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-   -   4db output from -15db professional audio from user, amplifer help please (http://www.diyaudio.com/forums/solid-state/25036-4db-output-15db-professional-audio-user-amplifer-help-please.html)

priscared 30th December 2003 01:16 PM

4db output from -15db professional audio from user, amplifer help please
 
Gday
I want to obtain a 4db output from a normal soundcard(about -15db or something) Does anyone know how to do this, and cheaply. I am on a tight budget and i didnt even know until two days ago that pro equipment ran at 4db, now i have spent $212au on a power amp i find i need to buy a mixer or something. Please help.
Daniel

Bo Hansén 3rd January 2004 02:14 AM

Hi Daniel,

I think it is -10dB out from your soundcard and in this case it´s 14dB up to get +4db out.

There are a lot of semipro to pro level interface on the market in varying price range, but one nice I have use a lot are Radio Design Labs "flat-pak range" type: FB-UBC2 unbalanced to balanced converter (input RCA connectors and output XLR connectors) and have adjustable gain from -5 to +10 dB balanced output in 600 ohms.

I think you can get it from the mostly pro-audio dealers.

If you have audioelectronics as a hobby you can easy build a own, tell me if you want some tips for this.

-Bo Hansén, Gothenburg, Sweden

priscared 3rd January 2004 02:24 AM

reply -
 
Yes that would be very good, i found that i had a yamaha souncard lying around, but it is pretty lousy although it does have a strong output. The amp i have got takes XLR sockets unbalanced. SO id need a converter from RCA to XLR (or that large headphone socket) but it needs to be unbalanced. if you could send me any cicuits of how to do this thatd be great!!
Thanks
Daniel

priscared 3rd January 2004 02:32 AM

i had a look at the product
 
Input impedance: 10 kOhm
Input configuration: Unbalanced
Output impedance: 150 Ohm balanced, drives 600 Ohm or 10 kOhm lines
Output configuration: Balanced or unbalanced - - - wow!!!
Frequency Response: 20 Hz to 40 kHz (+/- 0.25 dB)

One of these would be great, however i betcha itd cost an arm and a leg, if you know how to buil one anything like this id love to know.
Thanks
Daniel

priscared 3rd January 2004 02:48 AM

i had a look at the product
 
Input impedance: 10 kOhm
Input configuration: Unbalanced
Output impedance: 150 Ohm balanced, drives 600 Ohm or 10 kOhm lines
Output configuration: Balanced or unbalanced - - - wow!!!
Frequency Response: 20 Hz to 40 kHz (+/- 0.25 dB)

One of these would be great, however i betcha itd cost an arm and a leg, if you know how to buil one anything like this id love to know.
Thanks
Daniel

usekgb 3rd January 2004 04:30 AM

Here is an RDL product that already has the I/O jacks on it: RU-LA2D This is a little bit more money than the Flat-Pack, but it does have the jacks. This is a great sounding piece. If you need to do this on a smaller budget, try the Ebtech : LLS-2 .This still does a decent job and won't break the bank.

If you are handy with electronics, you can easily build a basic circuit around the BB DRV134 to balance your circuit and feed your amplifier.

Cheers,
Zach

Centauri 3rd January 2004 07:41 AM

Daniel,

What soundcard do you have ? - quite a lot of cards can get this sort of level (Soundblaster etc). However, changing a few resistors on the card could very well do the job.

Also, what power amp have you got? - some use pin3 hot on the XLR, whilst others use pin 2

Cheers

dhaen 3rd January 2004 10:10 AM

Remember that +4dBu / +4dBm is the operating level. Any circuitry you use should have a further 20dB of headroom.
This means you must buy a professional interface of some sort, or make one.
The suggestion by Usekgb of the DRV143 is a good one. You'll need +&- 18v supply rails at least. No non-prof sound card will be able to reach these levels.
You should be able to "****" the feedback of the 143 to get the gain you need. It may not keep all elements of it's exemplary spec, but will be well useable.

usekgb 3rd January 2004 03:25 PM

You could even put an op-amp before the DRV134 to get a little bit of gain. Also, when you balance a signal, you are actually sending two signals, thus doubling the voltage at the receiving end.

Also, for the most part, Pin 2 will be hot. That is the industry standard. There are still a few pro sound companie that use pin 1 as hot (what a pain!), but pin 2 hot is the standrd.

Cheers,
Zach

moamps 3rd January 2004 05:08 PM

2 Attachment(s)
one low budget example


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