that looks like class G ) will be a winner . It will not have the gutless sound of many class A designs .
My other experiments were very surprising . When the OPA 604 was replaced with 2 transistors ( 3/4 is better ) the control of distortion became easier !!!! Low distortion at 50 kHz with some cunning was possible . At -70dB 50 kHz I was happy ( 5 watts down to noise ) . 2 transistors was a stupid caprice . What it did prove was the following .
Bootstraps work .
Bootstraps are mostly wrongly thought out .
Single input is not a source of excessive distortion .
High DC stability is possible with a single input .
LTP input is not a source of instability to any great degree .
Single VAS is a bad idea
A small VAS emitter resistor is a fine tuning aid . It can do more good than harm .
Complimentary feedback pairs work well without obvious problems .
Class A to 5 watts is ideal because it requires no special bias system if heatsink is suitable .
I would say 5 watts regardless of load is practical and advantageous . No need for class A to increase with load .
I have to say when I turned down the bias it still was as sweet as I could hope for . The scope said it should be . The difference was the reality of voices with sensible class A .
I do think " wrong " class AB has an advantage . It gives the correction system two places to correct . OK it will produce more THD . The thing is the distortion is where we already are not able to turn down ear distortion . The amplifier now tells us detail is important and the thrill of loud is available on demand . With bad amps I just listen loud . " Good class AB " puts the distrotion where it dose most harm, makes me know it is amplified music .
It is often quoted that to our ears 10 watts is half of 100 watt , it is a quarter of 1000 watts . The reason most 10 watt amps sound gutless is a serious lack of current .
Dvv . I had a Naim Nait . 90% of the time I could hear what it did wrong . All of the time it was fine and had a feel good factor . It was like Burger King ( one shouldn't like it ) .
My previous research into this said that any amp that can offer 5 watts class A and then jump into class AB ( the much criticized bad type AB that looks like class G ) will be a winner . It will not have the gutless sound of many class A designs .
My other experiments were very surprising . When the OPA 604 was replaced with 2 transistors ( 3/4 is better ) the control of distortion became easier !!!! Low distortion at 50 kHz with some cunning was possible . At -70dB 50 kHz I was happy ( 5 watts down to noise ) . 2 transistors was a stupid caprice . What it did prove was the following .
Bootstraps work .
Bootstraps are mostly wrongly thought out .
Single input is not a source of excessive distortion .
High DC stability is possible with a single input .
LTP input is not a source of instability to any great degree .
Single VAS is a bad idea
A small VAS emitter resistor is a fine tuning aid . It can do more good than harm .
Complimentary feedback pairs work well without obvious problems .
Class A to 5 watts is ideal because it requires no special bias system if heatsink is suitable .
I would say 5 watts regardless of load is practical and advantageous . No need for class A to increase with load .
I have to say when I turned down the bias it still was as sweet as I could hope for . The scope said it should be . The difference was the reality of voices with sensible class A .
I do think " wrong " class AB has an advantage . It gives the correction system two places to correct . OK it will produce more THD . The thing is the distortion is where we already are not able to turn down ear distortion . The amplifier now tells us detail is important and the thrill of loud is available on demand . With bad amps I just listen loud . " Good class AB " puts the distrotion where it dose most harm, makes me know it is amplified music .
It is often quoted that to our ears 10 watts is half of 100 watt , it is a quarter of 1000 watts . The reason most 10 watt amps sound gutless is a serious lack of current .
Dvv . I had a Naim Nait . 90% of the time I could hear what it did wrong . All of the time it was fine and had a feel good factor . It was like Burger King ( one shouldn't like it ) .
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Nige, Frank,
It's all economics, NONE of it is electronics.
The industry wanted to make as much money as it could, so it did its best to create the idea that power equals quality. To reaffirm that, more powerful was also given extra faclities, so it would even look richer. Far too few people even dared think outside that box.
The few that did gained world fame.
I'm not sure whether our American friends had an opportunity to see Hiraga's legendary little amp. Just in case I'm right, the schematic is attached. Note the simplicity and right down to business approach. I have heard tens and tens of version of it, and most sound from very good, to outstanding, low power notwithstading. King of the road is a guy who ran his from two 22,000 uF caps - per channel.
It's all economics, NONE of it is electronics.
The industry wanted to make as much money as it could, so it did its best to create the idea that power equals quality. To reaffirm that, more powerful was also given extra faclities, so it would even look richer. Far too few people even dared think outside that box.
The few that did gained world fame.
I'm not sure whether our American friends had an opportunity to see Hiraga's legendary little amp. Just in case I'm right, the schematic is attached. Note the simplicity and right down to business approach. I have heard tens and tens of version of it, and most sound from very good, to outstanding, low power notwithstading. King of the road is a guy who ran his from two 22,000 uF caps - per channel.
Attachments
I'm not sure whether our American friends had an opportunity to see Hiraga's legendary little amp. Just in case I'm right, the schematic is attached. Note the simplicity and right down to business approach. I have heard tens and tens of version of it, and most sound from very good, to outstanding, low power notwithstading. King of the road is a guy who ran his from two 22,000 uF caps - per channel.
Wonder what the d.c. offset was? Rarely are PNP and NPN matched well enough, even when alleged to be complementary pairs, to have that current-mode input stage have low offset voltage.
Yeah , keep blaming me ..
Build a true voltage source and its all over, build a compromised amp and then in turn blame the speaker designer ...
OK, now do that experiment again with a 200w amp, obvious game changer
It was tongue in cheek and rhetorical DVV ........
Irresponsibility comes from bad sound, if the sound is good, then its a good design coupled to a bad amp ...
I hate toy amplifiers, despise them really, there is no reason mass produced amplifiers cant have enuff outputs and transformers for proper current protection without reverting to dumb down circuit protection.
Much better to have a 50watt per channel amp that is load tolerant than a 200 watt per channel 8 ohm only amp loaded down with sonic degrading protection ..
Hence i stay away from dinky toy designs ......
It was tongue in cheek and rhetorical DVV ........
So was my post.
... Much better to have a 50watt per channel amp that is load tolerant than a 200 watt per channel 8 ohm only amp loaded down with sonic degrading protection ..
Hence i stay away from dinky toy designs ......
Completely agreed. Power is not half as big a point as load tolerance is. Some have never figured this out, and others have a long time ago, like Harman.
With a conventional 200W amp there would be no point, I've just listened to a suite of such beasts at a hifi show, and there was only one there that had the goods, the top of the line Bryston.OK, now do that experiment again with a 200w amp, obvious game changer
If the 200W was as well sorted as the 20W there would be no difference, except that I could go louder, assuming the speakers could take the sustained drive at those levels; like having a top notch PA system and standing a foot away from a cabinet vs. 6 feet away ...
Frank
Not so, has nothing to do with playing louder, the 200 w amp will better the 20 watt amp with all being equal. I have done the comparison so many times over the years, there is no way to reproduce 20 db of dynamic range above listening Din with 20 watts.
Even high sensitivity speakers benefit from the extra power ....
Not quite sure what you mean by "listening din" ... as said earlier, I can go cleanly to around 106dB at a reasonably close listening position, which is plenty. With something like Foo Fighters my ears can start ringing in a matter of minutes, no trouble. The ideal is to go to say mid 120dB's cleanly, which is equivalent to standing a couple of feet in front of the brass section in an orchestra, as another player.Not so, has nothing to do with playing louder, the 200 w amp will better the 20 watt amp with all being equal. I have done the comparison so many times over the years, there is no way to reproduce 20 db of dynamic range above listening Din with 20 watts.
Even high sensitivity speakers benefit from the extra power ....
The key thing is, you have to be 100% certain you're comparing oranges with oranges -- why a normal 20W unit is, sounds flimsy is because the power supply is under-engineered. If you took a massive power supply, from a 1000W amplifier, and attached it to the 20W unit then the latter would sound like a 1000W unit. It's all about, and always is, engineering ...
Frank
That's where the audio industry has "got it wrong", so to speak. An amplifier shouldn't have a "sweet spot", if it does it's faulty, it's as simple as that. That's what all those beautiful THD, IMD numbers are supposed to tell you, that the amp has no problems in any area, but of course it does, your ears are telling you it's not working properly at high volumes. Those impressive distortion figures are essentially completely meaningless in terms of assessing how good an amp really is ...
A lot of the time my 20W amp would be running in the 5 to 10W range, that's about right for getting realistic piano volume. It's class AB, but the heatsinks are stinking hot because it's really being worked hard. But it doesn't sound stressed or outside its "sweet spot", because such a thing doesn't exist for it ...
Frank
A lot of the time my 20W amp would be running in the 5 to 10W range, that's about right for getting realistic piano volume. It's class AB, but the heatsinks are stinking hot because it's really being worked hard. But it doesn't sound stressed or outside its "sweet spot", because such a thing doesn't exist for it ...
Frank
I guess we are going to have to agree to disagree Frank , 20 watts cant power your speakers to 106 db and it takes a whole lot of speaker and amplifier to get realistic Piano sound and levels ....
Very Big speakers ....
Measure your amplifier's thd vs power , a sweet spot will emerge ...
Maybe only a "sweeter spot" will emerge. A great amplifier should be all "sweet spot".
Scusi, signore Wayne, but he sure can if he has something like Altec Lansing of old, which did 103 dB/2.83V/1 m. Frank might even hit 116 dB before his amp gives up.
Theoretically, with my speakers (which are not particularly efficient, just 92 dB/2.83V/1m), his 13 dBW could go pretty loud in absolute.
While I agree with Frank, just give it a good PSU and you're fine, I must also admit that there is some program material his chip amp might struggle with. I haven't studied the topic, but I believe chip power amps do experience problems with funny loads, as they are pretty strictly protected. For example, a tympani hit - it's low, it's powerful and it will tax the amp, any amp.
Point is, chip power amps don't have the dye for really high currents, so will Motorola please prepare.
Which is why I would investigate Nat Semi's driver chips, which require current stage(s) as an external feature.
Dvv and all . I heard the famous Yamaha class A / A/B amp in a good system about 5 years ago . Previously I had thought it anemic . Not so .
I once went out with a girl who is an identicle twin ( see her sometimes ) . Mildly I chose the wrong sister , Joe was the one . The Yamaha is like that . Joe is 20 W , she will win your heart even though she is the quiet one . Caroline is a little more exciting and can be mistaken for identicle . In life I could not easily have both ( don't ask ) . In electronics we can .
The Hiraga . 100 % right .
I once went out with a girl who is an identicle twin ( see her sometimes ) . Mildly I chose the wrong sister , Joe was the one . The Yamaha is like that . Joe is 20 W , she will win your heart even though she is the quiet one . Caroline is a little more exciting and can be mistaken for identicle . In life I could not easily have both ( don't ask ) . In electronics we can .
The Hiraga . 100 % right .
Life's made easy for my particular beast, because it only has to handle above about 180Hz, and there's no crossover, just uses a simple full range speaker. Separately powered single subwoofer which amusingly enough uses a single LM3886 more than adequately fills in the bottom.
But, an earlier exercise using LM3875 did drive a conventional 2 driver plus crossover box. These chips can put out a transient current pulse of nearly 10A, which should cover most situations.
What has overloaded both of these units, of all things, is opera! A soprano, hitting a pure, sustained note at full volume is very close to driving at high level with an audio oscillator, and the DIY unit started glitching as the internal protection cut in, the HT shut down and had to be powered off and on. In both cases it was thermal overload, the chips were starting to cook themselves ...
Frank
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This reminds me, the active studio monitors are a joke. Supposedly capable of hitting over 120dB, the top of the line Mackie was a pretty dismal specimen, the overload light was flashing continually in the showroom while producing not particularly impressive sound levels. And then the left channel died, and couldn't be resucitated.
Spec's only tell so much ...
Frank
Yes, and Dynaudio, JBL, a good range of near field units. I had an idea for a project and wanted to suss out what the commercial units were capable of. Spent a day going to all the pro shops in Sydney, and it was a bit of a shock when doing this exercise to hear their limitations. I suspect far field models would do somewhat better but didn't come across any on the day.
Probably my main criticism is that they all sounded very "small". Yes, they're physically small but if they are low distortion, high dynamics units they should project a bigger sound than they did. They all reminded me of a muscle bound midget trying to show off, and not making a very good job of it ...
Frank
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