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Old 16th February 2012, 01:37 AM   #21
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I am cought-up in same situation, got the original boards and the updated techdiy parts.

Here's the "un-official" missing parts list: 2-100K resistors
4- .47 3w resistors
4-47 resistors
4- 2.2K resistors
4-1K resistors
4-150 resistors
4-10K resistors
If you have boards with a status LED, you can use "un-used" 4.7K resistors
from the kit.

I ordered the missing ones staying with Dale's CMF series.

Please, correct me if i did a mistake somwhere guys!...
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Old 16th February 2012, 11:07 AM   #22
AndrewT is online now AndrewT  Scotland
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One+2,
if you are using a CRC filter for your power supply then the umbilical comes to your aid to assist with attenuating the unwanted frequencies that get past the rectifiers.

Keep the transformer and rectifier and first stage smoothing capacitance in a very tight low loop area configuration. That is the first part of your rCRC giving you r = lead and secondary resistance. C = first bank of capacitors.

The next stage is effectively located in the power amplifier box.
As you may already know, an LC filter performs better than an RC filter, when looking at attenuation of the unwanted versus the voltage stability at the output.

Think of your umbilical as a combined L+R where L = very low value and R = very low value.

Without adding any discrete inductor, nor adding any discrete resistor, the the umbilical impedance provides the L+R in the second stage filter.

This results in a rC(L+R)C cascaded filter. This performs very well if the impedances at either end of the umbilical are kept low.
The attenuation of the unwanteds improves as the L & R of the umbilical increases.
And just to help you along, the inherent core to core capacitance of the umbilical also aids attenuation of VHF trying to impinge on an exposed umbilical.
Use that to your advantage.
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Last edited by AndrewT; 16th February 2012 at 11:11 AM.
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Old 16th February 2012, 03:04 PM   #23
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Interesting. Thanks for the detailed response. If I may ask a follow up question, is there any special grounding scheme I need to follow as a result? (for context, I plan on having a 3 foot long 4 conductor umbilical with 14ga wires terminated with speak on connectors.)
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Old 16th February 2012, 03:17 PM   #24
AndrewT is online now AndrewT  Scotland
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Start with this.
understanding star grounding
Pay special attention to Mains Safety.
Then move on to
Audio Component Grounding and Interconnection - diyAudio

There are other threads discussing similar psus.
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Old 16th February 2012, 04:52 PM   #25
6L6 is offline 6L6  United States
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Read the links Andrew speaks about. Good stuff.

If you are going to have an outboard PSU you are going to need at least 2 more capacitors...

Put the transformer, bridges, and a pair of caps (Say 10,000uf or thereabouts and 35v or more, remember, they are going to get the brunt of the ripple) in the outboard case. Your red PSU board will be in the case with the amp circuit boards.
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Old 16th February 2012, 07:42 PM   #26
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Wow... this is complicated. I read through the links but only understood a small fraction. I'm a mechanical engineer... not smart enough to be an EE!

Would it be any simpler if I kept the rectifiers in the amp case and had AC go through the umbilical?

Maybe I'll just stick with the one box solution...
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Old 16th February 2012, 08:19 PM   #27
6L6 is offline 6L6  United States
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It's not that big a problem, and that article does make it seem much more complicated than it really is.

If you do choose to do the 2-chassis approach, you should make the umbilical DC, so the Transformer, bridges and 1st set of caps are in the same box.
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Old 18th February 2012, 12:32 AM   #28
lhquam is offline lhquam  United States
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Do you have any estimate of the thermal rating C/W/3" of those heatsinks. I am using Heatsink USA E007 heatsinks which are somewhat larger: 10"x7"x2.5" 24 fins, which has a rating of .7 C/W/3".


[QUOTE=oneplustwo;2901510]No pictures yet... but here's where I'm sourcing parts from so far:
...
Heat Sinks:
Got the ones that Antek uses for this enclosure. $25 each shipped with the trafo to help minimize costs (also ordered a B1 trafo and small heatsink.)
...
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Old 18th February 2012, 01:40 AM   #29
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According to them, they are rated at 0.6 C/W/inch.

Also, it's 160 sq in per lineal inch with 37 fins.

Last edited by oneplustwo; 18th February 2012 at 02:09 AM.
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Old 18th February 2012, 01:57 AM   #30
nrg2009 is offline nrg2009  United States
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Great looking build.
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