Coupling capacitor NAF845SE

TJS

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Dec 25, 2014
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Hi, im a proud owner of New Audio frontiers 845SE integrated amplifier. Im planning to upgrade the coupling capacitor in signal from the driver stage.

As i know a lot of members here have owned in the past and some probably still own NAF845SE, so probably can share the capacitor change experience. I matched the NAF845 with living voice OBX RW. I have few capacitors in mind, Hovland musicap (old version) with red and green leads, Jupiter copper foil, Duelund cast hybrid (But i doubt it can fit inside the chassis)

Any suggestions from the experienced member here??? Thanks in advance
 

rabski

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I have Living Voice and 845, plus my own build preamp(s) and phono stage(s) and I've spent countless happy hours playing with assorted coupling capacitors.

IME, if you have suitable voltage-rated Hovland 'yellow body' just put them in, sit back and don't even think about anything else. I think they're still among the very best. The newer blue versions are OK, but not as good.

Otherwise... Duelund have gone a bit mad with a million different varieties, but the 'cast' are extremely good. As noted, however, they are also extremely large (as not noted, also extremely costly). Other 'top drawer' alternatives: Miflex copper and Audio Note copper. The ClarityCap CMR are surprisingly good.

I've not bothered with Jupiter, because by all accounts there is a hair-width of difference between them and Audio Note copper. I have tried a great many of the other usual suspects and find a lot of them give a somewhat 'unorganic' sound. Things like the Mundorf silver/gold/oil sound detailed and clean at first, but it soon (to my ears) becomes a sort of artificial sound. I haven't tried the V-Cap CuTF, but they're frankly insane money and no way are they going to make that much difference. Like cables and resistors, these are small, subtle differences and sooner or later the cost vs improvement equation has to have a sensible limit.

Some of the Russian teflon capacitors are extremely good, but they are utterly massive and the 'real' teflon ones only come in small values. They just won't fit and the amount you'd need would take years to run in.

IME there is a balancing act. Too many of the same type in the signal path is not always good, even if individually they are excellent. I use ClarityCap in the phono, Audio Note in the pre and Miflex in the 845. My spare pre has Hovlands, but sadly the only pair I have. The other spare pre has ClarityCap. The Hovlands are totally unobtanium now, and the few I've seen on well-known auction sites are evidently fakes.

All IMHO and IME.
 

Psilonaught

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V-Cap CuTF or ODAM if you can't justify the high cost. Very small caps too.

I have CuTF in my atma-sphere amps and previously used ODAMs to very good effect.

ClarityCaps are meh in my experience.

Miflex and AudioNote also have to be on your shortlist, depending on space considerations.
 

pmcuk

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Russian teflon caps here - FT-2 for lower voltages and FT-3 for higher. You only need 0.1uF for coupling valve stages. I'd just find a way of making it fit. Nothing as clean as teflon.
 

TJS

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Dec 25, 2014
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I have Living Voice and 845, plus my own build preamp(s) and phono stage(s) and I've spent countless happy hours playing with assorted coupling capacitors.

IME, if you have suitable voltage-rated Hovland 'yellow body' just put them in, sit back and don't even think about anything else. I think they're still among the very best. The newer blue versions are OK, but not as good.

Otherwise... Duelund have gone a bit mad with a million different varieties, but the 'cast' are extremely good. As noted, however, they are also extremely large (as not noted, also extremely costly). Other 'top drawer' alternatives: Miflex copper and Audio Note copper. The ClarityCap CMR are surprisingly good.

I've not bothered with Jupiter, because by all accounts there is a hair-width of difference between them and Audio Note copper. I have tried a great many of the other usual suspects and find a lot of them give a somewhat 'unorganic' sound. Things like the Mundorf silver/gold/oil sound detailed and clean at first, but it soon (to my ears) becomes a sort of artificial sound. I haven't tried the V-Cap CuTF, but they're frankly insane money and no way are they going to make that much difference. Like cables and resistors, these are small, subtle differences and sooner or later the cost vs improvement equation has to have a sensible limit.

Some of the Russian teflon capacitors are extremely good, but they are utterly massive and the 'real' teflon ones only come in small values. They just won't fit and the amount you'd need would take years to run in.

IME there is a balancing act. Too many of the same type in the signal path is not always good, even if individually they are excellent. I use ClarityCap in the phono, Audio Note in the pre and Miflex in the 845. My spare pre has Hovlands, but sadly the only pair I have. The other spare pre has ClarityCap. The Hovlands are totally unobtanium now, and the few I've seen on well-known auction sites are evidently fakes.

All IMHO and IME.
I can buy hovland yellow body (with red n green lead) because i have friend that have not used them as he said its too "old school" sound. Based on your experience...probably will try to put the hovland. Probably i gonna tick off the duelund because of the size and also the price... i tried miflex in my dac output, yes...it really produce best bass, but i feel the sound is not so refined in mid and high. Hovland is cheaper than jupiter and audio note. But how the sound differ between hovland and audionote/jupiter??
 

TJS

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Dec 25, 2014
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V-Cap CuTF or ODAM if you can't justify the high cost. Very small caps too.

I have CuTF in my atma-sphere amps and previously used ODAMs to very good effect.

ClarityCaps are meh in my experience.

Miflex and AudioNote also have to be on your shortlist, depending on space considerations.
V cap have high price, and i read that it needs long burn in time, is that true??
 

TJS

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Dec 25, 2014
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Russian teflon caps here - FT-2 for lower voltages and FT-3 for higher. You only need 0.1uF for coupling valve stages. I'd just find a way of making it fit. Nothing as clean as teflon.
I opened my integrated, the coupling is 0.47uf if im not mistaken
 

rabski

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The value of the coupling capacitor(s) will depends on the circuit. Together with the input impedance of the next 'stage' in an amplifier, the coupling capacitor forms a high-pass filter. The aim is for the bass roll-off to be as low as possible (or sensible), whilst keeping the capacitor as small as practical. The problem is that the input impedance of the 845 is not a simple measurement. It depends on the grid bias circuit, the effective plate resistance, the effective plate load and the Mu of the valve, and some of these will vary in operation.

A 'back of a matchbox' calculation gives somewhere around 1 meg input impedance for an 845, but there's a lot (a big lot) of guesswork and approximation in that. Even so, 0.1uF would be marginal in my book. With capacitor coupling and assuming a normal driver circuit, I'd be happier with at least .33uF, and I use .47uF in mine.

The only downsides of higher capacitance values are physical size, cost and breaking-in time. The downside of too low a value is loss of bass, or loss of bass phase coherence.
 
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rabski

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Also, there is a major issue with capacitors, in that they change with use. The effects are real and proven, but they make assessing the 'sound' extremely difficult, because everyone has a relatively short audio memory and everyone adjusts to changes.

I can only say what I've been happy with, in terms of things that sound 'natural'. A few designers who have a great deal of experience also suggest the original Hovlands do something very good.

The worst-case scenario is that you take them out again. If you do, there are plenty of people who would be happy to buy them from you :)
 

pmcuk

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If a FT-3 can fit in, try a 0.1 and see if you like it. Cheap and very good indeed. Then consider your options. You may be happy with the teflon.
 

zeta4

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For info. I just measured a 0.1uf FT-3 and its approx 50mm long x 25mm dia. The 0.22uf
ones are 70mm x 30mm. As Andy says try them if you can, you wont be disappointed. There are some 0.47uf ones around (Im told) but they must be truly gigantic
 

JamieMcC

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Duelund JDM silver foil bypass cap £30ish each from hificollective amazing imo add in parallel to what's already in there.

Also have V-cap Cutf and Duelund Cast output caps in different amps both excellent but take a long time to come on song.

Russian teflon also good imo but again expect long burn in and maybe the odd period of mehh sound along the way.
 

JamieMcC

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Also, there is a major issue with capacitors, in that they change with use. The effects are real and proven, but they make assessing the 'sound' extremely difficult, because everyone has a relatively short audio memory and everyone adjusts to changes.

Totally agree one of the things I have done several times now in the past to help reference original sonics is after swapping output caps is then to go backwards after a few months use and reinstall the original caps its much easier then to notice the differences.
 

pmcuk

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Russian teflon also good imo but again expect long burn in and maybe the odd period of mehh sound along the way.

The burn-in may be exaggerated. I've never ever had "mehh" sound out of teflon caps, quite the contrary - they are very predictably clean and detailed. I use them exclusively and I can't say I've ever noticed any differences due to burn-in.
 

JamieMcC

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I've definitely had times with the Russian caps during the the first 100hrs of use when they have sounded off for a day or two to point where your tempted to take them out however from past experience I know that with more hours this passes and the better the sound gets.

I've built a few amps using them including two different phono Amps one solid state and one tube with full Teflon RIAA and output stages. They generally do sound as you describe from the off.

My current tube phono amp has a all full russian teflon hand matched RIAA stage it used to run teflon output caps as well for couple of years until I found some 0.47uf Dueland Cast Copper caps at half price.

One of the things that was a nice surprise when building it was I purchased a load of the surplus Russian capacitors these when new had a factory tolerance of +/-5%

When cherry picking the closest matching for the RIAA stage I had

3 roughly under 0.5% tolerance
3 roughly under 1%-1.5%
2 roughly at 2%

Of all the ones left over the most off tolerance was 3.5% which is still well within the original +/-5% spec and superb for a 30-40+ year old product and testimony to just how well constructed they were for military use back then.
 

rabski

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The FT ones are, I agree, very good indeed. I still can't usually navigate the size problem though. I have (some courtesy of Andy, thank you) a load of the .1uF ones, but in cases where closer to 1uF is needed, a garden shed would offer suitable casework.
 

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