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Old 20th November 2009, 08:01 PM   #501
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Interesting I have been having an issue with mechanical noise with a 1KW transformer and the manufacture mentioned the possibility rectifiers causing it. I kind of blew it off as passing blame but I may revisit it. I am disappointed there has not been more feedback on JX progress I have wanted to build an X amp but missed out on initial buy. I am curious how this design manages with offset.

Bill
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Old 20th November 2009, 10:15 PM   #502
Bengali is offline Bengali  United States
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Quote:
Originally Posted by Coreyk78 View Post
I actually had some mechanical buzzing coming from the transformer even after going up in size from the 400VA to the 600VA transformer. Thats when I checked the MUR860 rectifiers I was using and found they were running extremely hot. I decided to switch to chassis mounted 50A/1000v bridge rectifiers and the buzzing completely disappeared. Worked for me, YMMV.
Hi,

How did you sink the MUR860's? what size were the TO-220 heatsinks?
are you using the briangt aleph psu boards? I'll be using this board
with MURF1620 and 2.5" TO-220 heatsinks. I hope I don't run into the same
problem. I would think the heatsinks are fine since the briangt psu
boards were designed for aleph 30/aleph 5 use.

I just got my antek 18V 600VA transformer. will advise if hum/buzz is noted.
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Old 21st November 2009, 03:07 AM   #503
algg is offline algg  United States
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Default rectifier choices

Are the MUR860 suitable for the stereo J? Is the amperage rating of a bridge rectifier (e.g., 35A) the sum of individual diode ratings, or each diode rating?
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Old 24th November 2009, 12:48 PM   #504
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With the BrianGT boards MUR860 may work more easily since it has room for board mounted heatsinks.
I was running mine without any sinks at all, I'm using Peter Daniel's power supply boards and the rectifier section is scored so it can be snapped off and then you would have lots of heatsinking options, bend the rectifiers over and mount to the chassis or amp heatsink, etc. I just didn't feel like tearing down my amp yet again to drill more holes and I had the heavier duty bridge rectifiers on hand so I used those.

I initially did that when I was running 1 power supply board for 2 channels, with 1 board per channel the MUR860 would probably run a lot cooler and might be just fine, I don't know for sure though.
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Old 24th November 2009, 02:51 PM   #505
Bengali is offline Bengali  United States
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Quote:
Originally Posted by Coreyk78 View Post
With the BrianGT boards MUR860 may work more easily since it has room for board mounted heatsinks.
I was running mine without any sinks at all, I'm using Peter Daniel's power supply boards and the rectifier section is scored so it can be snapped off and then you would have lots of heatsinking options, bend the rectifiers over and mount to the chassis or amp heatsink, etc. I just didn't feel like tearing down my amp yet again to drill more holes and I had the heavier duty bridge rectifiers on hand so I used those.

I initially did that when I was running 1 power supply board for 2 channels, with 1 board per channel the MUR860 would probably run a lot cooler and might be just fine, I don't know for sure though.
The MUR860's should work just fine as long as you heatsink them properly.
They should heat up pretty quick since the spec. says 1.5V drop.
I believe you are losing about 3V just from these diodes alone.
You might want to check the bridge rectifiers as well for their voltage drop.
Lower drop, less heat, more voltage at the rails.
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Old 24th November 2009, 03:00 PM   #506
massimo is offline massimo  Italy
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MBR30H60 are TO220 Schottky 30A, 60V double diode (you can // them for lower V drop, no heat) not very expensive sugested by ON Semi "for audio" AFAIR
Also check MBR30H100

Last edited by massimo; 24th November 2009 at 03:02 PM.
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Old 24th November 2009, 03:08 PM   #507
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Do you think possibly that the mechanical buzzing may be related to using smaller guage wire or PCB's with small tracks?, I am considering rewiring a F3 handbuild PS with 12ga bus wire, the 18ga stuff, I am not sure if enough for the current presented.
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Old 24th November 2009, 03:19 PM   #508
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I am considering rewiring a F3 handbuild PS with 12ga bus wire, the 18ga stuff, I am not sure if enough for the current presented.
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Old 24th November 2009, 08:49 PM   #509
algg is offline algg  United States
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Default AJ grounding scheme

I thought I had this figured out, but after reading recent posts, I rewired my stereo J's grounding and now the hum has returned. Perhaps someone can tell me the proper grounding scheme at a real basic level. I am using Peter Daniel's signal and power boards and am using rca inputs exclusively (don't even have XLR's on the chassis). So rca center pin goes to PD in+. Rca shield goes to PD- and is jumpered to SG on PD board. PD board 'out' goes to red binding post. Black binding post goes to other side of CL60, which in turn is connected to chassis screw which is earth grounded to ground lead of power cord. Power supply ground also goes to signal ground side of CL60. This configuration hums. I avoided hum by lifting the ground connection between black binding posts and signal ground, and instead wiring black binding posts to ground/signal ground (circuit traces are connected) on PD board. However, this does not ground the circuit - the ground is kept only from the RCA shield. I have tried to attach a picture to help visualize. If someone would kindly help... thanks!
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Old 24th November 2009, 09:13 PM   #510
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You must also run the board grounds to the PS ground.
Best, Bill
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