Assuming that you don't want to spend a whole lot and that it doesn't have to be hifi I would look at a Radio Shack setup. That is what we had when our church was just starting (aka lower in budget...). We also used an RS wireless mike for large meetings with production employees at my last company. We had to hold those in the cantina since it was the only place where the fire marshall allowed enough occupancy.
The units are different now but still cheap:
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One of them is a complete set, mike and receiver. Then you only have to plug the receiver's line out into the PA system. The older one we had could also be operated from batteries and from a car battery which would be really nice for scout meetings in the outbacks.
I ended up using flameproof power film resistors for emitter Rs so that in the event of catastrophic failure - a cascade failure or 'burn up' as our repair guys used to call it, the emitter Rs went open fast. Usually little damage in that event. I do recall seing some TO-92s with their 'heads' popped off though !
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.
Yes, we'll certainly look into those. Especially if they are compatible with our existing Sennheiser UHF gear.
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.
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.
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.
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 !
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 snipped-for-privacy@anasoft.co.uk
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SuperSpice, a very affordable Mixed-Mode Windows Simulator with Schematic Capture, Waveform Display, FFT's and Filter Design.
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
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and for a simple pictorial description of the actual physics, see:
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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 snipped-for-privacy@anasoft.co.uk
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SuperSpice, a very affordable Mixed-Mode Windows Simulator with Schematic Capture, Waveform Display, FFT's and Filter Design.
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
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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.
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.
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 Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
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 Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
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
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They have a great budget when a certain benefactor makes equipment, and vans, etc., available for free ;-)
...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC\'s and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
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.
My inclination is to a multiple-microphone version for later expansion, since they do a lot of Flag Ceremonies with multiple speaking parts.
...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC\'s and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
Be prepared! That's the Boy Scout marching song Be prepared! If you should meet a Girl Scout who is suitably inclined Be prepared!
;-)
...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC\'s and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
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.
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.
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