Murata regs + Caiman = Problem??

[HighFidelityGuy]

Thanks chaps.
I'm happy to report that my Dexa's are installed and they've cured the hiss and the whistle!

The Murata regs were quite tricky to remove as their pins fit quite tightly in the PCB holes. The 5V reg was the worst as it's on a double sided board with through plated holes. Despite being very careful I managed to pull out all three of the through plating tube things. It wasn't a major issue though you can just solder the pins on both sides of the board. I also ended up needing to replace both ribbon cables with individual cables as they pretty much fell off. I'm not surprised really as I've taken the PCB's out of the case quite a few times and they're quite brittle. So those two little slip ups made the job take longer than it should have but the excellent result was worth the effort and time.

I'll report back in a few days on sound quality once the new regs have bedded in.

[HighFidelityGuy]

On the subject of heat output from the Dexa regs, the 5V one definitely gets rather hot. I removed the 10 Ohm 1W resistor from behind the 5V reg when I installed the Murata regs. So no doubt the excess heat from the 5V reg is due to the fact it's dropping 10-11V. Ideally we could do with dropping the input voltage to the 5V reg down to about 8V. Does anyone know what resistor value would achieve that?

EDIT: I guess I need to know how much current the 5V part of the Caiman draws through the resistor so I can plug that into ohms law. Does anyone know what the current usage is? Cheers.

[MartinT]

I've left mine without a heatsink, since the tilt required to get the Dexa inside the cover makes adding a heatsink difficult. I too have bypassed the dropper resistor.

[HighFidelityGuy]

Thanks Martin. I'm sure the Dexa regs work ok without a heatsink but when you read the installation info on the NewClassD it does recommend that if the original reg had a heatsink then you should also use a heatsink with the Dexa. So I'm just trying to follow their guidelines.

[Gazjam]

I've left mine without a heatsink, since the tilt required to get the Dexa inside the cover makes adding a heatsink difficult. I too have bypassed the dropper resistor.

Hi Martin,
do you mean you removed the resistor behind the 5v reg and replaced it with a wire link?
Thats how my dac is...would be great if I could stop tinkering with it now!

Dave,
have you sen this post?

http://theartofsound.net/forum/showp...5&postcount=41

[MartinT]

Yes, Gaz.

Hmm, nice heatsinks in Paul CZ's shots. Looks like they had the attentions of a hacksaw.

[slate]

Yes, Gaz.

Hmm, nice heatsinks in Paul CZ's shots. Looks like they had the attentions of a hacksaw.

a hacksaw!!! you make it sound so cheap and brutal. I am sure that it was done with a delicate touch and the use of a fairy's brom

[Gazjam]

Yes, Gaz.

Hmm, nice heatsinks in Paul CZ's shots. Looks like they had the attentions of a hacksaw.

Excellent, no more tinkering for me. (he says....again)

[MartinT]

Not ever having used the Muratas, I'm intrigued that two of you report a sound quality difference when swapping to the Dexas. Could you say what that difference is?

Perhaps Stan needs to switch to recommending the Dexas as the upgrade regs from now on. Certainly I've had no issues with mine at all since I put them in.

[Gazjam]

Not ever having used the Muratas, I'm intrigued that two of you report a sound quality difference when swapping to the Dexas. Could you say what that difference is?

Perhaps Stan needs to switch to recommending the Dexas as the upgrade regs from now on. Certainly I've had no issues with mine at all since I put them in.

Good point Martin.
the majority of folk had no problem with the Gator/Murata combination so it was a sound recommendation.
BUT...
the Murata's are switching regs, probably not whats ideal in a dac. I remember someone saying at the time (DJSR was it?) that it seemed an odd choice.
Regarding the Murata background noise, best theory I've heard came from Jimmy Dripps of Tirna (and I no doubt misquote), who thought it was a case of both regulators operating at a frequency too close to each other (just bad luck) and this caused an audible "beat" which manifested itself as the noise.

The improvement?
Apart from the obvious removal of the background tone I have a more solid soundstage with better placement.
Also the front to back stuff seems more obvious to me.
Biggest change though (in my system) is that it plays tunes better.
Rythyms flow better, it seems smoother but with more detail?

Maybe the hallmarks of cleaning up the power going to the dac chip?
Dunno..but it works.