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MartinT
03-11-2011, 22:25
This is part 1 of my rebuild of the Beresford Caiman DAC and my original external power supply to incorporate Paul Hynes' power supply regulator modules. These will replace the SuperTeddy in the external PSU box and the Dexa regulator modules inside the Caiman.

Many enthusiasts, and I am one of them, believe that great audio components are practically defined by the quality of their power supplies. This is my attempt to go all-out for the best performance possible from the already excellent Caiman, using power supply modules made by Paul Hynes.

Showing the PR3 +16V regulator module for the external PSU and the two S17LNS2 regulator modules for the +5V and +12V internal voltage rails (coming in part 2).
http://www.mtc.me.uk/images/P1000472.jpg

Offering up the parts in my stripped-out PSU case and things are looking tight. As it turned out, the transformer was the incorrect voltage for centre-tapped rectification and needed replacing. Its replacement (0-15V, 0-15V, 50VA) was slightly smaller - phew! I snuck a Nichicon MUSE capacitor into the external capacitor connectors in the hope of better high frequency reservoir performance.
http://www.mtc.me.uk/images/P1000474.jpg

The PR3 now attached to the front panel. Heatsinking is not really an issue due to the small load current drawn by the Caiman (as it turned out, there is precious little heating up at all).
http://www.mtc.me.uk/images/P1000476.jpg

Adjusting for exactly +16V output. No need to worry about on-load adjustment as I doubt the voltage drop is at all significant (my Caiman has passive coupling caps with no op-amp board so there is precious little +12V draw). That LED is bright!
http://www.mtc.me.uk/images/P1000480.jpg

The completed external PSU in place and operational. Those old Hi-Fi News Flux Dumpers are perfect for the job.
http://www.mtc.me.uk/images/P1000484.jpg

So how does it sound? Considering I haven't given it much time to burn-in, the answer is significantly better than the SuperTeddy. I am hearing a wealth of tiny details and aural cues, bass is tighter and the overall soundstage is well defined and very transparent. Sound quality from Sky HD over optical and Blu-ray over co-ax are equally superb, as well as CDs using the Sony as a transport. The Caiman is not normally used for CD playback in my system, but I would be very happy indeed with it, it really is a DAC in another league altogether when fed from a power supply like this.

The SuperTeddy is well known for being an ultra low noise regulator design, but to the detriment of current and instantaneous peak delivery. The PH PR3 design features heavily in transient power delivery and is no slouch in the noise stakes, either. It seems that the Caiman, and particularly the Wolfson 8716 DAC, benefits from being fed by a meaty, over-spec'd PSU.

Ancillaries: Multicomp MCTA050/15 0-15, 0-15 50VA transformer; Kimber PBJ DC cable; Maplin project case, really very bright blue LED.

Part 2, replacing the internal regulators, will come soon.
Reid Malenfant
03-11-2011, 22:33
Lovely pics Martin, however you make the PR3 look simple ;) All the real control is on the back of the PCB & is surface mount components, then it starts getting complicated :eyebrows:

I have a PR3i powering my Octava HDMI switcher, the difference between that & a regulated (non SMPS) wall wart defies description :cool:

On with the thread :)
MartinT
03-11-2011, 22:37
Oh I agree Mark. All of Paul's modules are full of cleverness with SM components on the back. I have sat and stared at them, trying to get the circuit in my head, and given up.
Paul Hynes
04-11-2011, 00:01
Hi Martin,

Thanks for taking the time to set this up and report your findings. That LED is bright! You can adjust the light output by increasing the value of the axial resistor to the right of the reservoir capacitors until you have the desired light level. This will have to be trial and error depending on the spec of the LED you have selected.

Hi Mark,

Nice to hear that the PR3 worked well with the Octava.

Regards
Paul
Butuz
04-11-2011, 00:52
Excellent thread!

Butuz
MartinT
04-11-2011, 06:18
That LED is bright! You can adjust the light output by increasing the value of the axial resistor to the right of the reservoir capacitors until you have the desired light level.

Yes indeed, it's just a matter of taking it apart again. I think I'll start by at least doubling that resistor value :)

I've left the PSU and DAC burning in all night and today with some Sky MTV, which should get it into its stride. Further listening tonight.
John
04-11-2011, 07:34
Lovelly write up Martin
HighFidelityGuy
04-11-2011, 10:48
Nice one Martin! I can see I'm going to have to invest in some of Paul's power supplies next year. :eyebrows:

EDIT: I seem to remember that someone else looked into using Pauls regulators in the Caiman but came to the conclusion that there was an issue with dropout voltage (or something like that) that would make them unsuitable. I may have remembered that wrong but perhaps someone can clear that up? :confused:
Clive
04-11-2011, 11:04
Nice one Martin! I can see I'm going to have to invest in some of Paul's power supplies next year. :eyebrows:

EDIT: I seem to remember that someone else looked into using Pauls regulators in the Caiman but came to the conclusion that there was an issue with dropout voltage (or something like that) that would make them unsuitable. I may have remembered that wrong but perhaps someone can clear that up? :confused:
The dropout voltage on Paul's regs has been between 4.5V and 6V IIRC. The variation is down which components were used for a specific board. I think Paul had recently re-worked the regs, I don't know if this has changed the dropout voltage. For the first reg inthe Caiman it seems like a PS outputting at least 18V would be needed, this is for the previous version of the regs.
MartinT
04-11-2011, 11:58
My 15-0-15V transformer gives 21V raw DC [15 x sqrt(2)], which is perfect for the PR3 to supply 16V (5V drop). When I next open up the Caiman I shall remove its protection diode so as to feed the new regulators with 16V direct and eliminate the 0.6V voltage drop.

P.S. don't do this if you have the original 16V reservoir capacitor in place.
Paul Hynes
04-11-2011, 12:14
The dropout voltage of all the regulators I supplied to Martin will be less than 3v3 up to 1 amp (much more than the Caiman requires) as the logic level mosfets I have fitted for the output devices have low gate threshold voltages. So the 12 volt internal regulator should be fine with 16vdc input.

Regards
Paul
HighFidelityGuy
04-11-2011, 12:23
The dropout voltage of all the regulators I supplied to Martin will be less than 3v3 up to 1 amp (much more than the Caiman requires) as the logic level mosfets I have fitted for the output devices have low gate threshold voltages. So the 12 volt internal regulator should be fine with 16vdc input.

Regards
Paul

Thanks Paul, that clears that up. :)

I was just a bit worried as from what I understand the headphone output on the Caiman takes an unregulated feed directly from the DC input. So going over 16V input could cause issues with cap values on the opamp board. The main resevoir cap on the Caiman is also 16V but I know Martin has upgraded that, so that's fine.

Sorry for the slight thread hijack Martin, I just wanted to clear that up as I thought it was important. :cool:

Good luck with the regulator swap. :)
MartinT
04-11-2011, 19:49
That LED is bright! You can adjust the light output by increasing the value of the axial resistor to the right of the reservoir capacitors until you have the desired light level.

I guessed that doubling it would be about right, and it was. I replaced the 4k7 resistor with a 10k and the light level is now fine.
MartinT
04-11-2011, 21:57
I've now installed the +5V and +12V regulators inside the Caiman.

Showing the PCBs after installation of the two PH regulator modules. It's a tight fit but it can be done and I used double-sided sticky pads to hold them in place.
http://www.mtc.me.uk/images/P1000485.jpg

This is a complete list of the mods made to these boards:
- All audio path electrolytics replaced with Elna Silmic II
- Main 10,000uF reservoir cap replaced with 2 x 10uF Panasonic film caps
- PSU protection diode replaced with a wire link
- Op-amp board and socket removed and replaced with 2 x 2.2uF Auricap coupling caps
- 3-pin regs replaced with +5V and +12V PH modules

The sound quality after replacing the Dexa regs was a smaller but further improvement in refinement and focus. I noticed especially a very high level of transparency with female voice and increased heft in the bass.

Listening to Barcelona from Jewel's Spirit album usually tells me all I need to know about sound quality. Her beautiful but powerful voice soars now with no hint of harshness, underpinned by a very potent bass line that is more textured than ever while having no remaining hint of boom. It's quite a performance and the Caiman sounds frankly fantastic playing it.

All in all a very satisfying modding experience. I'm going to leave well alone now, let it burn in some more and enjoy the fruits of my labours.