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Old 12th July 2012, 01:36 AM   #591
Salas is offline Salas  Greece
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You could get a couple of FG 3300uF/25V for now that I saw in stock, until deep August dispatch for KA?
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Old 12th July 2012, 05:07 AM   #592
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Just FYI, I used Panasonic FC 4700 uF 25V, and am happy with the result. About half the cost of the Nichicons, but many folks like the Nichicons in general. A higher-voltage part is usually a good idea, especially for electrolytic caps. At risk of heresy, I don't think the brand/type of filter caps makes a significant difference; but then, I guess if I really believed that I wouldn't have bought the Panasonic FC's (there are cheaper capacitors available). So that raises the question: What are the measurable properties of a capacitor that make it "good" in that application? I would assume that low ESR, low DF, and high temp rating are all good things to guide a choice. Other than dubious listening tests, are there any other objective criteria for selecting filter caps? (yeah, I know there are whole threads dedicated to that discussion)
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Old 12th July 2012, 08:21 AM   #593
Salas is offline Salas  Greece
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The lower the DF & ESR, the lower high frequency impedance the better are the objective criteria. The smoothness of the paper's fibers used in the winding and some properties that the manufacturers know in the chemical its soaked with are their ''claims'' area. DNM (BHC) had slits on the foil and had some more objective explanations about eddy currents in their literature. http://www.youtube.com/watch?v=kU6NSh7hr7Q
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Old 22nd July 2012, 11:56 PM   #594
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Salas,
Just finished a mesmerize board that i am using for input to active XO and for some reason i am having trouble with delay circuit. The regulator is not putting out 12V. Is bad transistor most likely culprit. Replaced 7912 and nothing.
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Old 23rd July 2012, 12:00 AM   #595
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7912 is a negative 12V regulator.
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Old 23rd July 2012, 12:04 AM   #596
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Typo.
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Old 23rd July 2012, 12:12 AM   #597
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aha so it is 7812
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Old 23rd July 2012, 12:39 AM   #598
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Bc550 was bad.
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Old 23rd July 2012, 05:35 PM   #599
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Default My first Preamp

Just finished a Mesmerize (my first preamp).

Getting the following voltages:
AC: 14.04 - 0 - 14.03
DC (rectified): +18.42 / -18.52

over current-setting resistors:
1.932 V (neg) | 1.812 V (pos)

out (of PSU part):
+10.270 V | -9.676

output (DC offset):
+0.5 mV (L) | 0.0 mV (R)

Very happy with the DC offset.
The LED quintuplet on the POS rail are slightly brighter than the NEG ones.
Maybe I fudged something up when matching them? The current setting resistors measure 33.8 ohm on each rail (perfect match).
This means that the NEG rail has 57.2 mA and the POS rail 53,6 mA going through them.

- Shouldn't this be matched?

Vdrop over LED quintuplets:
9.025 V (neg) | 9.604 V (pos)

Vdrop over LED triplets:
5.452 V (neg) | 5.455 V (pos)

So far so good.. (?) Even got the input relays up and playing.

Did a scope on the output of the PSU section. Ripple on the line is non-existent (0.5 mV or less). Looking forward to putting some music through this.

Last edited by nakamoomin; 23rd July 2012 at 05:50 PM.
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Old 23rd July 2012, 06:37 PM   #600
Salas is offline Salas  Greece
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No problem, the (+) leds quintet is designed to run more current in the Mezmerize specifically, thus perceptibly a bit brighter, and bit more +V. Goofs the offset and brings a bit different THD profile as I liked it during developement for low CCS feed. No point to match exactly the rails CCS, makes no difference in such Mosfets transconductance by that scale of difference. With a scope on rails you just make sure it has no oscillation waveform and you see a line close to its residual SNR for set bandwidth and probe's scale/pick up.
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