Hi,
I am going to build the Morgan Jones headphone amp. My challenge is that it requires a 470uF cap for output. The cap is so large such that a film cap is not possible and electrolytic is the only choice. Could anyone suggest a good electrolytic for me?
https://www.pearl-hifi.com/06_Lit_A...04/Sec_19/991_White_Follower_Optimization.pdf
I am going to build the Morgan Jones headphone amp. My challenge is that it requires a 470uF cap for output. The cap is so large such that a film cap is not possible and electrolytic is the only choice. Could anyone suggest a good electrolytic for me?
https://www.pearl-hifi.com/06_Lit_A...04/Sec_19/991_White_Follower_Optimization.pdf
I've used Elna Silmic RFS and Nichicon FG 'Fine Gold' electrolytics to good effect as output caps;
Elna Silmic RFS Electrolytics | Hifi Collective
Nichicon FG Type | Hifi Collective
I'm currently working on a HPA project and have a pair of the Nichicons installed for the output caps for 32ohm headphones, however, most of my headphone listening is with 600ohm BeyerDynamic DT880 heaphones and that impedance brings film output caps into range (I'm using 56uF film caps)
Of course these are just my own views on the suitability of those caps and YMMV.
Elna Silmic RFS Electrolytics | Hifi Collective
Nichicon FG Type | Hifi Collective
I'm currently working on a HPA project and have a pair of the Nichicons installed for the output caps for 32ohm headphones, however, most of my headphone listening is with 600ohm BeyerDynamic DT880 heaphones and that impedance brings film output caps into range (I'm using 56uF film caps)
Of course these are just my own views on the suitability of those caps and YMMV.
I can try to lower the DC offset to around 85VDC, question is is it safe to use 100VDC Nichicon or Elna electrolytic?
Why should you? There are plenty of suitable caps with higher voltage rating, such as these https://www.digikey.com/product-detail/en/rubycon/400MXC220MEFCSN30X30/400MXC220MEFCSN30X30-ND/3565526
Which is what I used when I built the MJ 14 years ago, //ed with some nice film caps.
It is because those audio grade electrolytic caps are limited to 100VDC, that's why I am thinking to lower the DC offset on the output. Is the Rubycon good for audio?
Rubycon caps could be considered audio grade... it is highly subjective. What makes an electrolytic cap 'audio'? It is still a electrolytic cap,
and I'd rather use one with the appropriate voltage rating (with a safe margin) than to alter the B+ of the amplifier (btw. this is not DC offset!!
100V of DC offset will absolutely positively destroy any headphone) which will likely have an effect on the sound of the MJ.
and I'd rather use one with the appropriate voltage rating (with a safe margin) than to alter the B+ of the amplifier (btw. this is not DC offset!!
100V of DC offset will absolutely positively destroy any headphone) which will likely have an effect on the sound of the MJ.
Any cap will do, nick one out of an ATX PC PSU or other SMPSU, but usually one made by Nichicon/Rubycon, Sony , Panasonic etc is a good bet, though it helps if you choose one with a nice paint job, something black with Gold writing : )
Actually thinking about it I'd presume you'd want one with low ESR but as most 470u 200v ish caps are made for use in SMPSU's they should be good at higher frequencies.
A look in Digikey and Mouser should give you some candidates though.
Andy.
Actually thinking about it I'd presume you'd want one with low ESR but as most 470u 200v ish caps are made for use in SMPSU's they should be good at higher frequencies.
A look in Digikey and Mouser should give you some candidates though.
Andy.
Two of these in parallel for each channel? You could spend $440USD in capacitors alone!
Mundorf Capacitor 220uF 250Vdc MCap® EVO
On the more - ahem - sane side, Nichicon KX electrolytics
Nichicon KX Series Electrolytic Capacitors
(note I'm not advocating buying from Parts Connexion - quickest link that came up for me)
Mundorf Capacitor 220uF 250Vdc MCap® EVO
On the more - ahem - sane side, Nichicon KX electrolytics
Nichicon KX Series Electrolytic Capacitors
(note I'm not advocating buying from Parts Connexion - quickest link that came up for me)
That capacitor would be large enough for a power amplifier that drives a big, inefficient speaker.
Perhaps they were trying to reduce hum, but that is very big. Both of those could be more
like 22uF instead. There could be more audible hum with the smaller value, though.
I calculate 26uf is fine if you can use 300 ohm headphones. I just happen to be bread-boarding a 6AS7 OTL headphone amp this week and just rationalized myself over this same issue!
C = 1,000,000 / (f * 2 * pi * R)
so for -3db down at 20Hz with 300 ohm phones.
C = 1,000,000 / (20 * 2 * 3.14 * 300)
C = 26uF
In that range you can use a polypropylene film capacitor instead of an electrolytic:
I'm waiting for delivery on this 30uF to try out, with Sennheiser 650 phones (300 ohms). 30uF will cutoof a little below 20 Hz I assume. The 450 volt AC rating should be fine for DC which would (I think be 1.414 * 450) even better.
CBB60 AC 450V 50/60Hz 30uF 8mm Thread Polypropylene Film Motor Run CapacitorZ7U5 191466582282 | eBay
With headphones you can actually hear down lower than you can with speakers. Ideally you would want to be flat at 20hz with little to no phase distortion. I found that 60uf does a really great job with 300ohm headphones.
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