Caiman passive output mod revealed

[Ali Tait]

Cool,I'll get some to try after these Mundorfs have had a fair go.

[NRG]

I have asked Jimmy at Tirna Electronics to supply them for the MOD21 on the TC-7510, and the passive mod on the TC-7520 and Caiman. Jimmy can be reached on:
Tel: +44 (0)1968 660605
Email: sales@tirnaelectronics.co.uk

He has agreed to ship to just anywhere on the planet . Price is around £2 delivered to the UK. I reckon it will cost a few pence more for postage outside the UK.

Thanks Stan (and Hamish for info re Tirna web site)

I think I've found another worthy contender the Starget ROD RS215-5708

Very solid presentation so far and seems to have not changed over the last few hours, another to add to the list

[fmzip]

In simple terms:
Capacitors pass AC and block DC.
Inductors pass DC and block AC.
The amount by which they pass AC is determined by their value. There's a lot more to it than that, but it'll do for now.

The output of the Wolfson DAC in the Caiman is at about +2.5V DC with the AC signal superimposed. If you were to connect it directly to your preamp/integrated amp you would be trying to amplify DC and either your speaker cones would come at you across the room or your amp would be uncomfortable, go into protection, overheat or otherwise. Some amps have an input capacitor and they would be ok, but in principle you need to block the DC so that only the AC gets through.

So you use a capacitor to pass the AC signal through. The value, together with the input impedance of your preamp/integrated, determines the lowest frequency (bass) that can pass. Simplistically. For common values of input impedance, values of 10uF to 47uF should be fine, as Stan says. The voltage handled needs to be 6.3V or higher (to comfortably deal with the 2.5V). The difference in sound quality is more likely to come from the different construction used to make different capacitors than its exact value. And that's where the fun begins...

Does that answer your question?

Excellent explanation, Martin!

I couldn't have said it better if I had your knowledge!

This forum is really a wealth of information, thanks for contributing !

[AndrewR]

On order and hopefully arriving Friday:

47uF 16V Rubycon ZA
47uF 16V Rubycon ZL
47uF 16V Jamicon standard ones
47uF 16V Nichicon MUSE ES
47uF 6.3V Nichicon MUSE ES
47uF 25V Nichicon MUSE KZ

Decisions, decisions...

Andrew

[fmzip]

Andrew, what other mods have been done to your Caiman?

[AndrewR]

Thanks Stan (and Hamish for info re Tirna web site)

I think I've found another worthy contender the Starget ROD RS215-5708

Very solid presentation so far and seems to have not changed over the last few hours, another to add to the list

Thanks NRG - solid presentation, sounds like my thing Will add to my list.

Andrew

[AndrewR]

Andrew, what other mods have been done to your Caiman?

It's actually a 7520 with Wolfson, MuRata, Silmic II and Bipolar Rubycons on the op-amp board (no longer installed).

Currently doing the passive thing with Black Gate FKs in socket PIN3B.

Also using the 7520 power supply, which I prefer to the Caiman PSU (odd I know, but it has more vitality and body) and the Maplin CB linear PSU (which I will mod with better caps and diodes).

Andrew

[Clive]

Also using the 7520 power supply, which I prefer to the Caiman PSU (odd I know, but it has more vitality and body) and the Maplin CB linear PSU (which I will mod with better caps and diodes).

Andrew, are you running a 12V MuRata from the 7250 supply? I've seen that you find it sounds better this way. I'd expect the reg to be dropping out due to not enough volts so I'm not sure what's happening here.

[HighFidelityGuy]

That's what I was thinking. The 12V Murata reg needs at least 13V input, so that means you need to use at least a 15V supply or you're not powering it properly.

[AndrewR]

That's what I was thinking. The 12V Murata reg needs at least 13V input, so that means you need to use at least a 15V supply or you're not powering it properly.

Hi HighFidelityGuy and Clive,

My thoughts also. However the Caiman supply I had sounded much worse (e.g. very flat) than the 7520 supply - just as it did when using the standard regulators. Also the 7520 worked well when the op-amps were installed (indicating that the 12V MuRatas were still providing a working voltage and current).

I think my experience is an anomaly - perhaps I had a duff Caiman supply and a 7520 supply passing more than 12V (yet to test that though). However, even my Maplin CB supply at 15V does not beat my 7520 supply in terms of sound - yet.

Andrew