Murata regs + Caiman = Problem??

[mcebrian]

Hi! I just upgraded my Caiman with Murata regs, and I'm a bit sad with the upgrade. Both new regs (5,12v) are in place (correctly soldered).

It works, but, there is a high level background noise that was not there before. Very annoying!!

Steps already taken:

• Use a medical-grade PSU 16V (instead of 15v because of Vdrop from the diode) :: Result: NONE. Same noise.
  
• Try to put two caps 100uF 25V between pin 1 and 2 of the regs (as described in datsheet). :: Result: NONE.

Same noise is at the headphone output as at the fixed line output. Noise is the same with the GATOR on or with the original PCB.
In my (bad quality) scope it appears as a constant 20-24mv wave when you generate a test signal (-120db no matters frequency) with the computer.


I paid for the Muratas and at the end it turns out that they perform worse?? At lest regarding noise performance.

On cans, background noise is perfectly audible from 12 o'clock knob volume position.

Parts involved:
Murata 7805SR-C 0.5A max Part n: B036C
Murata 7812SR-C 0.4A max Part n: B046C

[markf]

They are switching regulators, not sure why you selected those, what was your reason ?

[mcebrian]

Because I think they are recommended by Stan and many others: http://theartofsound.net/forum/showp...0&postcount=55

and they cost about 20€ not 100€ like the belleson which I prefer of course!

[slate]

If memory serves me well there is 1-2 guys in here with the same problem

Gazjam posted this on another forum yesterday:
"though I will be replacing the Murata 12V regulator with a Dexa UWB discreet to eliminate switching nose Im getting with the Gator in place"

When they get eyes I am sure that they will let you know... in the meanwhile you could give the search engine a spin

[leo]

I never tried these particular regs but their reported to be a noticeable improvement over the stock fitted ones, maybe you have one which is faulty Do you still hear this noise without any music playing? I'd have thought they would have filtering at the switching frequency .
What noise is it ? hum, hiss, buzzing?

[mcebrian]

If memory serves me well there is 1-2 guys in here with the same problem

Gazjam posted this on another forum yesterday:
"though I will be replacing the Murata 12V regulator with a Dexa UWB discreet to eliminate switching nose Im getting with the Gator in place"

I read it also! Thanks!!

I never tried these particular regs but their reported to be a noticeable improvement over the stock fitted ones, maybe you have one which is faulty Do you still hear this noise without any music playing? I'd have thought they would have filtering at the switching frequency .
What noise is it ? hum, hiss, buzzing?

No, I can't hear any noise without music playing. (due to auto mute relay I suppose). It's like white noise. The typical background noise with a spike around 15 Khz

Thank you guys! I think that the only solution would be to trash the murata 12v reg...

[StanleyB]

I'll try to find out if there has been any changes in the specs of the latest Murata regs and the ones that were used initially for this mod. So keep the regulators close by in case there is a simple solution.

[paul_cz]

I can also report that I noticed this noise since I installed the Muratas about a week ago. Seems to be a problem with the Gator board only (mine is from the first batch with replaced R1 & R2 to 15k to reduce Gain), as the noise is absent when running the Caiman with the passive mod. With the passive mod the Muratas a big improvement ...

Cheers,
cz

[Gazjam]

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...

[chapter three]

I never heard this with my Caiman/Gator which had Muratas but it distorted in my system with Mk 1 Gator, Mk 2 was fine.

I moved on to an M2Tech Young which I find significantly better than the Caiman/Gator in all aspects. Night and day etc.. YMMV..