R&S CMU200 - USB or PS2 version

[MagicSmokeGuy]

I have been offered a choice of 2 different Rhode & Schwarz CMU200 units.  The first has the USB ports but only a few options enabled.  The 2nd is the earlier unit with the PS2 keyboard port but has some additional options enabled including the Audio Analysis option and Bluetooth.  Any disadvantages with the earlier units over the later USB equipped versions?  Can both be taken up to the most recent software version?  The later unit is bit cheaper than the earlier better equipped one (£500 vs £850).

[ps]

The CMU is controlled by a MS-DOS computer which does not support any USB devices. So the only use for the ports is to connect a keyboard (which is supported by the BIOS without need for any DOS device drivers).

Usually USB means FMR6 which is the more recent CPU with more computing power. However, with MS-DOS running this does not really make a big difference.

So buy the unit with the Audio Analyzer option.

[TheDefpom]

You can also hack it and unlock any software options you want, its pretty easy to do... installed hardware dependant of course.

[pcwrangler]

USB is newer but as said already, that doesn't matter much in DOS. I actually dismissed the idea of upgrading from Celeron to P3 because it wouldn't make much of a performance difference but add more heat in the front panel enclosed area. The only factor I would consider is the R&S hardware options installed on each. Let us know what you choose.

[MagicSmokeGuy]

Thanks for the advice.

So the fact that the later version could have a faster underlying system actually makes little difference in the real world is interesting and I think helps my decision significantly, thanks guys.

I’m assuming the audio analysis and Bluetooth options on the more expensive one rely on hardware as well as software so with that in mind, it makes sense to go for the earlier version given that the performance will be similar.

Have I read this correctly?

[_Wim_]

Thanks for the advice.

So the fact that the later version could have a faster underlying system actually makes little difference in the real world is interesting and I think helps my decision significantly, thanks guys.

I’m assuming the audio analysis and Bluetooth options on the more expensive one rely on hardware as well as software so with that in mind, it makes sense to go for the earlier version given that the performance will be similar.

Have I read this correctly?

Yes, both audio (option B41) and Bluetooth (option B53) are indeed hardware options (in general all options starting with "B" are hardware options). Software options (starting with "K") can easily be enabled afterwards.

My CMU200 does have option B41, but I cannot say I find it very useful. A typical soundcard and some free audio analysis software performs much better (lower THD and noise, much more possibilities...) than this audio analyzer. I do not have the Bluetooth option, so I cannot say anything about it usefulness. But I would not spent 350£ extra for the audio analyzer, that is for sure (for that kind of money you can buy a quantasylum QA402, which is in a whole other league performance wise).  So for me the main question would be: "is the Bluetooth option worth 350£? " I would guess it isn't, but as said, I have no experience with it.

I agree with others that the more recent CPU will not make much difference, and if they were the same price I would for sure opt for the older better equipped version. 

[MagicSmokeGuy]

Very interesting feedback from _WIM_

I had not considered that using a soundcard with analysis software would offer comparable performance.  Given that you actually have the audio analysis option on your unit, an opinion based on actual experience is most useful.  The Bluetooth option is of some interest to me but for £350... not sure at this stage.

I'll look into the Quantasylum QA402 but I'm not sure it can be bought easily in the UK.

[_Wim_]

I do not think the quantasylum is really necessary.

Attached THD and noise (with averaging enabled) I made with and Echo Audiofire 2 soundcard in loopback. If you compare the measured THD to the spec of the B41, it is an order of magnitude better. And a program like ARTA has way more useful functions to test both amplifier and loudspeakers. Even a standard soundcard of a modern laptop will perform better than the B41. And they are typically not limited to 20kHz.

[MagicSmokeGuy]

Interesting, thanks.

I’m leaning more and more towards the cheaper unit.  The only thing I have thought about is that the one with the audio option does, I think, allow AM and FM signals being measured to be listened to and the modulation measured. Is this correct?

[Bicurico]

I would go for the newer USB version. As mentioned already, the audio analyser is not that much interesting and I doubt you would be using the BT option, either.
While the performance of the new board is not important, the fact that it is newer, means it should last longer. Same for the battery, RXTX boards, etc.
And being considerably cheaper, I think that is the way to go

[MagicSmokeGuy]

Sounds like I'll be getting the cheaper unit - just looked at the Arta software and it's very comprehensive and I already have a nice MOTU M4 audio interface I can use with it.

Thanks for the advice.

[_Wim_]

Sounds like I'll be getting the cheaper unit - just looked at the Arta software and it's very comprehensive and I already have a nice MOTU M4 audio interface I can use with it.

Thanks for the advice.

The Motu M4 will be excellent in combination with ARTA. Be sure to use the ASIO drivers and not the windows drivers.

Another software package that is free and very useful is Room Eq wizard. It is geared more towards acoustics and loudspeaker measurement only, but has an easier learning curve than ARTA. But ARTA with its LIMP and STEPS companion software packages is in my opinion still the best and most versatile.

[MagicSmokeGuy]

Quick Update.

Having spoken to the vendor at length, it seems the later unit has suffered some physical damage to the casing, is missing a rear foot which has broken off and also fails it's internal loopback tests 

Hoping to do a deal on the earlier higher specified one now, watch this space...

[MagicSmokeGuy]

Ended up with (what I hope is) a great deal on the earlier but with more options version.  Supplier offered a full 1 year warranty and did a calibration on it for me. 
Delivered this morning.
Only thing slightly out of cal is RF input 4 which is 1dB ish out at a couple of frequencies according to the calibration notes.
Overall I’m very pleased with it although I’m still finding my way around it.

[Bicurico]

Consider getting a (fake) Keysight USB GPIB interface and use it with my software...

See my blog for further information.

Nice purchase!

Regards,
Vitor

[MagicSmokeGuy]

Thanks Vitor.

Your software looks very interesting.  I have an NI PCMCIA to GPIB card and a Windows XP based laptop with a PCMCIA slot so I may try it out on that. Does you software run on XP or only later Windows OS?

[Bicurico]

Not sure - best is to just give it a try!

[MagicSmokeGuy]

Software will not install under Windows XP SP3 - installer is not recognised as a valid 32bit app.

However, I have managed to get my PCMCIA adapter running under Windows 7 32 bit and have just sent you a code for activation.

Thanks, Brian