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 Post subject: Re: Resistor values
PostPosted: Wed Jul 29, 2009 8:51 pm 
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Hi.

Whatever colour codes showing, even they looked the same, always try to measure to make sure.

That's I always do before I soldering them on to make they all get the same closest tolerance.This is important for stereo channel matching.

cheap-Jack

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 Post subject: Re: Resistor values
PostPosted: Fri Jul 31, 2009 7:44 am 
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Location: So. California
cheapJack wrote:
Whatever colour codes showing, even they looked the same, always try to measure to make sure.
Dude, you didn't read over this thread carefully. Elso already raised this point, and I responded...


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 Post subject: Re: Resistor values
PostPosted: Fri Jul 31, 2009 7:52 am 
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hollowman wrote:
I don't have this PCB -- I'm trying to work (reverse engineer the ckt!) from the image posted on a web site.
Can you charitable folks help me out a bit and look over this schema hack of the Tracking Pre-regulator. Figure many of you can o'scope it in your head with a quick glance.
Not sure of all the cap values, but tell me if I'm in the ballpark. Thanks!
(P.S. Sorry it's messy. I lazily hacked a figure from the National datasheet!)
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 Post subject: Re: Resistor values
PostPosted: Fri Jul 31, 2009 8:18 am 
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hollow_man wrote:
TragicallyDistorted wrote:
Well, it took me a minute that I"ll never get back but wtf... you'll kick yourself for this one.

Answer: They're all correct. You screwed your interpretation of the Leon Audio Company Resistor Colour Code Chart, likely because they were knobs and changed it ever so slightly from what you'd expect to see or are familiar with... leading one to assume. It's like when you read your mind ignores or takes for granted a large number of things so you end up blind to them.

Look closely at the "multiplier" column, they dumbed it down to "number of zeros".
Yeah, you're right. Big-time egg on my face here!

Too late to back out of my "tragic distortion" now, I suppose, but I'm used to 1K being brn-blk-red, not brn-blk-blk-brn.
BTW, I normally use this tool to confirm resistors (which is Google's #1 for "resistor calculator"):
http://www.dannyg.com/examples/res2/resistor.htm
Yeah, yeah...
"Failure is not an option."
"In space, no one can hear you scream".
"In the game of life, the teacher does not grade on a curve."
etc.


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 Post subject: Re: Resistor values
PostPosted: Fri Jul 31, 2009 10:25 am 
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Location: Scottish Borders
I don't understand the need for C3.
I would like to see a bit more voltage drop across the second regulator.
National using 1k+1k gives only 2.5V.
Try 1k+2k for 3.7V if you have the overhead.

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 Post subject: Re: Resistor values
PostPosted: Fri Jul 31, 2009 11:39 am 
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andrewt wrote:
I don't understand the need for C3.
I would like to see a bit more voltage drop across the second regulator.
National using 1k+1k gives only 2.5V.
Try 1k+2k for 3.7V if you have the overhead.
You're right about the voltage drop across reg 1, but that's not National -- TTBOMK, that's what the commercialized product (Avondale, shown in prev. post), which I'm reverse-engineering, is using. The National datasheet ckt uses diff. values for R1 and R2.
Both your observations, including reason for C3, are discussed by Martin Clark on the acoustica.org.uk site:
Quote:
Replacing both the pre-regs voltage set resistors with 1k items will set the voltage across the second reg at 2.5v, quite enough for most purposes. Add the Cadj cap [C3 = 10uF, discussed in PFM forum] across the lower voltage-set resistor - it still makes an audible difference (i.e this cap is connected between the 1st regs ADJ pin and the OUTPUT of the second reg.)


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