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voodooless		#1 Posted : Sunday, September 6, 2009 8:31:26 AM(UTC)
Rank: Advanced Member Groups: Member Joined: 6/25/2007(UTC) Posts: 35 Location: Netherlands		I received the Buf32S just a few days ago. First I build the PSU's and tested and trimmed them for 2x 5V, + and - 15V. Working just fine with a 30VA 15VAC and 30VA 6VAC transformers. However, after hooking up the Buf, the digital voltage drops below 4 volts and the Buffalo won't work. Nothing gets hot, not even warm... Could it be that the 6VAC is just not enough to power the thing?
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voodooless		#2 Posted : Sunday, September 6, 2009 8:49:59 AM(UTC)
Rank: Advanced Member Groups: Member Joined: 6/25/2007(UTC) Posts: 35 Location: Netherlands		I just put the two 6VAC windings in serial giving 12VAC, and now I do have 5V on the output with the Buf32S connected. The LM will probably get a little hot, but for now I can go on testing :) Tip: don't tell people that 6VAC will work
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Brian Donegan		#3 Posted : Sunday, September 6, 2009 11:03:27 AM(UTC)
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)		Interesting. This is with our LCDPS power supply? I have successfully used a 6VAC transformer.
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voodooless		#4 Posted : Sunday, September 6, 2009 1:55:44 PM(UTC)
Rank: Advanced Member Groups: Member Joined: 6/25/2007(UTC) Posts: 35 Location: Netherlands		Brian Donegan wrote: Interesting. This is with our LCDPS power supply? I have successfully used a 6VAC transformer. Yes! It works fine right now, but I will be getting a new 9VAC transformer. Sound is great though, there are definately differences to my Chineese SACD player using a PCM1738 (at the moment via SPDIF). Edited by user Sunday, September 6, 2009 1:59:46 PM(UTC)  | Reason: Not specified
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voodooless		#5 Posted : Monday, September 7, 2009 3:27:41 AM(UTC)
Rank: Advanced Member Groups: Member Joined: 6/25/2007(UTC) Posts: 35 Location: Netherlands		When you calculate it, it can't work: 6VAC = 7.2 VDC (after the diodes), then there is a 1.25 V drop over the resistor leaving about 6V. This is never enough for the regulator to make 5V...
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Beefy		#6 Posted : Monday, September 7, 2009 5:44:42 PM(UTC)
Rank: Advanced Member Groups: Member Joined: 5/9/2008(UTC) Posts: 62		voodooless wrote: When you calculate it, it can't work: 6VAC = 7.2 VDC (after the diodes), then there is a 1.25 V drop over the resistor leaving about 6V. This is never enough for the regulator to make 5V... It should only drop to 6VAC when the transformer is at 100% load. You should realistically get 7-8VAC with a sufficiently rated transformer. Edited by user Monday, September 7, 2009 5:46:23 PM(UTC)  | Reason: Not specified
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voodooless		#7 Posted : Tuesday, September 8, 2009 5:14:56 AM(UTC)
Rank: Advanced Member Groups: Member Joined: 6/25/2007(UTC) Posts: 35 Location: Netherlands		Beefy wrote: It should only drop to 6VAC when the transformer is at 100% load. You should realistically get 7-8VAC with a sufficiently rated transformer. Please look at the calculations, it just can't work... I transformer is rated much more than needed, and it just doesn't to the trick.. But I fixed it now: put 4.7 Ohm in parallel to the 10 Ohm resistors, and put 1000 uF capacity in for the first four capacitors. As a precaution I replaced the LM317's with LD1086's. Now it works just fine, with a little bit of overhead.
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Beefy		#8 Posted : Tuesday, September 8, 2009 6:26:38 AM(UTC)
Rank: Advanced Member Groups: Member Joined: 5/9/2008(UTC) Posts: 62		voodooless wrote: Please look at the calculations, it just can't work... I transformer is rated much more than needed, and it just doesn't to the trick.. What was the transformer's loaded voltage then?
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voodooless		#9 Posted : Tuesday, September 8, 2009 12:08:08 PM(UTC)
Rank: Advanced Member Groups: Member Joined: 6/25/2007(UTC) Posts: 35 Location: Netherlands		About 7VAC... Anyway, now all seems to work fine up until I connect the right channel. The opamp just before the ourput gets verry hot, and the digital supply shuts down... The negative voltage of the analog drops to below 12V (normally 15V). This seems not be be good.. I'm gooing to replace the opamp (I happen to have a bunch of them lying around)
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voodooless		#10 Posted : Wednesday, September 9, 2009 3:16:52 PM(UTC)
Rank: Advanced Member Groups: Member Joined: 6/25/2007(UTC) Posts: 35 Location: Netherlands		I have it all working just fine now! There was some problem with the positive voltage connection on the terminal. Sound is just great! I also made a quick optical input with a TROX173, a cap and a few wires. Works flawlessly
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