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Tubes in the AI Modulus 3

Posted by Bambi B (A) on October 10, 2009 at 10:46:50

In Reply to: Modulus 3/3A Question posted by Brent Powers on October 9, 2009 at 08:54:45:

Brent Powers,

I've never owned an Audible Illusions Modulus 3, but over the years learned that it tends to push it's tubes along in way similar to the Audio Research SP10. That is, choosing tubes for either requires similar attention to the ruggedness. Having tubes sound wonderful for only a few hours is very disappointing- and today very, very expensive with NOS. One of the best sounds I've ever heard from a preamp came from the SP10 when I tried some used Amperex, Heerlen white label ECC88, but these lasted only about 20 hours before going noisy. Fortunately, those were then only $10 tubes.

This is a chart worth sticking into the file with your manual:

6DJ8 ratings:

ECC88 = 6DJ8 130V/1,8W (2,500 hours)

E88CC= 6922 220V/1,8W (5,000 hours)

E188CC= 7308 250V/2W (also rated for low noise and low microphonics)

6H23P-EB Sovtek 6922 300V/1,8W

6H23P-EB EH 6922 300V/2W

-Notice the ratings for Volts and Watts. This is the reason the Russian EH6922 is a safe choice for the AI- as well as the SP10. the "-EB" suffix means a long life version and is given the equivalent to E88CC / 6922.

The sound of the Sovtek and EH is not so bad, but there are a lot of great choices with NOS will be better at getting the most out of the AI, steering it towards some quality you like.

Fortunately AI posts on their website a guide to NOS tubes for the Modulus series:

http://www.audibleillusions.com/technical/bulletin5.htm

- The importance of the ruggedness seems a bit understated, but is really a priority- the tubes have to survive if the good sound is to be of any use.

With 6DJ8 family tubes, I think the Philips ECC88 sound the best of about any 6DJ8- the 6DJ8 seems to me to sound more "open" than the 6922 or 7308, with Siemens E88CC being the best 6922, and the Philips E188CC and Siemens E188CC both excellent. Siemens tend to lean towards higher energy- more dynamic and punchy.

I recently replaced 8 of the 12- 6DJ8 family tubes in the SP10, so that the 4- phono and 2- line stage gain tubes are very nice Philips SQ E188CC / 7308 and the 6- cathode followers and etc. are late 60's Tungsram red label (military) E88CC.

By the way, one of my motivations in choosing Tungsram E88CC- I eventually bought 28- is that they are patterned after the Siemens- as well as being very rugged,.. The Tungsram are still around too in quantity and not expensive, in fact not a lot more than a new EH, whereas a Siemens can cost 10X as much as the EH. The sound of the Tungsram is really good- never harsh, and I'd say a very high percentage of the qualities of the Siemens.

By reputation, AI owners seem to really like the Modulus series. It's been too many years since I heard one.


Cheers,

Bambi B

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