Caiman passive output mod revealed

[MartinT]

Hi goody

The passive mod gives the Caiman higher output impedance, which will not suppress input noise in your preamp as well as with the op-amps in place. Unless you can hear hiss during music playback (unlikely), it is of no consequence.

[goody]

Thanks Martin. The hiss could not be heard during music playback and had no consequence during playback.

While most time we check the quietness of the system by setting the volume to max with no music playback...Is there a way we could get rid of those hissing at all?

[MartinT]

Only by using larger capacitors, which probably won't fit unless you want to use electrolytics. Also don't forget that the gain is lower so you are having to use a higher position on the volume control.

In my case, the sound quality is so much better with the passive mod that I'm not bothered, and I get no hiss anyway

[goody]

Hi, I m using 15uF bypass with 0.47uF caps. What are your values?

You mean to say that during no playback and the volume is set to max, you don't have any hiss at all...dead quiet? Is this your case?

Then something could be wrong with my dac, right? please let me know how to get rid of that hiss if you know..what's contributing it.

[StanleyB]

While most time we check the quietness of the system by setting the volume to max with no music playback...Is there a way we could get rid of those hissing at all?

Realistically speaking, you need the Gator upgrade board for your particular situation.
Let me explain why I say that. The WM8716 DAC chip does not have an inbuilt analogue filter, unlike say its nearest direct equivalent, the PCM1716 as used in the TC-7520. Wolfson recommends an external low pass analogue filter after the output of the WM8716. Both the standard as well as the Gator audio board have such a filter.
The passive mod breaks all the established rules as far as filtering the audio sampling residues is concerned. The payback of that is that you'll get a near unadulterated digital to analogue output. But it has a low level unfiltered sampling noise residue. The noise is at about -80dB level, so if you turn your volume control to max you are likely to pick it up.

[goody]

Thanks Stan. By adding the low pass filter after the Wolfson, would the unadulterated sound be significantly impacted or not?

[StanleyB]

Thanks Stan. By adding the low pass filter after the Wolfson, would the unadulterated sound be significantly impacted or not?

If you mean the active low pass filter as fitted on the Gator, then the answer is that the jury is still out on that. Existing Gator owners are in the whole still grinning from ear to ear and most have been unable to tear themselves away from the music to come and give a detailed before-and-after update.

If you mean adding a passive filter that you yourself knock up, then I would have to say that it is very likely to impact on the sound.
It's like fitting a racing exhaust on a car. You can't hide the noise, but boy do you get some extra performance or what .

[DSJR]

You know, I think a little added "clean" noise can actually enhance our listening, smoothing over any slight non-linearities down at minus 80 and lower. I wonder if this is what many valve output stages/buffers do?

[MartinT]

You mean to say that during no playback and the volume is set to max, you don't have any hiss at all...dead quiet? Is this your case?

Yes.

[larry]

I have spent about 2 hours reading this whole thread. It starts off with electrolytic capacitor ($) and end with polypropylenes capacitor ($$$$$). =D Here is my very entry level setup.

Laptop>TC-7520(Fixed)>CA 340A>PSB Alpha B1

My TC-7520 used to have THS4032 for the fixed. After reading this thread, I remove the active board and inserted two 2.2uf electrolytic capacitors. It is just a normal cap. I was surprise on how this mod changes the sound. I am poor at describe sound but I love my current mod. I decided to purchase polypropylenes capacitor. Input impedance of 100k is recommended to use 0.8uf, my a340 is 40k so will be 2uf. The cap in my mind was the Claritycap ESA 2uf 630V. Is there other alternative for the brand and value I should consider?