[3 Channel Spectrum Analyzer - question]

I got the sockets for the 2 CI's. Now another question before I can peacefuly begin asembling...

Can I use the power suply of my computer to power the circuit? 

I mean the cable which powers the harddisk, that type of cable. I have read the 4 "pins" are 5V Null Null 12V . But somebody told me that the voltage is not quite 12V and keeps fluctuating through 13 V .

Is that a problem for the op amps ???

Andrei

[3 Channel Spectrum Analyzer - question]

After a few hours of searching the internet I have discovered that this BM3900 has no datasheet or its datasheet can't be found with the most know search engines. All I could find, relevant, is this :

http://www.inginerie.protectia-mediului.ro/engineering/electronics/sale/ic.htm

IPRS Baneasa is a company from Romania. I hope I will find some info about this BM3900 and hopefully that it's as good as the original thing.
I'll be back with more questions after I solve this!

Thanks for all until now,
Andrei

[3 Channel Spectrum Analyzer - question]

I found an equivalent for the LM3900 at an electronics shop  - BM3900 . I hope this will work just as good as the LM3900. And I've also got the AN6884's.

[3 Channel Spectrum Analyzer - question]

      Ok...I think I should start with this : Thanks for looking up for that opamps, audioguru, but even there is a big problem and that is that I don't live anywhere near America. I live in Europe,Romania. And from what I've seen by checking a few electronics shops in the city, what you said about the AN6884 does not seem to be true. I had no problems finding a AN6884 but about the LM3915 and LM3900 I can't say the same thing. The only posibily of purchasing them is by making a special order and therefore the components would be imported from ...I don't know, I think Germany or maybe Hungary as being more closer to Romania.

  So my question this time is :

1. Using a LM3900 and a AN6884, for led control, would make the project to be put in action as in realised ? I don't think that finding the rezistors and capacitors would be a problem.
2. By using a LM3915 would I have to use the AN6884 too ?

Could you clear these things to my knowledge please,because right now I am kind of confused and because of the fact that I would have to order a LM39xx as I said before, if I don't get the right one things could go off the line.
Thaks again for all this info and I hope that my future questions will find their answers with you

Andrei

[3 Channel Spectrum Analyzer - question]

http://www.electronics-lab.com/projects/audio/037/index.html
- here is the project.
It really hit me when I read your reply and fopund out about the problem with the schematic. I have another question related to this project since I am still willing to go on constructing something like this :

1. Can  the circuit be modified so that it will work properly ?
2. Can this be donne without using a LM3900 ? The AN6884 could remain for ease of construction but I'm having a hard time finding a LM3900 on the local market, so I would have to order it if I use it wich involves quite a lot of lost time waiting.
3. If all the above, the proper schematic  and elimination of the LM3900, would be made , the power suply used could still be 12 V ?

Thank you for your time and if somebody if willing to help me build this thing I will forever be greatfull as it would be start of my education in engineering.

Andrei 

[3 Channel Spectrum Analyzer - question]

      I am new to electronics and I'm also in first degree at a engineering university. I have been requested to do a project of my choice for a class that I study - Electronic circuits and components.  I was very, very happy when I found a schematic on exactly the thing I desire to do - the 3 channel spectrum analyzer. I don't have any technical background or technical experience but I'm willing to learn some of the basics, and not only, in electronics through this project.
      Now...I have found certain schematics for a single VU meter but I thought that by making individual Vu meters for every channel I also had to make filters to separate the frequencies of the audio signal. But the most easiest to do project involved using a LM3915 for the VU meter, and I couldn't find any on the local market. Anyway...


        My only clear questions , for the moment, are :
1. The  U1A, U1B, U1C, U1D ,in the schematic, are they all LM3900  ?
2. Can I get intouch with the person who posted this project, since I am almost sure I will come up with more question related to the construction of the project?

That was all , thanks for the atention and I'm sorry for the spelling mistakes but english is still my second language and if I said something that was totally rubish, technicaly speaking, please let me know and please bear with me .

Andrei Kiss