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Old 15th December 2009, 10:37 AM   #1
oublie is offline oublie  United Kingdom
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Default 2 ohm stable low power amp

Hi folks,

I'll keep this simple. I'm building line arrays, 21 4" mids crossing to 7' electrostatic tweeters around 1500hz. I need some low power 2 ohm stable amps as i want to parrallel 3 of the mids (they are 6 ohm) anyone know where i can get something like this at a reasonable price? Every amp i've seen so far is high power and usually car audio.

Is there a class D that would do this?

were talking about quite a few amps.
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Old 15th December 2009, 11:25 AM   #2
Khron is offline Khron  Romania
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A quick browse through Texas Instruments' offer showed THIS chip as having a 2-ohm minimum load, described as "automotive amplifier". This one has single-ended inputs, and its brother (TAS5424A) has differential inputs. That is, if you're willing to go "full DIY"

Hmmm... On a second look, these seem to be I2C controlled, so that might be a disadvantage. A more detailed browse through the datasheet might show if it's possible or not to use these chips on their own.

Good luck with the project,
Chris

Last edited by Khron; 15th December 2009 at 11:35 AM.
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Old 15th December 2009, 12:21 PM   #3
oublie is offline oublie  United Kingdom
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Thanks Chris,

this is probably exactly what i need but full diy is a bit out of my league.

I was thinking along the lines of something like the sure type modules but with 2 ohm stability.

I'll be running active pc crossovers with 7 of these amps in total this will allow me to roll off the outer drivers from 0 db down to -12 db at the outer edges.
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Old 15th December 2009, 12:28 PM   #4
AndrewT is offline AndrewT  Scotland
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would 21 chipamps be out of the question? 15W to 50W into 6ohm from a single PSU and transformer per channel..
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Old 15th December 2009, 01:29 PM   #5
oublie is offline oublie  United Kingdom
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Hi Andrew,

Just a little bit on the pricey side for 21 amps.

I did look at the little 2w sure amps

2watt D-Class mono audio amplifier board EUA2005, 2pcs_Audio Amplifier Boards_Audio Amplifier and other Audio Boards_RF and Audio, Video Equipments_Sure Electronics' Webstore

but not sure of the quality of these.

Also looked at these

2*8W @ 8ohm/4ohm, MPS7720 D-class Audio Amplifier Board_Audio Amplifier Boards_Audio Amplifier and other Audio Boards_RF and Audio, Video Equipments_Sure Electronics' Webstore


but once again not sure on the quality of sound - has anyone tried them.

Please bear in mind that with 21 driver per side i'm not going to be putting much power through them. The drivers themselves are rated for 75w rms but i doubt if i'll ever push them past 1 w

I wonder if at the power level i'll be using them the 2x15w would do 3ohm? i.e 2 drivers parallel which would mean 11 amplifiers?
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Old 15th December 2009, 08:47 PM   #6
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Interesting project - What's your upper bound on price?
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Old 16th December 2009, 09:31 AM   #7
oublie is offline oublie  United Kingdom
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Quote:
Originally Posted by kristleifur View Post
Interesting project - What's your upper bound on price?
to start with i probably dont want to go over about 200 for amps bearing in mind i also have to get a decent amp to drive the electrostatic tweeter panels and transformer and ill be driving 2 sub/ infra bass speakers probaly inverted tapped horns. - i've a pair of dayton dvc 15" sub here for that purpose and have my eye on one of the new cerwin vega 2800w amps for sub duties.

eventually once all the prototyping etc is done ill move up to better amplification but i don't like the idea of running the speakers series and parrallel to a single amp - i'd like something a little more refined particularly since it will allow a lot more control while testing.

crossover duties are through the pc - currently running a pair of soundblaster audigy zs cards with the kx project drivers but one of these is being swapped out for an autotrax card thats on the way.

i'll be running extremely steep filters with phase control and convolution per per speaker bank.

So far the single prototype sounds great but i'm still tweaking baffle arangement.

btw these are open baffle with the curved esl tweeter acting as one side of the baffle in a half torus arangement.

lots of work still to be done.
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Old 16th December 2009, 10:55 AM   #8
tinitus is offline tinitus  Europe
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If your speaker design ends at 2ohm, you need a bit more than just 2ohm stable amps
A 2ohm stable amp will do good at driving 3-4ohm
Or bridged to drive minimum of 4ohm

What you suggest is like driving 8ohm speakers that in reality are 6ohm, like many speakers, and use amps that cant cope with 4ohm but only 8ohm stable

Many 150-200watt AB amp designs driven with lower voltage to make say 50watt will do what you want
With big heatsinks

You might be able to do the same with tough ClassD amps
Like say a 200-300watt 2ohm stable amp design, but built to do about 60-80watt, and I think you might be safe

Last edited by tinitus; 16th December 2009 at 11:05 AM.
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Old 16th December 2009, 11:11 AM   #9
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What's wrong with using a single amplifier for all the drivers?
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Old 16th December 2009, 11:44 AM   #10
tinitus is offline tinitus  Europe
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Quote:
Originally Posted by theAnonymous1 View Post
What's wrong with using a single amplifier for all the drivers?
Low impedance preamp load ?
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