Capacitors

[paulrichards7]

As Im not having any luck finding the source of the noise on the channels of Studiomaster 16-4-8
Im just gonna go ahead and do a recap and see if that helps
Here is a quote from Jim Williams

"Add some local .1 uf mono ceramic psu bypasses off these chips, pins 4 and 8 to ground. Check with a scope for stability.

Remove the green/red "chicklets" mylar EQ caps. Use Wima FKP-2 or MKP-2.

Replace electrolytic caps with Panasonic FM or Nichicon HE. This includes side chain and psu bypass caps. Bypass signal EL caps with Wima .01 uf MKP-2, these are fitted on the trace side of the pcb"

Ive read in other places about grounding the pins of ICs
Will definetely be changing those chicklet EQ caps
Now as my PSU is putting out 15v, I was thinking of replacing caps with 25v caps, unless it requires higher values
But what voltage should the Wimas be?
And any other tips or suggestions
Thanks
Paul

 

[jackies]

Apparently, that's Jim Williams stuff you copy/pasted in the beginning of your post.
I saw him say to use 250v. But those would be quite large.
Also he usually says 0.1, I think .01 is a typo.
I think minimum voltage on film caps is 63v so you can't go lower than that anyway...
Do you have certain channels that are noisy, or it's the whole console??

 

[gswan]

As Im not having any luck finding the source of the noise on the channels of Studiomaster 16-4-8
Im just gonna go ahead and do a recap and see if that helps.

Sounds like a deperate idea, rather than analyse and determine the noise source.

 

[hotbaby]

>>> PSU is putting out 15v, I was thinking of replacing caps with 25v caps

i took a similar question last days and some nice members did some examples with voltages...
you must stay minimum 30-40 above the voltage, so i would suggest that 25v is too less. i would change them first and replace with 64v wima.

 

[gswan]

25V caps are fine for a 15V supply rail.

 

[paulrichards7]

Thanks for all the great info guys
as of WIMAs, its definetely .01uf
he has posted that ifo quite a few times
paul

 

[gswan]

A 0.1uF monolithic is a better option for PSU bypass.

 

[rodabod]

I couldn't identify which caps you replaced from your drawing, but I would suggest replacing just the electrolytic caps in one channel and see how you get on. The film caps are much less likely to be a problem.

 

[1954U1]

With an ESR meter you can try to see if the electrolytic caps just on the noisy channels are gone defective,
you can do it with caps onboard.

 

[paulrichards7]

Thanks for that guys
yeah, im definetely gonna play with 1 channel first and see how that goes
ive got 3 channels that are working fine to compare them to
ive got a function generator and a scope, although just learning to use them
ive got very accurate ears
as of the esr meter, i was looking at DIYing one as i dont have the money for a new or used one
or rather just investing that money in the caps and having a go
paul

 

[Harpo]

Thanks for all the great info guys
as of WIMAs, its definetely .01uf
he has posted that ifo quite a few times
paul

These 10nF caps are obviously ment in parallel for the EL caps in the signal path (from your posted schematic these 33uF/35V, 100uF/6.3V, 100uF/16V, 100uF/63V, 470uF/6.3V) "Bypass signal EL caps with Wima .01 uf MKP-2, these are fitted on the trace side of the pcb".
I'd replace only these maybe dried EL caps with same value and rating and listen to the results.

 

[paulrichards7]

Hey Harpo
thanks for that
awesome(just the audio path)
now Jim williams recommended at least 220uf caps, it has something to do with the bandwidth and keeping it set to 2hz, so when the phase(i think)effects a decade above(20hz) it wont effect the signal as it is out of the badwidth of human hearing.
Heres it from Jim
Another problem with leaving in older caps is for one they are usually too small in value. Designers typically use the smallest and cheapest parts they can so low end roll off are set to 20 hz or so. That will create phase shift beginning at 200 hz.
To remove it, roll-offs must be set to 2 hz so the phase shift begins at 20 hz or lower = not audible. Soundcrafts and others have that problem as they use 47 uf/25v caps everywhere, the use of 220uf caps does wonders. Those are still quite cheap, a 1000 piece bag of Panasonic FM 220 uf 25 v caps costs only $80. That's 8 cents each. There is no reason to buy lesser caps when these are so cheap.
thanks once again
paul

 

[gswan]

Hey Harpo
thanks for that
awesome(just the audio path)
now Jim williams recommended at least 220uf caps, it has something to do with the bandwidth and keeping it set to 2hz, so when the phase(i think)effects a decade above(20hz) it wont effect the signal as it is out of the badwidth of human hearing.
Heres it from Jim
Another problem with leaving in older caps is for one they are usually too small in value. Designers typically use the smallest and cheapest parts they can so low end roll off are set to 20 hz or so. That will create phase shift beginning at 200 hz.
To remove it, roll-offs must be set to 2 hz so the phase shift begins at 20 hz or lower = not audible. Soundcrafts and others have that problem as they use 47 uf/25v caps everywhere, the use of 220uf caps does wonders. Those are still quite cheap, a 1000 piece bag of Panasonic FM 220 uf 25 v caps costs only $80. That's 8 cents each. There is no reason to buy lesser caps when these are so cheap.
thanks once again
paul

You need to analyse the impedance seen by the capacitor in order to determine where the poles and zeroes are. It's not a one size fits all situation. A good designer will use the correct capacitors, it does not make much difference to end price.

I find it strange that people with no apparent circuit design knowledge instantly assume that designers and engineers are less capable than themselves. Try to understand what the circuit does and why the components specified are the values they are, then see what changes will do to fix things. Using caps that are too large can also do bad things in some analogue circuits.

 

[Harpo]

should only clear the .1uF/.01uF confusion. Cap values from posted schematic seem OK. There is not much need to go below f.i. 1.08Hz at the phantom blocking caps [HPF -3dB=1/(2*PI()*100uF*(1K5||100K)], introducing a phase error of -ARCTAN(1.08Hz/20Hz)*180/pi() = -3.08° at tested frequency 20Hz, (version without the 1K5 resistors @ 0.016Hz) or even below 0.5Hz in the following stages. Only for the rare case gain-pot full cw the 470uF/22R has a HPF @ 15.4Hz, that drops to 0.03Hz turning the gain-pot full ccw. Bypassing these EL caps in the signal path with any lower value cap such as 10nF will probably not change the circuit behaviour to a noticable degree. Just exchange the 100uF with 100.01uF from the example above...even tolerances of these 100uF caps are much larger, but YMMV. As gswan already posted, before you for whatever reason want to change these values, do some math.

 

[paulrichards7]

Ummmm
You completely lost me there
Paul