Murata regs + Caiman = Problem??

[maniac]

Yup, I am having the same problem.
I recently fitted a gator board and thats when I started hearing the noise. I'd describe it as a low volume mid/high frequency whistle".

It wasn't there with the passive mod, only with the Gator in place.

My Murata's are from the original batch of mods. Stan reckoned it was probably switching noise from teh Murata's, the noise i'm hearing being "switching noise" from the regulators.

Most folk get their Gator's to play nice with the Murata's, so maybe its system dependant? Not sure how though but its maybe a possibility.
I read here that a couple of guys had the problem and solved it by hooking up an extra cap somewhere near the Murata.
Cant remember the details sorry! Would be good if one of those guys pitched up?

If its switching noise...the solution might be to get a non switching regulator.
as someone said though..they are pretty pricey...

Glad its not just me thats having this problem!

*EDIT*
any chance it could be power supply dependant?
I shortened the cable on my Maplins CB Radio linear supply and Im pretty sure the noise is even louder??
odd...

I'm one of the persons noticed the same noise/hiss issue with Muratas..
Here is some history of my troubleshooting:

http://theartofsound.net/forum/showp...9&postcount=25

http://theartofsound.net/forum/showp...0&postcount=37

http://theartofsound.net/forum/showp...1&postcount=41

http://theartofsound.net/forum/showp...8&postcount=48

http://theartofsound.net/forum/showp...1&postcount=60


To sum it up :

1. issue is there also with original Caiman PCB, but it's more emphasized with Gator PCB and still there with Gator PCB and Gator caps mod to enhance bass drive on HD800.

2. applying caps in parallel to Murata's Vin an GND changes the behavior of the issue - instead of faint tone about 1khz on background you will get unpleasant noise into whole spectrum (audible during critical listening - it sound harsh/digitally and also on spectral analysis) - therefore i've removed the caps at the end..

3. shortening cable between PSU and caiman (to about 23cm) did not helped.

4. the same situation if using original caiman psu or laboratory linear psu

5. i've replaced Muratas by freshly delivered new Muratas directly from USA - situation still the same.. I've ordered three pairs on top of one pair I already got from Tirna, just to be sure...

6. "SOLUTION" - there is one solution which is not nice, but actually WORKS with Murata's. You have to set PSU voltage to exactly 12,9Volt . I'm in this setup for some time already and I found this the only way to get rid of the background tone/noise after fitted the Muratas into Caiman.
This have one immediately noticeable drawback - the selected input LED indicators on caiman doesn't work reliably as Caiman require 15V to work properly, but once the desired input is selected it stays there and so I can live with that. Second drawback is not so noticeable but i believe to achieve the best sound quality Caiman requires between 15 to 16 Volt.

7. My hypothesis: Murata's start do regulating only if powered with 13.0 and more Volts. Therefore setting 12.9 Volt causes that power just pass thru Muratas without any action by Muratas. Therefore I believe the tone/noise (which BTW changes frequency dependently on input voltage) is cause of Murata's regulation.

8. I'm just hobbyist and therefore not able to design solution how to filter muratas properly, but if someone would be able to find some way how to get rid of the noise produced most probably by Muratas, i would really appreciate that I did not want to experiment further as Caiman PCB is now quite wounded by too many soldering during replacement of the regulators, but once there would be final solution I would go for it.. I was even thinking about going back to "cheaper" LINEAR regulators ...

[Gazjam]

Fantastic post Tomas, thanks.

Sounds like you have already thought of all the "what it's" and came back to the conclusion it's switching noise from the Murata's.
Not everyone gets it though...?

I had thought about swapping for a different PSU and different things, but you saved me doing that.
I feel though running the Dac at a lower voltage is a bit of a compromise...might as well get it running to it's maximum potential.

Anyways, for me it's a case of swapping out the Murata for something non switching.
Just to confirm though...
I've both 12v and 5v Murata's fitted, but would I only need to swap out the 12v, as that's the one which feeds the Gator?

This would dampen the dent on the wallet if I only needed one.

[MartinT]

Gaz - what Tomas has said pretty much proves that it's the 12V reg producing the noise, otherwise it would continue if the 5V one was responsible even if the input voltage were reduced to below 12.9V.

I don't have a Gator so I cannot say for certain that a 12V Dexa will cure the problem, but in passive mode there is absolutely no output whistle even if an ear is placed up to the speaker. I therefore believe that the Dexa has better noise performance than the Murata and is less likely to go into oscillation. However, if you have removed the big reservoir cap you must replace it with something to give stability close to the regs: I have 2 x 2.2uF polypropylene caps there.

[UV101]

OK, with my tin hat on.........

These Murata smps regs sound like they are more trouble than they are worth. I've said it time and time again, the psu is everything. Why not just push the boat out and try one of the decent linear regs out there? I believe mark from audiocom is a member here. I purchased a whole load of supereg 2's from him very cheap a while ago. They are 3 pin 78xx compatible. You could go even better and try a more expensive reg like a fidelity audio SPower (again 3 pin 78xx compatible) or even an off board reg like teddy or a more simple and much cheaper lm317 tracking pre reg (schema in the 317 datasheet or pcb's from Avondale).

Quite simply, my comments of a year ago seem to have been confirmed. Has anyone actually looked at the output and measured for noise etc.

There are affordable alternatives that have been designed with audio in mind, is it time to stop messing about saving £10 here and there and just bite the bullet??????

[Gazjam]

Thanks for that Martin, that confirms what you advised earlier about only needing a 12v reg.

I haven't replaced the big reservoir cap in my Dac,but will swap it out later.
For the moment though, will the Dexa run fine with the big cap in place?

You mentioned before that the Dexa is happier with 16v rather than the 15 I get from my Maplin linear supply, just need to source a good cheap linear supply.

[Gazjam]

UV101,

Any affordable Murata alternatives you can think of?

The Dexa reg is about £30 but it's spec looks very very good.

[MartinT]

Gaz - be careful with increasing the voltage to 16V only because that is the big electrolytic's rating, if I remember correctly. May be better to replace it and go for 16V to ensure that the 12V has plenty of voltage drop across it.

Ian - I quite agree with you, which is why I have a SuperTeddy powering it at 16V and two high quality Dexa regulators, +12V and +5V, in place with the electrolytic replaced with large polypropylenes.

[UV101]

UV101,

Any affordable Murata alternatives you can think of?

The Dexa reg is about £30 but it's spec looks very very good.

78xx compatilble

Fidelity Audio SPower RRP £42 High Current (Nominal 500mA can heatsink)
Audiocom Super Reg 3 RRP £32 Low current? Unable to heatsink (Poss Mark can confirm the current rating)
HifiCollective Class D (DEXA) RRP £29.70 Unable to see current rating but looks to be heatsink mountable (Not tried these myself)
Tent Labs shunt reg €39 (approx £35) Low current (Not sure of suitability for this use)

Off board options

Super Teddy Reg €46 (approx £41) High Current
Avondale TPR2 Price to be confirmedHigh Current - I've built a couple of TPR1's and they were excellent VFM approx £5 per PCB unpopulated. Not sure on the options now as the product range looks like its being updated.

Personally I like the SPower. I now build my own modified version of this regulator. In general, most of these boutique reg use some kind of feedback to as a noise cancelling circuit.

I know I keep harping on trying to persude you to spend your hard earned cash on nice low noise regulators but there is a reason I have 4 in my Squeezebox with another 5 on the DAC I use with it and 17 in my CDP! Marco's CDP had the works at Audiocom with so his will have a few. I really is worth the investment!!!!!

Trust me.......Treat yourself!!!!!

[StanleyB]

I would personally advise against going above 16V on the power supply.

I hope to start on another round of mods soon. I even made the TC-7520SEG case 2mm higher so that I can stick my THS4032 safely in it. But in the mean time I am playing about with the standard regs and a few test mods.

[UV101]

I would personally advise against going above 16V on the power supply.

I hope to start on another round of mods soon. I even made the TC-7520SEG case 2mm higher so that I can stick my THS4032 safely in it. But in the mean time I am playing about with the standard regs and a few test mods.

Hi Stanley - Is there a 16v Smoother pre reg? If so, would there be an issue running a higher voltage rail if this was replaced with a suitable 25v cap for example?