http://www.voxamps.com/forum/ VOX | Discussion Forums Topic: Alternate Valves in preamp/phase inverter of Night Train en Thu, 23 May 2013 21:38:42 +0000 http://www.voxamps.com/forum/topic.php?id=1394#post-31123 Thu, 15 Mar 2012 12:04:50 +0000 cracklefracture 31123@http://www.voxamps.com/forum/ <p>psycom:"The Phase Inverter is V3 the one closet to the Power tubes." As it appears to be right in common way,seems not correct here, on this amps layout. V3 is gain stages 1 and 2, V4 gain 3 and Phase Inverter.<br /> <a href="http://www.prowessamplifiers.com/schematics/images/Vox_NT15.pdf" rel="nofollow">http://www.prowessamplifiers.com/schematics/images/Vox_NT15.pdf</a><br /> Please do correct me if I were wrong, more offending would be not to.<br /> Mine has TungSol as PI and gain 3 now and Electroharmonix sovtek at V3. Really like what I hear. I aim at distortion, not metal but fair amount of gain breaking up the way that pleases my ear and gets the notes flowing like a brook. As others swap their Sovteks out, I place them in. </p> http://www.voxamps.com/forum/topic.php?id=1394#post-31106 Wed, 14 Mar 2012 20:14:05 +0000 cracklefracture 31106@http://www.voxamps.com/forum/ <p>Hello, swapped out the stock RUBY 12ax7ac5hg preamptubes and playing around with Sovtek 12ax7eh and Tungsol 12ax7. This far it sounds more melodic, has thump on the lows and sings legato on highs. The sizzle, blunt drive and thin edge that disturbed me are all gone.<br /> I found this thread most informative, but the valve layout is confusing me. Preamp tubes are label v3 and v4. I assume the V3 is preamp gain stages 1 and 2, whereas the V4 is gain stage 3 and PI? Right?<br /> Has anyone tried Sovtek 12AX7-LPS as phase inverter? </p> http://www.voxamps.com/forum/topic.php?id=1394#post-20661 Sun, 30 Jan 2011 17:43:55 +0000 fender56 20661@http://www.voxamps.com/forum/ <p>Keep in mind that the Night Train uses a cathodyne/concertina PI, instead of a traditional long-tail PI, like the AC15/30. The cathodyne PI requires only one-half of a tube, as the long-tail requires two-half (a complete tube). The NT has 3 gain stages (a la Trainwreck). The 3rd gain stage is shared with the PI in the same tube. Using a lower gain tube here will also decrease the overall gain. I think also the cathodyne PI usually has a much lower gain than the long-tail PI. </p> http://www.voxamps.com/forum/topic.php?id=1394#post-20144 Mon, 17 Jan 2011 17:31:45 +0000 psycom 20144@http://www.voxamps.com/forum/ <p>This is a cathode biased Class A amp. The Phase Inverter is V3 the one closet to the Power tubes. Same with most all of them. V1 is where the most "shaping" of your tone is gonna happen. Don't skimp there. You want a quality tube w/o any problems. The ElectroHarmonix AX7 gets good reviews for "tone" so you might want to try one. Then V2 does something a bit different and I'm not totally sure what. I do know you want a good solid tube there. </p> <p>V3 is what is driving the Output transformer in Class A amps. In A/B amps (Fender) its a balanced "mirrored" signal of a pair of 6L6's or what have you and it "drives" those tubes which in turn drive the OT. It all gets a little confusing but that's what I've been able to make of the Class A and AB differences. </p> <p>V3 the Phase inverter is something really cool and is good to learn about. Google it and read up. You'll find that using an AT7 instead of an AX7 is actually BETTER. Although it runs less total output it has something like 10's the available "headroom" (for lack of a better term) to push power with. When you drop to an AU7 you'll really notice a difference as it's running even less total output. </p> <p>There's charts around and a good article I've seen on Phase Inverters that's easy to find. Not positive but it's something like an AX7 = 100% an AT7 is 60% and an AU7 is 40%. I've not noticed a loss in volume in my other EL84 amps going to an AT7. Am in the process of changing ALL my amps to AT7's. On the A/B "Push Pull" amps itsimportant to have a "matched" PI (Phase Inverter) since its a "mirror image" of the 6L6's, 6V6's, El34's or what have you. This doesn't apply to "single ended" amps using a single 6L6 btw. Nor does it apply to a Class A amp as it's biased differently. </p> <p>"Class A" amps run their output tubes (EL84's in this case) at full throttle ALL the time when running and 50% when idling. Not so with the AB type amps. This is pat of the reason people like these amps. They are sensitive to your pick attack and break-up / distort easily at much lower levels than their counter parts in a AB Class amp where you gotta turn it up and run the piss outta it to get that power tube saturation. </p> <p>I like both designs but for the sheer smooth harmonically rich "jangly" sounds of tube distortion at reasonable levels noting beats an EL84 amp. I've got The Blues Jr, Laney L20H, Night Train &#38; Little Giant and have been loving them all since letting the old Super Reverb and Peavey VTM 60 take a rest. I have added an Eganter "Tweaker" running 6L6's and am digging that too. </p> <p>Bottom line for me, only use quality tubes and AT7's in the PI section. Anything else i bend, break or twist the rules and see what happens.</p> <p>My creed: "Don't buy it unless you can modify it!" :) </p> http://www.voxamps.com/forum/topic.php?id=1394#post-19524 Fri, 31 Dec 2010 02:27:52 +0000 perkmonster 19524@http://www.voxamps.com/forum/ <p>I'm confused.. Is there any difference between the v1 and v2 for the preamp? What's this about a phase invertor? Is there supposed to be that in v1 or v2 and not just two 12ax7 tubes? </p> http://www.voxamps.com/forum/topic.php?id=1394#post-17373 Wed, 20 Oct 2010 16:33:17 +0000 jerodq 17373@http://www.voxamps.com/forum/ <p>I have had my Night Train for over a year, and overall I am pleased with it. I play blues and rock (no metal for me) and I stay in bright mode. The main issue I had was that the tone would break up at a fairly low volume. The preamp overdrive just sounds a little too muddy for my taste. It doesn’t sound bad, it is just not the tone I want. I have been trying to dial in a fairly clean tone, that breaks up just a bit when you play more aggressively. I recently read about swapping out the V1 12ax7 (labled V3 in the NT) with a preamp tube with lower gain. I gave it a try and here is what I found.</p> <p>My NT has all Sovtek tubes, pre-amp and power. I pulled out the V1 (labeled V3) 12ax7 (with a gain of 100) and replaced it with a Groove Tubes Gold 12at7 (with a gain of 60). Sometimes with mods I wonder if the effects are more psychological than actual (people hear what they think they will hear), but the difference was immediately noticeable. </p> <p>Volume drop: The very first thing I noticed the drop in overall volume. For me, this was a welcomed change. I like my hearing, and I would like to keep it around for awhile. I play with other guitar players and a drummer who understands that he doesn’t have to beat the drums to death to get a good sound (a rare find). I prefer to mic my amps so I am not trying to fill an auditorium with sound from my single Greenback. This gives me much more flexibility in mixing the volume and the gain to higher levels. I feel like I have better control of the overall tone. </p> <p>Overdrive tone: The natural overdrive changes with the tube swap. I assume this is because the power tubes are working harder because of the pre-amp gain drop. The overdrive is less “treblely” and less sloppy. It has a beefier tone and better articulation of individual notes. I will state once again that I am not a high-gain player, so this is a welcomed change to me. </p> <p>A little surprise: The last major thing I noticed came as a surprise. I have the Fulltone OCD (v4) pedal. I love the pedal, but I have not loved it with the Night Train. It has just been too much for my taste. I fiddle with it constantly whenever I use it trying to get it to make the tones I think it should be making. With the drop in gain, this pedal now sounds absolutely fantastic with this amp. The overdrive is so clear and articulate now. I am finally starting to get the tones I want out of this amp and pedal.</p> <p>Overall, the 12at7 has been a welcomed change for me. But I imagine that these changes would be devastating to someone who is searching for a higher-gain tone. I will definitely keep the 12at7 in my Night Train for awhile, if not permanently. </p> http://www.voxamps.com/forum/topic.php?id=1394#post-9405 Fri, 08 Jan 2010 08:13:01 +0000 psycom 9405@http://www.voxamps.com/forum/ <p>which tubes are causing a hum in the 7.5 mode that is gone in 15 watt mode? You've all heard that familiar Fender idle sound ... low 60 cycle hum. well in half power I got it but at full power total silence. silence. This is with or without anything plugged in except speakers of course. No setting change it except flipping to 15 watts. any ideas? </p> http://www.voxamps.com/forum/topic.php?id=1394#post-9080 Wed, 30 Dec 2009 23:42:38 +0000 simonnq 9080@http://www.voxamps.com/forum/ <p>Don't forget the EL84's, you can get output tubes with less gain as well, this is also give you a bit more headroom. </p> http://www.voxamps.com/forum/topic.php?id=1394#post-9069 Wed, 30 Dec 2009 19:24:46 +0000 geekg 9069@http://www.voxamps.com/forum/ <p>sure it helps to put a lower gain or output tube in the v2 preamp. i tried this.<br /> but i for myself think the nighttrain has too little gain in bright mode so i am more satisfied with putting a very high gain tube in v2.. but it works the other way around also. i tried 12at7 and 12au7 in v2 and one made a huge difference the other not at all, but i can't remember which is which. try both, they are not expensive. but for me if i want to play not as gainy i just reduce the gain.. and i have less hiss and hum also. for me it makes more sense to use a higher gain tube in less "gain", and when i need gain i crank it. but maybe you have a point and a low gain tube will sound good cranked. </p> http://www.voxamps.com/forum/topic.php?id=1394#post-6715 Fri, 25 Sep 2009 00:30:09 +0000 andyjingram 6715@http://www.voxamps.com/forum/ <p>Hi there,<br /> Does anyone know if it will be safe to try any other valve types in the preamp and phase inverter of the Vox Night Train, such as Ecc81's or 82's? I suppose I'm thinking more of the phase inverter than the preamp, primarily.</p> <p> I am using the amp mostly for clean sounds, so might like to try some less 'gainy' valves if I can.</p> <p> Many Thanks, Andy </p>