[dimkasta]

I sanded the leads so they must be some issue with their innards as well. I will tear one apart and photograph it
 
I also received some K71-7 yesterday with 0.5% tolerances. They measure superbly on my CLR. It will take some time before I test them though. My Salas folded phono still needs lots of work...

 

[lehmanhill]

  By the way, I received a batch of 20 3nF FT-1s to check on my phono, but some of them were duds. That was the first time I came something like that in russian caps. About half of them were measuring ~1,4nF and the dissipation factor was all over the place. I managed to get 2 matched pairs with almost 0 D, but I had to discard around 10 of them as absolutely not usable.
 
As a first indication, the leads were almost black and had to be sanded. I guess they were stored in very bad conditions since it is the first time I see something like this, and I have bought a lot of Russians in the past.

I have had a similare experience with FT-1s.  From three batches, it seems like 1 or 2 in 10 arrive bad.  I contacted the seller, told him so many were out of spec, and he refunded that portion of my order.  I haven't had this trouble with any other Russian caps, including other teflon caps, but I understand that the FT-1 uses a very thin teflon film and that with age, holes in the film can develop and degrade the caps.
 
I never expected perfect results from NOS parts.  The recommendation is to buy a few extra if you buying FT-1s.

 

[dimkasta]

Perfectly sensible suggestion

 

[Jazzwallah]

Hi Jon
I have really found your musings on capacitors worthwhile in my mods. I am thinking of using .68 K75-10 capacitor and considering bypassing it with the V cap TFTF as you suggested in your post earlier in the thread. However reading your assessment of the Vcap CUTF I would like to consider it as the bypass for the K75-10.. Have you or any members of this forum tried this capacitor combination?. Your thoughts would be appreciated.

 

[dimkasta]

In what position?

 

[samoloko]

I really like to know from people dealing with russian caps how Is possible to find them better compared to new and highly priced and speced rivals
well I tryed russian K75-10 2.2 uF bypased with 0.1 FT3 In out coupling position Instead of MKP - the result - complete lack of bass and highly distorted unnatural sound
sure there Is a difference but I doubt that Is for better

 

[JamieMcC]

  I really like to know from people dealing with russian caps how Is possible to find them better compared to new and highly priced and speced rivals
well I tryed russian K75-10 2.2 uF bypased with 0.1 FT3 In out coupling position Instead of MKP - the result - complete lack of bass and highly distorted unnatural sound
sure there Is a difference but I doubt that Is for better

 
Well its a  subjective subject and not all combinations are going to work so it is very much a case of trial and error.
 
I have a couple of favourite cap combinations which are not audio caps. On of my favourite combos are these mgbo pio with Teflon bypasses total cost about £20 they replaced a pair of Mundorfs which cost £80 a pair, the Mundorfs are now in the parts box. I also have some Jantzen Z caps and they work brilliantly in one amp but in another amp I found them very fatiguing and had to take them out in the end as I could only bare to listen for about 30-40 minuets at a time.
 
The rule of thumb with bypassing seems to be best results come from using a bypass cap that is about a 100th of the value of the cap being bypassed 100uf =1uf bypass. Going lower seems to work as well. Going higher in value is often when the problems start to appear.
 
Something to think about is that the teflons take simply ages to burn in before revelling their true nature  200-500hrs is not uncommon and sometimes they can also be pretty much unlistenable to at times whilst burning in.
 
 

 
 

 

[samoloko]

you have 90 uF MBGO bypassed with much lower then 1/100 value of K72
which Mundorf replaced MBGO ? Supreme ?
what Is charackter of MBGO
I have used 10 uF MBGO as a power decoupling and find them too fluid and with lack of control, and very natural
did you tried Mundorf Evo Oil

 

[JamieMcC]

It was a standard Mundorf mkp 100uf don't get me wrong they are superb sounding capacitors I just preferred the Russian caps for this particular application there really was not much to choose between them save for the price/ I can assure you they would be out in a flash if I didn't think they where much cop. The thing with them I find is they could almost be described as boring when you first listen to the combination there is no wow factor at all its only after a while that it dawned on me that the sound is a shade more natural in presentation and tone.
 
At the larger uf values the boutique caps can cost a arm and a leg so its good to have options. 

 

[pelopidas]

Samoloko,
I tried pretty much the same combination, 2.2uf k75-10 bypassed with an FT-3. If you read a few pages back you will see that dimkasta and I also discussed this very combo. It seems to us all that 2.2uf k75-10 are just plain bad. Dimkasta noted that his large value (10uf if I remember) sounded good but I never tried those. K73-16 were a breath of fresh air after the 75's and are also better than Daytons or entry level mundorfs. They are neutral and revealing. Use your ft-3 on those and let that combo burn in for a good long while.

 

[JamieMcC]

These k75-40b's 100uf's pulse caps are simply epic but I'm going too need a bigger amp they have a different sonic character to the k75-10's.
 
I'm planning on building a OTL amp around them and some big 35 step rotary switched attenuators still collecting parts its going to be a fun project with all film caps.
 

 

 

 
Borrowed pics of the same switches
 

 

 

 

[pelopidas]

So what is the sonic character? Don't just leave us hanging!

 

[samoloko]

Samoloko,
I tried pretty much the same combination, 2.2uf k75-10 bypassed with an FT-3. If you read a few pages back you will see that dimkasta and I also discussed this very combo. It seems to us all that 2.2uf k75-10 are just plain bad. Dimkasta noted that his large value (10uf if I remember) sounded good but I never tried those. K73-16 were a breath of fresh air after the 75's and are also better than Daytons or entry level mundorfs. They are neutral and revealing. Use your ft-3 on those and let that combo burn in for a good long while.

thank you for reply
 
good to hear that I am not only one that dislikes K75-10
I am searching for a cap to replace 82 uF non polar electrolytic coupling cap
If you are sure that K73-16 Is better then Dayton that Is very good because these caps are used In highly priced loudspeakers

 

[JamieMcC]

  thank you for reply
 
good to hear that I am not only one that dislikes K75-10
I am searching for a cap to replace 82 uF non polar electrolytic coupling cap
If you are sure that K73-16 Is better then Dayton that Is very good because these caps are used In highly priced loudspeakers

 
How much space and what voltage? These 89uf 250v +/-  2.5% Epcos worked well for me .
 
http://www.aliexpress.com/snapshot/6096462870.html
 
In action used both as coupling cap and in power supply. There wasn't much difference between them and a Solen or JFX film audio caps. I brought five for $27.80 including shipping in May
 

 

[dimkasta]

Samoloko, Pelopidas said it all
 
But the biggest problem with the K75 was in the lack of highs, not so much on the lows. In fact I would call them rather sweet and darkish. And no amount of bypassing fixed things me (in fact I hate bypassing signal caps altogether). What is your amp's input impedance? Perhaps you need a bigger value.
 
For 22K amp, I found that 10uF had a very distinct effect for the lows with all the speakers I have tested.