NAD C515BEE mod help needed - diyAudio
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Old 29th October 2009, 10:12 PM   #1
nad is offline nad  United Kingdom
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Default NAD C515BEE mod help needed


I'm pretty new to modifying, I have changed most of the parts inc opamps, decoupling caps, regulators, clock, evey cap etc etc.

I'm in the process of replacing the opamp output resisors to Welwny rc55y's.

I've been looking at the output circuit and as a newbie, I'm unsure what the half moon shaped, black 3 pin components are? They're numbered D1302 and A102 and read 0/0/-5v on the pins.

Any idea what they are (regulators?) do I remove/replace them?

Also, I replaced the opamp output caps with Ruby ZA's, is it best to bypass them?

I also see folk remove the muting circuit, can I do this on the NAD?

Is there anyone out there who knows which components I can remove to attain a better output? or anyone who's modded a C515BEE past the level I have??????

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Old 30th October 2009, 12:54 AM   #2
Bill_P is online now Bill_P  United States
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Location: New York, the vampire state
The D1302 components are probably 2SD1302 transistors, used for output muting. There should be two on each channel if the 515 follows other NAD CD players' topology. Removing the transistors will of course remove the muting circuit connections to the outputs. If you do that, it would be best to test for unwanted noise when a CD is not playing. Turn on your amp and set the volume to a low level. Then turn on the CD player, load a disc, play a few seconds of music, and hit pause, play, stop, open the drawer and close it etc. Exercise all the CD player functions and listen for objectionable noises in the absence of muting.
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Old 31st October 2009, 04:33 PM   #3
nad is offline nad  United Kingdom
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Thank you BILL_P, really appreciate your reply. There are 2 pairs on the output so I will try removing them soon or can I not cut the muting input jumper?
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Old 31st October 2009, 05:50 PM   #4
Bill_P is online now Bill_P  United States
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Join Date: Sep 2009
Location: New York, the vampire state
When a CD is playing the transistors are turned off but still connected to the output. Removing the transistors insures that the muting circuit cannot affect the sound when playing a CD. Cutting the muting input jumper disables the muting circuit but leaves the transistors connected - not what you want.

I would be interested in details of what you modified. For example what part number was the original op amp and what did you replace it with? Is there a particular component upgrade that you found to yield a big improvement?
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Old 31st October 2009, 09:42 PM   #5
nad is offline nad  United Kingdom
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Default Thanks again BILL_P

Thanks again for your reply.

I have changed most of the standard components in the 515. I wouldn't say any single component swap made any big difference, but all the changes together made quite a difference.

I cannot remember the standard opamps numbers, they were changed to LM4562MA's (smt) which were ok but then I replaced them with LME49720HA (tin hat TO99 soldered directly to the surface mount) which was a upgrade worth doing.

I changed the 5v dac and +/-12v opamp regulators for 'Class D' modules which raised the voltage output from 4.4v (standard dac reg) and from +/-11.3v (standard opamp regs). They made a worthwile difference.

The capacitors have all been changed, starting with the opamp decoupling caps then moving on to change the whole lot with rubycon za's, sanyo oscon, panasonic fc's in specific locations.

The clock was changed to a 1ppm low jitter module which worked well.

To be completely honest, the biggest and most substantial upgrade in output was completely free. I found repositioning my speakers and changing my listening position made more difference than any upgrade component, interconnect or speaker cable.

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Old 9th July 2010, 11:35 AM   #6
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Please, anyone has the SERVICE MANUAL for NAD C515BEE because I want to do some changes, but better with the schematic diagram... please, send it to
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