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Old 19th May 2007, 01:22 PM   #1781
kmj is offline kmj  Sweden
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Hi Peter
Is it possible to buy some of the parts for the DAC from you? Not the entire kit but some of the ICs.

Another thing, I thought that I should use a single 12V transformer which are on sale at my local electronicsshop but I'm not sure about the VA-rating, how low can I go?

Kind regards
Ken
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Old 19th May 2007, 02:40 PM   #1782
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Any component is available separately, attached is the parts list for USB DAC.

As to the transformer, 12VA should work fine, however, performance may be better with higher power rating, so use at least 24VA. I'm using 50VA, 2 x 8V.
Attached Files
File Type: txt dac_usb_parts list.txt (499 Bytes, 259 views)
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Old 19th May 2007, 02:54 PM   #1783
kmj is offline kmj  Sweden
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Oh, you have two different kinds?

A year or so back I was given a blank board as a kind of "thank you" when I helped out in a group buy. This DAC uses
SN75179
and
CS8412 SMD

It was these parts I was refering to. Does the last reply apply to this to?
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Old 19th May 2007, 02:57 PM   #1784
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That would be SPDIF DAC, as the USB version became available just recently. Attached is parts list for that DAC. The transformer is the same for both versions.
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File Type: txt dac_spdif_parts list.txt (537 Bytes, 147 views)
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Old 25th May 2007, 06:11 AM   #1785
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Quote:
Originally posted by Peter Daniel
The difference between dual mono and stereo is the number of rectifier boards used in powering the amp. In stereo, both channels are powered from the same board, in dual mono each channel has its own separate board.

While in stereo setups with a single transformer you could still use two separate boards, on more than one occasion I had reports of humming supply so I always recommend using a single rectifier board.

That's also what I'm doing in all my stereo amps and in the picture below I'm showing trouble free way to connect power grounds: output grounds of both channels (OG) are connected with a piece of thick copper wire. Central point on that wire is power star ground and all 4 ground wires from rectifiers board (PG+, PG+ and PG-, PG-) are connected here. Output grounds are taken directly from the board, signal ground connects to the point on the board marked as SG.

Those boards were designed with dual mono operation in mind and as such they work well without any mods.
Click the image to open in full size.

I finished assembling my parallel lm4780 kit a few days ago, and am having a terrible humming problem. When only one channel is hooked up it is nearly completely silent (I can only hear a small noise when my ear is right next to the speaker). When I hook both channels up to the same transformer I get a terrible hum.

I have a few questions on the subject...

1. You said that you recommend only using a single rectifier board, is a single board sufficient to power two parallel 4780's?

2. From what I can see a solution would be to connect all of my ground points like in the quoted post above. Do the PG+/- have to be connected to the amp boards? It does not look like they are in the above picture. Also, is it fine if they ARE connected and I connect all the points to try to solve my humming problem?

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Old 25th May 2007, 08:53 PM   #1786
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Also, can all these points be connected directly to mains ground? It looks like you have a resistor before mains ground...
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Old 26th May 2007, 03:06 PM   #1787
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Quote:
Originally posted by phatcenter77
1. You said that you recommend only using a single rectifier board, is a single board sufficient to power two parallel 4780's?

2. From what I can see a solution would be to connect all of my ground points like in the quoted post above. Do the PG+/- have to be connected to the amp boards? It does not look like they are in the above picture. Also, is it fine if they ARE connected and I connect all the points to try to solve my humming problem?
In most cases a single rectifier board should be sufficient for two parallel LM4780; I've been using such configuration and it worked well. You may check the temp of rectifiers, if they run too hot use some heatsinking (isolation pads are required if diodes are mounted to a common heatsink)

In a pictured exampled, the output grounds of both channels are connected with a thick copper wire and all grounds from rectifiers boards (PG+/PG-) are connected to a central poin there (and they need to be connected).

More info on wiring amp kits has been posted here:

http://www.diyaudio.com/forums/showt...20#post1108820

http://www.diyaudio.com/forums/showt...773#post787773



Quote:
Originally posted by phatcenter77
Also, can all these points be connected directly to mains ground? It looks like you have a resistor before mains ground...
Those points are connected directly to the chassis, and they can be also connected directly to mains ground, although I'm using 10R resistor to separate chassis ground from mains ground.
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Old 27th May 2007, 04:08 AM   #1788
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Thanks again!
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Old 31st May 2007, 02:32 PM   #1789
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I cannot recomment Peter higher. I am a noob to this and his emails have been FAST and all my questions answered. Helped me get a nice order going! Thanks man, rare to come across a business that actually gives a crap about there customer during and after payment is made! Cannot wait to get these new toys singing!
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Old 31st May 2007, 11:20 PM   #1790
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I echo your warm sentiments regarding Peter Daniel. He has an A+++ from me for customer service. I just wish I would take more trips to Toronto so I could meet up with him and listen to his system. A gentleman, audiophile, and colleague.

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