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yay, now I can get help making my amp

post #1 of 21
6/20/01 at 8:14pm
Thread Starter 
I'm going to build a 47 amp, will I need four opamps? (By the way, I plan to use OPA2604's)

I'll post more questions as I remember them.
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post #2 of 21
6/20/01 at 9:35pm
4 opamps or 2 dual opamps
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post #3 of 21
6/20/01 at 10:06pm
what skip said (just blurtin "I'm here")
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post #4 of 21
6/20/01 at 10:08pm
Apheared: why did you call the 47 a dual output amp?
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post #5 of 21
6/20/01 at 10:09pm
Thread Starter 
damn, this is getting spendy! I've already wasted $40 on amp stuff. This thing had better sound good!

Hey, can someone explain resistor color code to me?
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post #6 of 21
6/20/01 at 10:26pm
$50-80 is average, dude. that's what it costs, sorry. You can get by cheaper of course; but if you're starting from scratch, need tools, have no components, and have to mail order from multiple places... $50 is about the cheapest you can pull it off.

hongda, dual output as in parallel output... the thing functions fine with just one, it's called a cmoy pocket amp! It just functions better with two. (specially for low-ohm things like Grados) NOT as in two individual outputs.
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post #7 of 21
6/20/01 at 11:00pm
Quote:
Originally posted by Neruda
damn, this is getting spendy! I've already wasted $40 on amp stuff. This thing had better sound good!

Hey, can someone explain resistor color code to me?
Neruda,

JMT built several amps for me, and the cost was always between $50 and $55 or thereabouts. Of course, if someone's buidling me an amp, I always make sure to throw in a little something extra.
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post #8 of 21
6/20/01 at 11:30pm
Thread Starter 
I know apheared, I just wish I had enough money to get everything. well, it's my own damn fault, I wasted the last of my money on a CD . Looks like the big project is gunna be postponed until I can pick up another $20, which shouldn't take too long. (damn, I need a job.)
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post #9 of 21
6/21/01 at 5:25am
Neruda,
Apheared's amp has parallel output opamps. Don't trust the resistor color codes on the RS metal film resistors. Email me if you need help with this. You really ned to check them with a meter.
My first step was to layout the parts locations. I think these amps are easier to make with dual opamps. Power supply wiring is easier with duals.
Dan
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post #10 of 21
6/21/01 at 10:24am
Yeah, glad to see this forum is here to hold us over for two weeks!
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post #11 of 21
6/21/01 at 12:22pm

Resistor color code

Mnemonic\color\value\Multiplier

Bad-----Black---- 0--------.0
Boys ---Brown----1---------0
Rape----Red------2--------00
Our-----Orange---3-------000
Young--Yellow----4-------0000
Girls----Green---5--------00000
But-----Blue-----6-------000000
Violet --Violet----7------0000000
Gives---Grey------8-----00000000
Willingly--White---9----000000000


Precision resistors have a 5th ring thus a brown\black\black\brown\brown resistor would be :1.000 ohms


If I made an error please forgive me, this is off the top of my head. I can look it up later.

Peace,
Andrew
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post #12 of 21
6/21/01 at 4:53pm
Thread Starter 
I should probably just get a multimeter, I've been checking a few resistors and I think I'm getting it wrong. Doesn't matter though, I can't start my amp for a bit longer.
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post #13 of 21
6/22/01 at 12:28am
There's usually also one additional ring, to mark the resistor's tolerance. For example, red is 2%, brown is 1%. It's unlikely you'll get better than that, and if you get worse it's probably a carbon film resistor, not a metal film one. This precision ring is usually separated from the others, on the very edge of resistor, although it's sometimes hard to judge.

Very high quality resistors usually have numeric markings for both value and tolerance.
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post #14 of 21
6/22/01 at 1:36am
Get a multimeter! Do not use the resistor codes. They are confusing and hard to see clearly. Besides a good multimeter costs around $20 and is a necessity for troubleshooting.
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post #15 of 21
6/22/01 at 1:43am
good to see you chu!
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