Dirty-South Blues Harp forum: wail on! > Hot Mics
Hot Mics
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jpmcbride
220 posts
Nov 07, 2019
12:01 PM
I know a lot of harp players like hot mics. The theory being that they push the amp harder and get a better sound. However, a hot mic tends to increase feedback. Lets explore this a little … just my experience here … YMMV ...

(1) The output from a guitar pickup is far lower than the output from a typical harp mic. And guitar players get plenty of overdrive from their amps.

(2) For live playing I use Astatic 335H-7 mics exclusively. These are not hot mics. The output is a lot lower than the typical bullet mic with CM or crystal element. My amp is a Fender Deluxe 1x12 40W tube amp. Its stock except for the two preamp tubes changed from 12AX7 to 12AT7. Let me tell you its loud! I can compete in any realistic situation with guitar players. At jams or live bar gigs, I set the amp volume at no more than 3.5 (at the most!) and its REALLY loud. I turn down the treble, and roll off the mids to about 1/3. With this setup I can hold my mic 6 inches directly in front of the amp with zero feedback. So I'm playing super loud, and getting no feedback. I attribute this to the low output of the mic. When I've tried to get this volume level with a bullet with hot CM element, it becomes feedback city.

What do you think? Has anyone else reached a similar conclusion about mics?




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Jim McBride
Bottle 'O Blues microphones
www.bottleoblues.com
nacoran
10188 posts
Nov 08, 2019
12:04 PM
I think it depends on the pairing. I've got a Bulletini. Great mic, but with my amp it is really hard to dial in crunch (not impossible, but more fiddly than with my cheap Shure Prologue). Of course, I can get a lot more volume with it, and with an amp with more headroom or going through the P.A. the Buletini is a better mic. (Better amp isn't in the budget right now.)

Of course, I've got a weird amp with two gain knobs and I do weird things already to dial in crunch.

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Nate
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dougharps
2029 posts
Nov 08, 2019
12:40 PM
I have found that with a hot mic on some amps I have to turn it way down and on other amps I can turn it all the way up.

To some extent is seems related to the amp circuit and perhaps the number of gain stages in the pre-amp section.

However, I have found that the speaker choice, the amp choice, and the mic choice all affect volume before feedback and amp-tone. I used to have mix and match sessions with different amp heads, speakers, and mics exploring this. I have several bullet omni mics, and some directional mics that can each sound good. I choose according to the volume needed and music I will play in order to choose the right gear.

Each room can make a difference, too. (Yes, personal tone is a major factor, too.)

When there are different players involved I have heard much greater variance in the sound of amplified harp due to change of player as opposed to change of mic.

I think that each player needs to explore their own sound with various combinations of gear and amp settings.

I don't think there is a one size fits all amplified harp setup. A hot mic can sound good with the right amp, speaker, and player.
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Doug S.
SuperBee
6261 posts
Nov 08, 2019
1:42 PM
I know a fellow who runs a hot mic with a volume control and never turns it up past halfway. He runs his amp at a higher volume accordingly.

This seems to be the same idea.

I’ve never gone that way, but it seems logical enough. I’ve been sucked down the path of building preamps which cope well with the output of the mic. I’m generally using a CM or CR shure type. I do often run a volume control on my mic but if so it’s usually wide open or off.
Some people believe there’s a compromise of the mic character comes with running a VC on it, and especially with a crystal element. I’m in that camp, but the other POV seems to be that opening the volume on the amp somehow allows the power amp to see a full signal. I’d say that demonstrates a misunderstanding of how amps work but I’m only a dabbler in electronics and there is a lot I don’t yet understand. When I see ‘power tube distortion’ mentioned though, well I think it’s pretty unlikely that most amps used for harp ever get near power tube saturation, and if they did I’m really not sure it would be desirable.

I understand the 335H-7 is a ceramic element. Have not used one.
I do know the amp though. Is it a Blues Deluxe or Hot Rod Deluxe?
Not that there’s a great deal of difference on the clean channel anyway and that’s the only channel to use.
If you can get it to 3.5 and you’ve swapped the preamp tubes to 12 AT7 I’d say your mic output is not all that low. I could likely get my CM to 3 no worries with that tube array.

A couple of times now I’ve tried changing the phase inverter tube instead of the preamp tube and found quite good results. In some ways the 12 AT 7 is more like a 12 AU 7. In the Deluxe and Deville amps though, you have to take care especially with the PI because the resistors are prone to burn out even when running the 12AX7. The AT and AU draw more current and can increase the strain on those plate resistors. I’ve replaced mine with some more robust types that are rated at a full watt, rather than the stock 1/2 watt types.
It’s a while since I’ve thought about it but I think I have a 12AT7 in my Deville preamp. I once had modified the preamp quite a bit but reverted it to stock config (with the exception of the stronger resistors) and swapped some tubes.

I sat that amp alongside my Sonny Jr 2 one day and worked on getting a comparable sound.

Notwithstanding all the BS I’ve written above, I found the closest I get was to go through a LW Mojo Pad Deluxe into the Deville.

The pad is basically knocking back the signal from the mic, so this I think brings me back to the position of wondering why one wouldn’t just use a lower output mic to begin with.
Great.

My father said a lot of things. One of the oddest was ‘there’s more ways to kill a cat than choking it with butter’
jpmcbride
223 posts
Nov 08, 2019
3:07 PM
@SuperBee

Blues Deluxe Reissue

Astatic 335H-7 is dynamic, not ceramic

12AT7 is a lot higher gain than 12AU7. I don't have the numbers in front of me, but its more.

It amazes me … I can be at full loud band volume and dangle the mic by the cable right in front of the speaker and not get a sound out of it! But if I turn up the midrange tone control on the amp to half, it squeals like crazy!


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Jim McBride
Bottle 'O Blues microphones
www.bottleoblues.com

Last Edited by jpmcbride on Nov 08, 2019 3:07 PM
SuperBee
6262 posts
Nov 08, 2019
4:27 PM
Yes, amplification factor was not what I was referring too. Internal resistance of 12at7 is more similar to a 12 au7 than 12ax7 and it’s relevant to the points I raised about plate resistors in the Deluxe and Deville amps. Also applies to the Bassman RI

Thanks for pointing out the mic is dynamic. There are several online references to it as ceramic, including from people I generally trust to know what they are doing with mics (Fritz H, Ron S). I wonder how that confusion happens. The catalog is fairly clear on the matter. I suppose it’s possible with old mics that components get recombined sometimes, just like all my Astatic mics have Shure elements.
jpmcbride
224 posts
Nov 08, 2019
6:59 PM
@SuperBee

OK, good info. I'll open up the amp have a look at the plate resistors. May have to change them as you said.

Yes, there is a lot of confusion on these mics. I know 100% that they're dynamic. I opened one up just this afternoon (not easy to do) and the element was definitely dynamic.
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Jim McBride
Bottle 'O Blues microphones
www.bottleoblues.com


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