Quick check RE: Murata regulator replacement for Caiman?

[chrism]

Hi Maniac,

I think that most people are setting the PSU without load.

Remember that you have a diode and a few tappings from the 15.3v voltage you have set the PSU at (and the 15.36v will be without load). I think that if you have the PSU connected and the DAC powered up and then read the voltage directly in front of the 12v reg I bet that you are well below the 15.36v you set. You may have to turn the PSU up to achieve say 14v at the reg.

Regards

[Canetoad]

Hi Chris, my laboratory linear PSU goes to 15.36V and even on this voltage the whistling is there. If I remember correctly the data sheet of 12V Murata this headroom should be OK. Anyways if I would like to go to higher voltage then the 10k 16V big cap would need to be replaced by something what can survive that voltage and then replace PSU which can go higher than those 15.36V.. Seems that I'll wait on report that Dexa newClassD solve the whistling even with using 15V PSU and then go for Dexas
BTW I'm not sure if only 12V Murata has to be replaced, if I remember correctly, even touching the 5V Murata changed the whistle frequency so possibly both has to be replaced - I would be interested if my assumption is correct

Tomas, I'm running mine using a Maplins linear PSU which is putting out about 15.1 Volts (no load) and I have no noise coming from my Caiman with the Dexas fitted. I'm going to replace it with a home made version set to just under 16 volts.

[chrism]

If your linear PSU has a decent smoothing cap say 10,000uf you can take out the one in the Caiman as it is rated at 16v. If you are worried about RF you could just use a small cap or tant rated at 25v say.

Not certain about the rating of the Gator as I don't use one (stayed with the passive mod). I think, but not sure, that the Gator takes an unregulated feed from near the input cap.

I still think that a dedecated 5v linear PSU inleau of the superreg is the way to go.

Regards

[Gazjam]

My linear PSU has smoothing and I removed the big cap in my Dac and replaced it with a 25v Oscon.
Well, I HAD to after the big cap burst!

Just ordered a set of the Dexa regs...HOPEFULLY this will be the end of my whistling dac!

[Canetoad]

I hope so Gaz. Good Luck!

What PSU are you using now?

[Gazjam]

Hi Bernie,

I'm using one of THESE hooked up with a meter of Mark Grants mains cable.
http://www.tdk-lambda.com/products/s...ns/indexe.html

NNS15-15 15V 1.4A 21W

You can set the voltage +-10%, so just a smidge under 16v into my Dac.
Good step up from the standard one, very clean, low ripple.

Oh, got the regulators at 20% discount, emailed to ask first and I got through to the boss!
That said, had to order via web which put it through at $39 each..so $90 all in - still got the discount to be applied.

Still cheaper than elsewhere, even at this price.

[Canetoad]

Gaz,

They should e-mail you a PDF invoice with the discount applied. Should end up being around $73 US including postage if they've given you the discount.

Thanks for the details on the PSU. I'll see how I get on with the one I'm going to put together. At some point maybe we could do a comparison between the Maplins, yours and mine.

[HighFidelityGuy]

On the subject of the 12V Murata reg possibly not getting enough head room; I've swapped the Caiman's reservoir cap for a 35V film version, removed the input diode, removed the resistor behind the 5V reg and set my linear supply's output voltage to 16V with the load attached. So I know that both regs are getting 16V, which is well above their drop-out voltage. Despite all that I still get hiss and whistling. So we can safely rule out the theory of the Murata regs not getting enough voltage.

The issue seems to be caused by the way the PSU, Murrata regs and Gator board interact with each other.

Is anyone having the noise issues with the Murata regs and Gator while using the original 15V Caiman supply?

[Gazjam]

Gaz,

They should e-mail you a PDF invoice with the discount applied. Should end up being around $73 US including postage if they've given you the discount.

Thanks for the details on the PSU. I'll see how I get on with the one I'm going to put together. At some point maybe we could do a comparison between the Maplins, yours and mine.

Hey Bernie...

what I've had from them is an email Titled "Your Receipt Order Number: xxxxx" which breaks down the cost showing both regs at $39.95 each + Tax@ $10.39, totalling $90.29

I'm guessing this is just to acknowledge the order and not the final invoice?
Sure it wont be a problem though

*EDIT*
Recent email: "The discount will be applied once we enter the order in and then you will receive an order confirmation from one of our sales administrators. "

Speaking of which,
we should compare dacs at some point - always nice to say howdy.

[chrism]

On the subject of the 12V Murata reg possibly not getting enough head room; I've swapped the Caiman's reservoir cap for a 35V film version, removed the input diode, removed the resistor behind the 5V reg and set my linear supply's output voltage to 16V with the load attached. So I know that both regs are getting 16V, which is well above their drop-out voltage. Despite all that I still get hiss and whistling. So we can safely rule out the theory of the Murata regs not getting enough voltage.

What voltage are you reading at the 12v regulator (pin in) with the DAC powered up?

Regards

Chris