Cornwalled Posted February 16, 2009 Share Posted February 16, 2009 Hello, I am looking for a little guidance regarding 12AT7 tubes in my VTL ST-85 power amp. It currently has Electro-Harmonix 12AT7EH and re-issue Mullard EL-34s. I haven't found too much info on the EH 12AT7, other than that it is a good reverb driver / phase splitter tube. That doesn't exactly seem like a compliment to me, as far as high end audio goes. I've considered grabbing some JAN Phillips 12AT7WC from tube depot since they're running a special on them, and I've heard good things about JAN tubes in the past, but wanted to check with you guys first. Also, tube depot offers different matching options (low noise, matched sections, etc) and I wanted to see what you guys recommend in that regard. Any thoughts / suggestions would be appreciated. Thanks, Jon Quote Link to comment Share on other sites More sharing options...
tigerwoodKhorns Posted February 17, 2009 Share Posted February 17, 2009 I use these Mullard 8162's in my Tercel: http://www.audiogon.com/cgi-bin/cls.pl?accstube&1238802959&/Mullard-M8162/12AT7-matched-pa I had new Philips tubes that came with an AH Cd plyer. They were 6DJ8's and sounded aweful. Thin and no bass. The Mullard's listed above are much better than the Electro Harmonex tubes that came with the Tercel. Quote Link to comment Share on other sites More sharing options...
seti Posted February 17, 2009 Share Posted February 17, 2009 I picked up some 1960 Mullard 12AT7 tubes from Brent Jesse http://www.audiotubes.com/12at7.htm He seems to be out at the moment but there are others. Great tubes, CV4024 / M8162 Mullard military type 12AT7, early 1960s vintageMATCHED PAIR NewOld Stock whitebox. A rare Mullard 12AT7 made for the British militaryin the 1960s. Used in British military radar installations. These arelong-lived and sweet in hi-fi applications. Carefully hand matched intopairs. RARE. Quote Link to comment Share on other sites More sharing options...
pauln Posted February 17, 2009 Share Posted February 17, 2009 That "reverb driver" and "phase splitter" lingo is in regard to how those tubes are used in guitar amps, typically the Fender "Black Face" designs of the sixties and current reissues of those designs. Those amps use that tube in position V3 to drive the reverb tank (both triodes in the tube being used in parallel - heavy duty service) and as the phase inverter ("splitter") in V6 to drive the power tubes. Those are not typical preamp tube functions in hifi gear, so the evaluation of them for guitar amp applications does sound sort of weird when looking at hifi... See this link for a good explanation of the preamp tubes for V1-6 in Fender amps here What attributes are desired for guitar amp tubes will not really carry over to the hifi world; but rest assured that guitarist are very particular about the sound qualities, noise floor, and resistance to failure of their tubes. I personally have an old Mullard from the late 50's that is just great in V2 of my Fender amp. Quote Link to comment Share on other sites More sharing options...
nu2toobs Posted February 17, 2009 Share Posted February 17, 2009 These NOS Mullards are what I use , and I'm very happy with them. I paid the extra $4 for low noise and microphonics. By the way, these are real NOS, never used. http://www.tubedepot.com/nos-12at7-mullard.html Quote Link to comment Share on other sites More sharing options...
rsp1068 Posted February 17, 2009 Share Posted February 17, 2009 I run RCA black plates in my VTL 5.5, and the driver stages of my VTL power amps, all purchased from Brent Jesse. They give the sound a texture that none of the other makes of tubes I tried would. He is a great guy to deal with, and has an exchange on most tubes in case you get something you absolutely don't like. Quote Link to comment Share on other sites More sharing options...
mike stehr Posted February 17, 2009 Share Posted February 17, 2009 I've only listened to one type of 12AT7, being a white label RCA blackplate. But it sounds rather good in this RH84 circuit with Sylvania black plate 6BQ5's and James OPT's. Quote Link to comment Share on other sites More sharing options...
paully Posted February 17, 2009 Share Posted February 17, 2009 Echoing another poster, the Mullard CV4024 (supposedly better than the ones marked 12at7 though I can't remember why) have made me very happy. They seem to be a tube of choice. They replaced some EH 12at7 in my system. $50 a pair, or less, should be easily doable if you look in places such as: http://www.langrex.co.uk/sales.html Quote Link to comment Share on other sites More sharing options...
Cornwalled Posted February 17, 2009 Author Share Posted February 17, 2009 Hello Everyone, Thanks for the tube suggestions. It seems that Mullard NOS tubes are a common choice around here! I should mention that price is an issue. My amp needs four 12AT7s, and I can't afford to be spending $200 on tubes right now. I really would like to stay in the $15-20 per tube price range. I will only spend a little more than that if it is really felt that the tube will be an improvement of the EH 12AT7s I have now, and be appropriate for my situation. To answer mdeneen's question about what sound I am looking for... I'm really looking for a neutral, accurate sound, with perhaps just a shade of warmth. I certainly don't want it to sound cold and sterile, but I don't want an overly fat, boomy, muddy sound either. Right now, with my Cornwalls and VTL amp, I feel my sound is a tad tubbier than I'd like. I'd like to tighten the bass up a bit and get a little more detail in the high end. I just feel like I'm getting a little too much of the "tubey" sound. I called VTL up and told them what tubes were in the amp, and got the impression that they did not like what was in it, and felt I wasn't getting the "VTL Sound" out of it. I really would like to get a neutral, accurate sound. To give you an idea, before I got this amp, I was actually looking at Audio Research and Conrad Johnson gear. However, the triode mode of the VTL amp attracted me, and I am very happy with my decision. I just want to make sure I'm getting the most out of this amp that I can. As always, your thoughts and suggestions are much appreciated! Thanks, Jon Quote Link to comment Share on other sites More sharing options...
Marvel Posted February 17, 2009 Share Posted February 17, 2009 Right now, with my Cornwalls and VTL amp, I feel my sound is a tad tubbier than I'd like. I'd like to tighten the bass up a bit and get a little more detail in the high end. That's probably the Cornwalls... []Not knowing the design of your amp,you might be able to replace just two of the 12AT7s, and get a lot differernt sound. I've found the EH tubes to be a pretty good bang for the buck tube. I have a couple of GE 6201 tubes, that might be able to be swapped for 12AT7s. I don't have a use for them and could send them to you to try if you would like.The 6201s are listed as a substitute, but the ratings are a little different. It would be your call, or perhaps VTL could tell you if they would work. EDIT: I just looked on their website, and noticed that it uses two 12AU7s and two 12AT7s. The 12AU7s are lower gain, and I have a bunch of those (GE and RCA), but I am starting a Dynaco mod that uses the 12AU7s so I want to hang on to most of those until I can check them out. Bruce Quote Link to comment Share on other sites More sharing options...
Cornwalled Posted February 17, 2009 Author Share Posted February 17, 2009 The website that Paully suggested has some Mullard CV4024s for 7.50 euros each, which is about $9.37, but it doesn't say if they are NOS or reissue. In the picture, I don't see "Made in Great Britain" on the tube, though I suppose it could be on the other side. However, they do have some Mullard M8162s, which do say Made in Great Britain on them, so perhaps they are NOS? Those are 10 euros, or $12.50 each. However, they don't offer any matching service. The thing I'm afraid of with NOS Mullards is, there seems to be a general consensus that they are dark sounding. I would be afraid they would make my system sound dull. However,t he deal on the tubes seems to be pretty good, so perhaps it might be worth checking out. I just don't want to buy something I would be unhappy with. Any thoughts on this? -Jon Quote Link to comment Share on other sites More sharing options...
Cornwalled Posted February 18, 2009 Author Share Posted February 18, 2009 Hey Bruce, Thanks for the offer on the GE 6201s. As far as their compatibility, VTL is completely ignorant of their own products. I called to see if KT-77s could be substitued for the EL-34s (a common swap) and the lady that picked had no idea. She then referred me to Luke Manley's voicemail. He of course never returned my phone call. So it's clear VTL doesn't care about their customers even in the SLIGHTEST! Totally different than what I've experienced with CJ and ARC. So, it's up to the members of the forum to tell me whether 6201s will work or not. Anybody know? Any thoughts on this tube? As far as the VTL website: it mentions the current generation ST-85. However, I have the previous generation amp. Mine uses four 12AT7s and no 12AU7s. -Jon Quote Link to comment Share on other sites More sharing options...
NOSValves Posted February 18, 2009 Share Posted February 18, 2009 The 6201 is a direct replacement for a 12AT7..... basically a high grade low noise military version of the 12AT7 Quote Link to comment Share on other sites More sharing options...
rsp1068 Posted February 18, 2009 Share Posted February 18, 2009 Hey Bruce, Thanks for the offer on the GE 6201s. As far as their compatibility, VTL is completely ignorant of their own products. I called to see if KT-77s could be substitued for the EL-34s (a common swap) and the lady that picked had no idea. She then referred me to Luke Manley's voicemail. He of course never returned my phone call. So it's clear VTL doesn't care about their customers even in the SLIGHTEST! While its true they prefer you stick with oem tubes, Bea has been very responsive to my needs. In their defense have you tried to contact any consumer electronics customer service departments lately? Give HP, or Dell, or one of those outfits a call and see how it goes, between answering systems and people you can't understand........ How many companies do you call and get the Presidents voice mail? It can take a time or 2 sometimes to get thru, but I can't help but be compelled to argue they do know there gear, and do care about their customers. Bob Quote Link to comment Share on other sites More sharing options...
Marvel Posted February 18, 2009 Share Posted February 18, 2009 The 6201 is a direct replacement for a 12AT7..... basically a high grade low noise military version of the 12AT7 Thanks, Craig. It thought that was the case but wasn't sure. I have two... I don't have a tester, but would be happy to send them to try. Quote Link to comment Share on other sites More sharing options...
Cornwalled Posted February 21, 2009 Author Share Posted February 21, 2009 Hello, I don't know how this amp is configured, as far as which tubes would be best to swap. I know in guitar amps, when you have multiple preamp tubes, they are usually arranged in gain stages, but I don't know if the same thing applies in home audio amps. Of course home audio amps aren't "high gain" so to speak, so perhaps there aren't multiple gain stages at all, I don't know. But if there are multiple stages, I have been told it's best to put the lowest noise tube in the first stage, to make it as quiet as possible. Marvel, how much would you be looking to get for the tubes? Obviously in unknown condition I couldn't offer you too much for them. Worst case, if there is something wrong with one of the tubes, can it damage my amp? I don't have a tester either, and just want to make sure my amp is safe. Thanks, Jon Quote Link to comment Share on other sites More sharing options...
Marvel Posted February 21, 2009 Share Posted February 21, 2009 Jon, PM or email me your address. I'll see it one of the few remaining TV repair places here has a tube tester. We'll at least know it they have a short in them. I ship them to you and you can check them out. They didn't cost me anything. If they work out, enjoy. I have a feeling they are ok, my son pulled them out of some test gear the school was tossing out. Bruce Quote Link to comment Share on other sites More sharing options...
Cornwalled Posted February 21, 2009 Author Share Posted February 21, 2009 Bruce, E-mail sent. Thanks, Jon Quote Link to comment Share on other sites More sharing options...
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