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Author Topic: Shure SM7B Mic, Preamp Needed?  (Read 2855 times)
KG5EJU
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Posts: 107




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« on: December 27, 2014, 10:24:17 AM »

This is for use with a Kenwood TS-590s.  Would like to know if anybody is connecting an SM7B directly to the mic input, and if the pre-amp in the TS-590s has enough gain to properly modulate this microphone.

For the sake of comparison, I currently operate with a Shure SM57, and need to set the Kenwood mic gain to 75 (out of 100).  The Kenwood hand mic operated at a gain setting of 50.  The SM57 has a sensitivity of -56 dBV/Pa (1.6mV), and the SM7B has a sensitivity of -59 dBv/Pa (1.12mV).  

Also, if anybody has figured out the "ALC Limit" mic setting on the Kenwood, I would like to hear how that is determined?  The Kenwood user manual is woefully inadequate on this point.  The only way I have been able to set the mic gain is with QSL reports.

Thank you for your thoughts.

73

- Dan

SM7B:
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KS2G
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Posts: 461




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« Reply #1 on: December 27, 2014, 02:31:59 PM »

No experience with those particular mics, so can't comment directly.

But...

There's an excellent document that explains of how to set-up that rig's mic levels and ALC on the Kenwood TS-590 Family Resources Page: http://homepage.ntlworld.com/wadei/T...setup_v1.0.pdf

The step-by-step setup instructions begin on page 14 of that document.

For LOTS of other good '590 info ... start at the home page:
http://homepage.ntlworld.com/wadei/ts-590s.htm

73,
Mel - KS2G
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KG5EJU
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Posts: 107




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« Reply #2 on: December 27, 2014, 04:30:26 PM »

Mel:  THANK YOU!  For that excellent resource.  Answer every question, and much more about the TS-590.

BTW, the PDF link was truncated by eham, but I found it.  I'll try to paste it below, hopefully, it won't get truncated again, hi-hi:

http://homepage.ntlworld.com/wadei/TS-590S_HOWTO_ssb_audio_setup_v1.0.pdf
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KS2G
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Posts: 461




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« Reply #3 on: December 27, 2014, 06:38:42 PM »

Happy to help.
Should have put the document link on a separate line.  Wink

And, yes, the '590 Resources Page is excellent -- and gets better all the time.
Lots of good info being posted about the new '590SG.

Very tempting ... but I'm sticking with my '590S to see how it works with the 2.0 firmware upgrade that's coming in January.

73,
Mel - KS2G



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KG5EJU
Member

Posts: 107




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« Reply #4 on: December 30, 2014, 07:08:24 AM »

OK, once I got through all that, I found that I was over-driving the mic preamp and the ALC was limiting my signal 100% of the time.  I have turned the Kenwood mic gain setting from 75 down to 55, and now have my mic-to-mouth distance and speaking volume under control.  QSL reports confirm this.

Even better, I now feel sure that there is enough headroom from me to operate with the SM7B without an external preamp.

73

- Dan
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KG6YV
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Posts: 519




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« Reply #5 on: January 01, 2015, 12:41:36 PM »

I run an SM7B thru an audio chain with preamp, EQ and Compressor Limiter to my FTDXZ 5000.  I have run other mics that are higher gain.  I think the SM7Bdoes have significantly lower gain so I would guess a preamp is in order.  People like the SM7B and I get very good audio reports...

FYI

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KG5EJU
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Posts: 107




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« Reply #6 on: January 02, 2015, 11:19:35 AM »

I run an SM7B thru an audio chain with preamp, EQ and Compressor Limiter to my FTDXZ 5000.  I have run other mics that are higher gain.  I think the SM7Bdoes have significantly lower gain so I would guess a preamp is in order.  People like the SM7B and I get very good audio reports...

FYI



Thank you for that.  I did order an SM7B, and it should be here early next week.  Hopefully, I can run it without a preamp, but I have a little mixer I could press into service if needed.

I'll report back after some test.

73

-Dan
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KG5EJU
Member

Posts: 107




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« Reply #7 on: January 08, 2015, 11:14:58 AM »

OP here, just want to provide a quick report.

The SM7B is here and I have run it a few days now.  I am happy with the modulation level when the MIC gain is set in the range of 80-85 (out of 100) on the TS-590s.  Does not appear to require an external microphone preamplifier.  I use the big wind screen, and speak with my lips just touching the wind screen.  No proximity effect from close mic'ing, and no plosives either.  This microphone is made for this kind of voice-over operation. 

I have the bass roll-off on as well as the presence boost on (I have a bassy voice).  I am also using a bit of mid-range emphasis in the Kenwood.  But all this depends on my voice, not yours.  PEP runs up to 100 watts regularly without the ALC threshold being over-driven.  The levels are all working quiet nicely, I would say.

It's a fine piece and will be my microphone for the long haul.  I run it on a scissors arm.

Overall, getting a few good QSL reports.  Time will tell.
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KG5EJU
Member

Posts: 107




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« Reply #8 on: January 20, 2015, 07:48:46 AM »

OP here, for a minor update.  I've now got the Kenwood mic gain set in the 70-75 range with the ALC (not limiting) and power out (reaching 100 watts) running where they should. 

More and more happy with this microphone everyday that I use it.
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K2RWF
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Posts: 1




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« Reply #9 on: Yesterday at 08:29:19 PM »

To piggy back of a few other comments, that SM7B is a great mic, but it's really really low gain.

I've used an SM7B, RE20, and now recently a Rode Procaster. All of these broadcast-favorite dynamic mics need a good, solid preamp driving them. DBS makes nice channel strips that are reasonably priced that not only will drive that mic nicely, but add some outboard things like compression, de-essing, and gate/limiter. I really like the DBX286s. There are other options out there as well (Symetrix 528E is great, but pricey), so feel free to look around.

Most mic preamps, such as ones built in to a cheaper Behringer board or virtually any USB-powered preamps, just don't have the muster to properly drive a mic like the SM7B. It's easy to notice - when you adjust the gain, you'll notice a noticeable hiss.

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