I was thinking about the DC blocking caps that are in the signal line between the input tube , the phase splitter tube and finally the output tubes.
also the input cap which is in the very signal input to the first tube.
I agree that much BS and loads of talk have been about this.
I guess I have chosen the Panasonic ECWF (A) polypropylene film.
Just out of curiosity is Panasonic considered good among DIY enthusiasts ?
also the input cap which is in the very signal input to the first tube.
I agree that much BS and loads of talk have been about this.
I guess I have chosen the Panasonic ECWF (A) polypropylene film.
Just out of curiosity is Panasonic considered good among DIY enthusiasts ?
Hello,
Most any decent brand polypropylene is better than polyester for this purpose and will work pretty well. Check out Cecil Bates articles if you want technical information by someone who did a lot of research on this. But what you selected is pretty decent.
That said, you will find opinions that only $200 caps are appropriate for this as well as that oil filled and other special types are the only way to go. You can search and find thousands of variations of opinions on this and still be in doubt.
Regards,
Greg
Most any decent brand polypropylene is better than polyester for this purpose and will work pretty well. Check out Cecil Bates articles if you want technical information by someone who did a lot of research on this. But what you selected is pretty decent.
That said, you will find opinions that only $200 caps are appropriate for this as well as that oil filled and other special types are the only way to go. You can search and find thousands of variations of opinions on this and still be in doubt.
Regards,
Greg
OK, these are not decoupling caps, they're exactly the opposite- they're coupling caps. If they're not leaky or defective, leave them be. At best, replacing them will give you no real improvement and at worst, the replacements (or the process of replacement) could degrade performance.
Most articles about the evils of capacitors (like Bateman's) are inapplicable to most capacitor use as coupling devices, but serve the useful purpose of driving aftermarket capacitor sales.
thanks folks, especially SY I like you're down to earth reasoning.
i don't change the cap values or other parameters , It's just that these original caps were not the best to begin with and I think some proper replacement is not going to hurt.
Also I want to change them because I have ordered new electrolytics for the same amp's power supply because the old ones have some 26 years and two were absolutely dead (no contact) the rest were with less than specified capacitance as I measured.
Also because this is an old Soviet amplifier I have learned over the years which soviet parts were of good quality and which were to be avoided.
the filter caps in this one were made in the worst cheap end soviet civil factory located in nowadays Armenia and add to that in the final years of the USSR so no wonder they lost contact before they lost capacitance.
(I have another amp like this which has much better factory made same soviet caps and they are still up to the task, I guess I like George Orwell when he said " All animals are equal, but some animals are more equal than others")
the small capacitance films usually last much longer and are not so prone to dying with age but still I think modern Panasonic is going to be better than the original 1989 manufacturing year civil thing that I have in this amp right now.
i don't change the cap values or other parameters , It's just that these original caps were not the best to begin with and I think some proper replacement is not going to hurt.
Also I want to change them because I have ordered new electrolytics for the same amp's power supply because the old ones have some 26 years and two were absolutely dead (no contact) the rest were with less than specified capacitance as I measured.
Also because this is an old Soviet amplifier I have learned over the years which soviet parts were of good quality and which were to be avoided.
the filter caps in this one were made in the worst cheap end soviet civil factory located in nowadays Armenia and add to that in the final years of the USSR so no wonder they lost contact before they lost capacitance.
(I have another amp like this which has much better factory made same soviet caps and they are still up to the task, I guess I like George Orwell when he said " All animals are equal, but some animals are more equal than others")
the small capacitance films usually last much longer and are not so prone to dying with age but still I think modern Panasonic is going to be better than the original 1989 manufacturing year civil thing that I have in this amp right now.
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What is "best"? If they were competently made (like almost all normal commercial caps) and of the right value (assuming the designer knew what he was doing) and appropriate dielectric (almost any film type) then they are fine.crazymechanic said:
Experience on this forum is that replacement could hurt. Two problems keep cropping up:
1. soldering errors when replacing caps
2. new large caps creating instability
You should assume that any competently made plastic film cap will last almost for ever. Replace only if found to be faulty.
well these (the original ones) are not exactly what you would think of plastic films , they are closer to aluminum film/foil i'm not sure what they are.
I will try to find a picture of them later.
as you said it's not so much about simply changing caps for the happiness of ones mind rather the manufacturing quality+age with these caps, well the electrolytics with the logo G are terrible to begin with any electrician coming from the former USSR would be willing to swear by that.
these low capacitance films are in a better position but still.
soldering is no problem in this case , I have done electronics pcb soldering for quite some years and it's all fine.
I will try to find a picture of them later.
as you said it's not so much about simply changing caps for the happiness of ones mind rather the manufacturing quality+age with these caps, well the electrolytics with the logo G are terrible to begin with any electrician coming from the former USSR would be willing to swear by that.
these low capacitance films are in a better position but still.
soldering is no problem in this case , I have done electronics pcb soldering for quite some years and it's all fine.
To add to this, I like to go with long life caps, they're generally still pretty cheap, but it's nice to have say a 10,000 hr lifespan, or longer even.. Just makes sense to me for a pretty negligible price difference.
Take a 47µF / 450V Electrolytic for example.
Nichicon 2,000 Hrs @ 105°C For $2.83 CAD:
UPZ2W470MHD Nichicon | Capacitors | DigiKey
OR
Nichicon 12,000 Hrs @ 105°C For $2.99 CAD:
UCA2W470MHD Nichicon | Capacitors | DigiKey
For electrolytics, I really like Nichicon.
At the company I work for, we have barcode printers that were installed over fifteen years ago that are getting replaced because of wear 'n' tear mechanical issues. However there has never been an electrical problem, and the last time I was replacing the head on a printer, I noticed the power supply guts were all Nichicons. On 24 hours a day, seven days a week for well over fifteen years in a rough production environment - not bad at all.
Another anecdote: I once owned a Threshold FET-10/HL, a very nice product from our genial host. I noticed the final output capacitors were 10uF Mylars. Ugh! I said to myself. The FET-10/HL is a very low-profile unit and finding a replacement was difficult. I ended up sourcing some polycarbonate Wimas that fit, provided they were resting on their sides(!). After much hassle I managed to get them installed. And immediately heard very little difference! At least nothing that I couldn't lay on imagination. It certainly wasn't worth the work.
At the company I work for, we have barcode printers that were installed over fifteen years ago that are getting replaced because of wear 'n' tear mechanical issues. However there has never been an electrical problem, and the last time I was replacing the head on a printer, I noticed the power supply guts were all Nichicons. On 24 hours a day, seven days a week for well over fifteen years in a rough production environment - not bad at all.
Another anecdote: I once owned a Threshold FET-10/HL, a very nice product from our genial host. I noticed the final output capacitors were 10uF Mylars. Ugh! I said to myself. The FET-10/HL is a very low-profile unit and finding a replacement was difficult. I ended up sourcing some polycarbonate Wimas that fit, provided they were resting on their sides(!). After much hassle I managed to get them installed. And immediately heard very little difference! At least nothing that I couldn't lay on imagination. It certainly wasn't worth the work.
Well Wavebourn I think if you are familiar with Russian tech then you know that the caps also varied from year to year and sometimes even from model to model because sometimes there was a surplus of good army stock and sometimes the army needed so much that the civil factories were left with scrap literally.
one of the priboi's has all good caps, the other one had most of the big GAVNO electrolytics dead or missing contact/capacitance and the smaller blue ones were with bad coating , the very same cap in others only sometimes some of their parts got worse treatment I dunno why.
one of the priboi's has all good caps, the other one had most of the big GAVNO electrolytics dead or missing contact/capacitance and the smaller blue ones were with bad coating , the very same cap in others only sometimes some of their parts got worse treatment I dunno why.
film + foil caps are boutique stuff today.
As others have said, unless there is reason to think they are damaged, foil caps should be expected to last forever.
Old electrolytics should generally be replaced in audio gear, generally regardless of their initial quality if they are now extremely old.
Because aluminum electrolytic caps, unlike other capacitor technologies, do in fact age. The oxide layer on the aluminum provides the actual dielectric, and it is continually being replaced and repaired by the action of the electrolyte. But eventually your electrolyte dries out, or in some other fashion stops helping, and leakage currents increase.
I, for one, don't completely buy the "this polymer is better than that polymer for X" dogma. Aerovox makes a lot of high voltage polyester caps that are truly excellent in signal coupling use, for example, and probably better than many polypropylene caps. You can make some predictions based on the dielectric polymer, but you have to actually try it to know how a given cap will perform in a given circuit.
And I'm pretty sure that the attractive plastic boxes are what make boxed caps from Wima and other brands so attractive to builders. Particularly Wima with the bright red, though AVX's bright yellow 'sounds' good too. I admit that I have a soft spot for them myself, that i cannot logically resolve. Also for wrap-and-fill films over epoxy dipped films, even though i know that the only difference is whether they can survive a solvent bath and the internal construction is exactly, precisely the same.
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