Caiman passive output mod revealed

[Marco]

Hi Larry,

Just a quickie, mate - when you get a minute could you add your basic location details to your proflle? This is now the requirement for all members of AoS.

Cheers!

Marco.

[larry]

I apologise. I have update my profile.

[MartinT]

Hi Larry

2-2.2uF seems to be a good value and should suit your input impedance. We have had good results from ClarityCaps and AuriCaps so take your pick.

[robyonekenoby]

I wanna add my experience with passive mod on the caiman

removed the analog section and connected wm8716 exit to the rca via two big MKP film foil cap, Audyn Mcap Plus 3.3uF

Dramatic improvement in clarity, definition, smothness, 3D... every aspect improved noticeably

but

the bass became too light for my taste

With this combination the bass is stronger, better defined, rock solid, tigth, but lack that depth in the very low frequency, that was present with the opamp stage

so just for fun I bypassed those two big caps with two small rubycon 47u

the bass is back !!!

but

midrange and high are messed up

in Italy we say "you can't have the bottle full and the wife drunk" ....

ok

so I replaced everything with two MKP film foil, always Audyn Mcap plus, but 6.8u (I had them on another DAC)

ok, this seem a reasonable compromise

mid and high seem loosing nothing, and bass quite a bit deeper, probably 10u
would be better, but when you speak about resolution on coupling cap, less is more, I mean, the bigger the cap, the greater the attenuation and phase shift due to dielectric absorption

But what I really can't understand is why I need such a big cap value when the math tell me that 3.3u should be more than enough (my amp has a MEASURED input impedance of 44k)

a fellow here in another thread told me it could be just a matter of dac output impedance

hmm, good explanation, but a lot of people in this thread affirmed they had good result with lower capacity, 2.2 or even 1.6u

this puzzle my mind

[HighFidelityGuy]

hi,
I had the passive mod done and is sounding very very good indeed.

I noticed that with no music playing into the DAC and the volume of my integrated amp is turn to the max, I can hear quite a lot of hiss from my speaker for both channel. But when I switch to another input of the amp, there is no hiss anymore. Could you please advise is the hiss coming from the DAC passive mod or not? Before the mod I think with the Opamp board there wasn't hissing...if I recalled correctly.

Hi Goody. What method of passive mod did you have done? If you've had caps wired directly between the DAC chip output and the RCA sockets then you've bypassed the Caiman's onboard muting relay. If the caps are inserted into the sockets where the opamp board used to be then you've not bypassed the muting relay. The muting relay turns off the audio output when the music is stopped and therefore prevents any hiss from getting to your amp. This could explain the hiss you're now hearing.

[goody]

Hi Goody. What method of passive mod did you have done? If you've had caps wired directly between the DAC chip output and the RCA sockets then you've bypassed the Caiman's onboard muting relay. If the caps are inserted into the sockets where the opamp board used to be then you've not bypassed the muting relay. The muting relay turns off the audio output when the music is stopped and therefore prevents any hiss from getting to your amp. This could explain the hiss you're now hearing.

Hi, Thanks for your inputs. I had the passive mod without bypassing the muting relay (with caps inserted into sockets).

[MartinT]

Hi Goody, that is really strange. With the DAC in mute mode, you shouldn't get any noise at all. It suggests that your preamp has a lot of self-noise when not loaded down with an input. If you unplug the DAC and turn the volume up (careful), do you get the same noise?

[goody]

Hi Goody, that is really strange. With the DAC in mute mode, you shouldn't get any noise at all. It suggests that your preamp has a lot of self-noise when not loaded down with an input. If you unplug the DAC and turn the volume up (careful), do you get the same noise?

Hi Martin,
Yea, without the DAC at the input of the integrated amp and the volume turn up to max, there is no hissing (it's quiet).

According to Stan's response, the Wolfson WM8716 DAC chip does not have a internal filter before its output (raw output) so about -80dB sampling noise get through into my integrated amplifier when I turn the volume max without music playback.

btw does sampling noises translate to audible hissing to our ears? please advise.

[MartinT]

Could you maybe try a different set of interconnects with different shielding? Perhaps RFI is getting in and causing noise? There should be no sampling noise from the DAC when in mute mode, i.e. no disc is playing.

[StanleyB]

Hi Martin,
Yea, without the DAC at the input of the integrated amp and the volume turn up to max, there is no hissing (it's quiet).

According to Stan's response, the Wolfson WM8716 DAC chip does not have a internal filter before its output (raw output) so about -80dB sampling noise get through into my integrated amplifier when I turn the volume max without music playback.

btw does sampling noises translate to audible hissing to our ears? please advise.

My response was based on the assumption that you had bypassed the mute circuit. But if you have not bypassed the mute circuit then my previous response is not valid. The DAC sampling noise etc. cannot bypass the relay when the relay is open.
I think that what you are experiencing is an impedance mismatch, which can produce a noise.
The passive mod is obviously causing you a problem, so revert back to the original board.