Does it matter if measured unit is 110V or 230V (or 110/230V switchable unit, 50/60Hz hum etc).
Is it possible to measure slew rate of an amplifier ? And how it is important ?
Demian Martin, designer of the early Spectral amps told me that slew rate wasn't the real reason for the extreme bandwidth. It was the ability to let go of a signal, the fall time, they were trying to make much better. The wide bandwidth, and the high slew rates, were simply side effects of getting extremely fast fall times to let go of signal transients. Those amps were spectacularly clean, transparent, and musical. Or so they seemed when driving my Quad ESL63 speakers which incidentally were the speakers Mr. Martin was designing for.There are standards for measuring slew rate of amplifiers and can easily be done.
You just need an oscilloscope with a bandwidth that is wider than that of the measured device.
Some manufacturers actually have slew-rate numbers in their spec sheet.
Slew rate is not something that is in a standard measurement suite.
Slew rate can also be asymmetrical (rise time may be faster or slower than fall-time)
With modern electronics slew-rate should not need to be a limiting factor for reproduction of audio.
In practice it depends on design, used components and feedback.
When one applies a square-wave (with steep edges) the feedback circuit can/will be saturated.
In this case the output goes to the intended positive (or negative) output voltage as fast as it can right up to the point where feedback takes over again. Weird over and undershoot can occur which is easily spotted in squarewave response plots.
It says something about how fast the circuit is and how well feedback works.
upper Bandwidth and slew rate as well as 2nd harmonic distortion levels near the frequency limit are related to this.
How high slew rate should be thus depends on the maximum output voltage the amplifier must reach (includes current under load) and maximum frequency it must be able to reach.
For electrostatic HP amps and high power amplifiers higher numbers are needed than for line level stuff as slew-rate is expressed in Volt per time-unit
(EDIT: seems I was crossposting with Blumlein 88)
Demian Martin, designer of the early Spectral amps told me that slew rate wasn't the real reason for the extreme bandwidth. It was the ability to let go of a signal, the fall time, they were trying to make much better. The wide bandwidth, and the high slew rates, were simply side effects of getting extremely fast fall times to let go of signal transients. Those amps were spectacularly clean, transparent, and musical. Or so they seemed when driving my Quad ESL63 speakers which incidentally were the speakers Mr. Martin was designing for.
Based on the above "answer", I have an EE question;
I have a wire energized with a sine wave voltage, and some current flow. Mabe later it is only energized, but no flow.
Is there one, or two fields around it... I'm thinking what I might call "electrostatic" induced by the voltage and the other "magnetic" induced by the current, or are they the same thing, or what?
Sorry if this is the wrong place to ask but I've been thinking about trying to measure the output impedance of the DX3 Pro V2 that I recently bought since Topping only specs it to be <10 Ohm, but I have a few questions about how I would go about to do that.Setup B is what I started with until some amps got so good that I also built a setup A (for Benchmark HPA4 for example). I still use my fixture for B since it is more flexible (multiple impedances) but if I suspect an amp is very good, I resort to A. Once I get some time, I will phase out B.
For speaker testing, it has been setup A (Kelvin-type connection) for a while.
This, would be the challenge. I don't know which meters have such wide bandwidth. Otherwise it is very simple. You play a low frequency tone. Set the output level to 1 volt or so to avoid clipping. Then load it down with a resistor. Then a simple formula will give you the output impedance.Also I would like to measure at different frequencies between 20 Hz and 20 kHz to see if the OI changes with frequency and from what I understand a lot of cheap multi-meters are only accurate around a certain frequency (200 Hz?) so how expensive would it be to get one that can measure accurately close to 20 kHz?
So if I only measure it at a low frequency I could get away with using a cheap multi-meter? Also exactly how do I load the output with a resistor, do I just put the end of one of these in the output of the amp and put the multi-meter on the other end?This, would be the challenge. I don't know which meters have such wide bandwidth. Otherwise it is very simple. You play a low frequency tone. Set the output level to 1 volt or so to avoid clipping. Then load it down with a resistor. Then a simple formula will give you the output impedance.
Setup B is what I started with until some amps got so good that I also built a setup A (for Benchmark HPA4 for example). I still use my fixture for B since it is more flexible (multiple impedances) but if I suspect an amp is very good, I resort to A. Once I get some time, I will phase out B.
For speaker testing, it has been setup A (Kelvin-type connection) for a while.
So if I only measure it at a low frequency I could get away with using a cheap multi-meter? Also exactly how do I load the output with a resistor, do I just put the end of one of these in the output of the amp and put the multi-meter on the other end?