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jessie.dazzle wrote:

One did; in reviewing the L2 preamp, John Atkinson (Stereophile) wrote: "...The absolute polarity was preserved from both sets of outputs with the front-panel switch set to "0 degrees," confirming that the XLR jacks are wired with pin 2 hot. Setting the polarity switch to "180 degrees" inverted the unbalanced output but not the balanced output..." From the manufacturing point of view there may be a good reason why this is the case, but from the consumer's point of view, it is not ideal.

Good one. I do not remember it. Still from the Atkinson language I see that it was written by Atkinson in his technical summary not in the review itself. In his technical measurement summary he just report data but not interprets data. So, users of L2 do not understand what it means. At the time when I used L2 I spoke with many L2 owner including with a few people who bi-amp. No one let me say again: NO ONE, including those who consider themselves the heavy L2 users realized that XLR jacks do not reverse phase. This type of setting is absolutely not permitted in a balanced preamplifier. Mind you that inverting phase is one of the main functions of this preamp as it is made with fully balanced topology; this is why is double all parts of the signal circuit.

jessie.dazzle wrote:

The part that grips the pin is made of several tiny contacts. I don't think they are gold-plated; in any case, gold would likely not fare too well in the presence of the heat generated by the 6C33C. Image below: In the case of the Teflon sockets for the 6C33C, the Teflon plays no roll in clamping the pin; there is in fact a generous gap around the pin receptacle and all clamping force comes from the springiness of the metal contacts, which are confined by a hollow cylinder. Next two images: The pin receptacles are composed of threaded parts, which, in my opinion, should be soldered as one to improve both electrical and thermal conductivity between the individual parts, as well as keeping them from coming loose over time. Image below: Here is the problem with these sockets... The threads of the large pin are not long enough (not enough of them protrude through the Teflon base) to allow proper threading of the securing nut. Threads on the smaller pins are longer and the smaller assemblies can be adjusted to compensate, but as this is not an option with the large pin; thickness of the Teflon base must therefore be reduced by at least 1.5mm. Image below: Showing material that needs to be removed to allow for short threads of large pin. Image below: Fully assembled after Teflon base has been reduced by 1.5mm; note, even after reduction in thickness of base, there are still no excess threads protruding past the securing nuts. In the case of the ML2, the four chassis mounting holes in the Teflon base must also be enlarged. Image below: New sockets have pin receptacles closer to the center of the socket... Lamm rightly leaves no excess length, so getting the original wires to reach the pin receptacles is tricky. In spite of the work necessary to correct the thickness issue, I'm very happy with the results and would in fact recommend these sockets. I do nevertheless have to admit, considering the price paid (something like $38 each plus shipping and customs), that it is reasonable to expect a finished product. I assume these are among the first that the manufacturer has produced for the 6C33C, as the thickness issue could be easily corrected during future production.

Very good job with the sockets. I did not see this type of the sockets you use. The only one Teflon sockets for this tube that I seen were $100 sockets by a Japanese guy, I think it was Yamamoto or something phonetically similar. They were a bit different; I like your better as they have better pin ventilation. Ideally I would like to have more air exposure to the 6C33C pins and the pin on this tube run very hot. I would like to have a micro heat sink on the pins to let them to be cool down. Two words of warning: make sure that you wind the wire around the pins and then fill it with plumbum. The old sockets had whole where the wires were able to be inserted and tighten before soldered. Another thing: do not use the low temperature soldering metal. Many of contemporary soldering metals have silver in them that lower the melting temperature. If you solder with this easy to use soldering metal then the temperature of the socket pit will eventually melt the join. I had a few times until I learn how it needs to be done properly.

 I have one question to ask. From what I see you changed the wire that goes to filament. Lamm has Brown-Brown/White cable but you have has White-Brown/White. Was any reason why you changed the wire?

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