Amplifier transistor matching?

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

On Sun, 05 Jun 2005 23:58:53 +0100, Pooh Bear
<rabbitsfriendsandrelations@hotmail.com> wrote:

>
>Jim Thompson wrote:
>
>> On Sun, 05 Jun 2005 23:00:52 +0100, Pooh Bear
>> <rabbitsfriendsandrelations@hotmail.com> wrote:
>>
>> >I'm guessing that budget is low in your case.
>>
>> Now why would you guess that?
>
>You mentioned Girl Scouts !
>
>Graham

My wife has been a Girl Scout leader for 40 years ;-)

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice480)460-2350 | |
| E-mail Address at Website Fax480)460-2142 | Brass Rat |
| http/www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

 

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

Hello Mike,

> Try the new G2 series Sennheisers. They use AA batteries and have 9hr
> battery life w/alkalines. With the new high capacity NiMh AA's out there
> you should get close to that or even longer life. They are not digital, but
> they do sound great. ...

Yes, we'll certainly look into those. Especially if they are compatible
with our existing Sennheiser UHF gear.

> ... Why do you need true digital?

We really don't. But spread spectrum is so much lower maintenance. Most
RF mikes including the Sennheiser SK series operate as UHF secondary
user. That has several disadvantages. One is that UHF channels get
kicked around a lot these days with new temporary DTV channels being
assigned and so on. Another issue is noise. When a large bank of
fluorescents gets turned on this is audible on pretty much any FM based
system. Not so with spread spectrum.

Other problems could have been avoided with clever engineering. Examples
are the pop noise when a mike is turned off, and sometimes even when it
is muted. The answer I got regarding the mute pop was like "pastors use
that switch too often and it wears out". Well, then why is there a mute
switch? And why isn't it properly debounced? After all, these systems
are also advertised for use in churches and smaller congregations do not
have an audio or mixer operator. So I'd expect proper mute switching.

On rare occasions we had mikes "forget" their programmed frequency. In
the middle of a worship service there is not much you can do about that
when it happens. At least not fast enough.

Regards, Joerg

http/www.analogconsultants.com

 

[Guest]

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

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?
>
> Thanks!
>
> Jim Thompson


MCM http/www.mcminone.com has a number of wireless mic systems,
starting at $39 and going up to $499.

--
Former professional electron wrangler.

Michael A. Terrell
Central Florida

 

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

Ron wrote:

> On Fri, 03 Jun 2005 22:10:02 +0100, Pooh Bear
> <rabbitsfriendsandrelations@hotmail.com> wrote:

< snip >

> I think the original post is misleading you a bit. The 2245 amp
> will run just fine with non-matched output transistors, without
> 'sever distortion problems'. However, to achieve the lowest possible
> distortion and stability, matched pairs are advisable.

For a design of that era I would tend to agree.

> This is true for *any* symmetrical audio amplifier design.

I have to differ with you here. Poor beta match is only an issue when the
output devices load a moderate impedance driver stage. This gives rise to
unequal open loop gain for positive and negative half cycles. NFB will only
*reduce* this assymetry.

The effect can be eliminated by use of a *low* impedance driver stage or a
high gain pre-driver stage, as I have always used. Remember the Quad
'triples' in the 303 ? My amp design in the Vision that spawned the D series
amps actually used quadruples - but the big devices were actually off under
quiescent conditions - so for low level it was essentially similar to a
'triples' design at low power.

High ac gain in the driver - pre-driver stages also improves load related
stability as the load impedance doesn't reflect back in any significant way
to the previous voltage gain stage.

Note *ac* gain. I was briefly misled in the development of that amp by using
DC gain requirements and it was unstable with some loads. Then I ran a gain
/ phase plot and the result became obvious.


> >Some circuits almost don't care. It depends a lot on the driver stage.
>
> True. Especially for low NFB, low gain designs. Still the better
> the complimentary paiss match, the better will the amplifier be.

See above... I do tend to use quite a bit of local feedback and close the
loop gently as it happens. 'Low NFB' as commonly used by the audiotwats as a
generalisation is misleading. There'll be NFB somewhere ! It doesn't just
vanish.


> >Incidentally I can't really see how a failed output device can be
> >responsible for severe distortion. Normally it's a works or not
> >situation with output devices.
>
> Well, when one side of a pair works while the other doesn't, you do
> get signal out, but it's seriously (50% and up) distorted. Not just
> 'poor fidelity' but 'the amp is definitely bad' kind of sound.

As I mentioned elsewhere - when an output device fails, I've rarely known it
to be anything other than a short. That normally takes out the other output
device(s) and fuses etc and there's no sound.

The exception to that rule is the Hitachi style lateral mosfets. They
usually fail open. You see the effect when a big Mosfet amp amp doesn't clip
symmetrically any more !

> I recently had a similar problem with an 2270 output block. I
> replaced the bad output device with a matched (measured out of
> about a dozen) transistor. The receiver sounds great, but the
> repaird channel now measures better than the originally good
> one.

That'll teach you !

Graham

 

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

Pooh Bear wrote:
> Ron wrote:
>
>> On Fri, 03 Jun 2005 22:10:02 +0100, Pooh Bear
>> <rabbitsfriendsandrelations@hotmail.com> wrote:
>
> < snip >
>
>> I think the original post is misleading you a bit. The 2245 amp
>> will run just fine with non-matched output transistors, without
>> 'sever distortion problems'. However, to achieve the lowest possible
>> distortion and stability, matched pairs are advisable.
>
> For a design of that era I would tend to agree.
>
>> This is true for *any* symmetrical audio amplifier design.
>
> I have to differ with you here. Poor beta match is only an issue when
> the output devices load a moderate impedance driver stage. This gives
> rise to unequal open loop gain for positive and negative half cycles.
> NFB will only *reduce* this assymetry.
>
> The effect can be eliminated by use of a *low* impedance driver stage
> or a high gain pre-driver stage, as I have always used. Remember the
> Quad 'triples' in the 303 ? My amp design in the Vision that spawned
> the D series amps actually used quadruples - but the big devices were
> actually off under quiescent conditions - so for low level it was
> essentially similar to a 'triples' design at low power.
>
> High ac gain in the driver - pre-driver stages also improves load
> related stability as the load impedance doesn't reflect back in any
> significant way to the previous voltage gain stage.
>
> Note *ac* gain. I was briefly misled in the development of that amp
> by using DC gain requirements and it was unstable with some loads.
> Then I ran a gain / phase plot and the result became obvious.

Could you explain what you actually mean here by "misled"? DC gain has
never had any relevance to amplifier stability. No one is going to
design an amp feedback loop based on DC conditions. Its only the phase
at the unity gain frequency that matters.

Kevin Aylward
informationEXTRACT@anasoft.co.uk
http/www.anasoft.co.uk
SuperSpice, a very affordable Mixed-Mode
Windows Simulator with Schematic Capture,
Waveform Display, FFT's and Filter Design.

 

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

Bob Urz wrote:
> Kevin Aylward wrote:
>
>> Pooh Bear wrote:
>>
>>> Ol' Duffer wrote:
>>>
>>>
>>>> In article <42A0C72A.68DD168@hotmail.com>,
>>>> rabbitsfriendsandrelations@hotmail.com says...
>>>>
>>>>> I've never specified matched pairs in any design ( pro-audio btw
>>>>> ) in my entire life despite being responsible for some 10s of
>>>>> thousands of amplifiers out there. It seems like poor design to
>>>>> need matched pairs to me.
>>>>
>>>> You should check a batch of power transistors on a curve tracer
>>>> sometime. The results may scare you. I routinely see a factor
>>>> of three variation in Beta within batches. Of course you can
>>>> use big, wasteful swamper resistors, or a bank of 5 unmatched
>>>> devices where 2 matched would be sufficient. Or you can let
>>>> the amps blow up and they I buy more transistors than I need and
>>>> select a good grouping from the middle of the range and fix them
>>>> so they don't blow up anymore...
>>>
>>> These devices which I currently use for example are pre-graded by
>>> the manufacturer. Worst case match is 2:1 in either gain grade.
>>>
>>> http/www.profusionplc.com/cgi-bin/gex/pcatdtl?ipartno=2SC5200-O
>>>
>>> A simple low value emitter ballast resistor overcomes the bulk of
>>> beta mismatch anyway and I would never fail to use them. You can't
>>> depend on paralled device temps being identical - in fact quite the
>>> reverse - never mind thermal runaway !
>>>
>>
>>
>> Well, it might be useful to explain just why beta/hfe matching is
>> important, considering that that the bipolar transistor is a voltage
>> controlled device!
>>
> A bi polar transistor is a current controlled device actually.

Here we go, yet again...

I see that you have succumbed to the Bantam paperback popular
misconceptions Bob. A Bipolar transistor is indeed a voltage controlled
device.

For example, see
http/www.anasoft.co.uk/EE/voltagecontrolledbipolar/voltagecontrolledbipolar.html

and for a simple pictorial description of the actual physics, see:

http/www.mtmi.vu.lt/pfk/funkc_dariniai/transistor/bipolar_transistor.htm

There is simply no mechanism as how a flow of base charge can instigate
a flow of emitter/collector charge. Its applied voltage that that cause
the injection of charge.

The relevent simplified equation is:

Ic ~ Is.exp(Vbe/Vt)

Note the lack of a base current term.

I would suggest obtaining good academic semiconductor physics text book
if you want more details on the correct operation of bipolar
transistors.

Kevin Aylward
informationEXTRACT@anasoft.co.uk
http/www.anasoft.co.uk
SuperSpice, a very affordable Mixed-Mode
Windows Simulator with Schematic Capture,
Waveform Display, FFT's and Filter Design.

 

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

Pooh Bear wrote:

> Midlant wrote:
>
>
>>Cor, I too have one of these. Is yours a made in California real Marantz
>>or a later one made in Japan. I have a scratchy right channel. I've
>>cleaned the pots, especially the volume pot, but it doesn't seem to have
>>helped. Have you had this problem? If so what did you do to rectify it?
>>John
>
>
> I've heard US contributors to the audio groups mention 'Caig' as good for
> switches - maybe pots too.
>

Caig stuff works great. Cramolin D5 or pro gold.
Its not cheap, but it will work better than anything else
i have tried.

One problem in the old Marantz is the tape monitor switches.
Its common to have them get oxidized internally and cause a channel
to cut out. These switches are sealed. My patented way to revive them
is to carefully burn a hole in the back with a thin solder pencil.
You have to be careful to work the switch in and out when you do
this so the plastic does not jam up the switch internally. You then
use some D5 or such and work the switch in and our for a minute or
so. Then seal it back up.

Bob

> I have no expereince of it though as it doesn't appear to be sold in the UK.
>
> Graham
>

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

jakdedert wrote:
>
> Pooh Bear wrote:
> > Joerg wrote:
> >
> >> Hello Graham,
> >>
> >>> Usually it's current gain that's matched. ...
> >>
> >> I'll second that, it's what I saw most in matched pairs or quads.
> >> Except for FETs where the match is usually Vgs versus resistance.
> >
> > Indeed.
> >
> >
> >> > ... I've never specified matched
> >>> pairs in any design ( pro-audio btw ) in my entire life despite
> >>> being responsible for some 10s of thousands of amplifiers out
> >>> there. It seems like poor design to need matched pairs to me.
> >>
> >> Yes, it is best to avoid matching. But when you can't avoid it and
> >> then specify a transistor array it can be acceptable. That shouldn't
> >> be some boutique part though. I have done a few matched designs
> >> (where there was no other choice) based on SD5400 arrays. All RF
> >> stuff though, not audio.
> >>
> >> 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.
> >
> > Hmmm.. I'm not specifically into wireless mikes and I think both the
> > older VHF ( certainly ) and newer UHF ones are good old analogue.
> >
> > A good place to ask would be alt.audio.pro.live-sound. The issue of
> > battery life with wireless mikes has come up a good many times.
> > That's where you'll find ppl who use this stuff all the time. I don't
> > think you'll avoid 9V batteries though from what I understand. You
> > might make your 5hrs with rechargeable NiMH but the pros seem to
> > prefer alkalines - just in case of a bad charge perhaps. The battery
> > ( alkaline ) gets chucked at the end of the gig.
>
> For most gigs, the price of a battery is negligible compared to the show
> going 'down.' That said, the new Shures seem to do that long on a 9v. The
> really nice ones have battery meters on the actual receiver, so that you can
> monitor the battery condition remotely. I've seen a bunch of these lately.
> They've performed flawlessly IME, but the included mic is a little large.
> There's an ultra small mic option which is less noticable, but the (big)
> stock mic sounds better than most lav's I've worked with....
> <http/www.musiciansfriend.com/srs7/search/detail/base_pid/270296?src=3WBZ4
> DS>
>
> jak
> >
> > Graham.

Matched pairs were nessary in the early days of transistor amps.
Manufacturing tolerances are tighter today and matching is not as big a
problem.

JAM

 

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

Joerg wrote:

<snip>
> We really don't. But spread spectrum is so much lower maintenance.
> Most RF mikes including the Sennheiser SK series operate as UHF
> secondary user. That has several disadvantages. One is that UHF
> channels get kicked around a lot these days with new temporary DTV
> channels being assigned and so on. Another issue is noise. When a
> large bank of fluorescents gets turned on this is audible on pretty
> much any FM based system. Not so with spread spectrum.
>
> Other problems could have been avoided with clever engineering.
> Examples are the pop noise when a mike is turned off, and sometimes
> even when it is muted. The answer I got regarding the mute pop was
> like "pastors use that switch too often and it wears out". Well, then
> why is there a mute switch? And why isn't it properly debounced?
> After all, these systems are also advertised for use in churches and
> smaller congregations do not have an audio or mixer operator. So I'd
> expect proper mute switching.
>
You'll like the Shures mentioned before. No such problems in my experience.
No pops, no noise when the receiver is operating without a transmitter,
extremely wide choice of frequencies...auto frequency search. If there is
an operator controlling the sound system, there's a lockout function which
takes the performer out of the loop in terms of unintended switch punches.
You must open the battery panel, press and hold *two* switches to re-enable
the user controls. Sure beats gaffing over the buttons...which I always do
when handing talent a mic not so equipped.

> On rare occasions we had mikes "forget" their programmed frequency. In
> the middle of a worship service there is not much you can do about
> that when it happens. At least not fast enough.
>
Not seen any of that, either. In any case, the problem can be minimized by
having a wired backup. Again, an operator is desirable so that the backup
doesn't need to be left 'open.' If none is available, a switched
mic--turned off, but left potted up--is a fair alternative. The talent
needs to be aware of the plan, of course.

jak

> Regards, Joerg
>
> http/www.analogconsultants.com

 

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

Kevin Aylward wrote:

> Bob Urz wrote:
> > Kevin Aylward wrote:
> >
> >> Pooh Bear wrote:
> >>
> >>> Ol' Duffer wrote:
> >>>
> >>>
> >>>> In article <42A0C72A.68DD168@hotmail.com>,
> >>>> rabbitsfriendsandrelations@hotmail.com says...
> >>>>
> >>>>> I've never specified matched pairs in any design ( pro-audio btw
> >>>>> ) in my entire life despite being responsible for some 10s of
> >>>>> thousands of amplifiers out there. It seems like poor design to
> >>>>> need matched pairs to me.
> >>>>
> >>>> You should check a batch of power transistors on a curve tracer
> >>>> sometime. The results may scare you. I routinely see a factor
> >>>> of three variation in Beta within batches. Of course you can
> >>>> use big, wasteful swamper resistors, or a bank of 5 unmatched
> >>>> devices where 2 matched would be sufficient. Or you can let
> >>>> the amps blow up and they I buy more transistors than I need and
> >>>> select a good grouping from the middle of the range and fix them
> >>>> so they don't blow up anymore...
> >>>
> >>> These devices which I currently use for example are pre-graded by
> >>> the manufacturer. Worst case match is 2:1 in either gain grade.
> >>>
> >>> http/www.profusionplc.com/cgi-bin/gex/pcatdtl?ipartno=2SC5200-O
> >>>
> >>> A simple low value emitter ballast resistor overcomes the bulk of
> >>> beta mismatch anyway and I would never fail to use them. You can't
> >>> depend on paralled device temps being identical - in fact quite the
> >>> reverse - never mind thermal runaway !
> >>>
> >>
> >>
> >> Well, it might be useful to explain just why beta/hfe matching is
> >> important, considering that that the bipolar transistor is a voltage
> >> controlled device!
> >>
> > A bi polar transistor is a current controlled device actually.
>
> Here we go, yet again...
>
> I see that you have succumbed to the Bantam paperback popular
> misconceptions Bob. A Bipolar transistor is indeed a voltage controlled
> device.
>

So, the manuals with transistor curve tracers which state
a change a base current and plot collector current and voltage
are wrong? With bipolar beta B=Ic/Ib?

And for FET's its a change in gate voltage vs Drain/source?

Bob


>
> For example, see
> http/www.anasoft.co.uk/EE/voltagecontrolledbipolar/voltagecontrolledbipolar.html
>
> and for a simple pictorial description of the actual physics, see:
>
> http/www.mtmi.vu.lt/pfk/funkc_dariniai/transistor/bipolar_transistor.htm
>
> There is simply no mechanism as how a flow of base charge can instigate
> a flow of emitter/collector charge. Its applied voltage that that cause
> the injection of charge.
>
> The relevent simplified equation is:
>
> Ic ~ Is.exp(Vbe/Vt)
>
> Note the lack of a base current term.
>
> I would suggest obtaining good academic semiconductor physics text book
> if you want more details on the correct operation of bipolar
> transistors.
>
> Kevin Aylward
> informationEXTRACT@anasoft.co.uk
> http/www.anasoft.co.uk
> SuperSpice, a very affordable Mixed-Mode
> Windows Simulator with Schematic Capture,
> Waveform Display, FFT's and Filter Design.


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

On Mon, 06 Jun 2005 14:34:24 -0500, BOB URZ
<"sound(remove)"@inetnebr.com> wrote:

>
>
>Kevin Aylward wrote:
>
>> Bob Urz wrote:
>> > Kevin Aylward wrote:
>> >
>> >> Pooh Bear wrote:
>> >>
>> >>> Ol' Duffer wrote:
>> >>>
>> >>>
>> >>>> In article <42A0C72A.68DD168@hotmail.com>,
>> >>>> rabbitsfriendsandrelations@hotmail.com says...
>> >>>>
>> >>>>> I've never specified matched pairs in any design ( pro-audio btw
>> >>>>> ) in my entire life despite being responsible for some 10s of
>> >>>>> thousands of amplifiers out there. It seems like poor design to
>> >>>>> need matched pairs to me.
>> >>>>
>> >>>> You should check a batch of power transistors on a curve tracer
>> >>>> sometime. The results may scare you. I routinely see a factor
>> >>>> of three variation in Beta within batches. Of course you can
>> >>>> use big, wasteful swamper resistors, or a bank of 5 unmatched
>> >>>> devices where 2 matched would be sufficient. Or you can let
>> >>>> the amps blow up and they I buy more transistors than I need and
>> >>>> select a good grouping from the middle of the range and fix them
>> >>>> so they don't blow up anymore...
>> >>>
>> >>> These devices which I currently use for example are pre-graded by
>> >>> the manufacturer. Worst case match is 2:1 in either gain grade.
>> >>>
>> >>> http/www.profusionplc.com/cgi-bin/gex/pcatdtl?ipartno=2SC5200-O
>> >>>
>> >>> A simple low value emitter ballast resistor overcomes the bulk of
>> >>> beta mismatch anyway and I would never fail to use them. You can't
>> >>> depend on paralled device temps being identical - in fact quite the
>> >>> reverse - never mind thermal runaway !
>> >>>
>> >>
>> >>
>> >> Well, it might be useful to explain just why beta/hfe matching is
>> >> important, considering that that the bipolar transistor is a voltage
>> >> controlled device!
>> >>
>> > A bi polar transistor is a current controlled device actually.
>>
>> Here we go, yet again...
>>
>> I see that you have succumbed to the Bantam paperback popular
>> misconceptions Bob. A Bipolar transistor is indeed a voltage controlled
>> device.
>>
>
>So, the manuals with transistor curve tracers which state
>a change a base current and plot collector current and voltage
>are wrong? With bipolar beta B=Ic/Ib?
>
> And for FET's its a change in gate voltage vs Drain/source?
>
>Bob
>
>
>>
>> For example, see
>> http/www.anasoft.co.uk/EE/voltagecontrolledbipolar/voltagecontrolledbipolar.html
>>
>> and for a simple pictorial description of the actual physics, see:
>>
>> http/www.mtmi.vu.lt/pfk/funkc_dariniai/transistor/bipolar_transistor.htm
>>
>> There is simply no mechanism as how a flow of base charge can instigate
>> a flow of emitter/collector charge. Its applied voltage that that cause
>> the injection of charge.
>>
>> The relevent simplified equation is:
>>
>> Ic ~ Is.exp(Vbe/Vt)
>>
>> Note the lack of a base current term.
>>
>> I would suggest obtaining good academic semiconductor physics text book
>> if you want more details on the correct operation of bipolar
>> transistors.
>>
>> Kevin Aylward
>> informationEXTRACT@anasoft.co.uk
>> http/www.anasoft.co.uk
>> SuperSpice, a very affordable Mixed-Mode
>> Windows Simulator with Schematic Capture,
>> Waveform Display, FFT's and Filter Design.
>
>
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Kevin has a hair up his butt about voltage control, a really long hair
;-)

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice480)460-2350 | |
| E-mail Address at Website Fax480)460-2142 | Brass Rat |
| http/www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

 

[Guest]

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

Hello Jak,

> You'll like the Shures mentioned before. No such problems in my experience.
> No pops, no noise when the receiver is operating without a transmitter,
> extremely wide choice of frequencies...auto frequency search. ...

That would be an alternative. This time though we'd insist on a serious
test drive before a purchase. The additional Shure system we have is
more than 10 years old but the noise tolerance (lamp switches etc.) is
not stellar, to put it mildly. The Sennheisers are a lot better.

>>On rare occasions we had mikes "forget" their programmed frequency. In
>>the middle of a worship service there is not much you can do about
>>that when it happens. At least not fast enough.
>
> Not seen any of that, either. In any case, the problem can be minimized by
> having a wired backup. Again, an operator is desirable so that the backup
> doesn't need to be left 'open.' If none is available, a switched
> mic--turned off, but left potted up--is a fair alternative. The talent
> needs to be aware of the plan, of course.

Frequency memory losses were rare, maybe a couple times a year. Yes, we
do have wired backups and the choir people are well trained. But some
performances require lots of movement and the cables would become a hazard.

Regards, Joerg

http/www.analogconsultants.com

 

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"Joerg" <notthisjoergsch@removethispacbell.net> wrote in message
news:4o1pe.612$Z44.509@newssvr13.news.prodigy.com...
> Hello Jak,
>
> > You'll like the Shures mentioned before. No such problems in my
experience.
> > No pops, no noise when the receiver is operating without a transmitter,
> > extremely wide choice of frequencies...auto frequency search. ...
>
> That would be an alternative. This time though we'd insist on a serious
> test drive before a purchase. The additional Shure system we have is
> more than 10 years old but the noise tolerance (lamp switches etc.) is
> not stellar, to put it mildly. The Sennheisers are a lot better.
>
> >>On rare occasions we had mikes "forget" their programmed frequency. In
> >>the middle of a worship service there is not much you can do about
> >>that when it happens. At least not fast enough.
> >
> > Not seen any of that, either. In any case, the problem can be minimized
by
> > having a wired backup. Again, an operator is desirable so that the
backup
> > doesn't need to be left 'open.' If none is available, a switched
> > mic--turned off, but left potted up--is a fair alternative. The talent
> > needs to be aware of the plan, of course.
>
> Frequency memory losses were rare, maybe a couple times a year. Yes, we
> do have wired backups and the choir people are well trained. But some
> performances require lots of movement and the cables would become a
hazard.
>

We have had our EW100 (not the new G2) for over a year and never had one
single frequency memory loss. It is used for 3 services a week and then for
special occasions. The only down side is the short rechargable memory life
with the 9v. My experience wiht the new AA's is comparable to alkaline,
close enough that if we get a new system we would definately use the
rechargable AA's. I think you shoudl have your system checked out.

Mike D.

> Regards, Joerg
>
> http/www.analogconsultants.com

 

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Hello Winfield,

> Nobody should be bound to the podium. Solve the problem.

When a friend was speaking I saw the field strength meter on the
wireless receiver for his mike go from near full scale to zilch. Oh no,
not now... The battery had given out. He has such a thunderous voice
that I could not notice a difference and I was way in the back, behind
the audience.

So it may just be a matter of training ;-)

Regards, Joerg

http/www.analogconsultants.com

 

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On Mon, 06 Jun 2005 19:31:02 GMT, Joerg
<notthisjoergsch@removethispacbell.net> wrote:

>Hello Winfield,
>
>> Nobody should be bound to the podium. Solve the problem.
>
>When a friend was speaking I saw the field strength meter on the
>wireless receiver for his mike go from near full scale to zilch. Oh no,
>not now... The battery had given out. He has such a thunderous voice
>that I could not notice a difference and I was way in the back, behind
>the audience.
>
>So it may just be a matter of training ;-)
>
>Regards, Joerg
>
>http/www.analogconsultants.com

Joerg, Can you recommend a Sennheiser model, with lapel microphone?
Thanks!

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice480)460-2350 | |
| E-mail Address at Website Fax480)460-2142 | Brass Rat |
| http/www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

 

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Hello Jim,

> Joerg, Can you recommend a Sennheiser model, with lapel microphone?

My experience is limited to their 9V wireless gear which I would not
recommend because of limited battery life and premature battery
failures. There is a new "SK 100 G2" unit which looks very interesting
and that is the one I am going to check out once we upgrade:

http/www.sennheiser.com/sennheiser/icm_eng.nsf/root/21411

The corresponding receivers are typically 19" rack mount and I believe
they do sell kits that contain transmitter, mike, receiver, diversity
antennas, power supply and the cables. The Sennheiser web site is not
very good so you may have to call them to see what the best deal would
be for the whole set. Believe it or not, their "search function" didn't
find their own SK100 mike transmitters, Google did...

Since this is professional gear the output is usually differential, for
connection to a large mixer panel.

To be honest, this professional gear takes more time to set up in the
field when compared to cheaper systems like the Radio Shack I mentioned
before.

My only gripe besides the 9V with our existing Sennheisers is the pop
noise upon turn-off and mute. But if your wife's scout presentations are
typically uninterrupted that won't matter. Also, these systems can be
upgraded to umpteen mikes if that was ever needed.

Regards, Joerg

http/www.analogconsultants.com

 

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Kevin Aylward wrote:

> Pooh Bear wrote:
> > Ron wrote:
> >
> >> On Fri, 03 Jun 2005 22:10:02 +0100, Pooh Bear
> >> <rabbitsfriendsandrelations@hotmail.com> wrote:
> >
> > < snip >
> >
> >> I think the original post is misleading you a bit. The 2245 amp
> >> will run just fine with non-matched output transistors, without
> >> 'sever distortion problems'. However, to achieve the lowest possible
> >> distortion and stability, matched pairs are advisable.
> >
> > For a design of that era I would tend to agree.
> >
> >> This is true for *any* symmetrical audio amplifier design.
> >
> > I have to differ with you here. Poor beta match is only an issue when
> > the output devices load a moderate impedance driver stage. This gives
> > rise to unequal open loop gain for positive and negative half cycles.
> > NFB will only *reduce* this assymetry.
> >
> > The effect can be eliminated by use of a *low* impedance driver stage
> > or a high gain pre-driver stage, as I have always used. Remember the
> > Quad 'triples' in the 303 ? My amp design in the Vision that spawned
> > the D series amps actually used quadruples - but the big devices were
> > actually off under quiescent conditions - so for low level it was
> > essentially similar to a 'triples' design at low power.
> >
> > High ac gain in the driver - pre-driver stages also improves load
> > related stability as the load impedance doesn't reflect back in any
> > significant way to the previous voltage gain stage.
> >
> > Note *ac* gain. I was briefly misled in the development of that amp
> > by using DC gain requirements and it was unstable with some loads.
> > Then I ran a gain / phase plot and the result became obvious.
>
> Could you explain what you actually mean here by "misled"? DC gain has
> never had any relevance to amplifier stability. No one is going to
> design an amp feedback loop based on DC conditions. Its only the phase
> at the unity gain frequency that matters.

I misled myself I'm afraid. It's that long ago that I forget the exact
details.

Graham

 

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Jim Thompson wrote:

> Kevin has a hair up his butt about voltage control, a really long hair
> ;-)

Especially considering he was explaining why beta matching is important !

Graham

 

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Hello Mike,

> We have had our EW100 (not the new G2) for over a year and never had one
> single frequency memory loss. It is used for 3 services a week and then for
> special occasions. The only down side is the short rechargable memory life
> with the 9v. My experience wiht the new AA's is comparable to alkaline,
> close enough that if we get a new system we would definately use the
> rechargable AA's. I think you shoudl have your system checked out.

We had sent them in a while ago. The frequency info losses aren't really
a big concern, battery life is the problem. Also, we have four
mikes/receivers so that waters down the statistical significance of the
memory failure events.

The mute buttons are a bit weak, too. We had one croak and another
become rickety. The handhelds have better quality mute buttons but they
are hard to operate because you have to turn a cover wheel and then
fumble around behind the mike to find it. So we usually just turn the
mike away from the pulpit after the scripture readings (our pastor wears
a lapel mike).

Regards, Joerg

http/www.analogconsultants.com

 

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Hello Graham,

> I'm curious why you'd send missionaries to Russia. They already have the
> Orthodox Church there which is making something of a comeback after decades of
> communism ( although it never ever truly died out ).

From what I know there was a school principal from Petrozavodsk who
visited a Christian school in the US. This was AFAIK back in the commie
times and he was not so much interested in the bible (I guess his gvt
didn't like that at all) but in why students were better motivated,
among other things, and what he could do about that back in Russia. That
is where the idea came up to send people over from here to teach the
students in Russia English, using the bible as a text book. So, now
there are regular missions to that city, not just from our church but
also lots of others.

Participation is voluntary for students. Usually 100-200 sign up from
what I heard. This year blew us away, a whopping 1000 signed up.

> Have your missionaries previously met the Russian Mafia btw ? ;-)

No, but I guess they wouldn't be interested much in missionaries.

Regards, Joerg

http/www.analogconsultants.com