Adaptor to connect balanced microphones in the line input of sound c

Question

)Many times we need the use of a professional microphone.But in which input of our sound card? Because the balanced signal produced, we need an adapter to connect it in the line input. In my site there is a proposed construction and complete instructions, plans and
photos. Visit my site at URL http://www.eal.gr where you can find the whole article.
2)Request
If you visit my web page and if you have the kindness, leave a comment, be it small about her appearance, how many is easily read, if she is narrow that is to say at width,
if the letters have small size, if the syntax and the spelling they have a lot of errors,
and anything other you do not like, because i do not have experience in the web pages
and my knowledge of English language is limited, thus my any comment is precious
so that i now correct my errors that are the beginning. I am not you to bother with e ? mails because it should you leave your mail address.
?hanks for your attention
Fotios Anagnostou
Message Edited by fotios on -23-20060:6 PM
Message Edited by fotios on -23-2006:03 PM
Message Edited by fotios on -27-20060:05 PM
Message Edited by fotios on -30-200608:42 AM

Answer 1

Dear Jutapa.
While i am occupied with electronics for more from thirty years, my experience in the web pages has age of fifteen days. Thus your comments about the appearance of my site are precious and be compelled to you. Thanks, but i do not understand what means ?IMO?. Also, what means that my site is very hard? Please inform me to correct it. Now the answers in your questions:
) Perhaps you decei'ved from the size of transformer because it is only 50VA (or 50W / 30V = ,66A) and his cost in Greece does not exceed the 8?. Keep in mind always that, the toroidal transformers cost at 70 percent least from the E-shaped transformers. But in any case the total cost of the unit does not exceed the 45?. Surely this cost approaches the cost of the available mini mixing desks in the market. But the sound quality of the unit is comparable only with the high quality professional mixing desks, because the structure of circuit is precisely same with a channel such desk, a thing that appears and only from the supply of +/-8Volts. The phantom power of 8Volts maximum is enough for all modern condenser microphones. There are in the market such type units from famous brands as dbx, bss, apex, rane, symetrix, dda etc. and their price exceeds the 300? as these units are addressed for use in studios.
2) The oscilloscope graphs quoted in the article, believe me it is the better method of estimate the unit ? especially the square wave response ? because they express her transient character as this is most important for a designer of electronic circuits while the usual graphs of THD+Noise are offered more for consumers. If study my article, you see somewhere my explanation about this. Anyway, the T. I.M. factor of a closed loop circuit (Transient Intermodulation Distortion) expresses the possibility of it to manage the harder signals ? this is the response ?speed? to fast transients ? without oscillations. In the software of my oscilloscope included and a FFT analyzer to give the THD but i do not use it because by default today yet the chipper units in the market has very low THD due to the evolved modern electronic parts. The same is also in effect for the noise produced by the circuit himself. As it is known, the fundamental Johnson noise or thermal noise from metal film resistors is too little and the NE5532 ? NE5534 produce noise of certain nanovolts.
3) About the EIN (Ein) - or the sensitivity of input so that us understand also the other ? reported in the schematic diagram in dBV. Why not in dBm? Because from habit i do not want to take into account the input impedance ? as get used almost all the designers of electronic circuits ? and in this way the logarithmic expression of the minimum gain of input it is given by the use of dBV (reference ratio to Vrms). Let to calculate the input sensitivity in dBm as you prefer: The input impedance of the balanced input is: Zin = R2+R3 = 20 K? approximately. The total gain of input presented at the output of the subtructer U2A and is: V = V3-V2. The minimum gain of the first stage composed by the two non inverting UA and UB with VR5 turned full CCW is: Av = +[2X(R4+R3)/VR5+R5] = +[2X000/47220] = +0,466 = ,466. In dBm the reference is 0,775Vrms thus Av = ,466X0,775 = ,36Vrms. And because the output of U2A is twice his inputs then: V = 2X,36 = 2,272 Vrms and the sensitivity in dBm is: Ein = 20 X log(2,272 / 0,775) = 9,34 dBm. And if we take the maximum gain of the first stage - by turning VR5 full CW - of 0 with the same equations in dBm, results: 46 dBm
Best regards
FotiosMessage Edited by fotios on -30-200608:43 AM