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RE: Tube rolling advice wanted - EAR V20, EAR Acute CD, & Conrad Johnson EV1

Posted by Bambi B (A) on August 4, 2009 at 18:35:15

In Reply to: Tube rolling advice wanted - EAR V20, EAR Acute CD, & Conrad Johnson EV1 posted by il toro on August 4, 2009 at 07:05:31:

il toro,

I think the first thing to do when considering tube changes is to learn which tubes have a noticeable sonic impact and which don't. I recently retubed my 1987 Audio Research SP10 preamplifier which uses 12- 6DJ8, two 5881's and a 12AT7. That's 15 tubes and to get the full potential, the gain tubes have to be very good- good sounding, quiet, low microphonics, and very tough. Even - an indestructable Sovtek- the Left channel line stage gain tube (V9) had gone noisy in the SP10.

It was useful- and a big cost savings, to learn that there are two really critical tubes- the first two gain tubes of the phono stage (V1, V2), and the first two of the line stage (V9, V10). Of second importance are the second two of the phono stage which are also phono gain tubes (V3,V4) while the other 6 are cathode followers and cascodes and are ideally quiet, equal triode sections, and rugged- the SP10 does push it's tubes.

With the knowledge of which tubes are important, I was able to use the really nice ones- Philips SQ E188CC 7308 (1963) as the two second row phono and two as the line stage gain tubes. Then, the other 6 are 1969 and 1977 NOS Tungsrams red labeled E88CC that cost $15 each. In using the expensive ones where they count, and the reasonably priced tubes where the sound will not be noticeably affected, many Obamabucks were saved. So, find out what the tubes are doing in your EAR and C-J stuff- which tubes have to be the good ones.

General Recommendations:

12AX7 : For a phono preamp, I imagine all the tubes, but probably the 12AX7s have to be especially high gain, quiet, and non-microphonic. For that, I think of the Siemens and Halske triple mica E83CC- a super sounding, long life 12AX7. This is a very energetic tube- not soft and not harsh, punchy, dynamic, and great bass, and every one I've had always was quiet and had well-matched sections. For a lower key presentation, I like the ordinary Philips / Amperex / Valvo ECC83 from the 60's. These do everything well and worked everywhere I've tried them- vintage and modern gear alike. - Not expensive still- buy these tested or NOS as Valvo off German Ebay- the same tube for quite a bit less than an "Amperex" in the US.

5751: If the 5751 is a gain tube- it's like a 12AX7 that puts out 70%, I'd say look for the late 50's Sylvania triple mica, black plate, square getter. These are just amazingly refined tubes, dynamic,and transparent. Expensive though now, so if the 5751 is not a gain tube, a new Sovtek or the ordinary grey plate GE will be fine.

12AU7: If this contributes significantly to the sound, the Philips / Amperex / Valvo 7316 / ECC186 is the thing, and the Siemens triple mica 5814A or triple mica E82CC /6189 if you want to lean towards energy and punch. I use the Siemens triple mica E82CC in the MPX section of a McIntosh MR67 tuner. I liked the 7316 so well I bought enough NOS to use in all 8 places I use 12AU7's, but these are like most of the premium types, now costly. However, you only need one and in a preamp I imagine this might run a very long time.

Sorry, I don't know the PCC88, except that I think it's not an automatic substitute for the ECC88 (6DJ8, 6922, 7308)

See what tubes have to be the good ones, do a search on this forum for opinions- tubes choices vary by the equipment they're going- vintage, and take your time finding them. In the long term, buying selected from a dealer may be a better use of you money and time. Don't do what I did and buy 200 bargains for four times the cost of the 20 perfect tubes I actually needed,..

Happy hunting!

Cheers,

Bambi B

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