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In the Forum: Audio Discussions
In the Thread: Initial thoughts about new/old Lamm ML2s
Post Subject: Lamms ML2 input impedancesPosted by Romy the Cat on: 12/31/2006
Paul I slightly surprised about your comments. The regulating aerial amplifier tube affected sound very mildly, if ever, at least it was my experience. I had a few different 6AK5 but changing them was not a highly notable effect. I still have left a dozen of so of Philips Miniowat 5654SQ “Special Quietly” tubes, if you wish I might send them to you, as I have no use for them. BTW, be advise the all this tubes need to be burned in and they will change sound after then…
About the input impedance - I do not remember the values now. I have the calculation sheets for my crossover somewhere and I might look for it… if I did not trash it… It has a voltage divider with I think slightly under one 1K in series and the shunt resistor that makes it 41K… Anyhow, why are you planning to drive the ML2 input to higher impedance? Your preamp can’t handle R41K? I usually peruse opposite and try to drive input impedance as low as possible with objective to load cables with current. I love drive cables with current, even with active bias current. If it were up to me then I would run 1A of DC though all system interconnects…. In fact I will do it sometimes…
Anyhow, the 41k is perfectly kosher impedance. As I understand Lamm made it to use with his line level preamps. His preamps are weak in output and they have difficulties to drive anything under 35K. In fact I make quite few experiments loading L2 with different values, even put there a very high quality trimmer and eventually I came up in my completely blind listening assessment with the best values…. To my satisfaction it was exactly near 40K…. Of course when I used 4 ML2 I was forced to increase the impedance as I paralleled the inputs. I use 80K in one amp and 105K in another. Do not ask me why they were not identical as it is VERY complex subject. Theoretically the balance loading should not affect anything but it did…Rerurn to Romy the Cat's Site