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haelius 12th March 2011 01:47 AM

The Active Studio Speakers Project
 
hello

recently i have discovered the wonders of DIY Audio, and im assembling parts to build some monitor speakers, since i been to a friends house and experienced some good Studio monitors (Roland MA15), my home cinema solution doenst have what it takes any more....

What i have so far besides good will and no money... lol

  • 2x Clarion SRF 1381 (2 Way @ 4ohm - it says 90W Music peak)
  • 2 bookshelf speakers EDIFIER USB
  • Creative Inspire 5100 set without transformer or Volume control (so i cant power on the Board
- 20W SW and crappy 8W*5 Speakers @ 8 ohm
- opened the sub and the board has a TDA7273a and a TDA8510J
  • Hercules XPS 2.1 (burn out power supply)
- 15W SW and 8W*2 @ 6ohm i think

  • A chinese Home Cinema 5.1 set, with DVD with a amplifier to a sub and the 5 sattelites (25W @3ohm sub and 5*15W@4ohm)


WHAT I WANT
Like i said, 2 good Active speakers, pref with volume and bass control, that i can take off the 5.1 creative board, and i am thinking of using the chips from the creative board (the TDA7273a and/or TDA8510J) to amplify the speakers

QUESTIONS

- Power Source
I have a 500W computer based PS, can it power 2 DIY for the speakers??

- anyone can kindly get some schemes to these chips, searched but couldnt find any



best regards and tks
Haelius

haelius 12th March 2011 02:15 AM

another question i have....


since the Edifier USB speakers are digital, i was wondering if there is any way to put the clarion drivers on it, with a more powerfull amp before the drivers, cause i think they are like 1.5W, but yet they deliver a good clean sound, and if i use the lineout from the PC to the DVD line in, its analog (isnt there loss of sound?)

PS... im a newbie at this forgive me for any mistakes lol


best regards
Haelius

haelius 12th March 2011 02:18 AM

2 Attachment(s)
posting some PDF that i had here

Arty 13th March 2011 03:48 PM

the 8510j chip is your friend i guess.
chematics are in the PDF you have just linkt.
page 11 shows you how to do it.
The chip has total of 4 amplifiers in it.
the chematic shows how to do bridged mode, and single ended mode.
You need to make both amp pairs to be bridged.
The computer psu can be modded to power this thing.
It may or just may NOT work, depends on the quality of the psu.
switch on voltage spike can kill this chip.
Dummy load and a delayd relay may solve this part of the problem.

Simple Tone Control

this is maybe something you can manage to do.


but honestly, if i was you, i would "just" save up some money and order a kit tda2050 stereo amp, a decent toroid, and a kit lm1036 tone controll board.
should give the clean sound you want, tone controlls, and in the end at least its something that is fun, and usefull/worth to have.

haelius 14th March 2011 09:27 AM

i know that is the best option ofc, but like i said, cant spend money on this now.... so these chips will have to do for experiments....


currently its kinda ok, i made some enclosures for the Clarion speakers and hooked them to the DVD, and at least they sound better than the original speakers that came with the DVD... although i think it has like 20W and the speakers are like 90W... so hasnt got the juice to power the drivers decently but at least it sounds better than the original ones...


Anyone knows how to "mod" a power supply from the PC to be able to power these wonderfull chips? its a good stable 500W so i think thats a good option...

pmbrunelle 14th March 2011 06:16 PM

Even if it's 500W total, much of that will be for the +3.3V and +5V rails, useless an 8 ohm audio amplifier.

There should be a +12V output with considerable current capacity, and *IF* there's a -12V output, it will probably be limited to less than 1 amp.

So you're stuck with a 12V single supply amplifier. Might be okay for quiet listening...

I would just hold out for something better. Ultimately, trying to use the wrong parts for the application ends up costing more money.

Arty 14th March 2011 08:39 PM

one can fool the sense circuits so the psu provdes more than +12 volts.
I blew a few psu with this trick in my life.
Thing is, even if you tweek it by fooling the voltage sense, you can not get over 15 volts . Even that is not safe. The elco caps are rated to 16 volts, so you just end up blowing those up.

You can power the tda 8510J chip with the psu, whitout modding it.
on an 8 ohm load you might get something close to 8 watts or so.
There is no way it will be any better.
And still you risk the switch on surge killing the poor ic.

haelius 15th March 2011 05:39 PM

correct me if im wrong...

  • AMP (8510J) according to ohms law

P = E 2 / R

so if i have 12V at 4ohms (like the clarion drivers) i will have 36W

  • on the power supply it has 4.5 amps on 12V so again on ohms law

P = I 2 x R 4.5amps x 4ohms = 81 W


so i think the power supply will give enough power


even so the amp gives only 2 x 13W on 2 channels

"TDA8510J - 26 W BTL and 2 x 13 W SE power amplifiers"

right??

Arty 16th March 2011 07:53 PM

You are right and wrong.
Yess, the formula is correct for power output.
But if he is supplying an amplifier with 12 V rails, you will not get a 12V output.
Prehaps I would say it will yield something closer to 10 volts.
Drivers are not pure Ohmic resistors. They have reactance/impedance not resistance.
Even if we say it is an ohmic load, the values change a bit since the output swing is less then the amplifier supply voltage.

P= U^2/R
P= 10^2 / 4
so.. output would be less than 25 watts into 4 ohms.
Maybe if you mesure with a square wave you get that 26 watts with a distorsion so horrid I can not describe.
With 8 ohm load..
something around 12 watts or so.
With acceptible distorsion figures the 8 or so watts I wrote can be a good estimated value.

Even so, 8 watts can be LOUD.
Depends on:
Speaker efficiency, and listening room size, listening distance, listener's personal taste.

The thing is, an ATX psu can with ease power an amp like that, and that amp is a good start. You can find hudreds of horrid commerical amplifiers with far worse specs.
(like chepoo HT amps. And some say there is NO devil. )

Question is the turn on surge of the given PC psu. If it does not kill the chip, then its all just fine.

Those chips exsist for a good reason. They are not highest grade, nor the worse You can get.

pmbrunelle 17th March 2011 02:30 AM

Note that you'll only be able to get 10V across the driver with a bridged amplifier.

Otherwise, you'll have +5V / -5V swing with a single ended configuation.

And then that 5V RMS would only be for a square wave.

If we want to amplify a sine wave, then 5V peak sets the sine wave amplitude to 5V / sqrt (2) = 3.54V RMS.

3.54V RMS into an 8 ohm resistor is 625 mW, or 1250 mW for a 4 ohm resistor.


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