External Audio Rack or 10 Dollar Dynamic Microphone

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W1AEX
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External Audio Rack or 10 Dollar Dynamic Microphone

Postby W1AEX » Tue Aug 08, 2017 7:45 pm

A comparison of my ANAN-200D on AM with an external audio rack vs. a 10 dollar dynamic microphone.

The audio rack is plugged into the ANAN-200D Line IN and is comprised of the following components:

Marshall MXL-770 studio electret condenser microphone
DBX-286S voice processor
DBX-166A soft limiter

The microphone is plugged directly into the ANAN-200D MIC IN jack and is a 10 Dollar Pyle PDMIC78 dynamic. (Chinese clone of the Shure SM-57)

As the Line IN and Mic IN TX profiles are switched back and forth I can hear a difference in the mid-range clarity between the two but I think with a little more work with the CFC Audio Tools that I can get the 10 dollar dynamic even closer in sound to the external audio rack. Over the past week I have switched back and forth between both setups in several different AM QSOs and the other stations did not seem to notice the difference. Food for thought, do you really need an external audio rack or can you get by just fine with a cheap 10 dollar dynamic?

73,

Rob W1AEX

"One thing I am certain of is that there is too much certainty in the world."
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Re: External Audio Rack or 10 Dollar Dynamic Microphone

Postby w-u-2-o » Wed Aug 09, 2017 1:23 am

No surprise here, Rob. Anyone who is being honest about microphones knows that, for any mic that costs more than $1, mic's are 70% frequency response, 20% sensitivity, and 10% other factors. Frequency response is trivial to match. Sensitivity can be worked around by adjusting gain such that one uses the microphone in the near field (and inch or two away from your face). That leaves that 10% set of factors which, for most hams, is inaudible. Those with discerning ears can certainly hear the difference, but so few people have the "ear" to do that.

There aren't that many factories in the world making microphone elements. You are likely to find the same element used in both high and low priced microphones. Imagine that! Don't tell Bob Heil ;)

I have used my DAW software to perfectly match the spectral output of my Microsoft Lifechat LX-3000 USB headset, AKG C555 wireless professional headset, and "reference" Behringer B1 large diameter condenser. To my ear the Behringer is the best, then the AKG, then the USB, but to 99% of the people I speak with on the radio, they are indistinguishable with the EQ matching. I've done this test "single blind" and people never catch on that I'm changing mic's. I've even done it to you :D

Listening to your recording, I'd say you have a little ways to go with respect to matching the audio from the two sources. However, with a little more time invested, I'm sure that you can make each combination nearly indistinguishable. I've nearly duplicated my DAW output with the built-in features of PowerSDR mRX. The DAW is, to my ears, clearly better, but the difference is small enough that most will never notice. I've done that test on the air as well.

Bottom line: the audio processing facilities now built into PowerSDR are sufficient to be 90% as good as the most sophisticated rack or DAW based audio processing chain. No reverb or other fancy stuff, but, even so, these facilities are so far beyond what is available built into any other radio, from the Flex stuff on down, that nobody else can even come close to matching it. Add that to the low IMD obtained from PureSignal and openHPSDR architecture radios with PowerSDR exhibit the best audio on the air, period, dot, if the operator is doing their job.

73!

Scott
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Re: External Audio Rack or 10 Dollar Dynamic Microphone

Postby W1AEX » Thu Aug 10, 2017 4:48 pm

I agree with much of what you have said Scott. I would add to the sensitivity aspect that the SPL spec on the microphone is also extremely important. After a lot of attempts to get that 10 dollar Pyle PDMIC78 Chinese clone to match the external audio rack it was the SPL that was the insurmountable problem. The mic transport in the Chinese clone simply could not keep up which is why that microphone sounds anemic even though the audio output was adjusted to match the external rack. When I plugged in a $19.95 Behringer XM-8500 which is a very smooth mic with much better SPL characteristics it took about 1 minute to get it right in the ballpark. The biggest difference was all the additional gain (12dB MIC gain + 20dB boost) that was needed to bring it up to the same level as the external rack. It was also necessary to use the downward expander in OpenHPSDR (which is excellent by the way) to reduce the background ambient noise in the room.

At any rate, in the end the $19.95 XM-8500 certainly beats the audio rack in the expense department and can closely match the sound of the audio rack with the help of the CFC Audio Tools. As you said, the audio processing power in the software goes far beyond what is available in any other radio that is out there.

73,

Rob W1AEX

"One thing I am certain of is that there is too much certainty in the world."
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Re: External Audio Rack or 10 Dollar Dynamic Microphone

Postby w-u-2-o » Fri Aug 11, 2017 1:07 am

I had an XM-8500 at one time. A great dynamic mic. I sold it with my old Flex 3000 and bought the B1 instead. The B1 is better, of course, and I believe very comparable to your MXL, including the price, $99.

You did a great job matching up the two profiles using the XM-8500. I can clearly hear the difference on the Youtube video, but on the air, if you did it without telling me, I don't think I would.

You should try the same exercise using the MXL directly into the radio vs. through the rack. I don't think the 5 or 8V that comes out of the radio for bias will do it justice; do you have a way to inject 48V into it prior to the radio? If you did, I suspect that removing the gain disparity that the dynamic microphone forces on you would make the difference almost completely transparent.

73!

Scott
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Re: External Audio Rack or 10 Dollar Dynamic Microphone

Postby W1AEX » Fri Aug 11, 2017 1:30 am

Scott,

Yes indeed, as far as the best bang for your buck the XM8500 is really hard to beat. I never measured it but I think the condenser mics have quite a bit more gain than the dynamics but it would be interesting to level the playing field a bit and run the MXL-770 right into the front panel of the ANAN. I have one of these so it would be easy enough to do:

Image

If I have some time I'll see how well that works. At this point, with the implementation of the CFC Audio Tools, if I was starting over I would not bother with the external audio rack. I think it would be very easy to create profiles for any voice mode that would be as close to broadcast quality as you could want, assuming that was the goal. I would have to say that the Sennheiser E935 that Simon mentioned several months ago is one of the nicest dynamics I have plugged into my equipment as far as reproducing a very natural sound. That being said, the XM8500 is pretty close!

73,

Rob W1AEX
"One thing I am certain of is that there is too much certainty in the world."
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Re: External Audio Rack or 10 Dollar Dynamic Microphone

Postby w-u-2-o » Fri Aug 11, 2017 1:57 am

Yep, that'll do it! I think you'll be very happy with the performance of the MXL directly into the radio. You shouldn't need Mic Boost at all. You'll need to do the balanced to unbalanced dance, of course, but I know you've got that covered with a drawer full of transformers ;) and you had to do that for the XM-8500 already.

To your point about "starting over", I have been committed to running just the built in processing since I started beta testing it. It's not quite as good as my DAW, but I've done single blind testing (you've been the subject of some of that) and people generally can't tell which way I'm running.

However, I am still using the DAW for two things:

1. I use an EQ to match whatever mic I'm running to the response of my reference B1 microphone. For this you need a much greater level of precision than that available in the 10 band built-in EQ.

2. I use the gate/expander in the DAW because it is head and shoulders above the gate/expander in PSDR. In the DAW I have control over threshold, slope, attack, decay and hold times. In PSDR, I only have control over threshold and slope. Also, most important for me, when I use the head-worn AKG microphone I need to reject artifacts from head movements, and with any microphone I need to reject keyboard and other shack transient noises. In the DAW gate this is easy, as I can select side channel audio to key the gate, and the side channel audio is band limited mic audio (the side channel passband filter is built into the DAW). By selecting that band to respond to the dominant harmonic in my voice, the gate almost never responds to anything except my actual voice.

I'm currently lobbying to get at least attack, hold and decay time controls in the PSDR gate :)

Looking forward to your MXL direct test!

73!

Scott

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