PSU capacitors question

KanedaK

Member
2011-02-07 8:32 pm
Okay so as you all might have already guessed I'm new to audio DIY... so I apologize if my questions seem stupid...

I'm recapping my ReVox B226 CD player. It's from 1987 and for electrolytics uses only Frako and Philips blue. I know both these types tend to go bad after a while.

Following some very basic rules I bought a few diferent series of capacitors, based mainly on availability, ease of payment, low shipping costs, and went all Silmic II for the samm value electrolytics, with just a few panasonic FC here and there where space didn't allow the silmic version (or when I couldn't find the right value in Silmic II)

For bigger caps, I'm now confused. I thought anything I could buy would be much better than Frako; so I first settled on Nippon Chemicon SXE for the 2200uF PSU caps (25v, three of those): they are now installed and the sound has improved greatly. For the 10000uF/25v I first ordered a Nichicon FW. It's about to be delivered, I couldn't try it yet.
Then on another website I saw they stocked Nichicon KW, so I ordered that same 10000uF in 50v version, plus three KW 2200uF 50V, thinking maybe I should replace the Nippon Chemicon I already installed with those, and thinking maybe it's better to have the same type of caps for the whole PSU section.

But now I'm doubting wether I've made a sensible choice. Does it make any sense to use KW as PSU caps? Will it degrade performance instead of provide any audible improvement? I read audio caps are best used in the signal path, but then why on earth do they make them also in such big values? Marketing only?

Same question for the Silmic II: not being really able to tell wich caps are in the audio path (except at the most obvious locations), i decided it'd be easier to use Silmic II everywhere space allows, but now I'm doubting: will they perform OK in locations where they're NOT in the signal path?? Revox uses the same Frako type all over, except for output coupling caps and opamps decoupling (?) where they put Philips blue. Would it make more sense to use a non-audio, good quality cap to replace the Frako, and use only silmic II to replace the Philips Blue?

I've spend some money already, rushing without thinking enough... I know it was a mistake.
I don't really wanna spend more but I love this CD player and I don't wanna mess things up or end up with mediocre results.
 

KanedaK

Member
2011-02-07 8:32 pm
The main thing is you replaced the old caps. All being the same series does not matter, even brand does not as long as they are a decent quality.

If you start trying to remove the new caps you put in you are likely to damage the PCB. Always keep rework to a minimum.

I only replaced the PSU caps (and a few small caps wich can stay). I might leave the ones I already replaced then, but what for the rest? I'm awaiting the delivery of the other caps, should I use what I ordered, or choose something else? Elna Silmic iI are more than decent quality for signal caps, are they also good for other parts of the circuit as I first assumed?

thanks!
 

mrWagner

Member
2006-10-27 1:34 pm
I don't think there is any cap in signal path in a CD. But I don't know this device. As sad before replace the caps with decent caps. No need for any fancy stuff. Don't really understand that you bought random caps or more can be replaced with same type?
Why did you get so many caps for one place?
 
Capacitors C106/206, 110/210 and 117/217 are on the signal path. Nichicon Muse BP would be an excellent choice. Think about replacing all capcitors, including those on the CD drive.
I would suggest using Nichicon KL for Servo and Drive PCB and Nichicon KZ/FG (depending on size/value) on the Decoder PCB. KLs should also be on the decoder board after the LM regulators.
 

KanedaK

Member
2011-02-07 8:32 pm
Capacitors C106/206, 110/210 and 117/217 are on the signal path. Nichicon Muse BP would be an excellent choice. Think about replacing all capcitors, including those on the CD drive.
I would suggest using Nichicon KL for Servo and Drive PCB and Nichicon KZ/FG (depending on size/value) on the Decoder PCB. KLs should also be on the decoder board after the LM regulators.

Thanks a lot! I'm learning every minute...

I have a theorical question:
in the B226, what would happen if I replace the 47uF caps that are after the regulators on the decoder board with 100uF? (C2, C6, C8, C9...) I ask because of course I didn't learn electronics, and I still don't really know when and where it is OK to derate. I also happen to have a bunch of brand new Panasonic FC 100uF/25v that I have no use for. Assuming I could derate, would they then be suitable? (I'm not cheap to the point of HAVING to use them, I'm trying to learn... ;) )

thanks again!
 
Increasing the value of the output capacitor after voltage regulator should not affect its stability - that's the primary purpose of the capacitor there. However, be aware that there are equal chances to improve and to deteriorate the sound by increasing the capacity. It is always best to stick to the original values, I am pretty sure that Studer engineers did not save money on capacitors.
 

Eldam

Banned
2012-09-13 12:25 am
France
Here the caps just after the regs are certainly here to drop the impedance : it works better withe old used caps (most of the time) than good brand new caps : you can consider to keep these 47 uF, although 220 uF could be even better (always with old caps or if brand new ones with bad ESR spec = the cheapest current lines) if those regs are the 78xx or 79xx marked.

At the opposite the cap near the last active device feeded by the reg should have very low ESR.

Just my modest experience : not technician myself either (that's my ears which rules my experience by default to have brain !)
 
I see no reason to use 30 years old capacitors which have capacity and ESR out of spec, and are prone to leaking. The regulators in question are LM317/337 and they do require a low-impedance output capacitor - either a tantalum or a wet electrolyte paralleled with a ceramic to lower the impedance.
 

Eldam

Banned
2012-09-13 12:25 am
France
Well I talked in the case of 78/79 regs at their output only! And here I know why I advised what I advised ! ;) ! And if you think tantalum+electrolytic sounds good at the output of a reg, it's up to you (can work for digital chip but never on the analog outputs circuits) ! But I disagree... (and btw Tantalum have poor ESR !)

Btw it's true for the others caps : no Worth to double the capacitance. Like the main caps if the PS traffo has been made for this capacitance value !

just my two cents
 
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KanedaK

Member
2011-02-07 8:32 pm
Another question: around the NE5532 dual opamps, there are a bunch of (polyester?) small value caps (2200pF, 6800pF...) with 1% tolerance. I'm sure those are very good, and I was not planning to change them; however, i would like in the future to fit Sparkos labs SS3602 discrete opamps.
Problem is this: with the actual caps, there won't be any room for the discrete opamps, even tho they are comparatively very small (versus, say, burson offerings).
So the only solution would be to fit smaller (in size), same value caps directly next to the opamps. Would axial, 2200pF 63V 2% EVOX-RIFA polystyrene capacitors fit the bill ( C103, C104, C203, C204), or is it a bad idea to go from 1% tolerance to 2% tolerance in that particular location? Axial caps would mount horizontally, and their diameter would be small enough to be under the discrete opamp, when it's in a dip8 socket, with enough clearance.
 
Those capacitors are in equalization/deemphasis feedback of I/V conversion stage and have tight tolerance for a reason. You do not need to change them.
Regarding the change to other operational amplifiers, you might have an additional work to do to tame them if they happen to oscillate in that particular circuit, plus putting 300USD worth of them in this CD player might be an overkill. If you do not like the sound with present NE5532s, you can try gradual upgrade to LME49720 which I did in my B226 and stopped there as the sound pleased me. The LMEs are direct-swap and all you should do is to bypass supply legs with 0,1uF MLCC.
 

KanedaK

Member
2011-02-07 8:32 pm
Those capacitors are in equalization/deemphasis feedback of I/V conversion stage and have tight tolerance for a reason. You do not need to change them.
Regarding the change to other operational amplifiers, you might have an additional work to do to tame them if they happen to oscillate in that particular circuit, plus putting 300USD worth of them in this CD player might be an overkill. If you do not like the sound with present NE5532s, you can try gradual upgrade to LME49720 which I did in my B226 and stopped there as the sound pleased me. The LMEs are direct-swap and all you should do is to bypass supply legs with 0,1uF MLCC.

Thanks for ur advice!
Sparkos labs discrete are a dream for the future maybe ($$$). The plan is to buy LM4562 for now.
I believe they're the exact same chip as LME49720, is that right?
I was unaware tho, that they needed 0,1uF to bypass supply legs. I thought it was a drop-in replacement for NE5532.
Would you be kind enough to explain me how that is done, practically? I'm not sure what "bypass" means in this case, and where i'm supposed then to solder the bypass cap on the board...
Thank you so much!
PS the LM4562 will be fitted in DIP8 sockets
 
Specs are identical for LM4562 and LME49720 but some claim audible difference in favour of LME. I have never used LM4562 so I cannot tell.
Operational amplifiers are placed at a considerable distance from voltage regulators without local capacitors, so bypassing is always beneficial, regardless of the op amp type used. I also think that LME is more prone to oscillating than NE, so another reason to do so.
Bypassing means connecting a capacitor from every supply pin to the ground, placing them as close to the IC as possible and with shortest possible legs - sometimes a plane ground is not near and in that case you will want the capacitor leg leading to the ground to be the shortest possible. In my opinion, 0.1uF is sufficient and the best type are multilayer ceramic ones. There are also other practices calling for other types of capacitors or for series of them (i.e. 1nf, 100nf, 10uF).
 
It is better to directly solder the op amps. Use sockets if you want to experiment and swap different operational amplifiers. However, once you make up your mind, just solder them. IC sockets may create oxidation and dirt on contacts over time and may even mechanically eject the chip.
 

KanedaK

Member
2011-02-07 8:32 pm
It is better to directly solder the op amps. Use sockets if you want to experiment and swap different operational amplifiers. However, once you make up your mind, just solder them. IC sockets may create oxidation and dirt on contacts over time and may even mechanically eject the chip.

I bought the "best" sockets I could find, machined and gold plated.
I like the innards of the Studer A727 with epoxy board and everything in sockets, so much easier to work on!
That said, it is possible than the B226 board SOUNDS better because all is soldered... I don't know...
thanks for your help! I will look up more on bypass caps and opamp theory.
 

dazzz

Member
2013-04-07 3:01 pm
ashdod
I see no reason to use 30 years old capacitors which have capacity and ESR out of spec, and are prone to leaking. The regulators in question are LM317/337 and they do require a low-impedance output capacitor - either a tantalum or a wet electrolyte paralleled with a ceramic to lower the impedance.

Be careful with the outpute capacitor
On the LM317
Not good that the ESR will be too low. Oscillations
If you replace the capacitor Check the cap ESR
Or do an easy solution.
Add resistor at the out of the LM317
0.47 to 1 ohm
It's is a low pass filter .
That way you do not have to worry that the cap esr will be too low
I'm usually on the outpute of the 317
resistor 0.47 Ohm in series with 470uf cap
 

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KanedaK

Member
2011-02-07 8:32 pm
I've now replaced the big 10000uF frako pSU cap with Nichicon KW.

I'm sure someone will tell me there would have ben a better choice of cap for that use, and I respect the opinion of everybody here (completely noob as I am) but I have to say the result exceeds my expectations! (the three other 2200uF PSU caps had already been replaced with Nippon chemicon SXE)

lower noise floor (I now hear musicians humming in the background on some jazz tracks I've listened to a thousand times), great overall balance, jump-off-ur-seat dynamics, I will stick to these caps for now and forget about the fact that I could have found better ones. It fits, it works, it sounds great.

Until now my humble and cheap Kenwood DP7090 still had the edge on overall transparency and detail, now the ReVox wipes the floor with it, sounding "real" wile the Kenwood now sounds "good" but with a sense of "hifiness" to the sound that doesn't involve you as much in the music.

I still have to replace all the small value lytics and very eager to hear the (hopefully) improvement.
 
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