Amplifier transistor matching?

[Guest]

Archived from groups: sci.electronics.basics,sci.electronics.design,rec.audio.tech,alt.audio.equipment (More info?)

On Sat, 04 Jun 2005 17:39:31 GMT, Joerg
<notthisjoergsch@removethispacbell.net> wrote:

> That is one reason why we changed to NiMH. The other was cost
>as 9V alkalines are really expensive. They rarely go on sale like AA
>batteries sometimes do.

The theatre technicians here in London UK seem to be able to source
alkaline 9v batteries at about a third of the retail price of a
Duracell.

 

[Guest]

Archived from groups: sci.electronics.basics,sci.electronics.design,rec.audio.tech,alt.audio.equipment (More info?)

Hello Laurence,

> The theatre technicians here in London UK seem to be able to source
> alkaline 9v batteries at about a third of the retail price of a
> Duracell.

That would be 30c US. Really?

Regards, Joerg

http/www.analogconsultants.com

 

[Guest]

Archived from groups: sci.electronics.basics,sci.electronics.design,rec.audio.tech,alt.audio.equipment (More info?)

Joerg wrote:
>
> Hello Laurence,
>
> > The theatre technicians here in London UK seem to be able to source
> > alkaline 9v batteries at about a third of the retail price of a
> > Duracell.
>
> That would be 30c US. Really?
>
> Regards, Joerg
>
> http/www.analogconsultants.com

Also, try to develop a connection with local hospitals and clinics. A
friend of mine used to get cases of alkalines (9V, AA, whatever) free.

Apparently, for medical use, they must be discarded by law when they meet
the expiry date. They were still good as new.

Mike Monett

 

[Guest]

Archived from groups: sci.electronics.basics,sci.electronics.design,rec.audio.tech,alt.audio.equipment (More info?)

Hello Mike,

> Also, try to develop a connection with local hospitals and clinics. A
> friend of mine used to get cases of alkalines (9V, AA, whatever) free.
>
> Apparently, for medical use, they must be discarded by law when they meet
> the expiry date. They were still good as new.

That is a good idea. Although nowdays they can have over 5 years of
shelf life. Yesterday I replenished the lab with AA and they expire in
May 2012.

Another source that was mentioned here or on a.b.s.e. are photo
processors. Apparently disposable cameras often contain an AA or AAA
cell with lots of life left in it.

Regards, Joerg

http/www.analogconsultants.com

 

[Guest]

Archived from groups: sci.electronics.basics,sci.electronics.design,rec.audio.tech,alt.audio.equipment (More info?)

Hello Walter,

> Agree. At the same gig where we've gone through literally tens of thousands
> of AAs in wireless mics with not a single problem, we've had probably a 1%
> failure rate in 9V batteries for the few wireless units we have that take
> those. Same thing as what you describe - they test okay, and then drain
> within minutes.
>
> I assume it's because of the multi-cell internal construction of a 9V.

That may well be the reason. The first time I looked at how they are
internally connected my confidence level dropped a lot. Statistically
the six cells of a 9V must have a higher combined failure rate than two
AA cells. But not by this much, there must be something else that causes
failures.

The contacts on a 9V are a pain as well. How many times has something
ripped out when disconnecting a 9V battery? A lot...

Regards, Joerg

http/www.analogconsultants.com

 

[Guest]

Archived from groups: sci.electronics.basics,sci.electronics.design,rec.audio.tech,alt.audio.equipment (More info?)

"Anno Siegel" <anno4000@lublin.zrz.tu-berlin.de> wrote in message
news:d8411o$4hj$1@mamenchi.zrz.TU-Berlin.DE...
> Mr.T <MrT@home> wrote in sci.electronics.design:
> >
> > "Jim Thompson" <thegreatone@example.com> wrote in message
> > news:m3u9a1dl28qjegf4qeshodsjc49mfhnekg@4ax.com...
> > > Be prepared!
> > > That's the Boy Scout marching song
> > > Be prepared!
> > > If you should meet a Girl Scout who is suitably inclined
> > > Be prepared!
> >
> > What, no attribution for Tom Lehrer?
>
> Perhaps because Tom Lehrer's text is different:

Which word?

MrT.

 

[Guest]

Archived from groups: sci.electronics.basics,sci.electronics.design,rec.audio.tech,alt.audio.equipment (More info?)

A good reason is because a 9V can't source as much current as even a single
AA cell for the same duration due to their much smaller individual cells.
There are six seperate 1.5V cells connected in series to produce the 9
volts. The cells internal electrodes have significantly less surface area to
interact with a much reduced quantity of electrolyte. If you still need 9
volts for a circuit try ganging six AA's in series. If weight is a concern,
even AAA cells aranged in a battery of 9 volts will outlast most 9V's.

Regards,
Chris

 

[Guest]

Archived from groups: sci.electronics.basics,sci.electronics.design,rec.audio.tech,alt.audio.equipment (More info?)

On Sun, 05 Jun 2005 23:00:52 +0100, Pooh Bear
<rabbitsfriendsandrelations@hotmail.com> wrote:

>Jim Thompson wrote:
>
>> On Fri, 3 Jun 2005 23:22:52 -0700, "Walter Harley"
>> <walterh@cafewalterNOSPAM.com> wrote:
>>
>> >"Joerg" <notthisjoergsch@removethispacbell.net> wrote in message
>> >news:d14oe.24267$J12.18509@newssvr14.news.prodigy.com...
>> >> BTW, since you seem to be an audio guru: Is there any truly digital
>> >> wireless mike system with a reasonable battery life (like >5hrs for the
>> >> lapel mikes)? Preferably with AA and not with 9V batteries.
>> >
>> >Dunno about digital. The Shure analog UHF packs, with lav mics, last more
>> >than 6 hours with a pair of alkaline AAs. One of my gigs uses a dozen or
>> >more channels of them; we put fresh batteries in at 4:30pm, and at 10:30pm
>> >when the show ends they're usually still showing three or four out of five
>> >bars on the battery life indicator. We replace them every night anyway - if
>> >we went for two nights, by the end of the second night we'd be too nervous.
>> >As jak said, the price of batteries is small compared to the price of the
>> >show going down.
>> >
>>
>> Can I interject and ask some advice?
>>
>> My wife has lots of Girl Scout speaking presentations, but she's a
>> walker... walks away from the podium and the microphone.
>>
>> Did it again last week with me frantically waving, "Go back to the
>> microphone."
>>
>> These presentations are usually in not-very-well or anciently equipped
>> locations... last week was in an old Catholic Church Parish Center.
>>
>> What should I buy in the way of a wireless microphone, with facility
>> to plug the receiver into almost any PA equipment I might encounter?
>
>About time to start a new thread ?
>
>It all depends. Depends on your budget and the quality you're looking for.
>
>I'm guessing that budget is low in your case. You *can* get cheap 'voice quality'
>radio mics but these aren't a patch on the Sennheisers that Joerg is using.
>
>You get what you pay for for the most part. The receiver should have no trouble
>interfacing with any kind of PA gear btw.
>
>I'm tempted to suggest looking on ebay for a cheap unit.

I remember reading years ago that the spoken human voice could be
intelligible at a quite high distortion level. I think the amplifier
in question was 30% or somesuch, but that sounds high even to me now.
Depending on the venue, even room acoustics may outweigh any
distortion issues, I'd guess. Think of the US National Anthem sung at
a sports venue...


"for th or e la and e nd of...you get my drift.

Tom

>
>Graham

 

[Guest]

Archived from groups: sci.electronics.basics,sci.electronics.design,rec.audio.tech,alt.audio.equipment (More info?)

On Fri, 10 Jun 2005 19:32:17 GMT, the renowned Tom MacIntyre
<tom__macintyre@hotmail.com> wrote:


>
>I remember reading years ago that the spoken human voice could be
>intelligible at a quite high distortion level. I think the amplifier
>in question was 30% or somesuch, but that sounds high even to me now.
>Depending on the venue, even room acoustics may outweigh any
>distortion issues, I'd guess. Think of the US National Anthem sung at
>a sports venue...
>
>
>"for th or e la and e nd of...you get my drift.
>
>Tom
>

Years ago, I heard a demo of the human voice with 1-bit resolution. It
was understandable, but not at all pleasant.


Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
speff@interlog.com Info for manufacturers: http/www.trexon.com
Embedded software/hardware/analog Info for designers: http/www.speff.com

 

[Guest]

Archived from groups: sci.electronics.basics,sci.electronics.design,rec.audio.tech,alt.audio.equipment (More info?)

On Fri, 10 Jun 2005 15:53:01 -0400, Spehro Pefhany
<speffSNIP@interlogDOTyou.knowwhat> wrote:

>On Fri, 10 Jun 2005 19:32:17 GMT, the renowned Tom MacIntyre
><tom__macintyre@hotmail.com> wrote:
>
>
>>
>>I remember reading years ago that the spoken human voice could be
>>intelligible at a quite high distortion level. I think the amplifier
>>in question was 30% or somesuch, but that sounds high even to me now.
>>Depending on the venue, even room acoustics may outweigh any
>>distortion issues, I'd guess. Think of the US National Anthem sung at
>>a sports venue...
>>
>>
>>"for th or e la and e nd of...you get my drift.
>>
>>Tom
>>
>
>Years ago, I heard a demo of the human voice with 1-bit resolution. It
>was understandable, but not at all pleasant.
>

So I think our point is the same, or at least similar...the human
voice, when spoken, possibly doesn't require the same low distortion
for reasonable intelligibility.

Tom

>
>Best regards,
>Spehro Pefhany

 

[Guest]

Archived from groups: sci.electronics.basics,sci.electronics.design,rec.audio.tech,alt.audio.equipment (More info?)

"Tom MacIntyre" wrote ...
> So I think our point is the same, or at least similar...the human
> voice, when spoken, possibly doesn't require the same low distortion
> for reasonable intelligibility.

And cell-phone manufacturers regularly plumb the depths of
low-res to see how much we will put up with!

 

[Guest]

Archived from groups: sci.electronics.basics,sci.electronics.design,rec.audio.tech,alt.audio.equipment (More info?)

Hello Spehro,

>>Depending on the venue, even room acoustics may outweigh any
>>distortion issues, I'd guess. ...

In a sports arena it will also have to do with the amount of booze that
was consumed.

Regards, Joerg

http/www.analogconsultants.com

 

[Guest]

Archived from groups: sci.electronics.basics,sci.electronics.design,rec.audio.tech,alt.audio.equipment (More info?)

Hello Richard,

> And cell-phone manufacturers regularly plumb the depths of
> low-res to see how much we will put up with!

Yes, it seems so. It could be the carriers since their currency is
kb/sec. Yesterday a long time friend called me on his cell phone. I
could not even recognize who it was until several seconds into the
conversation, and initially only by what he was talking about.

Regards, Joerg

http/www.analogconsultants.com

 

[Guest]

Archived from groups: sci.electronics.basics,sci.electronics.design,rec.audio.tech,alt.audio.equipment (More info?)

On Fri, 10 Jun 2005 20:25:31 +0000, Joerg wrote:

> Hello Spehro,
>
>>>Depending on the venue, even room acoustics may outweigh any
>>>distortion issues, I'd guess. ...
>
> In a sports arena it will also have to do with the amount of booze that
> was consumed.
>
The human ear + human brain synergy is an amazing tool for picking
information out of noise. Hasn't just about everybody been in a
crowded area with lots and lots of background noise, and yet been
able to figure out what the other person is saying, by sort of
mentally focusing on the subject?

And who amongst us isn't old enough to remember SSB? ;-) You can
pick voice information out of an incredible amount of noise!

Cheers!
Rich

 

[Guest]

Archived from groups: sci.electronics.basics,sci.electronics.design,rec.audio.tech,alt.audio.equipment (More info?)

"BCTweaker" <no.spam@orfrom.you> wrote in message
news:mz3qe.7046$_A5.4114@newssvr19.news.prodigy.com...
> A good reason is because a 9V can't source as much current as even a
single
> AA cell for the same duration due to their much smaller individual cells.
> There are six seperate 1.5V cells connected in series to produce the 9
> volts. The cells internal electrodes have significantly less surface area
to
> interact with a much reduced quantity of electrolyte. If you still need 9
> volts for a circuit try ganging six AA's in series. If weight is a
concern,
> even AAA cells aranged in a battery of 9 volts will outlast most 9V's.

Of course, since all of your above comments still apply.

Now try ganging 6 alkaline watch batteries together instead.
There is no mystery here. If one uses exactly the same battery technology in
each case, the larger battery will have more storage capacity.
(packaging excepted of course, and in the case of six separate cells, this
will usually increase)
So the answer may be to use a larger 9V battery. Unfortunately these aren't
common any more. Most people prefer to use the smaller size, and change it
more often.

MrT.

 

[Guest]

Archived from groups: sci.electronics.basics,sci.electronics.design,rec.audio.tech,alt.audio.equipment (More info?)

Joerg wrote:
> Hello Richard,
>
>> And cell-phone manufacturers regularly plumb the depths of
>> low-res to see how much we will put up with!
>
> Yes, it seems so. It could be the carriers since their currency is
> kb/sec. Yesterday a long time friend called me on his cell phone. I
> could not even recognize who it was until several seconds into the
> conversation, and initially only by what he was talking about.
>
> Regards, Joerg

They need to save their bandwidth for pictures & video....

jak
>
> http/www.analogconsultants.com

 

[Guest]

Archived from groups: sci.electronics.basics,sci.electronics.design,rec.audio.tech,alt.audio.equipment (More info?)

Hello Mr.T,

> So the answer may be to use a larger 9V battery. Unfortunately these aren't
> common any more. Most people prefer to use the smaller size, and change it
> more often.

Since AA packs a lot more Watthours per cubic inch than a 9V I think it
would great if all designers wised up and designed their stuff to work
with AA or a couple of them. It's not rocket science. I had a radio
30-some years ago that worked nicely with two AA. It boasted the longest
runtime on one set of any radio I ever had. Got lost in a move and now I
am using a 9V radio. It doesn't even last a day and the batteries cost
twice as much.

Regards, Joerg

http/www.analogconsultants.com

 

[Guest]

Archived from groups: sci.electronics.basics,sci.electronics.design,rec.audio.tech,alt.audio.equipment (More info?)

Hello Jak,

> They need to save their bandwidth for pictures & video....

Let's see how that goes. Maybe it's like with pool heaters. People love
it until that first bill arrives in the mail.

Regards, Joerg

http/www.analogconsultants.com

 

[Guest]

Archived from groups: sci.electronics.basics,sci.electronics.design,rec.audio.tech,alt.audio.equipment (More info?)

Hello Rich,

> And who amongst us isn't old enough to remember SSB? ;-) You can
> pick voice information out of an incredible amount of noise!

Hey, I am old enough to remember CW. With morse code it has been said
that the trained ear was on occasion able to beat Shannon's law. Depends
on the imbabitation status though.

Regards, Joerg

http/www.analogconsultants.com

 

[Guest]

Archived from groups: sci.electronics.basics,sci.electronics.design,rec.audio.tech,alt.audio.equipment (More info?)

"Joerg" wrote ...
> Hey, I am old enough to remember CW. With morse code it has been said
> that the trained ear was on occasion able to beat Shannon's law.

But so far we have not been able to even think of approaching the
speed and functionality of the human brain with any kind of
computer. There were seveal levels of "intelligence" operating
to decode CW in heavy QRM/QRN.