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Old 6th April 2007, 09:55 PM   #1681
orto is offline orto  United States
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Hello, I've ordered the LM4780 kit. I'm planning on running it in two monoblocks. Does anybody have a suggestion for a good transformer? This will be my first build and I'm not very savvy to the pro's and cons of a good power transformer.

P.S. this is extremely addicting I'm having a hard time not ordering several of each kit.
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Old 6th April 2007, 10:08 PM   #1682
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Plitrons are good transformers and I have 300VA units back in stock ($80/pc). You can also get cheaper Avel from Parts Express.
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Old 7th April 2007, 01:48 PM   #1683
rnzr is offline rnzr  Estonia
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One n00bish question about R3 on rectifier board...
If i use 50K resistor then what should be power rating if i use 2x21V 225VA toroids... 1W or 2W should be ok? 0.25W and 0.5W will burn in i guess?
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Old 7th April 2007, 02:54 PM   #1684
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0.25W is fine.
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Old 8th April 2007, 02:00 AM   #1685
DeanP is offline DeanP  Canada
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Thanks Peter for the quick answer to my "size" question.

I made it to the "big city" of Edmonton and wanted to pick up a copper "heatsink" at Metal Supermarket. I bought a piece so that each chip will recieve about a 3" by 2" by 1/4" "land" of copper. I'm still wondering if I need to attach an aluminum heatsink to this still?? I have plenty of old p4 cpu heatsinks around that I could attach. What are your opinions?
Also if I attach all chips directly to the copper heatsink without the thermal pad and keep the copper isolated from ground, would this work or do they have to be isolated from each other?
(The piece would hold 5 lm4780,three stereo,two parallel)
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Old 9th April 2007, 11:06 AM   #1686
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Default quick question about common mode choke for dac

Hey all.

I'm going to start purchasing components for the DAC kit.

Since I plan to build an external power supply, most of the PSU components will essentially be "off board", so I won't be hindered by size contraints.

In regards to the two common mode chokes, what is a suitable range of values/dcr for them, and what is the prefferred values ?

Same question in regards to the 1000uF capacitors (before and after the choke). Would there be any advantage to going larger ?

Thanks
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Old 9th April 2007, 03:33 PM   #1687
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The chokes are 0.6MH 3.0A , I guess anything similar will work here as well. My choices were based on the first Kusunoki DAC, I couldn't find a link anywhere, but whatever he used should work as well.

As to the caps, I like to use the smallest value suitable, that's why 1000uF only. You can try higher values (I was using 3300uF Elna Staragte too) but there was no improvement whatsoever, contrary, the type of the caps is more critical than the actual capacitance value. BG STD as first pair and BG NX as second work really well here.

Quote:
Originally posted by DeanP
I bought a piece so that each chip will recieve about a 3" by 2" by 1/4" "land" of copper. I'm still wondering if I need to attach an aluminum heatsink to this still?? I have plenty of old p4 cpu heatsinks around that I could attach. What are your opinions?
Also if I attach all chips directly to the copper heatsink without the thermal pad and keep the copper isolated from ground, would this work or do they have to be isolated from each other?
(The piece would hold 5 lm4780,three stereo,two parallel)
If the chips are powered from the same supply, they don't need to be isolated from each other, providing the copper is isolated from the ground. And you will certainly need to attach more heatsinking to such assembly, as copper alone will not be dissipating enough heat. But, I would probably use isolation pads anyway, to avoid any RF noise pick up.
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Old 9th April 2007, 03:38 PM   #1688
DeanP is offline DeanP  Canada
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Thumbs up Thanks!

Again,thanks for your knowledge.
I will then attached some sort of heat sink to this copper and use thermal pads...just have to order a dual mono kit from you eventually...then start building!
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Old 9th April 2007, 03:59 PM   #1689
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Default Re: Stereomojo amp shootout

Quote:
Originally posted by ttan98
Your comments because of your experience would be invaluable.
Quote:
Originally posted by ttan98
If you don't believe tweaking so then we may have agree to disagree.
Quote:
Originally posted by nycavsr2000
There is really not much else to do, except for fooling around with snubbers and perhaps the capacitors specifically on the amp board itself. BG STD 1000uf vs. BG NX 100 uf vs. etc...you could like one set with classical but hate it with rock. Too many variables, too many choices.
To give you idea how much tweaking went into the final Patek amp here is a link where I described my impressions with different capacitors and snubbers:

http://www.diyaudio.com/forums/showt...431#post574431
http://www.diyaudio.com/forums/showt...230#post581230

And here how I experimented with diodes:

http://www.diyaudio.com/forums/showt...303#post134303
http://www.diyaudio.com/forums/showt...ht=#post146704
http://www.diyaudio.com/forums/showt...ht=#post137191

Here's a link to my all tweaked version of the Patek amp, and I can't presently see a way to improve it any further, but the way it's built is based on 4 years of tweaking experiments

The most advanced GainClone amp yet

The LM3875 Premium kit has not been changed in the last 3-4 years and it still offers the best choices in chip amp configuration, resistor values and types. The only thing worth experimenting with are capacitors, and I expressed my personal choices already. IMO, Panasonics FCs are the closest thing to BG caps, if you don't want to pay for the caps same money as for the kit itself.
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Old 10th April 2007, 12:03 AM   #1690
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Quote:
Originally posted by Peter Daniel
The chokes are 0.6MH 3.0A , I guess anything similar will work here as well. My choices were based on the first Kusunoki DAC, I couldn't find a link anywhere, but whatever he used should work as well.

Given the same current rating then, would there be any adverse affects using a larger (or smaller) choke ?
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