[letterbeacon]

Previously when I've measured my DIY pre amp, I was running Windows and so was able to use RMAA to measure the frequency response.  I am now on OSX and I'm after a similar program.

I looked at Spectra Foo, but it looks like I'll be using a sledgehammer to open a walnut.  It also looks a lot more complicated than RMAA.

Can someone recommend a simple to use program for OSX to measure the frequency response of a pre amp/ compressor or maybe even how to get Spectra Foo to do it?

[bubbi]

Room EQ Wizard should be perfect for this job !
http://www.hometheatershack.com/roomeq/

[joaquins]

fuzzmeasure http://supermegaultragroovy.com/products/FuzzMeasure/
It´s not a real time but for measuring THD it do nice plots for 2nd and 3rd harmonics, nice impulse, etc... it runs a sweep

Smaart 7 also have some nice things but more for calibration like live aplications.
Acoustic toolbox is other option, not so nice, but it may like you better than me...
Spectre is other option out there.

I use fuzzmeasure for fast measuring, one sweep (or a couple with average, and with or without correction so you can measure your sound converters alone) and it gives a lot of data and plots... phase (normal, minimun, delay group) freq response, thd, impulse, RT (20/30/ETD) if you are with a room, waterfall, etc... For RTA Smaart 7 is what I choose, multiple simultaneous responses and nice, for filters and EQ I really like it.

JS

[Andy Peters]

Previously when I've measured my DIY pre amp, I was running Windows and so was able to use RMAA to measure the frequency response.  I am now on OSX and I'm after a similar program.

Frequency response = transfer function, which means you probably want Smaart 7.

SpectraFoo's "Complete" does transfer function, too, for about the same price as Smaart 7.

FuzzMeasure doesn't do transfer function; it does swept-sine, so I don't know whether it displays phase information properly (or at all).

Faber Acoustical's Signal Suite does FFTs but not transfer function, but is otherwise pretty nifty.

-a

[letterbeacon]

Thanks for the replies -looks like I'll give Room EQ Wizard a go first.

[alexc]

Frequency response = transfer function ..

I don't think so.

The (magnitude) transfer function of a system is output vs input magnitude, like a compressor 'knee' curve.

Frequency response is output amplitude vs frequency.

Or at least it used to be when I was at university 

[Andy Peters]

Frequency response = transfer function ..

I don't think so.

The (magnitude) transfer function of a system is output vs input magnitude, like a compressor 'knee' curve.

Frequency response is output amplitude vs frequency.

Or at least it used to be when I was at university 

Let me expand. Yes, transfer function is output vs input, but more precisely H(f) = Y(f) / X(f) where Y(f) is the system output and X(f) is the system input.

Note that all are functions of frequency.

And also note that transfer function is complex, meaning you get magnitude and phase. Both are important.

The usual transfer function plot one sees shows separate amplitude and phase graphs, both as a function of frequency. Where the magnitude plot shows 0 dB and the phase plot shows 0 degrees then the output equals the input. Transfer function is independent of input level, so we assume (or ensure) that nothing is clipping.

Yes, we often see an RTA display showing amplitude vs frequency and that's designated as "frequency response," and that's true but only part of the story.

-a

[alexc]

I also don't think that transfer response is always a function of frequency. It can be, for sure, but not necessarily.

It can just as easily be in the time domain, discrete time domain, s-plane, z-plane or any other complex plane or phase space representations.


And yes, the transfer function often is a complex representation which is why I mentioned the magnitude transfer function.

Anyway - not to get too narky but I never heard of freq resp and transfer response interchangably used.

[Andy Peters]

I also don't think that transfer response is always a function of frequency. It can be, for sure, but not necessarily.

It can just as easily be in the time domain, discrete time domain, s-plane, z-plane or any other complex plane or phase space representations.

That is true.

And yes, the transfer function often is a complex representation which is why I mentioned the magnitude transfer function.

But magnitude is kinda misleading. Is it the sqrt(re^2 + im^2) magnitude, or the real part of the complex transfer function?

Anyway - not to get too narky but I never heard of freq resp and transfer response interchangably used.

"transfer function" does have a defined mathematical meaning. "Frequency Response" means whatever the beholder wants it to mean, I suppose, and generally that means magnitude response and no phase data.

But the original poster asked about "frequency response of a preamp," and if I was measuring a piece of linear (hopefully) electronics, I'd want to know both magnitude and phase, hence, transfer function.

-a

[alexc]

All true in the context of this thread 

Thanks for expanding on that.

[Piotr]

Hi !

I second the Transfer Function recommendation (frequency response + phase information).

Smaart 7 is pretty straight forward since it originates in the live (read simple and quick) type of analysis and speaker system alignment.
Spectrafoo is also a great and more "tweekable" tool, check Metric Halo's website for the latest manual which might steer you towards Spectrafoo...

Regards, Piotr.

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