In the last couple of months I have been playing around with a bunch of Russian capacitors the K71-4, the MBM, FCH, MBGO-2, K40Y9, K72P-6, K73-16 and K73-11. In that time I have been visiting this thread quite a bit for information so I decided I should make a nice post about my experiences as some of these caps have not been mentioned yet. I have used these capacitors in a variety of applications; as input coupling caps in a modified Musical Fidelity A3-CR, in the crossover of my speakers, and inside a pre-amp which I am working on.
Input Capacitors
Clarity cap SA (10uf) Mundorf Supreme (1uf) and Vishay MKP1837 (0.01uf)
The combination of Clarity Cap SA and Mundorf Supreme is something Tony Gee of humble home made hifi suggests. I had these capacitors inside another amp which is why I gave these a try (I had them laying around anyway). Of course this was quite an improvement over the original Teapo capacitor. Overall this combination of capacitors is dark and lush sounding. While they did represent a big improvement over the Teapo capacitors this combination of capacitors is beaten in every way by the capacitors I experimented with after.
Russian MBM (1uf) paper in wax capacitor with Rifa PHE840 (8.2uf) film and foil polypropylene
This is a very interesting combination of capacitors which was suggested to my by a friend. It represents great bang for buck in a small package. Immediately I was amazed at how different the amplifier sounded first of all there was an openness to the sound which cannot be achieved with the Clarity Cap which sounds closed and congested in comparison. It became possible to easily pinpoint each instrument separately, each instrument now had air around it; breathing room. There was also a definite increase in tonality or timbre making the overall sound more natural. The highs are relatively smooth and have good extension, here too everything sounded more realistic. Overall this is a very good combination especially for the money. The only thing I have against it is that the low bass notes are just not very prominent with this combination. In quality of the bass is good but things are just a bit forward sounding, bass really remains in the background while not having much body. To add some lushness I tried adding a the 1uf Mundorf Supreme cap but this made everything sound more congested and more localised to the speakers. This made me remove the Mundorf caps again.
MBM (1uf wax) and Rifa PHE840 (8.2uf film and foil polypropylene)
K71-4 (10uf polystyrene)
The K71-4 are great capacitors. My experience with them was rather interesting. Previously whenever I have replaced components there have always been positive and negative effects. With the K71-4 this is not the case. When I installed them everything got better. They do their job without ever drawing attention to themselves. These capacitors do not seem to add anything to the music which makes it easy to forget that they are there at all. Compared to the combination of MBM and PHE840 these capacitors do everything the previous caps do right but improve things in a few important places. Overall these capacitors sound very neutral to me, perhaps slightly forward but this is a matter of taste. Highs and lows have great extension while the music becomes more detached from the speakers. These caps bring the sound into the room much more than the previous combination of capacitors. I consider the bass of the caps to be one of their strong points. I find that they strike a good balance between being punchy while also retaining enough body and lushness. Another advantage of this capacitor is that it is smoother sounding than many of the teflon capacitors. The leading edges of sounds are not as sharp, the transients seem more natural. It is however not as transparent as some teflon capacitors when I added a K72P-6 (0.01 uf) the sound became much more transparent while soundstage and detail were improved. The combination of K71-4 and K72P-6 is very good but also more forward sounding and slightly sterile. This made me add the 1uf MBM capacitors to this combination which gives everything just made everything more organic. It gave the sound a bit more body while reducing the forwardness while keeping the great transparency, detail, and soundstage.
After quite a bit of experimentation I ended up with a 10uf K71-4, 0.25uf MBM 700v and 0.1uf K72-6P. The input impedance of my amp is 31K; I might still mess around with this a bit.
K71-4 next to the Teapo NP which it replaced. These things are HUGE!!
K71-4's inside the Musical Fidelty A3-CR mounted on wooden struts.
MBGO-2 (2uf)
I tried these briefly in parallel with the PHE840. They are incredibly spacious, more so than any capacitor I have listened to, the sound seemed completely detached from the speakers. They are also extremely warm lush sounding bass is bloomy but not uncontrolled.
FCH (0.25uf) Teflon
I have used these in a very simple passive pre amp which I have built. I have been using it for a couple of weeks now so the caps must be burned in by now. The amp I built only has six components on each channel. There are only two caps on each channel and both of those are FCH caps. I did experiment with one FCH and one MBM but ended up just using the FCH caps. What I cans say is that the FCH is the type of capacitor which is able pull off a disappearing act; its sound signature is very neutral. It is transparent, open, and spacious in these departements it is probably close to, or on the same level as the K72-6P. They are also very confident sounding bass is nicely controlled. Last another plus is that these are relatively inexpensive at 3USD a piece. I have not seen any of a different value than 0.25uf though.
The MBGO-2 and FCH capacitors
Crossover
My speakers are a called the LBS (low budget speaker) designed by Tony Gee. While these are called 'low budget' they are pretty good. I spent about 600 euros building them and I am not frequently impressed when I walk into hifi shops. Anyway, inside these there is a crossover which uses a zobel network, to save on parts cost of course. You can have a look at the design
here. I did not originally intend to start messing with the corssover but once I realised how good and cheap these Russian NOS I started experimenting. I surprised myself with how much things have improved.
K73-11 (2.2uf) PETP/terephthalate
I used these terephthalates to parallel with the 3.3uf
Jantzen Audio Superior Z-Cap in the signal path of the tweeter which brought quite an improvement to the speakers. The most noticeable thing is that the sound opened up, there just seemed to be a lot more air between instruments. There was also an increase in treble detail while it also became more extended. I am happy with the amount of detail form the speakers, which has increased without the speaker becoming overly analytical. The most surprising improvement was in the lower end of the spectrum. Before the bass had a tendency to sound quite boxy but this was somewhat alleviated. The sound signature of the speakers did become a tad more forward after this modification but this was later corrected when I worked on the crossover some more.
K73-16 (22uf) PETP/terephthalate
Because of the success I had with the K73-11 I bought some K73-16 caps (also PETP) as these come in the large 22uf value I needed to replace the Jantzen Audio Cross Cap in the crossover. Overall the sound became much smoother, before the sound seemed to have a bit of a harshness to it. The Jensen Cross Caps also seem to really emphasise the 'S' and 'T' quite a bit. This problem was gone after adding the K73-16. Another positive effect was that the sound brought more into the room. Further the K73-11 also gave me increased insight into the mids while getting rid of more of the boxynes.The negative points of these caps are that the lower mids are a bit recessed and the bass is quite thin compared to the Cross Cap. Overall, although they are extremely transparent I would say these caps are also quite forward and a bit cold sounding. As reported on this thread bypassing these with a K72-6P works quite well.
K40Y9 (0.22uf) Paper in Oil
I have tried to use the K40Y9 as a bypass cap in several places on the K73-16 and K71-4. While I was not sure if this experiment would yield the desired results I tried it anyway. I had the K40 in my system for several weeks but in the end I decided not to use it. While it certainly has a very musical character actually using it seems to be difficult as there are a few tradeoffs with this cap. Mainly it just does it works really well for basically any kind of instrumental music but with most modern music it does not provide you with a sense of control. Also problematic is that somehow it just does not seem to mix well with other capacitors. Using these as a bypass has just not worked well. The sound signature of system always seems off balance when I use them.
