Caiman passive output mod revealed

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Originally Posted by AndrewR

Hmmmm... Have you plugged the DAC in via its variable output and with its volume knob turned down?

The other culprit could be PIN3B socket as it is a bit delicate, although you have checked the board. Might you have wobbled it when changing caps and loosened its soldering joints underneath? If it is not faint over the headphone output (via the op amp board), then that could also indicate you've cracked one or more solder joints under PIN3B.

The only other thought is static, or if you made the change when the unit was powered up.

Andrew

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Andrew,

I've tried the variable output, the fixed output, and the headphones output. All the same very faint sound on full volume. I've checked all the grey ribbon connections between the two PCB's with a multimeter all show to be ok. Looking under the PCB now around PIN3B, no obvious cracks. :scratch:

Bit of a mystery, a very expensive mystery, with the the murata regs, elna II's, god knows how many ops amps I've bought in the last 12 months. :(

I'll keep checking but may have to just bite the bullet and start again.

Hello Stanley any weekend Caiman specials coming up ?:eyebrows:

Frizzup

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Originally Posted by StanleyB

I would check that you have plugged your amp into the fixed output of the DAC, just in case it is the volume control.
But my biggest fear is that you might have swapped the caps round whilst the DAC was still connected to the mains supply. The WM8716 might have been knocked out. It's a 15 minutes job to change the WM8716, if you have steady hands like a surgeon, nerves of steel, and eagle sharp eyes.

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Checked that it is plugged in correctly. No the DAC was taken from the lounge into my office to change the capacitors.

Frizzup

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Originally Posted by Frizzup

Hello Stanley any weekend Caiman specials coming up ?:eyebrows:

Frizzup

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I would change the WM8716, or ask someone with the relevant skills to change it. The chip is not expensive from Mouser or Digikey.
If you are really stuck on replacing the chip, I can sort you out with a replacement unit under my beta tester scheme. Make me an offer via PM :).

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Originally Posted by AndrewR

If you are running a 7520 or Caiman, you may prefer the approach described in the following links:

http://theartofsound.net/forum/showp...&postcount=117

and

http://theartofsound.net/forum/showp...&postcount=381

By the way, still loving the Rubycon NA's - great weight and body while sounding even more tuneful and more open than before (starting to approach the Black Gates in that respect).

Andrew

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That is indeed very easy. I opened up the Caiman, pulled out the output board, stuck in the caps and it worked perfectly - five minute job, easily reversible.

Sadly I cannot talk about the quality yet as I haven't listened to the DAC on the main system before, and am in the process of swapping my amp! I may get onto that next weekend. It does sound very nice, although the loss in gain means that it doesn't go quite loud enough in the main system. The second system (which is where the B DAC was always intended) should be fine though.

Go to a couple of conferences for two weeks and another 200 posts to catch up on. Interesting to read peoples different findings with different output coupling capacitors. Looking at Rubycon CE's, they seem to used in flash guns etc, ie. rapid high current discharge. Can we correlate designed usage to sound quality I wonder?

Cheers Andy

These are just coupling capacitors, the same rules for sonics apply as they do for phono stages, preamps, power amps etc. Polarised generally sound poor in comparison to film, some will like PIO. Smaller values will sound better than larger values. There will be some very cost effective caps for the sound, eg photoflash. 47uF is used by Stan as it's good for a big range of preamps though this does push towards electrolytics, quite a number of people will have preamp with a high input impedance, eg 47k to 100k. Those of us can be using film or PIO of around 1uF.

Even for a 10k preamp input impedance, 3uF should be fine so a film is very viable. Or have a I missed something?

Hi Clive,

Is there an upper limit on dielectric strength that can be used, lots of the polyprop film caps are 600 or 1000 Vdc whereas electrolytes are down at a few 10's Vdc. I'm sure somewhere buried in the thread there was a comment about this but I've lost track.

Cheers Andy

I commented that someone I know tried high voltage caps in his diy dac and was unimpressed with the sound.I've fitted some SCR Obbligato 47uF 250v,which are too big for the case so I've just left the lid off for now.I may recase the dac if I like the caps enough.

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Originally Posted by Ali Tait

I commented that someone I know tried high voltage caps in his diy dac and was unimpressed with the sound.I've fitted some SCR Obbligato 47uF 250v,which are too big for the case so I've just left the lid off for now.I may recase the dac if I like the caps enough.

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The Obbligatos I'm using are 630V (they sound good), I agree it makes sense that 64V or 200V are used but in polyprops these ratings are rare, 450V or 630V being more common. Maybe there are some good MKP block style caps in 64V, possibly by EVOX / Rifa.

Re OLEDs comments, yes electrolytics can be got as 10V versions but you don't normally see electrolytics used as coupling caps in decent hifi gear, there's a reason for this.....they aren't the best sounding!

Some lower voltage caps are in the list described here:
http://www.humblehomemadehifi.com/Cap.html