oldmako Posted September 7, 2017 Share Posted September 7, 2017 (edited) Greetings. Long time no post. I finally got around to having my 500B serviced and the guy mentioned that it would benefit from some new tubes. Specifically 4 new output tubes, the 7591's. He said that I'd probably not notice that these are toast except when I had it wound up loud. At any rate, while it sounds great now and I'd like to begin the search for new tubes. Do you smart guys have any good recommendations for sourcing these? He said that I either needed a matched set of 4, or two sets of 2. I'm using it in my bedroom with a pair of Forte II's. I should add that the guy said that some replacement tubes from Eastern EU have "oversized" pins and that once you jam them in, you're stuck with them as the correct tube (smaller pins) won't fit properly into the stretched pin sockets. Obviously I'd like to avoid that dilemma. Thanks for reading and any replies. Edited September 7, 2017 by oldmako Quote Link to comment Share on other sites More sharing options...
NOSValves Posted September 9, 2017 Share Posted September 9, 2017 The service technician is confusing the 7868 tubes the Fisher 400 uses for the 7591. None of the modern production 7591 made today have a pin size issue like the 7868. There is one modern 7591 that has a really large glass bottle size both tall and fat. You have 3 modern production 7591 to choose from the EH 7591(really fat and tall), JJ 7591 (1/2" tall), Tung-Sol Reissue 7591 (1/4" tall). I personally prefer them is this order 1)Tung-sol 2)JJ 3)EH 4 Quote Link to comment Share on other sites More sharing options...
oldmako Posted September 11, 2017 Author Share Posted September 11, 2017 Many thanks for your expert advice! Quote Link to comment Share on other sites More sharing options...
muel Posted September 13, 2017 Share Posted September 13, 2017 On 9/9/2017 at 10:16 AM, NOSValves said: The service technician is confusing the 7868 tubes the Fisher 400 uses for the 7591. None of the modern production 7591 made today have a pin size issue like the 7868. There is one modern 7591 that has a really large glass bottle size both tall and fat. You have 3 modern production 7591 to choose from the EH 7591(really fat and tall), JJ 7591 (1/2" tall), Tung-Sol Reissue 7591 (1/4" tall). I personally prefer them is this order 1)Tung-sol 2)JJ 3)EH Interesting you list the Electro Harmonix last... is that based solely on the sound or because they are a little oversized? I haven't rolled through power tubes on my 500C but I've really liked the EH tubes. Actually, I never bought anything else because of all the happy EH owners that I've read about. One warning about the EH is that the wood cabinet will hit the top of the tubes if you try to remove the cabinet with the power tubes installed. You have to install and remove the tubes with the cabinet ON. There is just enough room to install them. 1 Quote Link to comment Share on other sites More sharing options...
muel Posted September 13, 2017 Share Posted September 13, 2017 That IS quite a size difference! It's been a couple of years since I've looked... prices seem to be going up. Quote Link to comment Share on other sites More sharing options...
muel Posted September 13, 2017 Share Posted September 13, 2017 Interesting info here: http://www.tronola.com/html/7591a_tubes.html The distortion tests look really good for the Tung-Sol. Quote Link to comment Share on other sites More sharing options...
mark1101 Posted September 14, 2017 Share Posted September 14, 2017 I have been using those big EH 7591s in my Scott LK-72 for the last few years and honestly I have been very happy with them. I don't think the Tung Sols were around when I put them in though. Next retube I'll give the Tung Sols a try. Quote Link to comment Share on other sites More sharing options...
muel Posted September 14, 2017 Share Posted September 14, 2017 Looks like the Tung-Sol might be in short supply as they are sold out at quite a few vendors. Jim McShane said that New Sensor told him they are discontinued. Looks like Tube Depot still has some though. Quote Link to comment Share on other sites More sharing options...
muel Posted September 18, 2017 Share Posted September 18, 2017 Well, I had to find out for myself... but I agree that the Tung-Sol is nice! Tube Depot was really quick to ship. Quote Link to comment Share on other sites More sharing options...
eq_shadimar Posted September 19, 2017 Share Posted September 19, 2017 I have used the JJ and EH power tubes in my 500B. I think the EH ones sound a tad better but I do run my 500B without the wood case so the extra size is not an issue for me. Laters, Jeff Quote Link to comment Share on other sites More sharing options...
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