Hi, Victor.
Thanks. From your endorsement, it seems the KOA should be plenty good for the purpose.
I looked up the KOA briefly, and are these also known as Kiwame?
A number of years ago I built a Sun Audio SV-300BE using Kiwame resistors, and the amp sounded great.
A sold that amp, and then a few years later, I built the same amp using the blue Riken Ohm carbon film resistors. Between the two amps, I thought that the Kiwame version sounded better.
It may have been a case of too many Rikens in one amp, but I came away from it really liking the Kiwames.
Thanks. From your endorsement, it seems the KOA should be plenty good for the purpose.
I looked up the KOA briefly, and are these also known as Kiwame?
A number of years ago I built a Sun Audio SV-300BE using Kiwame resistors, and the amp sounded great.
A sold that amp, and then a few years later, I built the same amp using the blue Riken Ohm carbon film resistors. Between the two amps, I thought that the Kiwame version sounded better.
It may have been a case of too many Rikens in one amp, but I came away from it really liking the Kiwames.
KT the Kiwame resistors are the same as KOA SPR series. They are green coated. The KOA resistors in the 8900 kit are the CF series. Both are good. You can get some values of the Kiwame/SPR resistor from Mouser. The Kiwame/SPR is usually found in 2 watt or 5 watt. I have some 1 watt and 3 watt, but they are hard to find. Lately I have been using the Takman. I really like Takman.
I am with you. KOA is not only good in audio performances but also Technicalities as well.
I think I got lucky. I couldn't see anything on the caps to indicate alignment - and hadn't stumbled across this part of the thread - so just installed them this way. The installation notes that Victor points to say: "Another way to identify outer foil is the writing on the label flows towards the outer foil." (since the leads were cut after soldering, I can't tell from the primary way,: The short lead indicates the outermost foil, and should be connected to the lowest impedance path to ground.) But as the picture shows, the writing flows in the direction of the grid side: whew! (Or am I missing something?)
I know this is an old question, but I just came across it after building my own 8900. In case anybody else is wondering…
Do NOT replace these capacitors with electrolyte capacitors.
These are NOT electrolyte capacitors. These are POLYMER capacitors. Even the most expensive audio grade electrolyte capacitor will have a much higher ESR (equivalent series resistance) than these capacitors. Polymer caps are extremely low ESR and this is critical to the sound and function of this amplifier. I believe these are kemet polymer capacitors that come with the kit. The “audiophile“ manufactures have not caught up with this type of capacitor… Yet. When they do I assure you they will sell them for outrageous prices.
If you want to fishing for a replacement search Digikey for polymer caps. They have compatible Panasonic hybrid polymer automotive capacitors with a slightly lower ESR and higher temperature rating. This is a very critical component of this amplifier though and you may or may not be pleased with the results.
I hear you on the upgrade bug. I put the Panasonic‘s in mine and some other changes. I never installed the original caps so I cannot tell you if it sounds better or not. I am however very, very pleased with the sound of this amplifier.
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thanks for reminder. Someone else here also recommended Panasonic OS-CON 35SEK330M but i have not tried it.
If you really want to look for lower ESR, film caps could be an option. Solen or Mundorf 100uF might be available. But size wise, it's a big problem.
Other potential upgrade is to use Black Gate N series in Super-E mode. But $$$ and availability wise, it's a big problem.
So stick with the original one probably best and spend money elsewhere
FWIW: I went ahead and paid $100.00 for the ODAM capacitors that Viktor offered as an upgrade to the 8900 - partly with a view of graduating later on from the COSSOR/Linlai Delux 2A3 + Sylvania 12BH7A tubes that I ordered. Of course, i can't make a comparison with the stock caps - but I will say that the sound is phenomenal and at least it feels like a bit of good insurance for the tube upgrade later on. Just my 2 cents -
In an earlier post, I mentioned that the included polymer caps are very low ESR and likely should not be swapped out. However, ESR ratings are not well defined. With regard to the polymer caps, in particular, these ratings are highly dependent on frequency. The ESR ratings for polymer are much much better at very high frequencies and diminished toward the lower frequencies—Sometimes not far off from a good electrolyte. It depends specifically on what you’re trying to do with the capacitor and what it is filtering or bypassing in the circuit however, I still would not recommend even the best of electrolyte capacitors in place of these. With capacitors it’s almost impossible to find the ESR ratings at specific frequency and unless you know the specific target frequency best to defer to the designer. I do agree you may find better ESR results with a film cap, however, these certainly would not fit on the circuitboard and likely not enough space even underneath. I did replace mine with Panasonic polymer hybrid automotive caps. They are part polymer and have some electrolyte. Best of both worlds, worst of both worlds, who knows? The sound is glorious, but for all I know it may have been better with the original.
