Murata reg for Caiman

[robyonekenoby]

Hello, I'm going to replace the 7805 with the murata 7805sr

My local dealer has two model, 0.5 ampere and 2 ampere

May I go for the smaller one? No idea about the total 5V section current requirement

thanks

[StanleyB]

Can you let us know the part number of the ones your local supplier has? There are a couple of different versions. The horizontal PCB versions won't fit!

[robyonekenoby]

Hi Stan,

Actually they have two different versions for 0.5 A

7805SRH-C and 7805SR-C

[Reid Malenfant]

Having had a quick think about the present circuit i'd say that the 0.5A regulator should be sufficient ;) You might well need to remove the resistor feeding the standard regulator input as i think i remember someone mentioning they need a higher input voltage to give the 5V output :scratch:

I'd check the specs of both regulators though. Obviously you are attempting to improve things & you might well find the higher current version would do a better job at the end of the day :)

[robyonekenoby]

Hi Mark,

so you suggest to go for the 2A version, but is quite larger, not sure it fit in the box

[Reid Malenfant]

No, i said look at the specifications & see which has the lowest noise, ripple on the output etc ;)

The 0.5A reg is man enough for the job, it doesn't mean it's the better regulator though, for that you need to look a little deeper :scratch:

[HighFidelityGuy]

You want the 7805SR-C. The 7805SRH-C is the horizontal version which as Stan said won't fit. Also, as Mark said you can replace the resistor behind the 5V reg with a wire link as the Murata has a wider input voltage tollerance and so doen't require the resistor. :)

[robyonekenoby]

Thanks Dave, I put it on order right now

Plus a Nichicon OS-CON 220uF to replace the cap after the regulator and a 100uF ceramic multilayer in place of the tiny cheap 100uF electrolitc in the dac area

[Gazjam]

You want the 7805SR-C. The 7805SRH-C is the horizontal version which as Stan said won't fit. Also, as Mark said you can replace the resistor behind the 5V reg with a wire link as the Murata has a wider input voltage tollerance and so doen't require the resistor. :)

Hey Dave,
I've got both the Mutara's fitted to my Passive Mod Caiman, and I've not done this "wire link" yet.
Sounds like i should! :)

How would I go about it...?
Is there a good pic on any of the threads showing where to remove the resistor?
Is it just a case of snipping the legs and soldering in a wire link?
Any reasonable hookup wire do the job?

Is it feasable for a soldering noob like myself to do?

Also, does removing the resistor make the Mutara work "better", i.e. an improvement in sound?


Thanks (and sorry for the dumbo questions!)
gary.

[HighFidelityGuy]

Hey Dave,
I've got both the Mutara's fitted to my Passive Mod Caiman, and I've not done this "wire link" yet.
Sounds like i should! :)

How would I go about it...?
Is there a good pic on any of the threads showing where to remove the resistor?
Is it just a case of snipping the legs and soldering in a wire link?
Any reasonable hookup wire do the job?

Is it feasable for a soldering noob like myself to do?

Also, does removing the resistor make the Mutara work "better", i.e. an improvement in sound?


Thanks (and sorry for the dumbo questions!)
gary.

Hi Gary,

Here's a photo that shows the resistor:

http://i273.photobucket.com/albums/jj220/kingbusoms/WM8716.jpg

It's the beige one in the top left hand corner directly between the space where the 5V reg goes and the RCA sockets.

As for whether replacing it with a wire link will make any difference to sound quality I wouldn't have thought so but Stan is the best person to ask. I think it's just that the resistor was required for the old reg but isn't really for the Murata. I doubt that leaving it in will cause enough voltage drop to lower the Caiman's 15V input to below the 7805SR-C's dropout voltage of 7.5V. So personally I wouldn't take the whole thing to bit's just to do that one thing but it's up to you. :)

[HighFidelityGuy]

Sorry, I didn't answer your other couple of questions...

Any copper or silver wire of a similar thickness to that of the resistors leads should be fine. Solid core will be much easier to work with.

Installing a wire link has got to be about the simplest soldering task possible, so I'm sure you'll manage that bit. De-soldering the resistor will be the trickiest part. I'm not sure what soldering tools you have but a pair of tweezers, a solder sucker and some small wire cutters would come in handy. Just snip the legs on eather side of the resistor leaving enough leg left to get hold of it with the tweezers. Then gently heat the solder pad and carefully lift the leg stub out of the hole. Repeat for the other leg then suck out the remaining solder from hole with the solder sucker after applying some more heat. Or you may find that you can suck the leg stub out of the hole as part of the desoldering. Somtimes that works, sometimes not. It'll depend on how tightly it's in the hole.

Failing that you could just snip out the resistor body and solder in a straight bit of wire between the two stubs. That will skip the de-soldering but will make the soldering more tricky as the stub may fall down into the hole as you apply heat. Good luck. :)

[Gazjam]

thanks Dave,


(not expecting a big change, but if things will be exactly the same sound wise I'm happy to leave it in place.
any other thoughts on whether its worth doing guys?

[Reid Malenfant]

I'd suggest it's worth doing as long as you feel you can do it ;)

The reason i say this is that the current draw from the circuits following the regulator won't be continuous, they'll vary somewhat.

The consequence of this will be that the regulator will see what looks like ripple on it's input due to the varying current causing differing voltage drops accross the resistor. This will obviously effect the output of the regulator as well because it won't have an infinite power supply rejection ratio. As well as that loop gain decreases at higher frequencies so there will be less gain to correct the output.

Removing the resistor eliminates this varying input voltage to the regulator & will result in a more stable output from it imo :)

[MartinT]

As Mark says, removing the resistor will improve the performance of the regulator provided the input voltage is fairly constant, and that applies whether using Stan's 12V PSU or something else as some of us have done. I put a link in there for my Dexa regulators and they work just fine, not generating any heat even without the original heatsinks.

[Gazjam]

Removed the resistor (thanks Ali!) and replaced it with a wire link.

Have to say its improved things, well worth doing.
Thanks guys for the tip and the info.