AlexI Posted March 13, 2003 Share Posted March 13, 2003 Im going to replace 12AX7 tubes in the preamp section of my Lk-48. According to reviews Sovtek 5751 are reasonably good (performance/price) tubes. Yet they have 30% lower gain than that of 12AX7. Anybody has experience with 5751 in LK 48, 222C or 299? Thanks for your help. Quote Link to comment Share on other sites More sharing options...
NOSValves Posted March 13, 2003 Share Posted March 13, 2003 AlexI, Never tried them myself. But if you do report back what you think ! You should find you have to turn the amp up little more to get the same gain which really isn't a great thing. The higher you turn up the amp the further you get out of Class A operation how much this will effect you really depends on what volumes you listen at. Craig Quote Link to comment Share on other sites More sharing options...
AlexI Posted March 13, 2003 Author Share Posted March 13, 2003 Creig, My typical listening level is 4-5. At this level the amp probably operates in ClassB 60-80% of the time anyway. Do you have any experience with Svetlana 12AX7? What tubes would you recommend? Thanks, Quote Link to comment Share on other sites More sharing options...
AlexI Posted March 13, 2003 Author Share Posted March 13, 2003 Craig, Im sorry for misspelling your name. Alex Quote Link to comment Share on other sites More sharing options...
NOSValves Posted March 13, 2003 Share Posted March 13, 2003 What 12AX7 do you have now ? Quote Link to comment Share on other sites More sharing options...
AlexI Posted March 13, 2003 Author Share Posted March 13, 2003 One GE and one British made (not Amperex). Both old stocks but in a good shape. Two unidentifiable new tubes, I presume Chinese. Quote Link to comment Share on other sites More sharing options...
NOSValves Posted March 13, 2003 Share Posted March 13, 2003 Well I would say any set of 12AX7's you buy will be a major improvement !! As far as new production tubes I have used JJ telsa and Electro Harmonix and also EI's . I myself use Telefunkens but these can be pricey little jewels. If you want to buy new I would go with either Telsa JJ or Electro Harmonix. Also any RCA, GE , Sylvania USA branded NOS are great tubes if you can find a set. Good Luck Craig Quote Link to comment Share on other sites More sharing options...
Dflip Posted March 13, 2003 Share Posted March 13, 2003 I have replaced the GE 12AX7's that were in my LK-72 with both Telefunkens and GE, blackplate, triple mica 5751's. I liked the 5751's better. I only turn my Scott up about 1/2 way and it is quite loud. They are a little brighter that the 12AX7's, but do give you more soundstage. The bass is similar in depth, but you do get a bit more in the upper mid range (may not be a good thing with horns, although you can you a little rope caulk on the squawker and rope caulk the basket of the woofer). I found this change to my liking. I had a friend over last night who described the sound as more analog than my SS equipment. I like it, very easy to listen to for hours at a time and good detail. Not the separation of my Accurus SS gear, but I can also really enjoy the sound for extended periods of time. Back to the topic, the 5751's are the same as any tube. You get what you pay for, good NOS tubes are pricy, but do make a difference. Sylvania, GE and RCA triple mica blackplates are the best, but $31-50 per tube. You would only use them in the preamp stage, not the phono stage (only 70% as efficient). I haven't had a problem with volume with these tubes, the walls are still standing and I have to leave the room well before I get to 7/10 in volume. Use 12AX7's in the phono stage. Good luck. Quote Link to comment Share on other sites More sharing options...
AlexI Posted March 13, 2003 Author Share Posted March 13, 2003 Craig, Dflip, As far as I understand I need to replace only two tubes. I use my Scott with CD player only. It means that only tubes in preamp section are working two other in phono stage are idle and dont draw any current. I can have different efficiency tubes in preamp and phono. Is it correct? Thanks. Alex Quote Link to comment Share on other sites More sharing options...
NOSValves Posted March 14, 2003 Share Posted March 14, 2003 Telefunkens are easy to find on Ebay in matched pairs when buying tubes on ebay just read the Sellers feedback if the seller sells lots of tubes and lists test scores your pretty safe. The great thing about Telefunkens is they last for ever almost unless the amp is operating out of spec. Another great thing is there easy to Identify with there diamond impression in the glass between the pins. Then there is the fact that almost every Scott amp was engineered around this preamp tube so they sound great ! Dflip, Your amp is a 30+ watt amp which can over come the loss of gain better the his 20 watt amp so what is good for you may not be good for him it all depends on his listening habits. Yes you only need two tubes if you don't use the phono section. Craig Quote Link to comment Share on other sites More sharing options...
NOSValves Posted March 14, 2003 Share Posted March 14, 2003 How did I double post ? Quote Link to comment Share on other sites More sharing options...
arfz28 Posted March 14, 2003 Share Posted March 14, 2003 Hi SCOTT EXPERT,I have a scott 299a that uses 2 6u8a or 6bl8 phase inverter tubes(i think thats what you call them). Can you get some telefucten to fit it?How much would 2 of these run me?.I have some telefucten 12ax7s for the preamp section already.THANKS. Quote Link to comment Share on other sites More sharing options...
NOSValves Posted March 14, 2003 Share Posted March 14, 2003 If you want nice Telefinken 6U8's upscale audio had some brand new ones another customer of mine bought. Be carefull who you buy tubes from ! Craig Quote Link to comment Share on other sites More sharing options...
mike stehr Posted March 14, 2003 Share Posted March 14, 2003 I'm still glad I scored the old Bell PA amp with 3 smooth plate Telefunkens for 5 bucks. Made 30 bucks off the RCA 6L6's that came with it. Those 12AX7 Tele's will outlive all of us! Quote Link to comment Share on other sites More sharing options...
NOSValves Posted March 14, 2003 Share Posted March 14, 2003 Hog wash !! Everyone that has 299's on this forum with 6U8's please tell the HH Scott Expert how much trouble your having with the Amp and distortion !! This is a question I posed on the HH Scott forum long ago and the answer I recieved on this issue. Okay I need some serious clarity on all the different Phase splitter tubes and which is the best to use in these amps? Is there a Sonic difference ? I now have 3 different Amps and they all spec for a different tube. 222C specs 6U8 , 299A specs 6BL8 and now LK-72 specs 6GH8. So are all these tubes interchangeable ?? Which tube is the best for the job ?? I know that everyone likes the Jan 6U8's that are available and really cheap these day's. But is it the best choice or more vintage offering's a better way to go ?? Please help me understand Craig Answer Craig: It is quite simple, Craig. The 6U8 and the 6GH8 tubes are identical in design and purpose to each other. On the other hand the 6BL8 tubes are different, they are a lighter duty (lower voltage ratings)tube and can be replaced by the 6U8/6GH8 tube (which is a far better tube for your set. The 6BL8 tube s and the 6U8/6GH8 tubes all have the same pin out). You can't replace a 6U8 with a 6BL8 tube, but you can replace a 6Bl8 tube with a 6U8/6GH8 tube. This is the only way it can work. Personally, I do think that the JAN Philips 6U8A tubes work really nice. For the buck, buy these....really quiet!!! Cliff Here is another reference fromt the HH Scott forum Paul: The differences are quite notable, but the 6U8 has much higher voltage ratings at the plates and the screen of the triode. This tube can be used as a substitute for the 6BL8. The 6BL8 can NOT be used to be as a plug-in substitute for the 6U8 without mods to your set. Use a 6U8 tube. It is a one-way street here... Thanks for your input, Paul. Have a fine Sunday. Regards, Sea-Bee USN(Ret.) Quote Link to comment Share on other sites More sharing options...
NOSValves Posted March 14, 2003 Share Posted March 14, 2003 I swear unless I'm going blind that my question to that forum and I also raised this same question on the list server which some pretty smart minds frequent and recieved the very same answer and I even would swear you were one of the reply's I recieved !! The Question was 222C specs 6U8 , 299A specs 6BL8 and now LK-72 specs 6GH8 and so on. Clearly the 299A and the LK-72 do not use the 6U8 tube The difference in tube ratings is there for sure but the end result is not what your potraying !! It works absolutley perfect in a 299A/B I have and also at least 20 members of this forum love this combo and your saying it produces distortion so I guess we all like distortion here. Oh I forgot you don't like Horn speakers because they don't produce the upper end of the spectrum *^$%maybe this is where the distortion is !! Quote Link to comment Share on other sites More sharing options...
NOSValves Posted March 14, 2003 Share Posted March 14, 2003 Read agian dude I was asking about all the different phase splitters. The 6U8 is a drop in replacement that will work perfect in a 299A or any other scott amp except one that uses a 7199 !! This is a absolute well known fact. Do you really think that everyone on this forum with above 100db speaker wouldn't hear the distortion your talking about ?? Do you think we are all deaf and you have the ultimate Ear or what ?? Your Completely wrong and basing your Opinion on specs rather than ear you also most likely tune your amp with a scope !! Quote Link to comment Share on other sites More sharing options...
NOSValves Posted March 14, 2003 Share Posted March 14, 2003 Go for it I've already done it and the answer is listed above. I tried to email Bill but evidently he has moved again. Besides why do we need to do that there are litterally many users here that have had there amps for ages and love them and your saying there distortion devices !! Your wrong. I have 6U8s in my 299B and also ran them in my 299A and have received many raving reviews on this forum and everyone of them was with a 6U8 tube are all these people wrong ?? Answer my question are we Deaf ?? I could care less about your engineering specs they mean nothing !! The 6U8 will not harm the amp in any way what so ever and if what you say is true which I guess its possible then this must accure at a point way past are 100+ DB speaker ever have to push the 299. Also why is it on a scope this distortion your talking about never shows up ?? I have scoped many amps now and never see any distortion to amount to anything until the amp is near its full usable output ! Your the Egotistic H H SCOTT EXPERT Answer these questions Craig Quote Link to comment Share on other sites More sharing options...
NOSValves Posted March 14, 2003 Share Posted March 14, 2003 There I put the question up with out Opinion added to keep it fair please be a gentlemen and don't throw your opinion in there and let them all answer for a day or two. Craig Quote Link to comment Share on other sites More sharing options...
NOSValves Posted March 14, 2003 Share Posted March 14, 2003 Ryan what does this say from my post above ?? Your something else !! This tube can be used as a substitute for the 6BL8. You can't replace a 6U8 with a 6BL8 tube, but you can replace a 6Bl8 tube with a 6U8/6GH8 tube. This is the only way it can work. Quote Link to comment Share on other sites More sharing options...
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