There is no specific orientation for AC1 and AC2. Here, as you can see, it doesn't make any difference which way you connect it: http://www.audiosector.com/lm4780 psu.pdf
Peter,
I got the amp up and running yesterday. Sounds good (i.e., it works, though I did initially take out one channel on the PS board due to faulty wiring
). While it is too soon to make any critical judgements since the amp hasn't burned in, it sounds better than I expected at this stage, and definitely different than my tube amps.
One thing that surprised me is there is much less gain than I expected, given how many people use it with a passive preamp. I am using a Allen Wright modified Sony CDP, passive preamp and Vandersteen 3a Sig's. With the volume pots at full volume I am just barely achieving my normal listening level. Any suggestions on what the best solution would be (short of recommending an active preamp or different speakers, of course)?
Regards,
Wade
I got the amp up and running yesterday. Sounds good (i.e., it works, though I did initially take out one channel on the PS board due to faulty wiring
). While it is too soon to make any critical judgements since the amp hasn't burned in, it sounds better than I expected at this stage, and definitely different than my tube amps. One thing that surprised me is there is much less gain than I expected, given how many people use it with a passive preamp. I am using a Allen Wright modified Sony CDP, passive preamp and Vandersteen 3a Sig's. With the volume pots at full volume I am just barely achieving my normal listening level. Any suggestions on what the best solution would be (short of recommending an active preamp or different speakers, of course)?
Regards,
Wade
Hi Peter. Just wondering if it would be possible to buy one (1) of this small green WIMA cap (3.3nF) that you use for the digital filter. I cannot find one and I'm building your DAC. I did my own PCB using your schematic and posted PCB images (thanks for sharing).
Let me know, all the others parts are already ordered.
Merry Christmas.
Bye...
Let me know, all the others parts are already ordered.
Merry Christmas.
Bye...
reMC said:
Maybe because I don't find it makes that much difference, beasides, customer knows what he's actually getting.
Algar_emi said:
I also can't get those Wima caps. I'm using Panasonics from DK, best grade polypropylene.
rdf said:
I never tried that. Quality of ground return wires is imporatant though.
rdf said:
Hi rdf,
I use a copper buss for my p2p gainclones that works very well, but in the BrianGT (shown in the picture) it didn't quite work as I have some hum. I forgot that the power and signal earths are connected on the amp pcb. I eventually removed the buss and did the earths as in instructions and guess what, it fixed the problem.
(BTW: I didn't connect chassis ground.)http://www.briangt.com/gallery/nigc-erskine/BrianGT_GC_2_800x600
I guess with a little more effort I could have gotten the copper buss to work but why bother and the results at the moment are excellent.
regards
Greg Erskine said:
Hi rdf,
I use a copper buss for my p2p gainclones that works very well, but in the BrianGT (shown in the picture) it didn't quite work as I have some hum. I forgot that the power and signal earths are connected on the amp pcb. I eventually removed the buss and did the earths as in instructions and guess what, it fixed the problem.
regards
Greg,
Nice looking layout, and nice separation from the signal path to the noisy stuff! Those look like the lower power LM3875 chips rather than the LM4780s, but your amount of heatsinking seems light. Is that an aluminum angle bolted to the rear chassis panel you are using to essentially heatsink the chips into the chassis? How warm are your chips running?
Robert
Greg Erskine said:
Thanks Greg. Were the amps which worked well single transformer? My torroid is a 1000 VA from a dead Zen project so the amp will use ony one. I also have some 2" x 1/4" copper flat stock sitting around, my thought was to use a physical layout similar to the Peter's Patek but mount the single rectifier board on the bar's end opposite the amps and use the flat stock as heat sink and ground return.
karma said:
received it today. one word wow
thank you.
There are 4 screws holding the whole chassis together. The wooden piece that I included, should be used to separate the channels from from front and rear panels (by tapping with a hammer). I don't have access to my email account presently, so if you have any questions, I can answer them here (directly from Cancun
)
wdavis009 said:
With a source having 2V output and 93dB speakers, the gain is enough for any normal listening levels.
You could increse it further by lowering the impedance of 680R resistor ( -IN to ground), but I can't say how well it will work.
A simple preamp implemented around OPA627 or AD815 might be a better solution, especially with chip amps, that work actually better with active line stages.
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