Members Sixtonoize Posted September 22, 2009 Author Members Share Posted September 22, 2009 Yup. You have to drill a few holes, though, because the VTM's chassis screws are on the sides, whereas the 5150 chassis mounts through the feet on the bottom. Link to comment Share on other sites More sharing options...
Members squealies6505 Posted October 1, 2009 Members Share Posted October 1, 2009 so tonight at band practice, first time with the VTM..it sounded amazing! but did anyone notice how tough this thing is to get out of the headshell? we wanted to look inside to see how the guts looked, but the little screw inserts on the sides of the chassis were stuck on the inside of the shell... took a few minutes to get it out, where as other amps we have worked on, it slides right out! pain the a$$. Link to comment Share on other sites More sharing options...
Members TU BE Posted October 1, 2009 Members Share Posted October 1, 2009 Yes, they are a pain in the ass to get out of the headshell. I had the same problem when I modded mine. Link to comment Share on other sites More sharing options...
Members squealies6505 Posted October 1, 2009 Members Share Posted October 1, 2009 Originally Posted by TU BE Yes, they are a pain in the ass to get out of the headshell. I had the same problem when I modded mine. my buddy JSutter was stunned..hes worked on all of his amps and he couldn't BELIEVE how tough it was to slide out, he seemed a little worried at first lol..when we go to mod the headshell and anything else, we'll be ready this time Link to comment Share on other sites More sharing options...
Members Edge11 Posted October 21, 2009 Members Share Posted October 21, 2009 Originally Posted by Sixtonoize That's actually pretty easy, because the DIP switches short to ground. All you'd need to do is connect the tip and ring of the setting you'd want to change in place of the DIP switch.To switch all of the functions, you'd need 4 stereo jacks. Any way of replacing the dip switches with spst switches ect?The schematic includes the board artwork in it, Im thinking about making a pcb and populating it myself. Link to comment Share on other sites More sharing options...
Members Sixtonoize Posted October 21, 2009 Author Members Share Posted October 21, 2009 That would actually be pretty easy - you'd just have to pull out the DIP switch board and replace the connections with wires that go to your SPST switches. Link to comment Share on other sites More sharing options...
Members naazrael Posted November 20, 2009 Members Share Posted November 20, 2009 Great thread, I just picked a VTM60 fullstack for 300 bucks yesterday (also got a PA in the deal). Sounds beastly! I need to work on it a bit, a few of the pots are scratchy, and it's noisy, even through the hum canceling positions on my Strat. I haven't messed with the hum balance control, though, so hopefully doing that will help. To change to EL34's, I would just need to rebias it (gonna put in the bias pot...), right? EDIT: I don't use all that much gain, probably around Guns and Roses status, at most, so using an A/B box for high/lo gain inputs should be good enough for me, when it comes to clean and dirty tones. Link to comment Share on other sites More sharing options...
Members Sixtonoize Posted November 20, 2009 Author Members Share Posted November 20, 2009 You can't use an A/B box to switch the gain levels in the VTM series. The way that the inputs work, as soon as you plug something into the Low input, both inputs become Low, which makes switching with an A/B box impossible. You can, however, mod the amp so that the two inputs are footswitchable, but it's a little complicated. Details on how to do it are in this thread. Switching to EL34s is more complicated than just re-biasing. It can be done, but there are a few resistors that have to be replaced to handle 34s. Link to comment Share on other sites More sharing options...
Members pioneerprogress Posted November 20, 2009 Members Share Posted November 20, 2009 Originally Posted by squealies6505 my buddy JSutter was stunned..hes worked on all of his amps and he couldn't BELIEVE how tough it was to slide out, he seemed a little worried at first lol..when we go to mod the headshell and anything else, we'll be ready this time yes it is. my triumph is also the same way, near impossible. Link to comment Share on other sites More sharing options...
Members naazrael Posted November 20, 2009 Members Share Posted November 20, 2009 Originally Posted by Sixtonoize You can't use an A/B box to switch the gain levels in the VTM series. The way that the inputs work, as soon as you plug something into the Low input, both inputs become Low, which makes switching with an A/B box impossible. You can, however, mod the amp so that the two inputs are footswitchable, but it's a little complicated. Details on how to do it are in this thread.Switching to EL34s is more complicated than just re-biasing. It can be done, but there are a few resistors that have to be replaced to handle 34s. Hm, okay. Well, the amp is already pretty British, so maybe I'll hold off on the tube type swap.That's disheartening to hear about the A/B box, thought I could get away with something so easy, haha.I saw your diagram, looks great, thanks for the work you've contributed! you said you added a transformer to cut down on noise, though?And when you say relay, what do you mean? Could you link to an example? Thanks! Link to comment Share on other sites More sharing options...
Members Sixtonoize Posted November 20, 2009 Author Members Share Posted November 20, 2009 Originally Posted by naazrael I saw your diagram, looks great, thanks for the work you've contributed! you said you added a transformer to cut down on noise, though? I actually built a mini-power supply that has its own power transformer. I originally powered the channel-switching circuit from the heater power of the VTM, but it created hum whenever the relay was switched on.My power supply is pretty simple - it's just a 120v-12v transformer, rectifier, and a cap to smooth out the pulses. Originally Posted by naazrael And when you say relay, what do you mean? Could you link to an example? Thanks! Here's the relay I used:http://www.radioshack.com/product/in...ductId=2062483 Link to comment Share on other sites More sharing options...
Members naazrael Posted November 23, 2009 Members Share Posted November 23, 2009 Seems a bit intensive... I may try this method of "channel switching".http://music-electronics-forum.com/t2495/ Link to comment Share on other sites More sharing options...
Members Ryan_F Posted November 23, 2009 Members Share Posted November 23, 2009 Making your own power system is actually easier than drawing power off the heater lines. You can do it from the ground up, and are guaranteed no hum issues. I did the music-electronics forum method on my VTM120. I've posed on here before some other help about the two channel mod. The trick is to have the relay powered on when you're on the channel with less gain. I set mine up for clean/high gain and have no more noise than when it was stock. The thing to remember with the music-electronics method is DO NOT SHARE GROUNDS. If you have a jack on the chassis, it MUST be isolated. Any interaction between the chassis ground and the relay power system = massive hum. Link to comment Share on other sites More sharing options...
Members naazrael Posted November 24, 2009 Members Share Posted November 24, 2009 Ah, I only quickly browsed the other link. It still needs power like this one. How do I make my own power system for the relay? Link to comment Share on other sites More sharing options...
Members naazrael Posted December 3, 2009 Members Share Posted December 3, 2009 Another question, my goal is to make this sound like a refined JCM 800. how do I remove that bit of top end fuzz. Does removing the bright cap do that? Link to comment Share on other sites More sharing options...
Members Sixtonoize Posted December 3, 2009 Author Members Share Posted December 3, 2009 That will definitely help. I added a switch to mine that allows you to remove the bright cap or leave it in the circuit. I like the added flexibility, but most of the time I leave the Bright cap off. Link to comment Share on other sites More sharing options...
Members naazrael Posted December 3, 2009 Members Share Posted December 3, 2009 Cool, good to know. I also re-read the thread, saw that changing R2 might help, as well. If I could find a place that sold 1W resistors locally before Sunday, that'd be brilliant... I know Radioshack has 1W resistors sometimes...Maybe they'll have the right value.. Link to comment Share on other sites More sharing options...
Members naazrael Posted December 15, 2009 Members Share Posted December 15, 2009 Changing that plate resistor to 220K really helped remove the fuzz! Really simple mod, big payoff, I think. My next two concerns are: - Punchiness - Noise Would doing the bias mod warm it up more, and give it a thicker, punchier sound? What can I do to reduce noise? Link to comment Share on other sites More sharing options...
Members Sixtonoize Posted December 15, 2009 Author Members Share Posted December 15, 2009 The bias mod definitely helps to warm up the tone, even at low volumes. My VTM was biased at around 14ma stock, and with 480v on the plates, that's SUPER cold. Link to comment Share on other sites More sharing options...
Members naazrael Posted December 16, 2009 Members Share Posted December 16, 2009 Ah, very true. Warming it up at low volumes would be amazing! I'll have to grab some more parts then. What wattage rating does the pot have to be? Is it specific? I was thinking about replacing the resistors in there for metal film. Worth it for lowering noise? Link to comment Share on other sites More sharing options...
Members Sixtonoize Posted December 16, 2009 Author Members Share Posted December 16, 2009 The pot doesn't have to be anything special. The bias circuit is only like 60v and it's low amperage. I used a 1/2 watt pot in mine and it's plenty...most amps use very low power trimmers (like 1/10th watt or less). It may help to replace certain resistors with metal film to lower noise...the earlier that they are in the preamp, the more effect that they'll have. I've never really thought about it myself, but I'm definitely interested in hearing the results. Link to comment Share on other sites More sharing options...
Members naazrael Posted December 16, 2009 Members Share Posted December 16, 2009 Perfect, I may have some Alpha pots that'll fit the bill, in that case. I need to get a new multimeter though, before I can even check anything like that. Yeah, I get a fair amount of noise. I only turn the first HIGH DIP switch on, and the MID switch on. Then my settings have the preamp gain turned up all the way, and the poweramp gain is at 2. The Bass is around 11 o'clock, and the mids is up all the way, and the treble is around 2 o'clock. The Prescence is around noon. I get a fair amount of noise, nothing insane, but it isn't cured by a noise gate in front of my amp. Through my Avatar cab, it sounds monstrous! Sounds massive and heavy, even though I don't have the extra gain stage on. I am tempted to try it through the fullstack I got with it, haha.... What are your settings? Link to comment Share on other sites More sharing options...
Members VTM Posted December 19, 2009 Members Share Posted December 19, 2009 tonight i was changing preamp tubes..the board makes me SO nervous, even though i know it's fine.... everything was going great..then i go to move one of the sovteks into the PI. and for some reason, it didn't want to go into the V4. I tried two sovtek LPS's in the same socket and it squeaked and wouldn't sit in the socket whatsoever. I also have JJ's, EH's, and Mesa STR pre's that fit perfectly fine in that same socket,and made no squeaky noises..the LPS's fit in the other sockets. very strange..i hope i didnt hurt anything trying to get it in there..i was pushing as hard as anyone would to get a tube in, heard the squeaking (probably the pins im guessing?) and gave up after 3 times and after trying my other tubes. any ideas? or just one of those freak things. edit: forget to mention it has no problem as far as how wide the tube is. the pins were lined up, and the tube had plenty of clearance. it was probably just a freak thing. NEITHER would go in though. dammit. Link to comment Share on other sites More sharing options...
Members Sixtonoize Posted December 20, 2009 Author Members Share Posted December 20, 2009 It could be over-sized pins, but I am not sure if Sovteks have over-sized pins. I wouldn't force it, especially if you have tubes that will work just fine in those positions. Link to comment Share on other sites More sharing options...
Members PlaysGuitar Posted December 20, 2009 Members Share Posted December 20, 2009 How are these unmodded? any good? Link to comment Share on other sites More sharing options...
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