Google Groups no longer supports new Usenet posts or subscriptions. Historical content remains viewable.
Dismiss
High Z And Low Z Mics
49 views
Skip to first unread message
jurb...@gmail.com
Feb 5, 2015, 8:23:56 PM2/5/15
to
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 with it. The boss thinks you should be able to do that but the fact is it SAYS LINE on it. Tht means it is meant to be fed by a mixer or something, right ? Not a microphone or guitar pickup.
There is no distortion and in the relatively simple circuitry there is almost no way you would lose gain without some distortion. Does anyone really think the AC bypass cap for the feedback is bad ? I don't. Not when every other cap in the thing doesn't seem to be causing a problem. It has clean output and nothing drastic in the frequency response.
Anyway, the ¼" jack is what they seem to want to use. From the line input 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 gain or so but bring down the input impedance. Should be OK for a mic or even 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 mixing board into it, it probably would not work correctly. (maybe to say the least)
However they would still have the line level XLR jack for that. If they had a mixer with only ¼" output, that should be adaptable to that input right ? 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 damn ¼".
Anyway, I am just wondering if there are any unforseen ramifications to cranking 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 about 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 low 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 that far I could really just drill a hole and put a switch on it.
Penny for your thoughts.
There is no distortion and in the relatively simple circuitry there is almost no way you would lose gain without some distortion. Does anyone really think the AC bypass cap for the feedback is bad ? I don't. Not when every other cap in the thing doesn't seem to be causing a problem. It has clean output and nothing drastic in the frequency response.
Anyway, the ¼" jack is what they seem to want to use. From the line input 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 gain or so but bring down the input impedance. Should be OK for a mic or even 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 mixing board into it, it probably would not work correctly. (maybe to say the least)
However they would still have the line level XLR jack for that. If they had a mixer with only ¼" output, that should be adaptable to that input right ? 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 damn ¼".
Anyway, I am just wondering if there are any unforseen ramifications to cranking 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 about 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 low 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 that far I could really just drill a hole and put a switch on it.
Penny for your thoughts.
Phil Allison
Feb 6, 2015, 1:26:50 AM2/6/15
to
jurb....
>
> 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.
** 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
>
> 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.
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
jurb...@gmail.com
Feb 6, 2015, 5:18:38 AM2/6/15
to
>"** Try a resistor of 680 kohms first. "
Not gonna work. I did't really splain it right I guess. This was a 33K running from the ¼" jack to the - imput of an OP AMP. The gain control is connected from the output to the input, which makes it control the gain. It is pribably a friggin 100K at least so even changing it to a one meg is not likely to get what he wants. And I do not feel like looking for the right pot to modify it.
The + is grounded, it is in inverting mode. It is a 4558.
I could cut the fucking foil to the +, put the input to that and then set the gain alot higher I am sure. But that is not easy. I would have to cut all the way around the pin and shit.
But then I do have a board with a bunch of 4558s IN SOCKETS so aybe I can do something with that.
Hell maybe just build a fucking preamp and be done with it. Put the thing back stock. How long will a 4558 run off a 9 volt battery lol ?
No, I would put it inside the in it and just run off its supply. I am in no mood to fuck around. Actually I will but I don't want them bitching about tinme on job because that is when the big test comes. I am making shit money, my idea is to do it the right way, to deliver the customer the fixed product in a reasonable time. I knowe alomost nothing of the rsates but they are low, rtoo low. The company might wat to give those rates as a "courtesy" to their customers, but they are not going to do it at my expense.
But anyway, that is all about what is worth it and what is not, and actually that the owner of the business does not understand about a line input. you cannot just plug a mic in there.
And if this is store stock I will have to snack him upside the head. just tell the guy it needs a preamp, like a mixer, to get enough gain. then you sell TWO units instead of one.
I ant ot say - "Why am I surrounded by such ignorance/" but reallly you gotaa give peole a chance. How would they know what I know. I been selling knowledge for good money for forty years. How WOULD they know.
I have learned a bit of tolerance actually. It pays. Just pay me for now. Lett me become a significant part of your business.
Then you are mine motherfucker. And there ain't mo "lol" on that. done it before and I'll do it again. Fucking assholes deserve to have theire popckets clipped by the likes of me because I make them that money.
I have already had that call. "Get in here as soon as possible". Case closed. I am working this one to fruition if possible.
Gareth Magennis
Feb 6, 2015, 4:02:15 PM2/6/15
to
rev.11...@gmail.com
Feb 6, 2015, 4:25:09 PM2/6/15
to
http://www.audio-technica.com/cms/electronics/f4b735b4cabc30ea/
Audio-Technica CP8201 In-Line Transformer
http://www.musiciansfriend.com/accessories/audio-technica-cp8201-in-line-transformer
Audio-Technica CP8201 In-Line Transformer
http://www.musiciansfriend.com/accessories/audio-technica-cp8201-in-line-transformer
Phil Allison
Feb 6, 2015, 7:35:12 PM2/6/15
to
Gareth Magennis wrote:
> http://www.markertek.com/product/lmx/pro-co-sound-lmx-inline-barrel-xlr-mic-to-1-4in-line-level-adapter
** 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
Gareth Magennis
Feb 6, 2015, 7:57:41 PM2/6/15
to
"Phil Allison" wrote in message
news:d00c612f-ec02-4d6c...@googlegroups.com...
Thing is, I can't quite make out whether the XLR is male or female, so at
this point the Jury is out.
Gareth.
rev.11...@gmail.com
Feb 6, 2015, 8:07:12 PM2/6/15
to
jurb...@gmail.com
Feb 6, 2015, 8:10:03 PM2/6/15
to
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 low impedace mic but it would have to be adapted to ¼". I did not modify the 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 just use a couple of resistors, and that also gives them balance ¼" 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.
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.
rev.11...@gmail.com
Feb 6, 2015, 8:13:38 PM2/6/15
to
Gareth Magennis
Feb 6, 2015, 8:22:50 PM2/6/15
to
FFS.
Buy a 15 dollar box and fix yours and the customers problem.
Sorted.
wrote in message
news:7984d8f8-418b-4aaa...@googlegroups.com...
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
low impedace mic but it would have to be adapted to ź". I did not modify the
Buy a 15 dollar box and fix yours and the customers problem.
Sorted.
wrote in message
news:7984d8f8-418b-4aaa...@googlegroups.com...
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
just use a couple of resistors, and that also gives them balance ź"
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
Phil Allison
Feb 6, 2015, 8:39:48 PM2/6/15
to
Gareth Magennis wrote:
>
> > http://www.markertek.com/product/lmx/pro-co-sound-lmx-inline-barrel-xlr-mic-to-1-4in-line-level-adapter
>
>
> ** 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.
>
>
>>
>
> > http://www.markertek.com/product/lmx/pro-co-sound-lmx-inline-barrel-xlr-mic-to-1-4in-line-level-adapter
>
>
> ** 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.
>
>
>>
> 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.
** No it isn't.
>
> Thing is, I can't quite make out whether the XLR is male or female, so at
> this point the Jury is out.
http://www.bhphotovideo.com/images/images2000x2000/231520.jpg
... Phil
Phil Allison
Feb 6, 2015, 8:43:07 PM2/6/15
to
rev.11...@gmail.com wrote:
>
> > > http://www.markertek.com/product/lmx/pro-co-sound-lmx-inline-barrel-xlr-mic-to-1-4in-line-level-adapter
> There is no 1/4" anything on the photo,
** 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.
http://www.bhphotovideo.com/images/images2000x2000/231520.jpg
.... Phil
>
> > > http://www.markertek.com/product/lmx/pro-co-sound-lmx-inline-barrel-xlr-mic-to-1-4in-line-level-adapter
>
> The photo doesn't match the description.
** It does actually.
> The photo doesn't match the description.
> There is no 1/4" anything on the photo,
The gadget plugs into a mixing desk and a jack lead from the line level source into it.
http://www.bhphotovideo.com/images/images2000x2000/231520.jpg
.... Phil
Phil Allison
Feb 6, 2015, 8:47:32 PM2/6/15
to
rev.11...@gmail.com wrote:
>
> > ** 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.
> >
>
>
>
> > ** 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.
> >
>
>
> The pictured unit, not the same as in the description, is bi-directional.
** Not meant to be - the male XLR on one end makes it impossible to plug a mic or XLR mic lead into it.
.... Phil
rev.11...@gmail.com
Feb 6, 2015, 8:50:12 PM2/6/15
to
Wrong part for solution to this problem.
Besides that, OP needlessly and incorrectly modified the amp.
Phil Allison
Feb 6, 2015, 9:02:38 PM2/6/15
to
rev.11...@gmail.com wrote:
> > > The photo doesn't match the description.
> >
> > ** It does actually.
> >
> > > There is no 1/4" anything on the photo,
> >
> >
> > ** 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.
> >
> > http://www.bhphotovideo.com/images/images2000x2000/231520.jpg
> >
>
>
> > > The photo doesn't match the description.
> >
> > ** It does actually.
> >
> > > There is no 1/4" anything on the photo,
> >
> >
> > ** 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.
> >
> > http://www.bhphotovideo.com/images/images2000x2000/231520.jpg
> >
>
>
> The Male XLR plug will not fit a 1/4" Female jack. D'OH
** 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 ??
> Besides that, OP needlessly and incorrectly modified the amp.
.... Phil
rev.11...@gmail.com
Feb 6, 2015, 9:05:47 PM2/6/15
to
ffs yourself
rev.11...@gmail.com
Feb 6, 2015, 9:28:25 PM2/6/15
to
I declare this thread a total troll on all of us here. Note missing XLR input information from original post. Note missing label info for this XLR jack.
Note the manufacturer's website description of its powered speakers. Also note 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, they 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. :(
jurb...@gmail.com
Feb 6, 2015, 9:28:57 PM2/6/15
to
>"> Besides that, OP needlessly and incorrectly modified the amp. "
Didn't that blown up picture depict an ATTENUATOR ? That's the last thing we needed.
>"** Bollocks he did. "
Don't tell me you are sticking up for me lol. But anyway, I will modify anything 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 years and never got into a problem over it.
In fact gained customers because of it.
jurb...@gmail.com
Feb 6, 2015, 9:35:28 PM2/6/15
to
>"Technical Pro powered speakers have Mic input. OP doesn't need to modify the >amp at all. D'OH "
There was ot enough gain. I connected line level to it and there was plenty of gain. The problem was the same on ¼" and XLR which feed separate OP AMPs.
BOTH INPUTS SAY "LINE".
So, are you really sure of that ? with a higher input to either the amp clips 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 ?
rev.11...@gmail.com
Feb 6, 2015, 9:35:59 PM2/6/15
to
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 someone actually using the microphone... And see how good it all would be with a Volume control mod instead. Or use the built-in Mic input already on the thing.
Yeesh
rev.11...@gmail.com
Feb 6, 2015, 9:41:26 PM2/6/15
to
http://www.audio-technica.com/cms/electronics/f4b735b4cabc30ea/
Audio-Technica CP8201 In-Line Transformer
http://www.musiciansfriend.com/accessories/audio-technica-cp8201-in-line-transformer
I never said you are wrong or incorrect in your approach, just time-wasting and too costly in the long run.
$10 and you'd be done. minus Volume control, that is... :)
rev.11...@gmail.com
Feb 6, 2015, 9:50:19 PM2/6/15
to
On Friday, February 6, 2015 at 6:28:57 PM UTC-8, jurb...@gmail.com wrote:
> >"> Besides that, OP needlessly and incorrectly modified the amp. "
>
> Didn't that blown up picture depict an ATTENUATOR ? That's the last thing we needed.
>
That red button is a locking mechanism, not a potentiometer.
>
> Didn't that blown up picture depict an ATTENUATOR ? That's the last thing we needed.
>
If you want to pay $20 more, use it plugged into the XLR Line IN, and your balanced microphone cable into it.
But, you still don't have a Volume control.
You could Manually PWM the mic's On/Off switch Really Fast to get a Volume control in there. :)
Peace
Out
0 new messages