From my perspective saving money means buy best quality at affordable price which is DC-Link in this case.
I am talking about $12-15 for 100-110 uF rated 500V @ 85Deg but in reality is 600V @ 70Deg or less, self healing with longer life, much lower losses of all types and of miniature type (respect to the average of the same kind) is no brainer. Tell what you want but arguing on this is simply pointless. It's just better.
I am talking about $12-15 for 100-110 uF rated 500V @ 85Deg but in reality is 600V @ 70Deg or less, self healing with longer life, much lower losses of all types and of miniature type (respect to the average of the same kind) is no brainer. Tell what you want but arguing on this is simply pointless. It's just better.
As for the question of DC Link (MKP1848 metalized polypropylene) vs electrolytic for tube amp power supply capacitors, it looks like a 100uF 450V DC Link cap is going to cost about $30, while an electrolytic cap of the same value and voltage rated for +105 deg C and 10.000 hours of use will cost $6 (USD, from Mouser).
ESR of the MKP1848 100uF 450VDC is stated to be 0.0235 ohms for the 2 pin version, 0.0025 ohms for the 4 pin.
ESR of the electrolytic cap is not stated in its data sheet.
The DC Link cap has 52.5 mm lead spacing, the electrolytic has 30 mm.
ESR of the MKP1848 100uF 450VDC is stated to be 0.0235 ohms for the 2 pin version, 0.0025 ohms for the 4 pin.
ESR of the electrolytic cap is not stated in its data sheet.
The DC Link cap has 52.5 mm lead spacing, the electrolytic has 30 mm.
$30 is a theft!
https://www.mouser.co.uk/ProductDetail/EPCOS-TDK/B32320I4207K000?qs=ti9wR6LxNKX1Cjf2o3j7DQ==
Nearly half price for 200 uF 450V.
https://www.mouser.co.uk/ProductDetail/EPCOS-TDK/B32320I4207K000?qs=ti9wR6LxNKX1Cjf2o3j7DQ==
Nearly half price for 200 uF 450V.
Good catch!
We're still looking at $19 for the film cap vs. <$6 for the electrolytic.
What is the purpose of the 5 lead connection?
If price is the major concern, motor run (not motor start) capacitors are usually metalized polypropylene film in oil construction, and have lower ESR than electrolytic caps. They're often available at low prices through surplus vendors. They do tend to be physically large.
We're still looking at $19 for the film cap vs. <$6 for the electrolytic.
What is the purpose of the 5 lead connection?
If price is the major concern, motor run (not motor start) capacitors are usually metalized polypropylene film in oil construction, and have lower ESR than electrolytic caps. They're often available at low prices through surplus vendors. They do tend to be physically large.
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16$ vs 6 $ is really peanuts in a 300B PSE amplifier and considering the better quality of DC-link. But you can try with motor run....
As someone said the other day in another thread, tube DIYers often drive themselves towards self-mutilation with pointless discussions.
The only good reason for using electrolytics is lack of space. If this is not a problem there is no discussion. But of course, everyone can think what he likes.
As someone said the other day in another thread, tube DIYers often drive themselves towards self-mutilation with pointless discussions.
The only good reason for using electrolytics is lack of space. If this is not a problem there is no discussion. But of course, everyone can think what he likes.
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https://ankaudiokits.com/product/300b-interstage-monoblock-power-amp/
If this is what the OP built, then even hundreds of dollars is peanuts! Also plenty of room in the chassis.
Still I think it is worth more in time AND money to start a new build and leave what appears to be an extremely nice 300B amp alone. Do something new instead of looking for an additional 1% of performance.
If this is what the OP built, then even hundreds of dollars is peanuts! Also plenty of room in the chassis.
Still I think it is worth more in time AND money to start a new build and leave what appears to be an extremely nice 300B amp alone. Do something new instead of looking for an additional 1% of performance.
Film caps with multiple leads are usually meant for high current pulse applications. I haven’t seen the above configuration before. Possibly the four are meant for ground and shield reasons?
Thanks for all the responses. I'm going to hold off making any changes to these amps until I get my next amps built (another pair of SET monoblocks but these will have to wait until my preamp projects are complete). When I do update them, I will switch out the B+ supply electrolytics for film caps, as well as the cathode caps.
@Thekak - I used the basic ANK design as well as the C-Core transformers, but made a lot of changes. Here are a couple of photos.
@Thekak - I used the basic ANK design as well as the C-Core transformers, but made a lot of changes. Here are a couple of photos.
That's what I found. I did find the differences were audible in a SE amp. I use Kemet DC Link caps. Pretty satisfied with those for both cathode bias and PSU. For the first cap in the PSU I use KBG-MN 4uF which is better still. It's not too difficult to rig up a shootout between various caps and decide for yourself, and that was the result I came up with. I've seen others who came up with similar results.
Found this thread after meaning to start one on DC link caps for cathode bypass. I have breadboarded pushpull monoblocks (only motor run caps in the PS). Didn't think I would need cathode bypass caps in the output stage (class A) but testing stuff I hooked up some motor run caps, and it was an improvement. My breadboards are quite large, but there was no room for these huge caps. Which got me to look for something smaller. Those DC link caps are still large, but not 'coke can' size.
I haven't tried electrolytics, and I don't have a strong urge to do so. Seems most here agree that DC link caps are up to the job.
I haven't tried electrolytics, and I don't have a strong urge to do so. Seems most here agree that DC link caps are up to the job.
What are your preferred ways of mounting the DC-link caps? Glue to chassis, mount on PCB, or clamp down in horizontal position á la Thomas Mayer?
https://blogger.googleusercontent.c...BOmnrKHu679jemAxB4t0SPFrhDeQMRk/s1500/P13.jpg
https://blogger.googleusercontent.c...BOmnrKHu679jemAxB4t0SPFrhDeQMRk/s1500/P13.jpg
In my experience the lower the ESR of the given capacitor, the "better" it sounds for me. DC link unfortunately is hard to get where I live otherwise that would be the way to go. I notice online in tests people do, they almost always settle on the DC links which happen to have the lowest ESR of all. 2nd place has a bit higher ESR etc...
I settled on low ESR audio capacitors (Nichicon Gold Tune) as they color the sound the least in my opinion (did not test DC links) and were available where I live. Any cheaper electrolytic with higher ESR sounds considerably worse because of the added distortion. The ideal capacitor would be none in my opinion, at the sacrifice of gain and potential phase issues because of the high ammount of local feedback introduced. But it is worth experimenting. No capacitor was not an option for me as I got phase issues in the lower frequency ranges.
Speaking about ESR: What resistors do you use on the cathode bias? Wire wound resistors (the very cheap ones) have small ammounts of capacitance which does make a difference. Not as notable as the capacitor though. I settled on Ayrton-Perry style wound resistors. You can get very close with several metal film capacitors in parallel.
I settled on low ESR audio capacitors (Nichicon Gold Tune) as they color the sound the least in my opinion (did not test DC links) and were available where I live. Any cheaper electrolytic with higher ESR sounds considerably worse because of the added distortion. The ideal capacitor would be none in my opinion, at the sacrifice of gain and potential phase issues because of the high ammount of local feedback introduced. But it is worth experimenting. No capacitor was not an option for me as I got phase issues in the lower frequency ranges.
Speaking about ESR: What resistors do you use on the cathode bias? Wire wound resistors (the very cheap ones) have small ammounts of capacitance which does make a difference. Not as notable as the capacitor though. I settled on Ayrton-Perry style wound resistors. You can get very close with several metal film capacitors in parallel.
<< I settled on Ayrton-Perry style wound resistors.
Same here. Failing that other good quality wirewounds.
Same here. Failing that other good quality wirewounds.
From my experience, the BEST Capacitor is NO capacitor. I retrofitted my SE amps with Shunt Regulator in the cathode circuit instead of RC. Excellent performance. Also, it has a trim pot to adjust the voltage/bias current for best performance like the fixed bias arrangement.
Johnny
Johnny
I don't think anyone would disagree with the statement that the best capacitor is no capacitor. There are various ways around the whole question of bias. I find the purest sound is a resistor, and with DHTs I use filament bias. I removed all the SIC diodes I tried because they sounded awful to me. A bit better in conjunction with a resistor, but still worse than just a resistor. I'm very wary of solid state here, though I do use Coleman regs.