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KBG-MN Incredible as coupling capacitor!!!

85.164.176.195
Posted on April 22, 2017 at 10:56:58
vbenonisen
 On a whim I just changed my output capacitors on my 1541a D3a diy DAC from V-cap Cutf to KBG-MN. Blimey!!! Incredible! The best and most natural sounding paper in oil capacitor I've ever heard. This must be Russias finest capacitor for audio.

Anyone agrees?

 

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RE: KBG-MN Incredible as coupling capacitor!!!, posted on April 22, 2017 at 13:03:39
sser2
Audiophile

Posts: 2571
Location: Pittsburgh USA
Joined: July 30, 2003
 Yes, KBG-MN it is second to none in PIO foil capacitors, together with KBGI (if you are looking for lower values). The later K40 series is re-named KBG.

KBG-MN are also superb as power supply filter capacitors.

 

RE: KBG-MN Incredible as coupling capacitor!!!, posted on April 22, 2017 at 13:04:19
twystd
Audiophile

Posts: 2723
Location: Austin,Texas
Joined: December 9, 2000
 I've been using Russian caps exclusively for many years now. I wouldn't think of using western commercial caps after the experimenting I've done over the years with bread boarded projects. The KBG-MNs are my favorite cap when you need values from 1-10uf. I use them as parafeed caps (really great in that ap.), preamp/line stage output caps, and in speaker crossovers.

For small value coupling caps ~ .1uf my faves are the SSG silver and micas (incredible detail, yet very smooth) they really disappear, followed by the FT-3 and K72p teflon caps (best if you cut off the steel case, wrap in duct tape, and solder directly to internal leads). The K75-24 hybrid PIOs have fantastic "technicolor" mids, great bass, just loses a little in the extreme highs. If you get the versions with the big funky round steel case and leads, like the K72Ps they also benefit by removing the steel case, wrapping with duct tape, and soldering directly to the internal leads. I've bypassed the K75-24 with SSG silver and micas in parafeed with great results. The K40-Ys are best when you want more of that classic PIO sound. To me they are as smooth as Vit Qs, but better detail and speed.

The MBGO family of caps aren't as nice as the KBGs, but close. They are available in much larger values. These are metalized PIO caps, impregnated with a grainy waxy like substance. IMO they are unbeatable in power supplies, and cathode bypass duties, anywhere when you need the larger values, much better than motor runs.

Finally the Russian SGM silver and micas are great in phono stage RIAA use or anywhere when you need a small value tight tolerance capacitor.

The only drawback with the Russian caps are that they are built like Russian tanks, and require a lot of room. That's not a problem for me, as I exclusively scratch build. Hope this helps, and encourages other DIY builders to explore these wonderful caps. To me these are the greatest value in audio, but as more catch on, the prices have gone up. Not a problem for me, as I long ago acquired a lifetime supply, get them while you still can.

Russian tubes are a whole other story, incredible value for DIY. IMO some Russian tubes are better than their western equivalents. Some Russian tubes are super useful, and have no western equivalents. However that's subject for another post.

twystd

 

RE: KBG-MN Incredible as coupling capacitor!!!, posted on April 22, 2017 at 13:42:54
dhsettim
Audiophile

Posts: 181
Joined: January 10, 2002
 Hi Twystd,
Have you tried cutting off the steel case of the SSG silver micas and then using a non metallic or non magnetic case?
The famous (or infamous) Thorsten advised it was a good improvement.
I haven't tried that myself.
tim

 

RE: KBG-MN Incredible as coupling capacitor!!!, posted on April 22, 2017 at 14:01:36
twystd
Audiophile

Posts: 2723
Location: Austin,Texas
Joined: December 9, 2000
 I've cut these things apart and found the silver and mica was sandwiched between two pieces of Teflon. This Teflon silver/mica sandwich is suspended in an oil reservoir inside the case, the case is also lined with some type of high quality oil impregnated cardboard. Seems as if that'd be pretty hard to beat. The only tweak I've used for them is to remove the solder tab on these and solder directly to the post.

twystd

 

RE: KBG-MN Incredible as coupling capacitor!!!, posted on April 22, 2017 at 14:02:06
banpuku
Audiophile

Posts: 1008
Joined: January 19, 2006
 I too love the russian caps. I use K40Y as interstage coupling caps. They have a ton of rich tonality and texture. I also use the K75s in my power supply.

You stated the MGBO caps are good for cathode bypass. I do need a good cathode bypass cap in the 50uF range. Ebay has 30uF for sale. Question: the caps listed on Ebay are rated 150V. Do you see any issue using the 150V caps for cathode bypass duties?

Thanks,
Pat

 

RE: KBG-MN Incredible as coupling capacitor!!!, posted on April 22, 2017 at 14:11:03
twystd
Audiophile

Posts: 2723
Location: Austin,Texas
Joined: December 9, 2000
 I use those 30uf 160V MBGOs a lot for cathode bypass, when I can't eliminate the need for cathode bypass. I parallel 4 of them to bypass 300Bs. You'd be fine with 2 in parallel. It'd help to know what bias voltage you have across them, for instance the 300Bs were biased at 75V. When you parallel them you reduce their ESR (a good thing).

twystd

 

RE: KBG-MN Incredible as coupling capacitor!!!, posted on April 22, 2017 at 14:44:25
banpuku
Audiophile

Posts: 1008
Joined: January 19, 2006
 My 2a3 tubes are biased at 50V, so I should be fine. I like the idea of using only 1 for cathode bypass duties, but I will order 2 per channel so I can parallel them just in case. thanks for the input, as I have been looking for a capacitor to replace my ClarityCap TCs which is more suited as a power supply cap.

 

RE: KBG-MN Incredible as coupling capacitor!!!, posted on April 22, 2017 at 15:06:12
vbenonisen
 I'm still stunned by the sound. I've tried some K40's before, but to me the KBG-MN's are better. I have no idea how they are made and what's in them except the paper of course but judging from the sound it has to be gold (just kidding). And they aren't even burned in. I'm extatic. It's like finding a fortune in the dumpster.

 

Russian paper in oil capacitors, posted on April 22, 2017 at 17:13:34
sser2
Audiophile

Posts: 2571
Location: Pittsburgh USA
Joined: July 30, 2003
 KBG-MN are actually big capacitors in rectangular metal cases. What you are talking about is likely axial KBG-M1 or KBG-M2. M1 was superceded by M2 in early 1970s. All M1 and M2 capacitors were made by the OZR factory. I don't know what was the difference between M1 and M2, but it would be interesting to compare them sound wise.

KBG-M2 was discontinued in late 70s (I haven't seen any with dates later than 1979), and replaced with K40. K40-P look much like KBG-M2 - they have one lead connected to the body, and were made by the same factory (OZR). K40-Y have both leads insulated, and they were made by the different factory.

In basic construction they are all the same: aluminum foil electrodes with oil-impregnated paper dielectric. However, technological details such as sources of paper and oil at different factories could have been different.

You might have discovered that there is something special about OZR capacitors...

 

From Russian tube DIY forums and data sheets, posted on April 22, 2017 at 18:41:59
sser2
Audiophile

Posts: 2571
Location: Pittsburgh USA
Joined: July 30, 2003
 "Good in sound".
"KBG-M2 are very good capacitors. I use them in most of my projects. BTW, K40-Y9 I like much less".

From specification sheets of Russian PIO capacitors:

KBG maximum temperature - 70 degrees centigrade.
K40Y maximum temperature - 130 degrees centigrade.
Apparently, they use very different dielectric materials.

Basic KBG dielectric material: condenser paper 8 or 10 micron thick.
200V - 2 layers 8 micron
400V - 3 layers 8 micron
600V - 3 layers 10 micron
1000V - 4 layers 10 micron
1500V - 5 layers 10 micron
Impregnation medium - petroleum jelly.

KBG capacitor AC component should not exceed:
20% working voltage at 50 Hz
15% 100 Hz
10% 400 Hz
5% 1 KHz
2% 10 KHz

The foils of Russian KBG capacitors are not welded or soldered to leads, therefore they should not be used at very low voltages. Biasing voltage of at least 10 V should be present when these capacitors are used for coupling duty.

 

"Biasing voltage of at least 10 V "..., posted on April 22, 2017 at 18:58:28
Steve O
Audiophile

Posts: 12359
Location: SE MI
Joined: September 6, 2001
 ...so K40 and KBG no good for input coupling or anywhere in many solid state apps because 10V bias won't be present? Hmmmm!

 

Sorry, my mistake, it only applies to KBG, posted on April 22, 2017 at 19:24:39
sser2
Audiophile

Posts: 2571
Location: Pittsburgh USA
Joined: July 30, 2003
 K40 leads are welded to foils, so they are OK at very low voltages. BTW, this is also one of the differences between FT and K72 capacitors: the latter are welded, but the former are not.

 

RE: KBG-MN Incredible as coupling capacitor!!!, posted on April 22, 2017 at 19:25:35
lokie
Audiophile

Posts: 1988
Location: Georgia, USA
Joined: January 28, 2003
 Great info. Thanks for sharing.

I have various Rusky's on the way. I'll be checking your post for various applications. It's funny- I thought it was a bit of a stretch to try as coupling caps. Good timing on your your endorsements.

 

RE: KBG-MN Incredible as coupling capacitor!!!, posted on April 22, 2017 at 19:34:24
twystd
Audiophile

Posts: 2723
Location: Austin,Texas
Joined: December 9, 2000
 Since capacitors are basically many plates in parallel, there is no harm in paralleling them. 50uf is very low for bypass caps on a 2A3. No harm if you are running subs, but if you are running them full range they will be bass shy. For full range, parallel 3 or better yet 4, they are cheap enough.

twystd

 

RE: KBG-MN Incredible as coupling capacitor!!!, posted on April 22, 2017 at 19:54:10
twystd
Audiophile

Posts: 2723
Location: Austin,Texas
Joined: December 9, 2000
 I too like the KBG-MNs very very much, pretty unbeatable when you need a parafeed cap. I cut open a 400V 2uf KBG-MN. When I unrolled it I swear it had copper foil. I've heard from others that it just looked that way, but was really aluminum foil. Not so sure, as the cap construction of Russian caps vary.

For example, a K40-Y I cut apart was oil impregnated paper with aluminum foil for the outer 2/3 or so of the winding, the inner 1/3 of the winding was copper foil (with an obvious splice) the copper foil part of the winding used some type of plastic as a dielectric.

twystd

 

Seems like the KBG has issues..., posted on April 22, 2017 at 20:59:12
Triode_Kingdom
Audiophile

Posts: 10044
Location: Central Texas
Joined: September 24, 2006
 So, the leads aren't welded? It sounds as though the 10V is required in order to overcome contact potential. With or without bias, contact potential has the potential to create sonic coloration and ambiguity.

Then there's this:

KBG capacitor AC component should not exceed:
20% working voltage at 50 Hz
15% 100 Hz
10% 400 Hz
5% 1 KHz
2% 10 KHz

That's a very small margin for an audio coupling cap, particularly in the region of 100 - 400 Hz.

If any of this information is correct, I wouldn't even consider using these in the signal path.



 

This rather reflects, posted on April 22, 2017 at 21:39:50
sser2
Audiophile

Posts: 2571
Location: Pittsburgh USA
Joined: July 30, 2003
 a very cautious approach of Russian component manufacturers.

From manufacturer's standpoint, it is very difficult to forsee what kinds of abuse the components will be subjected to by end users, so they have to build in a margin of reliability.

In the US, if components fail at unusual rate, it could be expensive recalls, or a lawsuit at the worst case scenario.

In the USSR, it was accusation of sabotage under Penal Code Article 58, "Anti-Soviet Activities", and sure death in Gulag.

Hence the very cautious approach.

The same data sheet hints though, that under normal use conditions and in non-critical equipment, ratings could be considerably exceeded.

Out of curiosity, I once plugged a 160 VDC-rated Russian capacitor into 220VAC outlet for 24 hours, and nothing happened.

 

RE: Seems like the KBG has issues..., posted on April 22, 2017 at 21:43:39
twystd
Audiophile

Posts: 2723
Location: Austin,Texas
Joined: December 9, 2000
 Yeah you're right, they are total crap, and I'm obviously tone deaf.

twystd

 

Copper foil, posted on April 22, 2017 at 21:45:25
sser2
Audiophile

Posts: 2571
Location: Pittsburgh USA
Joined: July 30, 2003
 Oil-impregnated Russian capacitor paper is translucent and has reddish brown tint, which may make aluminum look like copper.

 

RE: This rather reflects, posted on April 23, 2017 at 00:01:21
twystd
Audiophile

Posts: 2723
Location: Austin,Texas
Joined: December 9, 2000
 I've observed that Russian caps and tubes are frequently very conservative in their ratings. I also think that your observation about quality control via the Gulag, explains a lot of the difference between Soviet era and modern Russian tube quality.

twystd

 

RE: Russian paper in oil capacitors, posted on April 23, 2017 at 00:15:46
vbenonisen
 It IS the big capacitors in rectangular metal cases. They simply shouldn't sound this good. But indeed they do. There has to be some synergies happening with the rest of my gear. It's the only plausible explanation.

Update: Tried some other coupling capacitors in the following preamp stage, and there definitely is some synergy involved. The magical combination was and is with KBG-MN and FT-3 teflons. Even a Sprague Vitamin Q or a V-cap Cutf in the latter position can't beat it.

Update II: The KBG-MN's seems to have opened up a little bit with some burn in. Probably much more goodness awaits. Anyhow I changed back to Sprague Vitamin Q in my preamp just to have another listen to this combination of paper oils. I think it sounds great as well. A little warmish perhaps but the midrange is splendid. It's official. KBG-MN IS a great capacitor. Don't let anyone tell you otherwise.

 

RE: This rather reflects, posted on April 23, 2017 at 08:05:29
Lew
Audiophile

Posts: 10911
Location: Bethesda, Maryland
Joined: December 11, 2000
 I think USSR manufacturing standards of quality were just as dubious (good and bad) during the Soviet era as they are or may be now. Sure, people were assassinated or sent to Siberia seemingly at random, but not over the issue of blown capacitors. I have many Russian ex-pat scientist friends who are old enough to corroborate this idea. The difference between Soviet and post-Gorbachev Russian goods, if one perceives that quality went down, may be attributable to the decaying economic conditions and of funds to support their military in Russia that led to the dissolution of their empire in the first place. And actually, they are making some good stuff these days. (By the way, one can still be assassinated or sent to prison seemingly at random.)

 

I don't think so, posted on April 23, 2017 at 10:30:16
Triode_Kingdom
Audiophile

Posts: 10044
Location: Central Texas
Joined: September 24, 2006
 "In the USSR, it was accusation of sabotage under Penal Code Article 58, "Anti-Soviet Activities", and sure death in Gulag."

The same was true in China. They still made junk.


 

RE: This rather reflects, posted on April 23, 2017 at 21:27:58
twystd
Audiophile

Posts: 2723
Location: Austin,Texas
Joined: December 9, 2000
 Actually Lew my comment was somewhat tongue in cheek, and your reasoning sound. I Do believe there was a downturn in Soviet era tube quality during the Gorby years due to other factors as well. Since this is a cap thread and I don't want to hijack it, I'll save that for another post.

twystd

 

RE: KBG-MN Incredible as coupling capacitor!!!, posted on April 24, 2017 at 03:31:32
Michael Samra
Dealer

Posts: 36118
Location: saginaw michigan
Joined: January 30, 2005
Big Nose hear no evil,see no evil,smell no evil./


" Roe
When I cut open the K72 teflon and tried to tape it,the thing unraveled..Part the reason we like the SSG and the Teflons could be because we can put our own leads on them.When I put silver stranded leads on the K40y pio caps,there was a nice improvement.
Anyway,when the K72 unraveled,my daughter who was 12yo in advanced gymnastics at the time, got the brilliant idea to string the teflon tape up like a tightrope between the two chain link fences from my house to my parents house, Needless to sat she walked about 10 feet on it before falling on her keister.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken

 

Yes, 6C33Cs..., posted on April 24, 2017 at 07:04:14
Lew
Audiophile

Posts: 10911
Location: Bethesda, Maryland
Joined: December 11, 2000
 are a case in point. I think that the ones made in the Ulyanov (sp?) factory up to the early 90s are superior, at least more reliable, than ones made since.

 

RE: KBG-MN Incredible as coupling capacitor!!!, posted on April 24, 2017 at 14:46:01
twystd
Audiophile

Posts: 2723
Location: Austin,Texas
Joined: December 9, 2000
 Michael I just cut apart 8 K72s Ruined 2. The method I use is to use a Dremmel with a cut off wheel to CAREFULLY cut around the case in the middle without damaging the Teflon winding. Next remove 1/2 of the case, be very gentle here as the internal lead is attached to steel posts. If you pull too hard the case will come off quickly and detach the the lead from the foils, then you're hosed, that's how I ruined 2. There's a little extra lead inside the case that allows you to have the room to cut the lead where it connects to the steel external solder post. While grasping the Teflon coil repeat with the other 1/2. While still holding the coil (so it doesn't unwind) wrap the coil tightly with tape (I used electrical tape). Now you've got a world class Teflon cap for cheap.

Beeg Nose

 

RE: KBG-MN Incredible as coupling capacitor!!!, posted on April 24, 2017 at 15:43:03
used-hifi
Audiophile

Posts: 1100
Location: Surprise AZ
Joined: March 18, 2003
 Hey Guys I would like to offer my services if you need to de-shell round capacitors I have a precision lathe with collet setup


say 5 bucks each with guarantee not to muck it up :)

5 PIECE min

 

I like to do things the hard way, that's why I'm into DIY. :-)) (nt), posted on April 24, 2017 at 20:22:57
twystd
Audiophile

Posts: 2723
Location: Austin,Texas
Joined: December 9, 2000
 twystd

 

RE: KBG-MN Incredible as coupling capacitor!!!, posted on April 26, 2017 at 06:06:11
banpuku
Audiophile

Posts: 1008
Joined: January 19, 2006
 What do you think about the following for a cathode bypass cap parallel combo:

30uF MBGO
30uF MBGO
10uF K75-10

Would the 10uF (being the smallest value) have a discernible difference versus using 3x 30uF MBGO? The sonic qualities of the K75-10 are very very good. I am not sure if the MBGOs are of similar quality or not.

 

RE: KBG-MN Incredible as coupling capacitor!!!, posted on April 26, 2017 at 15:01:48
twystd
Audiophile

Posts: 2723
Location: Austin,Texas
Joined: December 9, 2000
 Usually bypassing caps is done if there is a roll off of highs, and the value is significantly lower than you propose (~.1uf). Also the K75-10s have a wonderful mid range, but they do roll off slightly in the highs, so don't know what you'd hope to accomplish with the k75. Of course you could always try it. I'd compare with 3 (better yet 4) of the 30uf MBGOs. Of course it would help if I knew if your amp runs full range or not. Even 3 MBGOs in parallel will probably still introduce some phase shift in the bass. Again working in a vacuum here.

To know the optimum value bypass cap it'd be nice to know your cathode resistor value, the operating points of the 2A3 (so I could refer to the plate curves to determine Rp), the impedance of your output transformer, and the lowest frequency your speakers can reproduce.

twystd

 

RE: KBG-MN Incredible as coupling capacitor!!!, posted on April 26, 2017 at 15:25:17
banpuku
Audiophile

Posts: 1008
Joined: January 19, 2006
 My amp schematic is attached. Here are my operating points:

driver tube
RCA 12bz7
plate voltage: 208V
grid voltage: 2V
current: 1.5mA

output tube
JJ 2A3-40
plate voltage: 320V
VDCp-k: 270
grid voltage: 50V
current: 50mA

Output Transformer
Hashimoto H-20-3.5U
Can be set to either 2.5k or 3.5k Ohms

my speakers are quad ESL-63s. They go to 40hz -3db. Subjectively, the amps and speakers play low bass (100-50hz) fairly well. Since I listen to chamber music almost exclusively, I don't get much bass below 50hz. I have not tried any cathode bypass caps with a greater value than 65uF. So, I am not sure if 2x or 3x or 4x 30uF MGBOs is the way to go. Any input would be appreciated.



 

RE: KBG-MN Incredible as coupling capacitor!!!, posted on April 26, 2017 at 19:25:23
twystd
Audiophile

Posts: 2723
Location: Austin,Texas
Joined: December 9, 2000
 Are you sure about that schematic. Looks to me like one end of the cathode bypass would go to ground like you are showing, however the other end should be at the top of the 1K cathode resistor. Even if you were doing some type of ultrapath amp, the cap would go from the power supply and transformer node to the top of the cathode resistor.

twystd

 

Here's what I'd do, posted on April 26, 2017 at 19:57:47
twystd
Audiophile

Posts: 2723
Location: Austin,Texas
Joined: December 9, 2000
 Replace your .47uf K40Y coupling cap with a smaller value ~.1uf. I'd really recommend a SSG silver and mica. Too big of a coupling cap is as bad as too small. In my experience big couplers reduce speed and microdynamics, with that 330K grid leak resistor on the 2A3 .1uf should be fine. Second make sure that the cathode bypass cap bypasses the cathode resistor by being connected to ground on one lead, and the top of the 1K cathode resistor with the other lead. I have calculated the value to be ~80uf to not have a phase shift at 40hz, so I'd parallel 3 of the 30uf MBGOs. I'd be willing to bet that you will like what you hear.

 

One other thing, posted on April 26, 2017 at 20:49:44
twystd
Audiophile

Posts: 2723
Location: Austin,Texas
Joined: December 9, 2000
 Looks like your transformer is set up for 2.5K, that's awfully low for a 2A3. 2.5K will give you more power than 3.5K but it will have more distortion. Your quads aren't all that efficient, who knows you may prefer more power rather than lower distortion.

twystd

 

RE: KBG-MN Incredible as coupling capacitor!!!, posted on April 27, 2017 at 04:58:18
banpuku
Audiophile

Posts: 1008
Joined: January 19, 2006
 You are correct, the schematic incorrectly shows the cathode bypass cap going to ground when it should be at the top of the 1k resistor, my bad.

I have a 0.22uF cap that I can use to replace the 0.47uF cap. I will give it a try.

Easy enough to try 3x or 2x 30uF MBGO caps.

Thanks for all the input and time. Great stuff!

 

RE: Here's what I'd do, posted on April 28, 2017 at 07:57:16
banpuku
Audiophile

Posts: 1008
Joined: January 19, 2006
 Update: I replaced the 0.47uF K40Y coupling cap with a 0.22uF K40Y cap. While the 0.22uF cap needs to be broken in, there was a perceived improvement in the dynamics and transients. Sharp attacks appeared my startling and noticeable.

I also discovered that using multi-stranded silver coated copper hook-up wire is a no-no in my system. I switched over to using solid 99.99 silver and the sound improvement was very noticeable. No more glassy, etchiness in the upper mids and lower treble region. For whatever reason, my amp does not like the silver coated copper hook-up wire.

 

RE: Here's what I'd do, posted on April 28, 2017 at 23:31:37
twystd
Audiophile

Posts: 2723
Location: Austin,Texas
Joined: December 9, 2000
 I think you will find a similar improvement in coupling if you go to .1uf, and really, the SSG silver and micas are worth a try. BTW, I don't like to use stranded silver coated hookup wire either, my preference is for dead soft 99.99% solid silver as well (teflon tubing for insulation). Dead soft copper solid wire works well too, when you can't afford silver. I have just soldered up 33 step TVCs and switches. That took right at 50' of wire, just couldn't justify the cost of silver there, especially since the windings themselves are copper.

twystd

 

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