My NAD C515BEE is finished.............

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#161
nad said:
Got you. Do you consider opamps as the most important part of a system?

Do you listen to music for the music or for the tone of the opamps, seems you have changed between quite a few.

Don't take this the wrong way but it seems you are a bit of a 'pusher' of various opamps, Personally I'd go with the majority of folk and choose bursons then leave them be. I couldn't be doing with listening to the opamps rather than the music and changing them to another, then another, then another and maybe trying another etc etc.

I'm not after 'transparency' here, just dynamics
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Obviously no; obviously no; and I wouldn't go for the Burson because I'm not with the "majority" (eh?).


It was you who wanted to replace all the caps again because sound was bright... I suggested an easier way to make things right. Not guaranteed to give 100% satisfaction, but given the small hassle it would be worth a try before you go for the harder route.
 
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#163
Well, as the title says I changed some caps back.

If Mikesnowdons reading..... I swapped the cap you said could be the feddback, the ZA's in place were 25v 47uf but it read 47v on the board so I swapped them for 50v 100uf and it balanced it out a bit.

Then I went on to revert back to the standard caps (mainly the FC's) but putting elnas in the signal path and that helped. Then I found 2 tiny FC's (not to ground) which I missed near the Mundorfs which were 50v 10uf so I swapped them back for the originals and that gave much more bass.

I'm going to leave it playing to itself for a few days to a week or so to let the caps burn in, as after I swapped the whole lot, it's only had a 24 hours or so of use.

Later............
 
#165
nad said:
Well, as the title says I changed some caps back.

If Mikesnowdons reading..... I swapped the cap you said could be the feddback, the ZA's in place were 25v 47uf but it read 47v on the board so I swapped them for 50v 100uf and it balanced it out a bit.

Then I went on to revert back to the standard caps (mainly the FC's) but putting elnas in the signal path and that helped. Then I found 2 tiny FC's (not to ground) which I missed near the Mundorfs which were 50v 10uf so I swapped them back for the originals and that gave much more bass.

I'm going to leave it playing to itself for a few days to a week or so to let the caps burn in, as after I swapped the whole lot, it's only had a 24 hours or so of use.

Later............
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Good news.

What type of cap was e 50v 100uF you repaced the 47uF ZA with?
 
#167
nad said:
Just a standard cheap jobbie that used to be in the amp before the re-cap mission, think it's a JH or something??

Are you sure it's the feedback cap??

Could really do with a schematic, any ideas??
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If making this one single change brought back some balance to the sound then its quite likely that is the feedback cap. Worth putting a good quality cap here, but one that will balance the overall sound well. Like weve been discussing; A Simimc, or Tantalum could work well. Silmic will probably have a bit more clarity whereas a Tant should give a dynamic punchy sound.

Amplifiers usually work on feedback. They take some of the output and pump it back into the input, this is what amplifies the signal. Components in this 'feedback loop' are critical to the sound quality of the amp and have a major bearing on the overall sound. You cn play with the value of the feedback cap a little but going too small (under 47uF) will result in weak bass. Ging above 100uF will also be a waste of time as the amp will be reproducing inaudible low frequency signals. 47-100uF is the norm.

I would leave the feedback cap alone now and try a few different types in the signal path. If you can, get the 10uF Wima MKS2-XL they are excellent. However, if your still finding the sound overly bright go with Silmics. The 10uF/25v from Hihicollective will be fine. Make sure yo fit them with correct polarity, signal in to + lead, out from - lead.

If you cant find schematics there are a couple of other options:

Trace the circuit and draw up your own schematic to post up here. (You could download ExpressPCB, free software from drawing schematics)

Learn a bit about amplifiers so that yours makes more sense to you giving you a better idea of what the different parts of the circuit are doing.
 
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#168
Bang on the money...........

Well.......... Found the cure to much more dynamics!

If mikesnowdon is reading, the 25v 47uf ZA's weren't the culprits to no dynamics. I swapped a load of caps pair by pair and found the newly replaced 63v 47uf Nichicon Fine Golds to be the 'bad eggs', I replaced them with an unbranded 50v 100uf (reads 24v on the pcb) and wahey, low volume kick.... Good stuff eh??

Because of the swap back on loads of other caps the output was a bit 'mellow' so I reverted again to the newbies all but the new/old 50 100 and blimey charlie, bloody great! just need to order the replacements silmics for the std elnas I put in and a 'better' 50 100 and jobs a good un.

Just when I thought the nads were likely for retirement, they hit back!

Sooooper stuff!!!!
 
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#178
nad said:
Checked a load but I think its around 25v ish
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You ideally need a bit of headroom so 25v caps on a 25v rail is no good.

As for the cap we thought might be the feedback: If its measuring 24.8vdc I don't think it's the feedback capacitor. What voltage does the power-amp run on?? (measure across the main smoothing caps, the big 10kF Mundorf's)

EDIT: Trace that 'feedback' cap and let us know where it goes....
 
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