Just got two Fixer-upper mics for $11 each on Ebay

[Paul[_13_]]

They were both easy soldering fixes.

One is the Audio Technica AT811. It's actually
a good, darker microphone, with very little
high end. So it's not very good for acoustic
guitar, but it might be good for someone's vocals,
because it has very warm, full bodied mids, low-mids,
and bass end. Or it might be good for a really
shrill instrument, when you want to take the high end
off. Someone mentioned these are good for horns.

The problem is, someone made the ****-poor decision
to make this battery powered only, so it cannot use
phantom power stock. I'm sure there's a way to
convert it to phantom power, so if someone
knows how, please let me know, as it would likely
increase the output, which is a bit low.

If I don't end up using it, I'll sell it for
$50 or so.

The other mic is a mystery mic:

http://farm4.staticflickr.com/3686/9113658956_24a58573ca_b.jpg

http://farm8.staticflickr.com/7387/9111437551_8012b09898_b.jpg

Anyone know what it is? There are no markings at all.
It works, but has a very tinny tone. I'm thinking of
replacing the capsule with my old SP-1 capsule.

[PStamler]

Nothing wrong with a good battery-powered mic; it'll work in places where a phantom-only mic won't. Like plugged into a guitar amp, Little Walter style.

My memory of the 811 from several decades back is that it had a nice flat high end. If you've gotten used to shrill, peaky high frequency response it'll sound relatively dark, but I really remember it being nice and natural-sounding.

Peace,
Paul

[Mike Rivers[_2_]]

On 6/22/2013 11:39 PM, Paul wrote:

> One is the Audio Technica AT811.
> The problem is, someone made the ****-poor decision
> to make this battery powered only

It wasn't a **** poor decision in 1979 or so when that mic was made. How
many consoles owned by people who could only afford mics that cost less
than $100 had phantom power built in?

Buy a six pack of AA cells and use it with a battery until you get tired
of it. Then sell it for $50 or so. Include a new battery so the buyer
can tell that it works. You'd be amazed at how long one battery lasts.
I've had an AT813 since it was new, still use it occasionally, and I
think I may have used half a dozen batteries in it over its lifetime.

By the way, according to the data sheet, the AT811 has a rising high
frequency response, so maybe if yours sounds dark, there's something
wrong with it. It's a fixed charge electret and I'm not sure how
permanent those were in that day. The data sheet recommends it for brass
and reeds. Try that.


--
For a good time, call http://mikeriversaudio.wordpress.com

[Paul[_13_]]

On 6/23/2013 5:42 AM, Mike Rivers wrote:
> On 6/22/2013 11:39 PM, Paul wrote:
>
>> One is the Audio Technica AT811.
>> The problem is, someone made the ****-poor decision
>> to make this battery powered only
>
> It wasn't a **** poor decision in 1979 or so when that mic was made. How
> many consoles owned by people who could only afford mics that cost less
> than $100 had phantom power built in?
>

I see.

> Buy a six pack of AA cells and use it with a battery until you get tired
> of it. Then sell it for $50 or so. Include a new battery so the buyer
> can tell that it works. You'd be amazed at how long one battery lasts.
> I've had an AT813 since it was new, still use it occasionally, and I
> think I may have used half a dozen batteries in it over its lifetime.
>

Well, if the battery lasts a long time, I guess it's not the end
of the world.


> By the way, according to the data sheet, the AT811 has a rising high
> frequency response, so maybe if yours sounds dark, there's something
> wrong with it. It's a fixed charge electret and I'm not sure how
> permanent those were in that day. The data sheet recommends it for brass
> and reeds. Try that.
>

Yeah, someone on Ebay mentioned it was good for horns, but someone
else agreed his was lacking clarity and high end.

Perhaps the older electret capsules go bad with time? Maybe
I could replace the capsule.

Do you have a link to the datasheet?

[Mike Rivers[_2_]]

On 6/23/2013 9:12 AM, Paul wrote:

> Perhaps the older electret capsules go bad with time?

I have a couple of Sony ECM-21 mics that I bought in 1969 that have lost
a good bit of their charge and aren't much good for anything any more.
Of course by today's standards, they wouldn't have been much good for
anything in 1970 either, but they were quite useful when I got them.
Modern electrets are better at this, but maybe they just haven't got
that old yet.

> Do you have a link to the datasheet?

I could send you a picture of my file cabinet. <g>
Or I could send you a poor scan of the catalog page made with my poor
scanner. The info on what it's good for came from a 'slide rule' kind of
thing, not easy to copy.

--
For a good time, call http://mikeriversaudio.wordpress.com

[Paul[_13_]]

On 6/23/2013 9:39 AM, Mike Rivers wrote:
> On 6/23/2013 9:12 AM, Paul wrote:
>
>> Perhaps the older electret capsules go bad with time?
>
> I have a couple of Sony ECM-21 mics that I bought in 1969 that have lost
> a good bit of their charge and aren't much good for anything any more.
> Of course by today's standards, they wouldn't have been much good for
> anything in 1970 either, but they were quite useful when I got them.
> Modern electrets are better at this, but maybe they just haven't got
> that old yet.
>
>> Do you have a link to the datasheet?
>
> I could send you a picture of my file cabinet. <g>
> Or I could send you a poor scan of the catalog page made with my poor
> scanner. The info on what it's good for came from a 'slide rule' kind of
> thing, not easy to copy.
>

I'll take your word for it, and thanks for the feedback.

And I'll look into possibly replacing the electret capsule on mine
with a new modern one. If anyone has any advice on this, I'm
all ears.....

[Nil]

On 22 Jun 2013, Paul > wrote in rec.audio.pro:

> The other mic is a mystery mic:
>
> http://farm4.staticflickr.com/3686/9113658956_24a58573ca_b.jpg
>
> http://farm8.staticflickr.com/7387/9111437551_8012b09898_b.jpg
>
> Anyone know what it is? There are no markings at all.
> It works, but has a very tinny tone. I'm thinking of
> replacing the capsule with my old SP-1 capsule.

It looks similar to my Optimus 33-3017, which is a cheap mic I bought
at Radio Shack many years ago. Mine has an on/off/standby switch, yours
doesn't, it appears. It looks like the label ring with the model number
is missing. Here's a picture of one like mine:

http://i24.photobucket.com/albums/c18/balin64/optimus.jpg

So, maybe yours is yet another cheap old RS mic.

[Scott Dorsey]

In article >, Mike Rivers > wrote:
>On 6/23/2013 9:12 AM, Paul wrote:
>> Perhaps the older electret capsules go bad with time?
>
>I have a couple of Sony ECM-21 mics that I bought in 1969 that have lost
>a good bit of their charge and aren't much good for anything any more.
>Of course by today's standards, they wouldn't have been much good for
>anything in 1970 either, but they were quite useful when I got them.
>Modern electrets are better at this, but maybe they just haven't got
>that old yet.

On the other hand, if you'd bought an SM-81 at the time, they would be
only 6% down in charge at maximum. Shure's electrets were a lot better
than Sony's.

I don't know how stable the AT stuff was, but I'd suspect it was pretty
stable.
--scott


--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Paul[_13_]]

On 6/23/2013 7:02 PM, Scott Dorsey wrote:
> In article >, Mike Rivers > wrote:
>> On 6/23/2013 9:12 AM, Paul wrote:
>>> Perhaps the older electret capsules go bad with time?
>>
>> I have a couple of Sony ECM-21 mics that I bought in 1969 that have lost
>> a good bit of their charge and aren't much good for anything any more.
>> Of course by today's standards, they wouldn't have been much good for
>> anything in 1970 either, but they were quite useful when I got them.
>> Modern electrets are better at this, but maybe they just haven't got
>> that old yet.
>
> On the other hand, if you'd bought an SM-81 at the time, they would be
> only 6% down in charge at maximum. Shure's electrets were a lot better
> than Sony's.
>
> I don't know how stable the AT stuff was, but I'd suspect it was pretty
> stable.
> --scott
>

Well, at the moment, I'm having a hard time accessing the
capsule, just to take a look at it (possibly replace it later).

There is the metal collar with the threads on each side,
that you unscrew from the main body to install the battery:

http://img.auctiva.com/imgdata/9/2/8/3/5/7/webimg/661575044_tp.jpg


It appears that you can also unscrew it from the head-basket,
to access the capsule, but I was not able to budge it. I
even tried heating it up a bit with my hot-air gun, and still
no-go....

But at any rate, is there a good modern electret replacement
capsule that you could recommend?

[Mike Rivers[_2_]]

On 6/23/2013 10:02 PM, Scott Dorsey wrote:

> On the other hand, if you'd bought an SM-81 at the time, they would be
> only 6% down in charge at maximum. Shure's electrets were a lot better
> than Sony's.

I have a couple of SM-81s that I bought a few years after the Sony
ECM-21s and the Shures still seem to work fine. As does my Audio
Technica AT-813, which I bought at the same shop as I bought my vacuum
cleaner.


--
For a good time, call http://mikeriversaudio.wordpress.com

[Paul[_13_]]

On 6/23/2013 11:55 AM, Nil wrote:
> On 22 Jun 2013, Paul > wrote in rec.audio.pro:
>
>> The other mic is a mystery mic:
>>
>> http://farm4.staticflickr.com/3686/9113658956_24a58573ca_b.jpg
>>
>> http://farm8.staticflickr.com/7387/9111437551_8012b09898_b.jpg
>>
>> Anyone know what it is? There are no markings at all.
>> It works, but has a very tinny tone. I'm thinking of
>> replacing the capsule with my old SP-1 capsule.
>
> It looks similar to my Optimus 33-3017, which is a cheap mic I bought
> at Radio Shack many years ago. Mine has an on/off/standby switch, yours
> doesn't, it appears. It looks like the label ring with the model number
> is missing. Here's a picture of one like mine:
>
> http://i24.photobucket.com/albums/c18/balin64/optimus.jpg
>
> So, maybe yours is yet another cheap old RS mic.
>

Ok, the mystery mic is some sort of AMR Audio
mic. It doesn't look like they stayed in the
mic business very long, and judging by the sound of this
mic, I can guess why.

The audio totally lacks the low bass end. Here
is a very rough schematic I drew up (I know, the N-channel
JFETs are drawn incorrectly):

http://farm8.staticflickr.com/7312/9144472886_4c5e3e6aae_o.jpg

It appears the JFET is Darlingtoned to the bipolar, and
I would assume the transformer is part of the reason
the bass frequencies are so attenuated.
Someone else noticed the similarity to the AKG C414:


http://cdn.recordinghacks.com/images//mic_extras/akg/C414EB-schematic.png


Here is the electret capsule:

http://farm8.staticflickr.com/7366/9142246653_0a056e2025_o.jpg
http://farm6.staticflickr.com/5323/9144473184_a6c6962cdb_o.jpg

It's quite likely this old capsule has lost its charge, so
I'm thinking of ordering one of these:

http://www.transsound.net/electrets/tsb-160a.htm

I measured the electrolytic and the tantalum, and they are fine.

Ideally, I'll replace the capsule, and optimize the circuit.

Any advice is GREATLY appreciated. Thank you.