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Old 22nd April 2003, 11:05 AM   #31
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Dear Peter,

Nice work you are doing on the gainclones. You have inspired other members also. My question is if the gainclone can drive loudspeakers with resistance about 2 Ohms. I am building the Scan Speak Reference Monitors and was wondering if I could use the Gainclones as amplifiers or an Aleph30.

Thanks
George
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Old 22nd April 2003, 12:06 PM   #32
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Quote:
Originally posted by gchrist
My question is if the gainclone can drive loudspeakers with resistance about 2 Ohms.
You quite probably can, if you lower your voltage or parallel two or more chips on each channel to handle more current.

If you parallel chips using a +/-24v supply you may get good results with those speakers.

In any case 2 ohms is a tough load for any amp. Let's hope you are not paralleling speakers that are already 4 ohms, because that's nominal and on some cases can dip lower, particularly if they are subwoofers.


Carlos
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Old 22nd April 2003, 12:22 PM   #33
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For 2R loads, I'd advice you to use maximum 20V DC rails, with a LM3875, this would give you a little more than 40W

or, have a look at the datasheet, they show how to bridge them to work nicely with 2R loads
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Old 22nd April 2003, 10:21 PM   #34
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If I use the OPA541... do I need the current limit resistor? I plan to make PC boards for this... so, I am limited on room. A big 5 or 10W resistor just won't fit. So, can I just take the current limit pin and connect it directly to the output pin of the amp chip?
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Old 22nd April 2003, 10:50 PM   #35
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Quote:
Originally posted by trespasser_guy
If I use the OPA541... do I need the current limit resistor?
So, can I just take the current limit pin and connect it directly to the output pin of the amp chip?
It certainly works that way with the other BB power opamps, but check the data sheet just in case

http://focus.ti.com/docs/prod/folders/print/opa541.html

(edit) Sorry, on the other chips the Ilim pin is connected to V-
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Old 22nd April 2003, 11:13 PM   #36
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I just spent the past 3 hours staring at the data sheet... I honestly have no clue whether it is necessary or not. I mean... having something there (a .01 ohm resistor) seems to be pointless. .01 ohms! Why not just connect it straight to the output pin. That is just the way I see it... But, I don't really know. I would rather not use it... but if I don't order a resistor for it, then I won't have one if I do need it, but if I don't need it, I just wasted money... I am on a VERY strict budget, where any mistake means the difference in being able to do the project or not.

I never build anything because I am afraid it won't work... because I really don't know. This project is stressing me out... I may abandon it soon as well.
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Old 22nd April 2003, 11:23 PM   #37
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A 0.01 ohm resistor should be very easy (and exact) to make diy. But i fear if you soldier it to something the value will change significantly.

I would not order one.

why not 549?
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Old 22nd April 2003, 11:24 PM   #38
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Hey mate, chill!

Why don't you try the 549 or 548 chips, they both work without the limiting resistor, I know that for a fact as I have built GCs with them both!

They are also a bit easier to mount than the T03 packages, and the only thing you loose on is the slightly lower Vmax, at 60V rather than 80V.
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Old 23rd April 2003, 12:32 AM   #39
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Sorry about that... I get kinda stressed when I cannot understand...

EDIT: Wait... I just read further in the data sheet and can see what to do with the REF and Ilm pins...

What do I do with the E/S pin? Just leave it unconnected?

And the biggest question of all: How do these chips sound? Do they sound like Burr-Browns, or are they dead, lifeless, ect.
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Old 23rd April 2003, 01:01 AM   #40
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No problemss mate

Yes, you can just ignore the E/S pin unless you want to implement a Mute function.

Hmm, stand by for subjective comments

IMHO the OPAs sound better than the LMs. Bass is better, the brittleness at the top end is gone, and the sound in general seems more accurate. They certainly don't sound cold.

However now we get really subjective... Peter Daniel agrees with all the above observations, but he prefers the LM chips, so it all comes down to personal taste in the end!

(note- neither of us has done blind testing or objective measurements)
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