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High Z And Low Z Mics

Guy wants to use a powered speaker, I tbink a "Technical Pro" brand with a microphone. I couldn't get a print on it but I see there is nothing wrong w ith it. The boss thinks you should be able to do that but the fact is it SA YS LINE on it. Tht means it is meant to be fed by a mixer or something, rig ht ? Not a microphone or guitar pickup.

There is no distortion and in the relatively simple circuitry there is almo st no way you would lose gain without some distortion. Does anyone really t hink the AC bypass cap for the feedback is bad ? I don't. Not when every ot her cap in the thing doesn't seem to be causing a problem. It has clean out put and nothing drastic in the frequency response.

there it goes through a 33K resistor to the inverting input of an OP AMP ( one side of a 4558). I paralleled a 10K with that resistor, making it what, about 8K ? Arond in there. Technically this should just about triple the g ain or so but bring down the input impedance. Should be OK for a mic or eve n a guitar pickup.

I can't reverse engineer this whole damn thing, but have a question.

In case that the customer already has a low impedance mic and wants to use it, really I should be able to decrease the value of that restitor to like

200 ohms. I should get the required voltage gain but it will load the input a hell of alot more, probably to the point of having a problem with other sources. Not just the impedance but the gain, if someone was to plug a mixi ng board into it, it probably would not work correctly. (maybe to say the l east)

However they would still have the line level XLR jack for that. If they had

t ? Because it will have stock gain, I am not modifying that one. That is a little too much reverse engineering to do something wrong. Just use the da

Anyway, I am just wondering if there are any unforseen ramifications to cra nking that value down to like 200 ohms. Another thing is protecting the OP AMP. If somneone plugs a powered mixer in there is it possible to blow that OP AMP ? Figure a 200 ohm. Can that damage a standard 4558 such as used in these things ? Should I look for a special 1/100th of a watt resistor for this ?

I am sure it can blow it if some goob connects a speaker output to it. But will a well buffed line level possibly kill it ? I don't care that much abo ut the OP AMP, I care more about the thing being walked back into the shop. think, the person using it might not be aware of all the intense gain... I don't care about waking up the neighbors I care about shit coming back for stupid reasons.

I already told the PTB that the unit is working right, and does not have lo w level imputs. They don't seem to care and want to make it usable this way . Really, I should stick a sticker on it that it is modified, but if I go t hat far I could really just drill a hole and put a switch on it.

Penny for your thoughts.

Reply to
jurb6006
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jurb....

** Try a resistor of 680 kohms first.

That gives you a gain of 48 times, which should be OK with most dynamic mics, and does not load the mic too much even if it' a 600ohm model.

Any more gain and you will lose high frequencies and have a lot of noise.

.... Phil

Reply to
Phil Allison

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Reply to
Gareth Magennis

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Audio-Technica CP8201 In-Line Transformer

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Reply to
rev.11d.meow

** That gadget ( likely a transformer ) is meant to take a line level input ( keyboard etc) and convert it to suit an XLR mic input.

IOW it's DI box.

... Phil

Reply to
Phil Allison

** That gadget ( likely a transformer ) is meant to take a line level input ( keyboard etc) and convert it to suit an XLR mic input.

IOW it's DI box.

... Phil

Pro Co Sound LMX InLine Barrel XLR Mic to 1/4In Line Level Adapter

Thing is, I can't quite make out whether the XLR is male or female, so at this point the Jury is out.

Gareth.

Reply to
Gareth Magennis

The photo doesn't match the description. There is no 1/4" anything on the photo, only XLR, probably female and male, one on each end.

Reply to
rev.11d.meow

Well I told them they could probably use a high impedance mic on it success fully. I alkso told them tha tI MIGHT be able to make it work with a low im

R input. It is separate and goes to the other side of the dual OP AMP. The outputs are mixed after that. Maybe they did that to make it work better if you want to use both inputs simultaneaously. Why else ? Alot of things I s

ability. But not this one. No ring at all, just shield and tip.

I think the guy is just going to use a high ipedance mic on it and be done with it. I stuck one rsistor in it, I paralleled a 33K with a 10K. That sho uld quadruple the voltage gain right ?

I didn't want to go higher gain because then it would be way too touchy on a line input like a mixer. I would do it, but if so I would mark it, that i t is no longer a line level input.

It probably owuld have been better to modify the XLR input gain. It is more logical but it takes more reverse engineering. tyhat means time and money and htis place doens't want ot make too much. Their rates are very low, whi ch is something we will have to discuss one of these days. Seems like more stuff is coming in though. The one main place in town charges over double w hat they charge. Get a foothold aand then I will tell them what they should be charging. By then I will know what I am talking about because I will re search it.

But really, the same bullshit exists as in the TV business. People put 25 a mp fuses in, stick paper or something under whatever to make it work. Let t heir idiot borther in law work on it.

Got an amp I almost rejected but the boss said it belongs to our pizza guy. Someone puit a wrong screw in the front panel ant it busted the cleat OUT OF ALUMINUM ! And I have never had to drill out more screws in my life. Sol dered it up a binch of times and now the thing won't come out of protect. S hitcan it, I already got too much time in it to even lose reasonable money at what they charge.

And that one with the class D Icepower module ? I put a note on it, forget it and stick it out there and then find out LATER that they just sold the t hing !

Same shit, different day and less money.

Whatever. Go ahead and rant, I do.

Reply to
jurb6006

The pictured unit, not the same as in the description, is bi-directional.

Reply to
rev.11d.meow

FFS.

Buy a 15 dollar box and fix yours and the customers problem.

Sorted.

Well I told them they could probably use a high impedance mic on it successfully. I alkso told them tha tI MIGHT be able to make it work with a

XLR input. It is separate and goes to the other side of the dual OP AMP. The outputs are mixed after that. Maybe they did that to make it work better if you want to use both inputs simultaneaously. Why else ? Alot of things I se

capability. But not this one. No ring at all, just shield and tip.

I think the guy is just going to use a high ipedance mic on it and be done with it. I stuck one rsistor in it, I paralleled a 33K with a 10K. That should quadruple the voltage gain right ?

I didn't want to go higher gain because then it would be way too touchy on a line input like a mixer. I would do it, but if so I would mark it, that it is no longer a line level input.

It probably owuld have been better to modify the XLR input gain. It is more logical but it takes more reverse engineering. tyhat means time and money and htis place doens't want ot make too much. Their rates are very low, which is something we will have to discuss one of these days. Seems like more stuff is coming in though. The one main place in town charges over double what they charge. Get a foothold aand then I will tell them what they should be charging. By then I will know what I am talking about because I will research it.

But really, the same bullshit exists as in the TV business. People put 25 amp fuses in, stick paper or something under whatever to make it work. Let their idiot borther in law work on it.

Got an amp I almost rejected but the boss said it belongs to our pizza guy. Someone puit a wrong screw in the front panel ant it busted the cleat OUT OF ALUMINUM ! And I have never had to drill out more screws in my life. Soldered it up a binch of times and now the thing won't come out of protect. Shitcan it, I already got too much time in it to even lose reasonable money at what they charge.

And that one with the class D Icepower module ? I put a note on it, forget it and stick it out there and then find out LATER that they just sold the thing !

Same shit, different day and less money.

Whatever. Go ahead and rant, I do.

Reply to
Gareth Magennis

** No it isn't.

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... Phil

Reply to
Phil Allison

** It does actually.

** Yes there is - a Neutrik style, locking jack socket.

The gadget plugs into a mixing desk and a jack lead from the line level source into it.

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.... Phil

Reply to
Phil Allison

** Not meant to be - the male XLR on one end makes it impossible to plug a mic or XLR mic lead into it.

.... Phil

Reply to
Phil Allison

The Male XLR plug will not fit a 1/4" Female jack. D'OH

Wrong part for solution to this problem.

Besides that, OP needlessly and incorrectly modified the amp.

Reply to
rev.11d.meow

** FFS what planet are you on ?

The MALE XLR plugs into the MIC input on a desk.

It's a mini DI (Direct Injection) box

- got a clue what that is ??

** Bollocks he did.

.... Phil

Reply to
Phil Allison

Technical Pro powered speakers have Mic input. OP doesn't need to modify the amp at all. D'OH

ffs yourself

Reply to
rev.11d.meow

input ( keyboard etc) and convert it to suit an XLR mic input.

l.

a mic or XLR mic lead into it.

Didn't you say the XLR Male plug guzzinta the mixing board?

I declare this thread a total troll on all of us here. Note missing XLR in put information from original post. Note missing label info for this XLR j ack.

Note the manufacturer's website description of its powered speakers. Also n ote they have at least one model with a built-in mixer. With that I vote he goes with his mod and a microphone plugged into it. When it's too loud, t hey can adjust the Volume on a powered speaker with no volume control.

Sounds like this whole plan is not only a troll, but a totally abysmal FAIL as well.

Boy, did I ever fall for this one, yeesh. :(

Reply to
rev.11d.meow

Didn't that blown up picture depict an ATTENUATOR ? That's the last thing w e needed.

Don't tell me you are sticking up for me lol. But anyway, I will modify any thing as long as it is a safe and reliabale design. I am goood enough to kn ow when it is and when it isn't. I have done so quite a bit over the years and never got into a problem over it.

In fact gained customers because of it.

Reply to
jurb6006

the >amp at all. D'OH "

There was ot enough gain. I connected line level to it and there was plenty

MPs.

BOTH INPUTS SAY "LINE".

So, are you really sure of that ? with a higher input to either the amp cli ps just fine, no distortion. If there was a fault in the amp it would have to be rtow separate identical faults causing the same reduction in gain in two separate OP AMPs.

Is this what you're telling me ?

Reply to
jurb6006

we needed.

nything as long as it is a safe and reliabale design. I am goood enough to know when it is and when it isn't. I have done so quite a bit over the year s and never got into a problem over it.

Why doesn't your mod include a Volume control then?

They should've purchased the model with the built-in mixer.

If you want to add a mixer, feel free.

You could always do your Gain adjustment mod, then test it that way with so meone actually using the microphone... And see how good it all would be wit h a Volume control mod instead. Or use the built-in Mic input already on t he thing.

Yeesh

Reply to
rev.11d.meow

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