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Paul S wrote:

Any ideas for sources for 6AK5 and 5651A?  Seems like most of the ML2 tubes are "hard to find" from local sources.

I do not know why you say it. Both 6AK5 and 5651 are very common and very inexpensive tubes. The 6AK5 are penthode and dozens and manufactures made them. I had few or them, perhaps a half dozen of different brands, and I did not detect any huge differences in their sound. As I understand Lamm uses it as aerial amplifier in his B+ regulator to drive with 6AK5’s plate the grid of the 6C33C regulator. It is HF penthode and it is fast, nothing more requires from this tube, so it is no surprise that it did not affect sound tangibly. I ended up to catch a party of Western Electric 6AK5. Honestly they did not sound better or worth then anything else and I used them juts because the sexy yellow Western Electric letter across the tube.  I think I paid for them a few bucks per tube…

5651 is also is very common tubes. It is actual not a tube but a low current gas regulator on 80-90V. You can use in there absolutely any type of gas voltage reference diode that could regulate near 85V and can handle under 3.5mA. There are many substitutions for 5651 and many different manufacturers made them. I also did not detect any big difference in Sound in those tubes.

Do not confuse the Gas tubes that Lamm used in his regulator and the gas tubes that Melquiades uses.  If you read the thread from my bookmarks:

http://www.goodsoundclub.com/TreeItem.aspx?PageIndex=2&postID=2792#2792

They you might be under impression that gas tubes do affect sound, however Milq and ML2 use them differently. In ML2 the gas tubes are juts the voltage reference for stabilizer but in Milq the gas tubes supply bias, driving the grid of driver stage. Evan it took place via a large resistor but still it is way more mending duty. If I had ML2 I would change one resistor and would try a 35mA gas regulator instead of 3.5mA. In Milq the 35mA-type were better but it not necessary would means that they might be better in ML2. Those gas tubes are also a couple to few dollars per tube and they are good for years. The good part about the 3.5mA-type gas tube that there are practically not fake tubes among them…

The cat

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