CA 340A SE LM3886 based amp - Upgrade advice please.

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Ahh I see. It sounds like a good idea but bear in mind your signal is going through the carbon, metal films, brass end caps and tin leads of resistors, tin plates of caps and other imperfect conductors, so keep things in perspective. Also high level (speaker) conductor improvements are nowhere near as important (to my ears) as low-level ones. Gold-over-copper is still a good bet if you can't find what you most want (which will tarnish like a brute).

Let us know what you find.

Simon
 
Will it be ok to run the amp with these clamps removed?

s320x240


s320x240
 
I think Cambridge fitted that clamp to improve reliability by keeping the chip cooler.
It may also keep the output further from protection locus which reduces as temperature increases, i.e. Cambridge might think it sounds better done their way.
 
You can add that Caddock below the PCB and leave the heatsink on. I use a similar arrangement when I do LM4780 amps and is beneficial for mounting and heat removal.

When you finish this sucker then try one as SimontY said without all the "extras". They are really not required and have built plenty of LM3875 and LM4780 from AudioSector.
 
Cheers Rabbitz.

I was thinking about removing all the extra's. As the DC offset going into the LM3886 is so low I reckon I'll be fine. As its an integrated there may be noise issues due to the large PCB and not ideal layout. If so I'll put it back in.


Mike.
 
Hi all.
About differences in SE Vs Non_se:

1. Line in (Ipod in). Not interesting now... And also 10000uF vs 6800 uF big smoothing caps.

2. Input before selector:
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3. Input Buffer:
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4. Power Amp:
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mikesnowdon said:
Cheers Rabbitz.

I was thinking about removing all the extra's. As the DC offset going into the LM3886 is so low I reckon I'll be fine. As its an integrated there may be noise issues due to the large PCB and not ideal layout. If so I'll put it back in.


Mike.

If you are going to do one without the extras, I'd use one of AudioSector's or Chipamp's PCBs from scratch in another case as they are laid out better for that purpose. Then just add a dedicated active pre.

These chips can give high DC offsets but normally not an issue unless it's excessive.
 
I want to try linking out the input cap and FB cap, then check for DC with the meter. Whats the correct way to check for DC?

It was mentioned earlier that the output filter (Resistor & coil) could be there for a reason, but also could be something I dont need. It was suggested that the chip could be unstable without it, however the audiosector and chipamp.com dont have these filters. I want to see if there is a difference in SQ with the filter conponents removed, is it safe to do this?

Mike.
 
Completely safe - do it. Set your multimeter to DC volts and put the probes across the + and - speaker terminals, with the amp turned on. Do this with no speakers connected and make a note of the reading. If it's under, say, a volt it's safe, but you want it lower than that!

Excessive DC will reduce the effective power handling of the speakers by heating up the voice coils, which also changes their impedance (and therefore messes up the crossover slopes). It also uses up excursion so they can't play as loudly in the bass. But there shouldn't be much DC if you're lucky.

Simon
 
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