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Questions about Buffalo32 connections, associated parts and configuration options
Rank: Member
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Joined: 4/11/2009(UTC)
Posts: 9
Location: Luxembourg
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Hi all,
being new to the DIY world, this DAC is my first build, and so i have many stupid questions :)
Having soldered the PSUs, and assembled the case, i'm now close to mounting the DAC and finishing the build. Here i have some questions:
1) in the documentation of the Buffalo32, I read that the default output in balanced mode is at 4VRMS. I want to connect the DAC to a Parasound JC2 preamp, is it necessary or recommended to solder in some resistors to bring the voltage down? which voltage level would be ideal?
2) i remember reading that i need to connect some "L" traces for joining the grounds on the DAC board. did i remember this right?
3) for the digital part i have a 7V, 15 VAC transformer. will this do? what voltage should or can i dial in at the LCDPS?
4) for each LCBPS, i have a transformer of 15v rated at 15VAC. is this sufficient?
Thanks a lot :)
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Rank: Advanced Member
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Joined: 6/12/2008(UTC)
Posts: 79
Location: Norway
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Hi!
1) I would leave it at 4V for now. If you find that this gets to loud, then you can put in some resistors later. What is ideal depends on a lot of things; how loud you like to play, how much gain your amps have, how efficent your loudspeakers are and how big your room is.... With my set up I find that 2V is most suitable.
2)If you have one of the new boards (v 1.1) there is already a 0Ohm resitor connecting the two grounds.
3)7V should be OK. Set the LCDPS to 5V.
4)A transformer with dual 15V secondaries is optimal. 15VA is enough. I know someone are using 30 or even 50VA, but I dont think that is worth the extra cost and space requirements.
Good luck!
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Rank: Administration
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Quote:A transformer with dual 15V secondaries is optimal. This is key. A single secondary or center tapped transformer will not work.
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Rank: Member
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Joined: 4/11/2009(UTC)
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Location: Luxembourg
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Thanks for the very quick response :D I proceeded with connecting my 2 LCBPS and one LCDPS to my transformers (they are these here: http://www.thel-audioworld.de/module/NT1525/NT1525.htm), to the 4 AC connections. On the 15v transfos i measured 18VAC, on the 7V it was 9ish VAC. (i suppose that's how it's supposed to be?) Problem is... few seconds after i switched on the power, a capacitor on one LCBPS decided to suddenly blow up. I am a bit clueless, thanks for all help
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Rank: Administration
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You connected U-AC1 and U-AC2 to the input terminals on the LCBPS, leaving U-DC1 and U-DC2 unused, correct? Also, I hope you are doing this power supply testing without the supplies connected to the Buffalo. Edited by user Wednesday, October 28, 2009 12:55:57 PM(UTC)
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Rank: Member
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Joined: 4/11/2009(UTC)
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Location: Luxembourg
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hi brian,
yes, i connected them to the AC ones only, and i didnt have the buffalo connected, that one's still soundly safe in its box. cap was in the right direction too.
The other LCBPS and LCDPS seem to run fine... but i didnt leave them connected to power for long after that.
I think the circuit ran for some 20 seconds before the cap decided to blow.
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Rank: Administration
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Could you post a close-up picture of the LCBPS in question? This would help identify the problem.
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Rank: Member
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thanks brian, here are the pics of the LCBPS:   hope that helps, Christian
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Rank: Member
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actually, before hooking it up to power, i checked all connections with the multimeter if they did transmit a signal here's a better pic of the back: 
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Rank: Administration
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Your negative rail capacitors are all backwards.  That would do it. I can send you some replacement capacitors.
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Rank: Member
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thanks brian,
... i feel incredibly stupid now... and i thought i checked all double and triple... oh well, lesson for the future.
The first LCBPS and DPS are working great, and are at target voltage, so i'll be able to listen to the DAC soon with some chance, albeit with only one LCBPS.
As for the capacitors, i'd love if you could send me some (the C1, c2, c3-c6, c9, c10), but i insist i pay for them... i believe i should always pay for my stupidness :).
Do you still have an LCBPS kit lying around? i think i'd like to order one of those too... in case i do stupid things again
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Rank: Member
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ah, one last question:
would it be alright to connect the 2 analog stages from the buffalo32 to just one lcbps running off just a 15VAC 15v transfomer? (can it take the load?)
until i complete the second lcbps :)
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Rank: Administration
Groups: Administration, Customer
Joined: 10/24/2006(UTC)
Posts: 2,868
Location: Massachusetts, USA
Thanks: 2 times
Was thanked: 141 time(s) in 134 post(s)
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