funky Vox AD120VTH

iekobrid

New member
Picked up a last-in-the-building $399 stereo Valvetronix head at GC last Sunday. The amp models and effects all seemed to work properly and sound decent in the store, even through the stock 2x12 cab.

After a week of tweaking, I gotta say: this thing is either broken or grossly overhyped. Most likely the former.


Clean and low-gain settings were dull... lackluster... even with the recommended help from the OD pedal sims. Also the strings of every guitar I tried sound a bit muted, as if a loofah sponge had been crammed under the picking area.

Mid- to high-gain settings were even more disappointing. All of the noise and squeal of a cranked tube amp, but none of the crunch or balls. Regardless of which amp model it was set to, turning the gain knob above 11 o'clock resulted in an imitation of a fuzz pedal with a dying battery. Not fizzy, even -- just farty.


On top of all that, when playing with a guitar plugged into either input jack on top neither left channel speaker output produced any sound, whether by itself or as part of a stereo pair. Both right channel speaker outputs seemed to function normally.

I tried bypassing the internal preamp by running an external OD pedal (a Mesa Bottle Rocket) directly into the Valvetronix's power section via the left channel effect loop return jack. That got some sound out of the left side speaker jacks, but only half the volume of doing the exact same thing with the right side loop and speaker jacks. Also, the general fartiness was still present.


Current/former Valvetronix owners: Is it there a chance that the tube in the power section went scrubar on the trip home from the store and is responsible for the symptoms described above? Reckon it's worth digging inside to swap it out? And even if the amp were operating corrently 'mechanically', should the sound quality be significantly better than I've experienced so far, or is simply not a good match for my ears and/or cabs (a Carvin Legacy 212 w/ V30s, an Avatar 212 with V30 "Hellatones", and a Jackson 212 w/ 1 GT75 and 1 Eminence Gov.)?
 
Re: funky Vox AD120VTH

It should NOT sound like your description! Since it was the last one in the store, I would at least try replacing the tube. At that price, I would gladly pay for a new 7 dollar preamp tube. Its not difficult to replace, and the amps actually sound much more alive if you will replace the tubes every year or so anyway. In my experience, the Electroharmonix 12ax7 it comes with is the best brand to replace it with. Every other brand I have tried changes the channel voicings in a bad way.
 
Re: funky Vox AD120VTH

I've had mine now for over 2 years,have gigged extensively with it also and it doesn't sound like the way mine sounds! These amps are also pretty cabinet and speaker specific in that they sound best to my ears with V30s...

Also....You need to keep the master volume level as high as you can keep it so you drive those 2 12AX7s hard.If the amp is too loud at the 60/60 setting in order to drive the output stages harder,try knocking it back to the 30 or 15 watt settings..I Love my VTH 120 and I'm fussy about my tone or I'd have sold mine 2 years ago...I'd have your's looked at or return it..My amp has consistently given me great tone,the effects are god enough,but it's the versatility I Love most!
 
Re: funky Vox AD120VTH

It should NOT sound like your description! Since it was the last one in the store, I would at least try replacing the tube. At that price, I would gladly pay for a new 7 dollar preamp tube. Its not difficult to replace, and the amps actually sound much more alive if you will replace the tubes every year or so anyway. In my experience, the Electroharmonix 12ax7 it comes with is the best brand to replace it with. Every other brand I have tried changes the channel voicings in a bad way.

The 120 watt version has 2 12AX7s running as the output stage tubes..I use RCA Long Plate 12AX7s and these have been in my amp since I bought it new over 2 years ago...My amp sounds really great actually!:bigok:

As I Mentioned,Vintage 30 speakers in a good quality cab,really help the overall tone of this amp.
 
Re: funky Vox AD120VTH

Mine is extremely flabby and lacking balls.

Then again it sounds like all the clips I've heard. Something has to be wrong to have speaker jack issues though.
 
Re: funky Vox AD120VTH

Mine is extremely flabby and lacking balls.

Then again it sounds like all the clips I've heard. Something has to be wrong to have speaker jack issues though.

Are you using a closed back cab with good speakers? Shouldn't sound anything like what you're describing!
 
Re: funky Vox AD120VTH

Since the problem is with one stereo side, it's highly likely a tube is malfunctioning.

Find some new preamp tubes. Take the chassis out. It's almost impossible to pull the tubes out, so you may need to go in sideways with a flathead screwdriver and use it as a wedge to pry them out. It's tricky, but you can do it. After both 12AX7's are replaced with fresh ones, you'll either hear a healthy amp, or something else is wrong with it. It could have been a display unit for 3 years, often being left on overnight. Those tubes might be shot.
 
Re: funky Vox AD120VTH

It could have been a display unit for 3 years, often being left on overnight. Those tubes might be shot.

It was indeed a display model, though I've no idea for how long.


Here's another question -- does the 120 need to be hooked up to a stereo cab or cabs at all times, or is it okay to hook up just one side or the other? The back panel says to never connect less than 4ohms per channel, but nothing about always using both channels.
 
Re: funky Vox AD120VTH

It's almost impossible to pull the tubes out, so you may need to go in sideways with a flathead screwdriver and use it as a wedge to pry them out. It's tricky, but you can do it.


I removed the chassis from the head box last night, just to get the lay of the land. What are the two small screws on the outside of the chassis next to each tube 'porthole'? Do they hold the sockets in place, or might loosening them loosen the grip on the tubes themselves?
 
Re: funky Vox AD120VTH

Ha! :blackeye: Always a possibility, no doubt, but I tested that component with a couple other amps and didn't experience the same problems.

Was messin with ya! Hope you get your's figured out...Mine is really a great amp.:headbang:
 
Re: funky Vox AD120VTH

I removed the chassis from the head box last night, just to get the lay of the land. What are the two small screws on the outside of the chassis next to each tube 'porthole'? Do they hold the sockets in place, or might loosening them loosen the grip on the tubes themselves?

Any screws in the area will be for something else.....probably holding the socket.
The only thing holding the tubes in are the pins pushed into the sockets. Unfortunately, the tubes are surrounded by metal and the rubber grommet, so you can't pull them out by hand. I had the best luck by using a small flathead screwdriver and prying them away from the socket. Make sure you line up the pins on the new tubes perfectly so you don't bend them when pushing them in.

Once you do this, the amp should be good as new. I think you can use a mono cab with one of the outputs, but refer to the owners manual to be sure.
My head is the 60W mono version, so it doesn't matter.
 
Re: funky Vox AD120VTH

Mine sounds good.It sounds as good as my bandmates 900!And we playing both live withe them without a problem!
 
Re: funky Vox AD120VTH

Monday night I replaced the stock (?) Sovtek 12AX7WAs with a pair of GT 12AX7R2s. I didn't see a convenient angle for prying the tubes out with a flat head screwdriver of any length without unfastening the main circuit board and heat sink, so instead I removed the rubber grommets with needlenose pliers and wiggled the tubes out by hand.

The new tubes fixed the problem with no sound coming out of the left channel, but overall the amp still sounds as bad, if not worse. Mid- to high-gain tones are still fuzzy and farty, and now clean tones have an irritating digital artifacty noise as if the Octave pedal sim is on but mixed low 100% of the time.


I printed out a dozen or so highly rated sample settings from www.valvetronix.net before I left work today, hoping I was simply a complete moron at dialing in useable sounds. No such luck. Awful, every last one of those recommended settings. No amount of EQ fiddling could add any bite/brilliance or subtract any lo-mid woof. It was as if Korg/Vox intentionally designed the amp's controls to frustrate me personally. I even took the backs off both of the cabinets I was using just to make sure they weren't wired out of phase with one another, so wholly unusable were the tones I was getting. :(
 
Re: funky Vox AD120VTH

Hey man, I suggest you go out and try another valvetronix amp, even the silver grill series, and see if you can get good tones out of it, if you can't it's probably just not the amp for you.
 
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