hello i am just wondering, what makes a amp realy fast and have a nice tight grip over the speaker? is it the transformer or is it realy good and big capacitor? or both? 
Lets try to reason it.
The transformer is disconnected from the power supply and from the amp about 80% of the time (that's when the diodes are not conducting), so to me it seems that the transformer has only a very limited impact on speed, if at all.
Then the caps. You can have all the power in the caps you want, but if the amp cannot get it to the output, that doesn't help either.
Also, an amp has what is called a 'power supply rejection ratio'. This says how insensitive the amp output is to any power supply variation. So an amp with a reasonable PSRR doesn't see much of what happens at the supply cap (as long as the voltage remains high enough for the required output signal).
So it appears that 'amp speed' depends on other factors.
jan didden
The transformer is disconnected from the power supply and from the amp about 80% of the time (that's when the diodes are not conducting), so to me it seems that the transformer has only a very limited impact on speed, if at all.
Then the caps. You can have all the power in the caps you want, but if the amp cannot get it to the output, that doesn't help either.
Also, an amp has what is called a 'power supply rejection ratio'. This says how insensitive the amp output is to any power supply variation. So an amp with a reasonable PSRR doesn't see much of what happens at the supply cap (as long as the voltage remains high enough for the required output signal).
So it appears that 'amp speed' depends on other factors.
jan didden
It's not that straightforward...
Damping factor (how low an impedance the amp output is) is perhaps the "conventional" meaning of an amp having a tight grip on the speaker. In theory 🙂 In practice it's somewhat different.
A fast amp is thought of as one with high slew rate and extended frequency response.
The transformer and big capacitors can go some way to making a good amplifier but it's not the whole story by any means.
Different amplifier topologies sound different, some prefer the "blameless" and technically perfect amps and other the less perfect but perhaps better sounding ones.
Damping factor (how low an impedance the amp output is) is perhaps the "conventional" meaning of an amp having a tight grip on the speaker. In theory 🙂 In practice it's somewhat different.
A fast amp is thought of as one with high slew rate and extended frequency response.
The transformer and big capacitors can go some way to making a good amplifier but it's not the whole story by any means.
Different amplifier topologies sound different, some prefer the "blameless" and technically perfect amps and other the less perfect but perhaps better sounding ones.
Janneman: so you mean that the layout and the parts on the PCB is what makes it fast and have a good hand with the speakers ? =)
Mooly: so what makes an amp to have high slew rate and extended frequency response?
and what is slew rate ?
hehe i think that i like the amps that sound a bit better then the "blameless". but to get that there has to be more experementation right ? =)
Mooly: so what makes an amp to have high slew rate and extended frequency response?
and what is slew rate ?
hehe i think that i like the amps that sound a bit better then the "blameless". but to get that there has to be more experementation right ? =)
Its getting a happy medium.
You dont want a low amp becasue it cant cope with higher frequencies.
You dont want too fast an amp because it could oscillate.
On my designs the last part of designing is getting the amp damped correctly at the VAS.
Or if a quasi also getting the lower driver damped enough to stop oscillation.
You dont want a low amp becasue it cant cope with higher frequencies.
You dont want too fast an amp because it could oscillate.
On my designs the last part of designing is getting the amp damped correctly at the VAS.
Or if a quasi also getting the lower driver damped enough to stop oscillation.
Slew rate is how fast the output of the amplifier can change with respect to time. It's usually measured in "volts per micosecond".
To design an amp for high slew rate means paying attention to the issues that normally limit it. For example having sufficient current available in the various stages within the power amp to charge and discharge any stray or internal component capacitance.
It's worth you getting hold of some of the books written by Doug Self such as the "Audio Power Amplifier Design Handbook"
The Amplifier Institute.
Fast means high slew rate - affects high treble. Tight grip means low output impedance - affects low bass. The two are unrelated. To a first approximation, high slew rate means adequate current drive within the amp so that capacitances can be charged/discharged sufficiently quickly. Low output impedance means having sufficient negative feedback.Chrabban said:
What makes an amp have good control over the speaker?
Multiple output transistor pairs
Strong VAS to drive the output stage
Multiple output transistor pairs
Strong VAS to drive the output stage
Thanks all for the response =D
(i have orderd doglas self´s book so i will know more about this shortly )
what is the negative feedbak and what can be done to have more ?
dose VAS have something to do wit the negative feedback?
(i have orderd doglas self´s book so i will know more about this shortly )
what is the negative feedbak and what can be done to have more ?
dose VAS have something to do wit the negative feedback?
You need to do a lot of reading on the basics of electronic design.
Try and get hold of a copy of this,
The art of electronics - Google Books
Try and get hold of a copy of this,
The art of electronics - Google Books
okey is that a good book? what do you think about doglas self books on amp building and designining ?
fasts equal high bandwidth nothing more nothing less. For a power amp that means high slew rate into loads. The small signal bandwidth should reinforce the slew rate ie keep the amp from going into slew rate limitation. For example If a desired audio signal causes an amp to slew limit then it goes open loop or is discontinuous > very bad (edit but I doubt the OP really wants the answer to that Q)
tight grip means high loop gain (Open LG (minus) Closed LG) over all frequencies esp bass. this translates to damping factor
tight grip means high loop gain (Open LG (minus) Closed LG) over all frequencies esp bass. this translates to damping factor
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The Art of Electronics is THE BOOK. Very few books in electronics have this status. Another will be Radiotron Design Handbook I guess.
I discovered that the fuses in the mains can be killers for transients and imaging. Not without risk i shorted them by connecting my audio ampilfier mains lead directly above the headswitch where the mains comes into the house. I was really impressed with the results. More attack and 3d presentation.
Absolutely NO! This is a serious safety hazard.
There is something wrong with an amplifiers psu if you can hear the effect of fuses.
It is a common trick to get a "fast" sound by rolling of the low frequencies a little. (Did anybody say Naim?)
That sounds a bit slow to me 😉
If you look at CD as the source then any input signal is by definition bandwidth limited.
100 watts into 8 ohms needs around 5 volts per micro second slew rate to reproduce a 20k sinewave. And from CD that's as good as it gets. Remember a CD can't even reproduce a 1khz squarewave... as shown here. Even a 741 opamp has little trouble with this.
If you want to reproduce say 100khz squarewave at 100 watts then the slew rate needs to be far far higher.
So 40v/uS is a typical value that many would work to.
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