Replace Tube Mic's Power Supply Resistors?

[xqtion]

Hi Experts,

Does it make a difference in sound quality if resistors in the tube mic's power supply are replaced with higher quality resistors (Vishay/Dale) ?

Or is it sufficient to just replace the resistors in the mic itself ?

Thanks!!

[S2udio]

In a word...No.
Just improves reliability

[Jim Williams]

Probably not. You can try some Mills or larger Dales or something, let us know.
The caps that follow will remove any thermal noise contributions.

I like a larger wattage as I prefer them to run cool.

[theBF]

Ditto

[xqtion]

Thank you guys!!

One more question, but replacing the capacitors in the power supply does make difference in sound quality of the tube mic right?

[illacov]

I will say yes.

But I would rather Jim and Jim give the answers to those questions.

Jim and Jim both have done some excellent work on PSUs over the years and I'd say that both are rather exceptional as to how they address PSUs.

Peace
Illumination

[xqtion]

Here's a pic of the power supply.

So the ones circled in red are the aluminium electrolytic capacitors I should replace with high quality polypropylene caps right?

Thanks!!

[Ike Zimbel]

Originally Posted by xqtion

Here's a pic of the power supply.

So the ones circled in red are the aluminium electrolytic capacitors I should replace with high quality polypropylene caps right?

Thanks!!

Nope. Film caps are physically much larger for the same value than an electrolytic. I can't make out all of the values on the board, but a 47uf/50 film cap would probably be at least the size of a D-cell battery. Seeing as there's already some film caps in there (like the red box in the lower left of the picture), I imagine the designers would have used film caps elsewhere if they could have fit them in.
Best,
Ike

[xqtion]

Then would my only option as far as the red circled caps go is to replace them with better brand electrolytics such as Panasonic, Nichicon or Rubycon with same values?

Right now the power supply has LSHC brand with values as following:
47uF/50V x2
22uF/400v x2
1000uf/50v
220uF/16v
1U/450v

[Haz-Mat-Strat]

I have used the Mills wirewound resistors in tube mic power supplies and they are dead quiet.

I would replace the caps to these values:

47uf 50v = Nichicon Muse
22uf 400v = 47uf 450v Axial The power supply was designed for axial capacitors.
1000uf 50v = 2200uf 50v
220uf 16v = 330uf 16v or 470uf
1uf can be replaced with a Polypropylene film cap

.

[xqtion]

Awesome just the info I needed!! Thank you so much Jim!!

More question though

Would changing those blue ceramic caps that are circled in black to something better result in better audio quality?
Also what are those in the middle with red arrows surrounded by blue ceramic caps?

Also are those white circled things diodes? Is it also preferable to replace those with soemthing better?

[Jim Williams]

Not knowing if your high voltage B+ lines are regulated, I would fit in the largest 400 volt caps I could. In fact, I would measure the rectifier voltage and if it's lower, like 325 volts I would step down to 350 volt rated caps and increase the values. I recently replaced 47 uf 450 caps with 470 uf's in a tube mixer, that really sucked the residual ripple down to almost nothing. Same in LA2A's, I use 220 to 470 uf mains caps in place of the 47's and that always makes them quieter. Then you will also need to address the heater lines but if they are regulated they won't make as much difference.

My 1960's Fender guitar amps came with small 22 uf caps, I installed 220 uf's and that made a world of difference, no hum anymore, nothing.

[Ike Zimbel]

Since no one else has mentioned this: While you are in there, be VERY CAREFUL, there are some VERY HIGH VOLTAGES inside.
Keep breathing...
Ike

[xqtion]

Thank you so much! I'll becareful too

So those components circled in black and white in my previous post aren't something I should worry about too much ?