bluefoxicy Posted March 8, 2008 Share Posted March 8, 2008 Is it doable to build a 12AX7 pre-amp and feed it into the VJ for bigger overdrive, or into a separate 6L6 power-amp? Is it doable to feed VJ output into a separate power-amp or will that blow the power tube? (Second stage power amping...) Link to comment Share on other sites More sharing options...
stumblinman Posted March 8, 2008 Share Posted March 8, 2008 You need an output load or it will blow the OT, I believe. I looked into the same thing to run direct to my PA system, has to do with the resistance necessary. I don't know the mumbo jumbo of it all. As far as the input side, are you saying you want more gain to push the preamp tube harder for more saturation? Just get a cheap distortion/eq pedal, both of which have volume boost which will push the tube harder for more saturation. A good cheap distortion pedal that works well for this and doesn't suck the tone out is a Danelectro Fab Distortion: http://www.musiciansfriend.com/product/Danelectro-D1-Fab-Distortion?sku=151847 They can be found for 10-20 bucks online or at some local music stores, and it's actually a very nice sounding pedal on it's own. I've used mine for both uses, volume boost to preamp tube as well as just for distortion. It's cheaper than building some monster setup, and if you aren't satisfied with the result, you can probably return the pedal if you bought it locally. Another option is the ART Tube MP: http://www.musiciansfriend.com/product/ART-Tube-MP-Studio-Mic-Preamp?sku=180581 It might accomplish what you are trying to do. Good luck in your search! Link to comment Share on other sites More sharing options...
TWANG Posted March 8, 2008 Share Posted March 8, 2008 I've looked all over for a diy tube preamp schemo.. no luck. another gain stage, pure tube, is what I was looking for. you can add a tube, but I wanted it seperate. seems like the answer was too costly or near as difficult as a scratch build.. so everyone says pedals. which I just really didn't want. Link to comment Share on other sites More sharing options...
bluefoxicy Posted March 8, 2008 Author Share Posted March 8, 2008 I think Eric Johnson built himself an overdrive pedal out of a 12AX7 tube he found. Like, he's got a pedal with a tube in it. o_o It shouldn't be too hard to preamp the signal, should it? It's pretty much an extra tube before the input jack; but erase the input jack from the diagram and it looks like you just added another tube... Link to comment Share on other sites More sharing options...
stumblinman Posted March 8, 2008 Share Posted March 8, 2008 There are several pedals with tubes in them. If you are looking for a cheap tube preamp, I'd recommend the ART MP. Read some reviews and see what you think. It just might be what you are looking for. It says it's a mic preamp, but almost everyone using it is using it in a guitar chain. Link to comment Share on other sites More sharing options...
cGil Posted March 8, 2008 Share Posted March 8, 2008 You won't need an OT for a tube preamp. If you're looking for ideas to build a tube preamp/distortion pedal, Adam's Amps is a good place to start... http://amps.zugster.net/articles/tube-pedals Gil... Link to comment Share on other sites More sharing options...
stumblinman Posted March 8, 2008 Share Posted March 8, 2008 Gil, I think he is trying to say he wants more saturation/overdrive when the amp is dimed. More guitar line-in juice I believe. The OT part of the conversation came from talking about adding more volume on the output side, if I read that right. More clarification on the original subject might give a better idea how to help. Also, in my previous post, I said a "cheap tube preamp" by which I meant "inexpensive yet awesome", not "of poor quality". Twang, the ART Tube MP I mentioned might be an item of interest for you as well, if I'm reading your post correctly. Looks like it can give boost/overdrive at lower volumes for extra gain. I guess it's sort of a pedal though, but not really an on/off thing. It's always on unless it's unplugged. Link to comment Share on other sites More sharing options...
strangedogs Posted March 8, 2008 Share Posted March 8, 2008 I picked up the ART TUBE MP when I grabbed a KORG AX5G from MF... not a bad lil' preamp - but it's a tad noisy... I'm using it now with my computer as a DI for LOGIC (Guitar Rig 2 and Amplitube 2) - you can actually overdrive the tube somewhat and it does add a touch of "warmth". I'm gonna rehook it to my VJ and test out the boost theory. Link to comment Share on other sites More sharing options...
tunghaichuan Posted March 8, 2008 Share Posted March 8, 2008 I've heard bad things about the ART MP "tube" mic preamps. Mainly that the tube is there for looks only, and isn't in the signal path. The "heater glow" is nothing more than LEDs behind the tube. Some info here: http://www.record-producer.com/learn.cfm?a=2838 The Behringer was copied from the ART mic pre: http://www.tomshardware.com/forum/page-49043_6_200.html From this thread: http://www.tomshardware.com/forum/49043-6-behringer-disturbing-article Now the ART mic pre might sound good, I've never heard one in person, but to call it a "tube" preamp is a stretch. tung Link to comment Share on other sites More sharing options...
cGil Posted March 8, 2008 Share Posted March 8, 2008 I've heard bad things about the ART MP "tube" mic preamps. Mainly that the tube is there for looks only' date=' and isn't in the signal path. The "heater glow" is nothing more than LEDs behind the tube. Some info here: http://www.record-producer.com/learn.cfm?a=2838 The Behringer was copied from the ART mic pre: http://www.tomshardware.com/forum/page-49043_6_200.html From this thread: http://www.tomshardware.com/forum/49043-6-behringer-disturbing-article Now the ART mic pre might sound good, I've never heard one in person, but to call it a "tube" preamp is a stretch. tung [/quote'] I had an ART Tube MP and Tube compressor. I'm pretty sure the tubes in the MP at least are functional cuz I had one go microphonic and wound up using adhesive automotive dampening pads to help reduce vibration noise coming in through the pedalboard. Traded 'em in many years ago on a couple of Tube Pacs, which I still have and use occasionally. They're useful bass, acoustic guitar, or the occasional quick microphone solution. IIRC, the ART preamp gear actually got the bad rap just for being a hybrid SS/Tube circuit with crummy TL072 opamps driving the input and output. I remember hearing that simply swapping that (or those?) out for Burr-Brown opamps would do wonders for it, but I don't remember the equivalent chip number to look for. Gil... Link to comment Share on other sites More sharing options...
stumblinman Posted March 8, 2008 Share Posted March 8, 2008 Let us know how that goes strange, I'm considering picking one up myself for PC recording as well as for my PA for vocals, the boost for the VJ would just be gravy. Link to comment Share on other sites More sharing options...
TWANG Posted March 9, 2008 Share Posted March 9, 2008 presonus blue tube is nice. gain volume.. good stuff all around. good for mics, used it on bass, makes a good preamp 12ax7 sound to me. unfortunately, if you plug it in while something else is on.. it fries your stuff. blew my tascam porta studio out. warned a guy in a band once.. let me turn this on first.. oh he says we got the 220 hooked up no surge from there. we'll never know you plugged it in. ok I says. POP! I sold it. good unit but a serious flaw. Link to comment Share on other sites More sharing options...
strangedogs Posted March 9, 2008 Share Posted March 9, 2008 Here's the test results from testing my ART TUBE MP http://www.musiciansfriend.com/product/ART-Tube-MP-Studio-Mic-Preamp?sku=180581 WOW. It really does BOOST the VJ's volume and gain. By boosting the INPUT and OUTPUT levels it adds much more of both - you can overdrive the tube easily. It also has a +20db gain button (right below the green led) that slams it like a tubescreamer. The extra "noise" isn't that bad really with the VJ (noticed it more with my computer when using it as a DI in Logic)... It adds a true TUBE warmth that isn't bad at all - I'm probably going to order another one and keep this lil' baby hooked to the VJ. It not only boosts the overall volume for clean & wide open "dirty" but it will make it louder and Dirtier too even dimed. I love it and for $30 it's a great addition to the family. I'm gonna take it apart tonight and try an EH 12AX7A I have in my drawer. Another bud of mine in a guitar forum says changing the tube really helps it "shine". I recommend this baby to anyone as a cheap "boost" and a great gain boost too at lower volumes. It works like a Tubescreamer! BUT A REAL TUBE Tubescreamer. I'm loving the differences I'm getting from it. I'm posting this as a seperate topic also for those who aren't reading this thread. Link to comment Share on other sites More sharing options...
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