The Dude Posted April 18, 2017 Share Posted April 18, 2017 I was down at a local shop on Saturday looking for some tubes for the Little Delights. Usually when I go in there, its a two-three trip, hanging out, talking tubes, all that good stuff. The shop owner and myself got to talking about the new preamp I purchased last week (SP12 from tubes4hifi). He pointed out that it appears that the designer had cascaded the 12au7, he had believed that the only tube that should have been cascaded is the 6dj8. Could someone confirm this? If this is true, (I will ask the designer) why would one design a topology to do something that the tube isn't designed for? Quote Link to comment Share on other sites More sharing options...
Schu Posted April 18, 2017 Share Posted April 18, 2017 Is your tube shop guy familiar with the aikido circuit? The magic probably comes from the dual power sources. Quote Link to comment Share on other sites More sharing options...
tube fanatic Posted April 20, 2017 Share Posted April 20, 2017 On 4/18/2017 at 1:49 PM, The Dude said: He pointed out that it appears that the designer had cascaded the 12au7, he had believed that the only tube that should have been cascaded is the 6dj8. Could someone confirm this? If this is true, (I will ask the designer) why would one design a topology to do something that the tube isn't designed for? Tubes don't necessarily have to be designed for a particular mode of operation. It's all about the voltage/current relationships between the internal elements. If those are kept within its design parameters it makes no difference how a tube is run. To the tube it will all "look" the same. For example, if a tube is run at 100V between the plate and cathode, one can create that by biasing the tube at -10V (cathode at +10V) and putting 110V on the plate. Or, if it won't exceed maximum ratings, you could bias at -20V (+20V on the cathode) and put 120V on the plate. To the tube it will look identical. Maynard 1 Quote Link to comment Share on other sites More sharing options...
alzinski Posted April 28, 2017 Share Posted April 28, 2017 Cascade or Cascode? If indeed the triode is a common cathode stage why would it care if there was another common cathode stage after it? I presume it's probably a half-mu follower which gets confused as an SRPP. It looks like an SRPP but it's operated single ended, no push pull operaton into the load. Quote Link to comment Share on other sites More sharing options...
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