Amplifier Measurement Equipment

[syzygetic]

I'd like to measure some home built amplifier circuits objectively (SINAD, Multitone), and I'm debating between two interfaces for performing the measurement:

1. Cosmos ADC & a good dac, or
2. Motu M2

Here's what I'm thinking:

I only want to measure amplifiers, not DACs or anything crazy. The Cosmos ADC is clearly more capable when it comes to being an instrument, but the Motu M2 might be useful beyond that, as a simple one-box interface for input and output.

What would audiosciencereview do? Absolute reference grade or useful decent all in one?

 

[solderdude]

I would not want to be limited to 80kHz BW when testing amplifiers when you want to run stability tests so the M2 is out.
Also you will need some serious dummy loads.
The Cosmos has a good input voltage range and 180kHz is at least better than the M2

Maybe buy something like this as well?

 

[Matias]

My vote do Cosmos ADC and "Absolute reference grade". You never know if you would use it for sources later.

 

[HarmonicTHD]

I'd like to measure some home built amplifier circuits objectively (SINAD, Multitone), and I'm debating between two interfaces for performing the measurement:

1. Cosmos ADC & a good dac, or
2. Motu M2

Here's what I'm thinking:

I only want to measure amplifiers, not DACs or anything crazy. The Cosmos ADC is clearly more capable when it comes to being an instrument, but the Motu M2 might be useful beyond that, as a simple one-box interface for input and output.

What would audiosciencereview do? Absolute reference grade or useful decent all in one?

It simply depends how deep you want to get into the hobby, what your personal expectation are in terms of measurement accuracy and how many more amps you want to measure in the future.

I once used my Focusrite 4i4 and REW, which is somewhat comparable to your option 2). It gets down to about 90dB SINAD as far as I remember, which might be good enough from an audibility point of view but certainly not to measure at SOTA level. (MOTU might be a tad better even).

 

[DonH56]

For amplifiers a decent audio interface is probably adequate. I agree with @solderdude that, especially for home-built, you want a way to check HF stability and look for unexpected ringing/oscillation that can occur in the low MHz region (and rarely above that, though SMPS and class D designs reach well into the MHz region). I would look for a decent new or used oscilloscope, either analog or digital, with ~100 MHz bandwidth to help monitor the output. (I have a cheap 100 MHz USB-based DSO.) For DIY amps, I would get a decent selection of capacitors and inductors to add to the resistive loads. Make sure they can handle the voltage and current needed. Hopefully you already have a decent multimeter (DMM) to check for biasing and output offsets and such.

FWIWFM - Don

 

[pma]

I only want to measure amplifiers,

Please define your position first, what do you want to do and measure.

1) Just for fun, when you get in touch with some standard product to collect some numbers? Then a sound card or DAC + E1DA Cosmos ADC may be enough.
2) Do you design or repair amplifiers? Then you need an oscilloscope at first place, at least with 50MHz or better 100MHz BW. Soundcard like Motu would be enough then to check some basic distortion measurements, if you repair only and do not design new amplifiers.