Caps for my valve RIAA

[Alvolake]

My phono stage uses 8n2 - 300vmin. in the RIAA. I have been using a 6n0 and 2n2, both teflons NOS in parallel but the 6n0 has gone tits up and I need to replace it. Not easy. So I´m looking to buy a pair of 8n2 caps - highish voltage, not necessarily teflon - I´ve got teflons everywhere else and fancy a mix. I suppose I need say 1% tolerance min. Any ideas ?

 

[hearingisbelieving]

Good selection of no-nonsense caps available here:

http://www.cricklewoodelectronics.com/Cricklewood/home.php?cat=111

These could could do the trick:

http://www.hificollective.co.uk/catalog/-c-61_68_355.html?page=2&sort=1a

 

[awkwardbydesign]

I have Russian teflon caps, 8200 and 2200 pF FT1s, can't remember where the hell I got them though. Sorry.

It'll be one of the Russian or Ukranian eBay sellers I use, I'll have another look.

 

[Alvolake]

Found some Russkies on the Bay at a Ukraine supplier I have used before. Ordered 6.

Thanks all

 

[awkwardbydesign]

Found some Russkies on the Bay at a Ukraine supplier I have used before. Ordered 6.Thanks all

What voltage are they? Mine were 200v, which is fine in my Yaqin, but you were looking for 300v. I could do with the higher voltage now for my power amp.

Is it SOVCOM?

 

[Alvolake]

Yes, it is Sovcom - that is where I bought my other larger teflons (0.47uF-200v) which in parallel pairs act as output caps and singly for the interstage - so 6 in all - mechanically a problem fitting them but soundwise they are great. I have discovered that for the first 30 seconds or so, until the filament circuit stabilizes, the circuit may receive up to 260v so, with a bit/lot of help from a mate, we will install a small relay timer circuit so the filaments come on say 30 seconds or so before the high voltage circuit kicks in and hopefully that way no damage will be done.

You need a mortgage to go for higher voltage things like Vcaps and Duelund teflons. I wouldn´t like to have to buy 6 of the buggers.

 

[awkwardbydesign]

OK. I have also bought some of the square polystyrene caps from him, but never used then. I may buy some more, as I need 47nF for coupling, and the Teflons are too big; I only have 20mm betwen the board and the case, top or bottom. K40Y-9 PIO might do if I parallel smaller values and bypass with Teflons or MKP 1837s. Too many possibilities!

And not enough money.

EDIT; the polystyrenes came from Useful Components in Southampton. http://www.ebay.co.uk/itm/110819708164?var=410112773369&ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649

 

[i_should_coco]

I'm not sure 1% will be accurate enough for RIAA. You'd probably need to get a bunch and measure. Accuracy is super important. When I did the LCR, I measured the inductors and caps and spent lots of time simulating and used custom 0.1% resistors to get an acceptable response.

 

[awkwardbydesign]

Sadly most of us have neither the measuring equipment nor the expertise to use it properly anyway! I have some tools, but not of great accuracy, so have to rely on others.

The debate, if that is the word, about accuracy of phono stages when compared to huge variations in transducer response is something I find fascinating. Personally I would like to start with accuracy even if it goes downhill afterwards. But skill and money are limited around here.

 

[i_should_coco]

Yes, of course. It's just that in EQ networks it can make a surprisingly large difference, some of the LCR values are critical, even a 1% difference to some values had a big impact when simulating in SPICE. It also makes listening to different types of components difficult - is it the 'upgraded' component? or just because the response has been affected? You can end up spending a lot of money for the wrong reasons!

 

[awkwardbydesign]

I spent a lot of money sat here with a broken collar bone. Boredom is also a wrong reason!