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Cathode bypass capacitor shootout - DC Link caps are very nice!


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The voltage rating is a bit of a waste, and assuming you accept capacitor burn-in exists (I do), then this may be something of an issue, as experience suggests a capacitor run substantially below its rating will correspondingly take substantially longer to reach its stable operating state. On the other hand, capacitors certainly exert an effect and if the best sounding ones have higher than ideal ratings, so be it.

I've tried battery bias between cathode and ground, gounded cathode with battery grid bias, bypassed resistor, LEDs and SiCs. Ignoring DHTs and constant-current catode biasing methods, for IDHTs I've found all of them to have a small, though notable effect on the sound, and battery or SiC to be consistently slightly better. Annoyingly though, different batteries can also have a notable effect. LEDs seem a bit hit and miss in terms of noise. For bypass I've stuck with Blackgate electrolytics, based on reputation as much as anything to be honest, and also as I still have a handful of low-voltage ones in the box. They're running out though, so the Vishays are certainly worth a look.

Mind you, most of the part-built pile includes DHTs, so it's a different problem. I'm more interested in those Vishays' potential for PSU applications. Bang goes my 'try not to order anything from RS for a week' resolution...

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Yes, I agree that there are ways round having to use a bypass capacitor and no capacitor at all eliminates capacitor-related problems.  You can either use just a resistor and let it create some feedba

These caps are designed to source and sink high currents (20A + ripple) for many hours at high voltages so the internal connections have to have very low resistance and inductance. Some of the larger

I just spent over £100 at RS on 15uF and 45uF caps - cheaper in 10s. I've done cathode bypasses for the outputs in two 300b amps so far and it's made quite a difference.  No turning back now! I'm

Ive been using 100uf/400V Kemet DC Link caps on the o/p of my 2P29L headphone amp. I prefer them to Mundorf polyprops. They sound more natural to me. 

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6 minutes ago, pmcuk said:

The best cathode bypass cap is no cap at all, but if you have to use one like for a 300b in self bias, then the quality matters. You're paying upwards of £100 for a pair of the cheapest 300b and if the cathode bypass cap improves the sound quite audibly, then it's a defensible choice. When i did the shootout the differences were certainly audible. 

I haven't started on the PSU yet - these caps may well improve that as well. 

It would be useful to hear from anyone else who has tried these. 

Zeta4 has mentioned these to me in the past WRT power supply use and made a firm recommendation.

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Just now, rabski said:

Zeta4 has mentioned these to me in the past WRT power supply use and made a firm recommendation.

Didn't see your post!

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2 hours ago, pmcuk said:

The best cathode bypass cap is no cap at all, but if you have to use one like for a 300b in self bias, then the quality matters. You're paying upwards of £100 for a pair of the cheapest 300b and if the cathode bypass cap improves the sound quite audibly, then it's a defensible choice. When i did the shootout the differences were certainly audible. 

I haven't started on the PSU yet - these caps may well improve that as well. 

It would be useful to hear from anyone else who has tried these. 

Have you tried Solen Fastcaps? These sound great in cathode bypass or signal coupling duties and are rated at 400v or 630v so you can save some size. 

David

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3 hours ago, Juancho said:

Have you tried Solen Fastcaps? These sound great in cathode bypass or signal coupling duties and are rated at 400v or 630v so you can save some size. 

David

I haven't. But would they be any better than ICW Clarity Caps? 

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These caps are designed to source and sink high currents (20A + ripple) for many hours at high voltages so the internal connections have to have very low resistance and inductance. Some of the larger value ones have 4 wires ( 2 per side ) to aid this. This is not quite a kelvin connection but pretty near. Also the leadout wire connections to the capacitor foils is special. Kemet say they use welding but quite how they weld aluminium to copper beats me. Wima say they use the usual sprayed molten aluminium (schloopage) but in some fancy way.

This construction sets them apart from other polypropylene capacitors even motor run. Of course this doesnt mean they will sound good but in my limited experience they do. I first used them in valve psu,s then tried them as coupling caps with better results than with standard Mundorfs. Havent tried a wide range of caps though but Im happy with them. Im certainly going to try them as bypasses ( currently black gate) in my 300B  amp when I get it going again, after Andy's recommendation.

I found the Kemet ones to be a good bit cheaper than say Wima with the same and sometimes slightly better spec. Prices seem to have gone up a bit though. 

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10 minutes ago, pmcuk said:

I haven't. But would they be any better than ICW Clarity Caps? 

As a coupling cap I prefer Solens to Clarity caps. I havn't tried a Clarity cap as cathode bypass but don't rate them for decoupling or coupling

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4 hours ago, zeta4 said:

Kemet say they use welding but quite how they weld aluminium to copper beats me.  

In this sort of application Ultrasonic welding would be used to produce a 'cold fusion' connection. This process is often used in electronics where the joints are not suitable solder ie to small for solder/mechanical connection and/or are of the intermetallic variety. 

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I have enough capacitors to start a museum. I have enough really decent electrolytics to build more than a few really decent HT supplies and the usualy collection of quality coupling stuff: Russian teflons, Audio Note, Miflex, Hovland, et al. So obviously, I've just hit the RS website and ordered a selection to try in PSUs first.

Going to need more storage space...

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I just spent over £100 at RS on 15uF and 45uF caps - cheaper in 10s. I've done cathode bypasses for the outputs in two 300b amps so far and it's made quite a difference. 

No turning back now! I'm starting on the power supplies......

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38 minutes ago, pmcuk said:

I just spent over £100 at RS on 15uF and 45uF caps - cheaper in 10s. I've done cathode bypasses for the outputs in two 300b amps so far and it's made quite a difference. 

No turning back now! I'm starting on the power supplies......

Always nice to know I'm not the only one.

I seem to recall both of us talking about getting rid of some stuff this year...

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If it makes you feel better, I have done similar. I also had a quick check in the pile and decided to attack Farnell for a few more assorted chokes while I was at it.

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Swapping out the electrolytic cathode bypass for films made a noticeable difference in my phono stage I used Valab (Taiwanese a modern film foil in oil) they were 250v 100uf mind and took up a fair bit of space but as I had them already it's what was used.

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34 minutes ago, JamieMcC said:

Swapping out the electrolytic cathode bypass for films made a noticeable difference in my phono stage I used Valab (Taiwanese a modern film foil in oil) they were 250v 100uf mind and took up a fair bit of space but as I had them already it's what was used.

Cathode bypass caps make a very audible difference in my experience. No cap is the design goal so I use plate chokes with high inductance so I can use typically 270R as cathode resistor. But if you need to use a bypass, use the best possible one. I hope Rabski can report on the difference between DC Links and Black Gates. That would be interesting. 

If you want to go nuts, Blitz reports on DIY Audio: "I tried different DC-Link types and brands. CDE 947D is for me heads and shoulder above the rest. Need one week of burn in." Farnell have a range of them. Not cheap. These are the only ones in stock but other values are "cheaper"....

https://uk.farnell.com/cornell-dubilier/947d881k901blmsn/cap-880-f-900v-10-pp/dp/2361714 Cornell Dubilier CDE

https://www.mouser.co.uk/ProductDetail/Cornell-Dubilier-CDE/947D131K132ACGSN?qs=%2Fha2pyFadugAPtBaaxs6hGxu1dDgrIT7QElFPHPSy78%3D Cheaper 

https://www.digikey.co.uk/product-detail/en/cornell-dubilier-electronics-cde/947D191K132AEGSN/947D191K132AEGSN-ND/4466340 Need to order

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