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Posts: 10777
Location: Keepin' It Weird in Portland, OR | The title is the question, pretty much...
For background, this is a hybrid tube amp with a bunch of amp modeling and wah/reverb/chorus/delay/etc.
Yes, it makes noise, and yes, I had to wait for it to warm-up.
But there are solid state processors in there that could be amplifying stuff.
Isn't the tube supposed to light-up? |
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December 2006
Posts: 6996
Location: Jet City | *excerpt from web article*
Without getting too geeky, the Valvetronix amps uses digital modeling technology for the creation of the basic tones of the eleven modeled amps it contains, and then puts those tones through an analog (solid state) power section that uses a 12AX7 (ECC83) tube (valve) and a virtual output transformer to provide the characteristics of a real tube power amp circuit. This patented circuitry is unique, and only found in Vox Valvetronix amps.
Are you playing with the amp cranked? If that's too loud decrease the wattage on it. Doesn't it go down to 1w? If you got the main volume cranked I would think it would light up some.
I dunno for sure though. I have the AD120VTX and AD60VTX. Same concept. I've never checked for tube glow. |
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Joined:
September 2006
Posts: 10777
Location: Keepin' It Weird in Portland, OR | The title is the question, pretty much...
For background, this is a hybrid tube amp with a bunch of amp modeling and wah/reverb/chorus/delay/etc.
Yes, it makes noise, and yes, I had to wait for it to warm-up.
But there are solid state processors in there that could be amplifying stuff.
Isn't the tube supposed to light-up?
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Copied my post to add photos...
This is the amp...
Here is the back...
This is the tube, in there... And it is plugged-in and ON... See? No Light. Shouldn't there be Something?
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May 2009
Posts: 364
Location: Bellevue, Washington | Mine does not glow, just checked after playing for about half an hour... |
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September 2006
Posts: 10777
Location: Keepin' It Weird in Portland, OR | Okay, Thank You.
Y'see, I had a Behringer Vintager AC112 with 198 presets (that I should NOT have sold)...
It had a grill on top where you could see the tube, and it used to get a coupla red wires.
I also freaked-out for a moment when I turned this one on...
I kinda forgot that I have to wait for it to warm-up. |
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Posts: 1132
Location: NW Washington State | I would expect the heater on a 12AX7 to light up- it only takes 6 or 12 volts which should be available in a solid-state amp. Depending on the brand of tube, it might be hard to see the glow. Just a little bit of orange- it won't light up like a Christmas tree.
There are lots of amps, pedals, and even a Brand-X acoustic guitar where a 12AX7 is thrown in as a marketing gimmick. It has a toob so it must be good! Most times the 12AX7 is run at very low voltages so that it's working nothing like a 12AX7 in a "vintage" amp. I think I've read that sometimes it's used like a diode so it's just clipping. But it really doesn't matter- if you like the amp, it's good.
-Steve W. |
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Posts: 10777
Location: Keepin' It Weird in Portland, OR | Research proves you correct Steve.
"Vox Showroom" sez: "The concept of the circuit is to use a 12AX7 preamp tube in an unusual way - as the heart of a one watt power amp. This one watt power amp even includes a small output transformer to simulate the electronic interactions that happen in high powered tube audio output circuit. The one watt output from this 12AX7 then supplies a solid state power amp to achieve the final 15 watt (AD15VT), 30 watt (AD30VT), 50 watt (AD50VT), or 100 watt (AD100VT) output."
So yeah, maybe it's little more that a Diode... But!
I have been fingering around on the Parker PM20 while watching the tube (TV) and now the tube (12AX7) actually has a faint red glow on two thingies inside there. |
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October 2005
Posts: 4081
Location: Utah | A 12ax7 can be driven to distortion yet puts out little total power. The ART Tube preamp does just this, making for a nice warm tube sound at low gain or plenty of tube distortion at high gain. But it isn't enough to drive a speaker loudly, it is just a preamp module.
I suspect the Vox circuit does this, plus they have some kind of transformer in there. The tube would drive the transformer input. The transformer output, instead of driving a speaker, will drive the input stage of the solid state power amp. Possibly smoke and mirrors, or possibly there is something to it sonically.
Some cool tube circuits are curious, as the tube cannot possibly be working normally at such low voltages. The description of the Vox circuit doesn't sound like one of these applications. |
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April 2006
Posts: 2491
Location: Copenhagen Denmark | Basically ..
Git. feeds , in this case , a transistorized control-amp. ( the one with knobs and buttons), which in turn feeds a valve driven power-amp.,that drives a transistor amp., ..
The transformer is there to lower the impedance of the valve amp.,and .. works as a galvanic shield ( electrons jump from one coil to another .. there`s No physical contact )..
Valves distort in a Pleasing/Musical way, due to a slow rise compared to output ( distortion comes on slowly ) and by distorting EVEN Harmonics,..
as opposed to transistor amps., where distortion comes on " right-away" , known as " clipping ",plus, distortion is at Un-Even harmonics, .. sounds Terrible..
The Distortion at EVEN Harmonics is a feature often cherished by Gittrists,..witness the resurrection of Valve driven equipment in the music-biz ,..as those amps. are Heavy/Costly,..the idea of the hybrid was applied..
Basically ,..the power of the Transistor at reasonable cost , coupled to that "wonderful and expensive " sound of the valve-amp.
Vic |
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Posts: 1132
Location: NW Washington State | Looking at the service manual , it appears that the tube is running at relatively low voltage and there is no transformer following it. A good designer can make a nice sounding amp with a device that's labeled "12AX7", but it doesn't have much to do with tubes as we used to know them. The tube is there for marketing purposes (aka "spoo").
If you like the amp, it doesn't matter. I have a couple of TubeWorks "Real Tube" boxes and I like them, even though the tubes aren't running like "real" tubes.
-Steve W. |
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January 2006
Posts: 5881
Location: Colorado Rocky Mountains | If you want a tube that glows, get one of these . . .
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September 2006
Posts: 10777
Location: Keepin' It Weird in Portland, OR | Yeah! Like That! :D
ProfessorBB sez:
If you want a tube that glows, get one of these . . .
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January 2006
Posts: 5881
Location: Colorado Rocky Mountains | A Genz Acoustic Pro has a tube that glows about this shade of blue, and it sits behind a grill on the front panel where the glow through the grill can be prominently seen. Great cool factor. |
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Dumb Question... Is the "Tube" on a Vox AD30VT suppost ta Light-up?
