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Old 22nd January 2013, 02:32 PM   #51
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In that case, here's an original =>
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Old 22nd January 2013, 02:59 PM   #52
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Oh MY!
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Old 22nd January 2013, 05:49 PM   #53
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Hehe, When I think twice, seems that, even if we had a bag full of Jfets, few among us would have the time and patience to solder, solder and solder...what comes to mind is a prefabricated board with 2000 smd jfets each. Then you could go and build amps with 1, 2, ...10 boards..Mega beast bridge/parallel with 20000 jfets. Fiction? MUAHAHA....
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Old 22nd January 2013, 05:52 PM   #54
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Here's an interesting and similar build:

SoundStageXtreme.com | UltraAudio.com | Blue Circle Audio NSL Stereo Amplifier

Using op-amps
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Old 22nd January 2013, 06:09 PM   #55
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I assembled a pair of Mr Self's 5532 Opamplifiers, amusing, but just that.

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Fiction?
Oldy, but with SMD, it can get even prettier.
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Old 22nd January 2013, 06:22 PM   #56
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I built a headphone amp using the OPA2134PA which sounds amazing when paired with my Sennheiser HD280, so would paralleling a load of these produce the same when paired with some full size speakers?

What would be the best way to safely parallel these op-amps? Anyone got an idea component values and how much each you could drive each op-amp? You can get them for as little as $1 each if you buy from aliexpress.com: 10PCS/LOT OPA2134PA OPA2134P OPA2134 2134 TI/BB DIP 8-in Integrated Circuits from Electronic Components & Supplies on Aliexpress.com, minimum order is 10, but as loads are needed, no problem
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Old 22nd January 2013, 06:23 PM   #57
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I tihnk i like it better than the tires
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Old 22nd January 2013, 06:55 PM   #58
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OK. I found this circuit about paralleling op-amps:

Increase output current of the op-amp IC LM324 in 85mA size | Eleccircuit.com

OK, do my calculations work:

Now, if we had say a +/-18V supply, our input pk/pk was 2Vrms, could we set up each op amp with a gain of say 12 and use a resistor on the output of each to limit the current and parallel them all together? To limit the current to 25mA, we could have an output resistor on each op-amp of (18v / 0.025A) = 720ohms.

If you want to power a 4ohm speaker:

Power = I² R, so I² = P / R, so I = sqRoot (P / R), to get a 20W rms, we would need sqRoot (20 / 4) = 2.236A

Total current required is 2.23 amps, each op-amp will give us 0.025A, so 2.236 / 0.025 = 89.44 (45 x dual op-amps) per channel.

Would this work, and do the calculations look right?
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Old 22nd January 2013, 07:44 PM   #59
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Just re-read the data sheet. The OPA2134PA can give +/- 35mA at the output, so we could safely use it at 30mA, so you could 560ohm resistors on each op-amp output, giving you 18 / 560 = 32mA. If you used 50 dual op amps per channel, you could get a max of 3.5A (100 op-amps in parallel), that would be 3.5² x 4 (P = I² R) = 49W into 4ohm load.

Any thoughts?
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Old 22nd January 2013, 07:49 PM   #60
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Quote:
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I tihnk i like it better than the tires
I'm sure that I like tires better

Jaccolina , certainly too ; speaking of gummi and latex things .......
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