AudioSector-chip amp kits, dacs, chassis

[orto]

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.

 

[Peter Daniel]

Plitrons are good transformers and I have 300VA units back in stock ($80/pc). You can also get cheaper Avel from Parts Express.

 

[rnzr]

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?

 

[Peter Daniel]

0.25W is fine.

 

[DeanP]

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)

 

[lordvader]

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

 

[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.

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.

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.

 

[DeanP]

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!

 

[Peter Daniel]

Re: Stereomojo amp shootout

Your comments because of your experience would be invaluable.

If you don't believe tweaking so then we may have agree to disagree.

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/showthread.php?postid=574431#post574431
http://www.diyaudio.com/forums/showthread.php?postid=581230#post581230

And here how I experimented with diodes:

http://www.diyaudio.com/forums/showthread.php?postid=134303#post134303
http://www.diyaudio.com/forums/showthread.php?s=&postid=146704&highlight=#post146704
http://www.diyaudio.com/forums/showthread.php?s=&postid=137191&highlight=#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

http://www.diyaudio.com/forums/showthread.php?s=&threadid=76609&highlight=

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.

 

[lordvader]

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 ?

 

[DeanP]

refering to Post #1641,what size pot is that and where can I get it? or do you sell it?

 

[Peter Daniel]

It is Noble pot, available from percyaudio.com I also have 50k units in stock presently.

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

I certainly prefer when choke is in a circuit, but how different value will affects the sound is hard to say, at least for me.

 

[DeanP]

Okay Dumb question coming...

I'm using your lm4780s and Marchand's electronic x-over. You said to use a 10k log before amp(I believe this size), while Marchand says to use a 10k linear after x-over. Could I use the PEC dual linear or should I use a log? And what size would be good? Thanks for your help!

 

[rickmcinnis]

Bridged 4780 Subwoofer Amp

I need your advice.

I am using 1000uF BG STD on the amplifier board.

Would your same recommendations apply (as far as any additonal capacitance) to this application? Should I stick with 10 uF on the rectifier board or could there be some advantage to using a larger cap in this application?

Please advise what you would recommend.

I guess these boards were not made with the RIKENS in mind!

THANKS,

 

[Peter Daniel]

You can use linear, but it may appear that control range is not really convenient. If that happens, you can always switch to logarythmic taper.

Personally, I wouldn't use linear pot for volume control and Digi Key also carries log pots from PEC now.

 

[DeanP]

So is 10k good?

 

[Peter Daniel]

It should work fine, but the value is also dependant on the output of Marchant crossover. More details here: http://www.diyaudio.com/forums/showthread.php?s=&postid=1179940#post1179940

 

[Pocoyo]

Plitron

Hii

sometimes i look you have cheaper product
so why not i call you

Peter do you have Plitron torodial, i need
- 1 X 400W, 50/60 Hz, +/- 60 V output or
- 2 X 200W, 50/60 Hz, +/- 60 V output

and please give me big discount for it

oh yes please answer my last letter in your email,
realy realy your advice man

thank u, goodbye & best regards

jeffry_w

 

[Pocoyo]

voltage

sorry forgot something

my home electricity is 220 V 60 Hz

 

[vorpal]

Newbie here...

Interested in building a 5 channel amp for theatre use. Any recommendations on Peters' kits?

Also, what type of transformer should be used? Should I use 1 or 5?

Looking for high power and great fidelity.

Also interested in DAC if this is still available.

Thank you!