Paradoxically strange >
If I ever get my 'curiosity amp project' off the ground [ with the help of diyAudio members ]
it will exhibit > low slew rate, rounded square wave and rather high THD performance > all because I have never listened to such a thing 🙂
If I ever get my 'curiosity amp project' off the ground [ with the help of diyAudio members ]
it will exhibit > low slew rate, rounded square wave and rather high THD performance > all because I have never listened to such a thing 🙂
The ringing (at square-wave) shows primarily raising of the high frequency response, which can sign of instability (but not only because of). For example, see the well compensated amplifiers with output LR-filter at parallel RC-load. The RL-component and RC load make an damped LC-tank, but there isn't any instability (but there is a lot of ringing🙂)
That's the thing. Slew rate limiting does not create nicely rounded square waves - it creates straight line edge square waves. The slew rate of the edges is limited and they rise (or fall) at a constant rate (the max SR) and thus are straight lines.
Jan
Well, I think I said 'plain language', before starting the sentence !!
I don't think anyone here is disagreeing with this.
Basically I agree your opinion, but "the too fast" isn't problem alone. The input filtering can handle the overload. I think, the slew rate is an indicator too: within one OPA-family, you can see faster and slower types (with similar or near identical inner architecture). The higher slew rate and BW-product sign the "lighter" inner compensation. This causes higher open-loop gain and lower distortion with feedback, but it does not guarantee the better sound (often this indicates opposite result), especially if the closed loop gain curve shows a little bit rising at top end (phase-margin insufficiency).
Exactly.
Even with no dedicated L for filtering, short output wire inductance is enough, like measured here:
https://www.diyaudio.com/community/...y-simulated-vs-real-world.407089/post-7548890
I'm relatively new in this hobby, this is my opinions: I have a feeling that with a small slew rate, the measurement is better, but the sound is somehow flat and boring and not dynamic enough, muddy, while with a huge slew rate, the measurement is significantly worse, but the sound is incredibly fuller, better localization of instruments, greater dynamics... etc
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It's completely unclear to me what you mean.
Do you mean that when you preamplify an audio signal with an OPA2134 and then put it into a main amplifier, the main amplifier goes into slew rate limiting because of the high slew rate limit of the OPA2134?
If so, that's only true if the original audio signal had an unusually high rate of change. Using a slower op-amp in the preamplifier would then lead to slew rate limiting in the preamplifier instead of the main amplifier. I'm at a loss to understand why that would be preferable.
I suspect that most music, played at comfortable levels, will not challenge the slew rate spec of any competent amplifier.
I suspect you're right. But I would still argue that the amplifier should be able to deliver a 20 kHz sine wave at the full rated output power without slew-rate limiting in order to be considered competent. But that's me. You're free to have different standards. 🙂
Tom
Tom
The sound description in Post # 45 is bordering audio phoolery.
The audio amplifier has to respond properly to input signals, and reproduce sound faithfully, within the standards set by RIAA, DIN, JIS, GOST and other organisations.
First, it is not clear if the OP is just discussing this, or has a project in mind.
Second, there are many posts here and on other forums about op amp rolling.
Third, the slew rate of the pre amp section must be close to the slew rate of the input signal, and also the main amplifier section. Otherwise result will not be stable.
Fourth, that is usually the job of a design engineer, not somebody with less experience, no offense intended.
Last, what will be achieved result of this discussion?
The term slew rate is also used for earthmovers and tank turrets!
Used to compare how fast the thing will move in an arc...that was my analogy.
The audio amplifier has to respond properly to input signals, and reproduce sound faithfully, within the standards set by RIAA, DIN, JIS, GOST and other organisations.
First, it is not clear if the OP is just discussing this, or has a project in mind.
Second, there are many posts here and on other forums about op amp rolling.
Third, the slew rate of the pre amp section must be close to the slew rate of the input signal, and also the main amplifier section. Otherwise result will not be stable.
Fourth, that is usually the job of a design engineer, not somebody with less experience, no offense intended.
Last, what will be achieved result of this discussion?
The term slew rate is also used for earthmovers and tank turrets!
Used to compare how fast the thing will move in an arc...that was my analogy.