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Re: 7241, 7242

Posted by kolbay@axelero.hu (A) on October 20, 2004 at 22:42:56

In Reply to: Re: 7241, 7242 posted by Lew on October 20, 2004 at 08:24:16:

Going from 6C33C to 7241 is not especially simple. Russion 6C33C has 1 triodes, 7241 has 3. They also use different kind of sockets, and may require different power transformer, and other parts.

My DIY OTL amp has free versions:
1. One monoblock of the first version uses 4 pcs 6C33 tubes.
2. One monoblock of the second version uses 4 pcs 6336 plus 2 pcs 6528 tubes.
3. One monoblock of the third version uses 2 pcs of 7241 plus 2 pcs

In tube characteristic 6536 is similar to 7241, while 6528 is similar to 7242. 7242 has quite different characteristic than 7241. They are not replaceble. They have different roles in my amp: 7241 is responsible for those musical low level details, while 7242 takes role when fast, huge mass of sound requires very smart action of the power amp. The amp also works if I remove the two 7242, but unquestionably it losses some dynamics. If I replace 7242 with 7241, the same effect takes place.
I have to note that the OTL also seems to be dynamic without the 7242s relative to my Jadis JA30 amp, but what’s the different beetween the 2x7241&2x7242 and 4x7241 configuration !

According to the sound: version 1. is the worst, 2 is more better, and version 3. is the best. It’s not only my taste, everybody who have heard has similar opinion.

Notes:
1. The Russion tubes are a bit unreliable, one-two pcs have to be replaced in every year. According to the amp’s designer, they are also bad constructions. But they are very cheap tubes here in Europe.
2. 6533 & 6528 works fine in this construction. Every tubes operate flawlessly in the last 10 years without changing one of them !
3. We have no practice yet of the reliability of the 7241/7242 line. My OTL monos are in use within a month only.

I aggree with Jim, that difficult to find 7241s with matching sections. You need a lot of tubes to select appropriate ones. Especially hard in symmetrical design, as my amp.

-Ferenc

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