Elna Duorex Capacitor Replacement?

Bratwurst7s

In The Frying Pan
Subscriber
I'm looking for information, opinions and experience concerning the best choice for replacements for Elna Duorex capacitors.

I've searched diligently for a data sheet for these, as well as a general search here at AK. And found little to nothing.

I'm still completely unsure about the main attributes of these caps. Are they low-leakage? Or low ESR? Or High ripple? Or a combination of high ripple/low ESR?

No manufacturer uses premium higher cost caps just for grins and giggles so obviously they have a specific special attribute needed for them to be used instead of general purpose caps.

In the past I've just been guessing and used Nichicon KZ or Elna Tonorex. But perhaps a low-leakage like a Nichicon KL would be more appropriate?

I would like to stop guessing and be able to make some informed choices, hence this post.

Thanks in advance to anyone that has any info to share,
James
 
Armchair speculation- if it were very low leakage, they'd tout the fact. They don't, nor are the Silmic parts unusually low leakage. It seems to be an economy line of audio caps. They do tout high c/p, which I think is size to capacitance ratio in this case, but not sure. I'd look at the circuit and if you think low leakage would be a factor, use a UKL series part. If it's in a power circuit, maybe use a low ESR part. Otherwise, use your favorite series, be it FC, Silmic or other. Go by the circuit, not by a bunch of marketing hype.
 
Thanks guys. I've been seeing these caps in all of the Yamaha AX series integrated amps that I've had. Never in the signal path, and never in the main part of the power supply. Usually in values of 470µF and higher.

There are also some in the CX-1 pre-amp that I just bought, in the 20-db amp section and in the phono section. In the past I've usually been using Nichicon KZ to replace them. In this case some of them are 2200µF so KZ won't work (1000µF max). I have a max dia limit of 16mm because of space. I've been leaning towards Nichicon FG or KL. But I don't have the knowledge to evaluate their specific function in the circuit to decide if the low-loss KL is the better choice. A Panasonic FC would fit also.

I've used a lot of FG's in amps but have become a bit leary of using them in values of 1000µF and higher because a lot of them have been measuring fairly low out of the box. Like in the low 900's for a 1000µF cap. These are caps purchased from Mouser.

The thing that has me concentrating on finding out more data about the Duorex is that most of the caps in the amp(s) are brown Elna caps which I've been guessing are general purpose caps. So if Yamaha went to the extra expense of putting a special cap in a few spots they must have had a goal in mind. Hence me searching for facts as to the main intended purpose of the series.

Cheers,
James
 
My PC2602 was full of Duorex everywhere as well. I pulled a few and checked them and they all tested ok so they seem to have long life. Other than that I have no idea.
Yamaha puts special caps in weird places sometimes. My A-1020 had a Black Gate in the protection circuit and almost all of the A series have some sort of audio cap in the DC filtering of the various stages.
I've never been able to figure this out exactly but I've been replacing them with power supply caps as they seem to take a beating. I haven't heard any difference in sound between the factory caps, new audio caps like Silmic and various Nichicon or the new non-audio marked replacements (I restored three M-60s and went various directions with cap replacement just for science sake).
 
Last edited:
IMO, no sensible designer would put a large value cap in a circuit expecting low DC leakage. The two things just aren't compatible. Caps today are better than ever, so I wouldn't hesitate to put any decent cap of your choice in a 1000 uF and up location. For a variety of reasons you also won't find ultra-low esr caps in very large values. FWIW, I've never seen a measurement difference between good commercial cap series and "audio" cap series, nor has any manufacturer of the latter ever published a test or parameter where the part was superior to any other part. They talk about vibration and damping with the Silmic II, but offer no tests, specs or evidence that it's better. It's most important specification is the fact that it's larger than most caps and often doesn't fit where you want to put it. That leads to some (IMHO) sloppy work where it would have been better to choose something else.

The best thing you can do to improve cap performance and life is just choose one voltage range higher than what was there. 25 instead of 16, 35 instead of 25, 50 instead of 35. I don't think it should be carried further than that- I wouldn't put a 200 volt cap in a low voltage location for no reason, though I've seen Sansui do it. Probably had excess inventory. Anyway, that voltage bump will buy you better dissipation factor and lower esr, plus longer life, usually at very little extra cost. Hint- a higher voltage commercial cap will beat a slightly lower voltage "audio" cap almost every time in terms of losses. Unless you're working with switching regulators, ultra low esr caps are probably a bad choice. Moderation in all things.
 
IMO, no sensible designer would put a large value cap in a circuit expecting low DC leakage. The two things just aren't compatible. Caps today are better than ever, so I wouldn't hesitate to put any decent cap of your choice in a 1000 uF and up location. For a variety of reasons you also won't find ultra-low esr caps in very large values. FWIW, I've never seen a measurement difference between good commercial cap series and "audio" cap series, nor has any manufacturer of the latter ever published a test or parameter where the part was superior to any other part. They talk about vibration and damping with the Silmic II, but offer no tests, specs or evidence that it's better. It's most important specification is the fact that it's larger than most caps and often doesn't fit where you want to put it. That leads to some (IMHO) sloppy work where it would have been better to choose something else.

The best thing you can do to improve cap performance and life is just choose one voltage range higher than what was there. 25 instead of 16, 35 instead of 25, 50 instead of 35. I don't think it should be carried further than that- I wouldn't put a 200 volt cap in a low voltage location for no reason, though I've seen Sansui do it. Probably had excess inventory. Anyway, that voltage bump will buy you better dissipation factor and lower esr, plus longer life, usually at very little extra cost. Hint- a higher voltage commercial cap will beat a slightly lower voltage "audio" cap almost every time in terms of losses. Unless you're working with switching regulators, ultra low esr caps are probably a bad choice. Moderation in all things.

Thanks Conrad! This is very helpful. The main caps in question are 2200µF/25v. I had looked at going with a 35v Nichicon FG (based on a post you made a while back concerning upping cap voltage :)) until I saw that they are 18mm dia. But a Panasonic FC in 35v is only 16mm and would fit. That's going on my short list now.

Cheers,
James
 
As far as my experience goes I have found Panasonic FC to be a very versatile electrolytic capacitor, performing well in almost any situation in the kind of gear we encounter here. :)
 
...The best thing you can do to improve cap performance and life is just choose one voltage range higher than what was there. 25 instead of 16, 35 instead of 25, 50 instead of 35. I don't think it should be carried further than that- I wouldn't put a 200 volt cap in a low voltage location for no reason, though I've seen Sansui do it. Probably had excess inventory. Anyway, that voltage bump will buy you better dissipation factor and lower esr, plus longer life, usually at very little extra cost. Hint- a higher voltage commercial cap will beat a slightly lower voltage "audio" cap almost every time in terms of losses. Unless you're working with switching regulators, ultra low esr caps are probably a bad choice. Moderation in all things.

Furthering my search for capacitor information nirvana I stumbled across an interesting paper that I'd say backs up everything that you wrote.
http://www.tadiranbatteries.de/pdf/...perties-of-modern-electrolytic-capacitors.pdf

Interesting what they write about leakage being higher as voltages and temps rise. And now I have a better understanding about cap forming and how it's happening every time my amp (etc) is first turned on. And that the leakage drops after the first few minutes because of forming and self healing. This makes me feel that I'm not doing anything wrong by letting my amp warm up for a few minutes before putting it to work.

Cheers,
James
 
As far as my experience goes I have found Panasonic FC to be a very versatile electrolytic capacitor, performing well in almost any situation in the kind of gear we encounter here. :)

I've actually been using a lot of FC's the last few years, in both amps and CD players. I've been pretty happy with them and have decided on using a fair amount of them in my pre-amp re-cap.

Cheers,
James
 
Back
Top Bottom