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Connecting microphone to stereo amplifier

Discussion in 'Hi Fi Systems & Separates' started by blacklion, Oct 9, 2009.

  1. blacklion

    blacklion Member

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  2. Roger Thornhill

    Roger Thornhill Member

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    That's exactly the thing you require.

    Can't comment on the quality of that one and no-one's reviewed it on the Amazon site but the spec sheet reads quite well.
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  3. blacklion

    blacklion Member

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    Thanks! Can you recommend one then? Cheers!
  4. Roger Thornhill

    Roger Thornhill Member

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    Sorry, didn't mean to imply that that one is no good, just that i haven't used one.

    I'm sorry, i can't recommend a model as haven't had the need to use one for years.

    The one you have found i am sure will do very well, i just cannot personally recommend it as i haven't used one.
  5. eviljohn2

    eviljohn2 Member

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    Watch out for creating an acoustic feedback loop! Microphones run through to a pair of speakers require some care or the signal constantly amplifies itself into a characteristic howl or squeal. :)
  6. BlueWizard

    BlueWizard Well-Known Member

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    Ah... NO!... the preamp you listed in NOT the type of preamp you need for a microphone. The one you choose is specifically a TURNTABLE Phono equalization circuit, it work only with turntables.

    What you need is a simple PA microphone mixer like this -

    M-AUDIO - Audio Buddy - Budget Microphone Preamp

    M AUDIO AUDIO BUDDY - MICROPHONE PREAMP- EACH

    This has four microphone inputs for two microphones, of either the unbalanced (1/4" phone plug) or the balanced (XLR 3-pin) type. It then has two volume controls, one for each microphone, and two separate outputs.

    The price is about £65 each.

    Steve/bluewizard
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  7. KJ Palmer

    KJ Palmer Member

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    The unit linked in the original post actually has both microphone and turntable inputs (switchable), so would in fact be suitable for a mic with 1/4" stereo/mono jack. I've got a similar one myself, bought a couple of years back from Maplin's. It seems to work OK, though I haven't compared it with alternatives. I daresay a dedicated mic pre-amp would be better though.
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    Last edited: Oct 9, 2009
  8. D.D.D.

    D.D.D. Member

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    I've seen some Behringer preamps on eBay - those are a bit cheaper - around 40£ - item=130334130980 and item=160361889703
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  9. BlueWizard

    BlueWizard Well-Known Member

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    Sorry, you're right; I seem to have missed that detail.

    Still, while certainly cheap enough, it also seems somewhat limited.

    I guess it is down to budget.

    Steve/bluewizard
  10. blacklion

    blacklion Member

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    What kind of outputs does it have? Are they line level RCA red and white? My amp has only line level RCA red and white cable inputs. Cheers!
  11. blacklion

    blacklion Member

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    Is this the same thing as a 3.5mm RCA jack? Pls excuse my ignorance.
  12. KJ Palmer

    KJ Palmer Member

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    No, the 1/4" (6.35mm) jack plug is the larger type used in Hi-Fi etc. If your microphone has a stereo 3.5mm jack, you can easily get a suitable adapter, eg. this one at Amazon, or from Maplins etc. You would need to use the left (Stereo) input for this set-up in the pre-amp you linked to. The right input is for mono mics, or use both inputs for mics with split left/right jacks or 2 mono mics.

    Hope that makes sense.
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  13. blacklion

    blacklion Member

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    Thanks! Can you tell me if pre-amps have line level outputs? I'm still confused how to make the last mile connection to the amp. Cheers!
  14. KJ Palmer

    KJ Palmer Member

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    Hi. Yes, that's really their purpose in life, to take a weak signal, eg. microphone or (unamped) turntable and boost it up to line level.

    By the way, regarding the pre-amp you linked to - though it does it's job, it has no output level control, so if you plugged it straight into the amp, you would need to use your amp's volume control, which may be OK, or may not be ideal. I actually use mine plugged into my MD recording deck (a tape or CD recording deck would do just as well), and use it's input level to control the volume to the amplifier.

    The pre-amps in BlueWizard's post may be better as they have volume controls, and should be better anyway, as they seem more for serious use.
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  15. blacklion

    blacklion Member

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    I looked at the specs and regarding output, here what it said - "2 x professional balanced/unbalanced line output ". Now, for the life of me, I haven't the least clue what balanced and unbalanced outputs are. I'm just thinking about rigging a mike up to the amp for karaoke for the kids:) Now I feel like I need an engineering degree to sort this out:D

    Can you please explain the difference between these balanced and unbalanced outputs or point me somewhere I can learn?

    Also, what kind of cable do I use to connect from these outputs to the line level inputs on my amp? Would this be like a Y mono RCA cable with stereo red and white at the other end?

    I looked up this unit on amazon and read through the specs and previous purchaser comments. Most of the comments had to do with computers and laptops - like people using this unit to hook a guitar to a computer. Does this unit actually work for stereo amps or is it really for computers?

    Thanks for your kind patience!
  16. KJ Palmer

    KJ Palmer Member

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    I'm afraid I don't really know too much about balanced and unbalanced inputs/outputs. Something to do with impedence matching and being able to use long cables.. I think.. Perhaps this info will help explain.

    Like you, I just wanted something to plug my microphone in to feed into my hi-fi, and it seems to work OK. You just need an ordinary stereo RCA cable to connect the pre-amp to your amplifier, the same as you would for connecting your CD player or tuner etc. You could also hook the pre-amp to a computer's line in if you wanted, though most already have a microphone input, so I'm not sure why anyone would want to do that. Well, presumably the output from the pre-amp to computer line-in would be 'cleaner' than from a computer mic input, but the principle is the same whether it's a PC's or hi-fi amp's line input.

    But anyway, this pre-amp is basically for a hi-fi amp and would be suitable for your purpose.
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  17. D.D.D.

    D.D.D. Member

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    BEHRINGER: MIC100
    page 8

    So, with this model you need mic with "big" 6.3mm connector (or adapter 3.5-6.3mm), and adapter/cable for connecting it to your amp, similar to this: http://www.nedis.com/images/products/HQM-239.JPG

    Hope it helps!
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  18. blacklion

    blacklion Member

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    Thanks guys for sharing! I really appreciate.

    I went with Steve's suggestion and ordered the M. Audio Buddy from amazon. Should be here soon.

    AVForums rock!!!
  19. Wally B

    Wally B Member

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    Hi All

    Have been following the above exchange with interest. Question i have, is it possible to safely avoid the mic pre-amp by connecting the mic via a 1/4" jack to 2 x RCA plugs direct into the phono input to utilise the pre-amp there?

    What I did (not realising the left or white socket is the mono input) was to cut one end off a stereo-to-stereo RCA lead, solder together the like polarities then solder these to a mono 1/4" female socket. Mono to mono/stereo! My amp is a 200w RMS Sony TA-FA-3ES and I am running Bose 300w speakers.

    Have tested and got much better volume result through phono versus tuner input but didn't want to arc it up too much for fear of blowing something.

    Does anyone know if running thru Phono input (without Earth) is likely to cause damage please?

    thanks!
  20. Roger Thornhill

    Roger Thornhill Member

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    Yes you can use the Phono input, the gain will be ok but the frquency response will not be suited to microphones.

    Turntable cartridge outputs are not linear and need 'equalising', the Phono inputs on Amps are frequency compensated to ensure a flat frequency response.
  21. BlueWizard

    BlueWizard Well-Known Member

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    Right, you can't use the PHONO for a microphone, but you can use the AUX or TAPE or CD input. However, the volume level is likely to be very low. Having a Mic Pre-amp will bring the output levels up from Mic level to a higher Line level, and will also give you better control over the microphone levels.

    But there is nothing to prevent you from tying to RCA connectors in parallel, then tying that to a 1/4" phone connector for the Mic.

    Steve/bluewizard
  22. Roger Thornhill

    Roger Thornhill Member

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    Right, yes you can, but as i said, the frquency response will be incorrect. The gain will be correct and if frequency response not a problem, then, yes you can use the Phono input. I have done it myself.
  23. BlueWizard

    BlueWizard Well-Known Member

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    Well, you have a point. There is nothing to stop you from using the PHONO input. It will certainly function. I'm mean nothing will blow up or anything like that. But, because of the frequency response and equalization issues you point out, doing so will make is sound like crappola.

    The physical medium of vinyl records demands that the bass, which takes up a lot of room and makes for very wide grooves, needs to be greatly attenuated, and the treble needs to be exaggerated. To get things back to flat when records are played back, the PHONO equalization circuit needs to do just the oppossite; highs are greatly attenuated, and bass is greatly emphasized, thus making the final result Flat.

    So, literally - yes, but functionally - no.

    Steve/bluewizard
    Last edited: Nov 10, 2009
  24. Roger Thornhill

    Roger Thornhill Member

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    I think that's what i said.

    :confused:
  25. Wally B

    Wally B Member

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    Hi all

    Thanks for quick responses. You are all right!

    I have just tried it through phono and yes, plenty of volume but sooo low and bassy that words are indistinguishable, only a bison would pick it up.

    When plugged into aux,tuner, etc it sounds heaps better but even on 10 there's virtually no volume.

    So I guess it's off to the shop to buy a mic pre-amp.

    thanks again, this is a great site!

    cheers
    Wal

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