vox valvetronics head

[Gunn_Slinger]

I bought a vox valvetronics head used.
The sound is good except that there seems to be a lot of break-up when I let a palm muted note ring.
I tried 3 different 4x12 cabs.....same sound.
Could vox have engineered the amp modals with this break-up?....or is there a problem with the head?
thanks for any help
Clay

[olddawg]

I bought a vox valvetronics head used.
The sound is good except that there seems to be a lot of break-up when I let a palm muted note ring.
I tried 3 different 4x12 cabs.....same sound.
Could vox have engineered the amp modals with this break-up?....or is there a problem with the head?
thanks for any help
Clay

If it does it on all of the modeling modes the first thing I would suspect would be the single 12AX7/ECC83 tube in the preamp since the amp is used. From what I have heard the factory tube is a cheap Chinese one that may rapidly deteriorate and replacing it with a better quality tube improves the amp significantly.

[Gunn_Slinger]

thanks old-d
I changed the ax7 when i encountered the prob with a mesa ax7...best ax that guitar center had....I dont know?
The tone was better but the problem continues.
the head is an AD60VHT.
STILL LOOKIN...LOL...THANKS AGAIN....IM NEW HERE AND THINK THIS SITE IS GREAT.

[Enzo]

First, try to determine if it is a defect or a characteristic. Find another one to play through to see if others sound the same. The 120 is the same except power output, so try it if no 60s emerge.

Isolate the problem: Does it sound like this in the headphones? How about the effects send? Play into the effects return, does it make this noise that way?

You could have a missing or stuck low significance bit.

[Robert M. Martinelli]

diagnostics using the send/return loop

Hi,
the first thing I would do is to try to determine if the failure is located in the preamp or the power amp section, so I' d try to connect the guitar, or an audio signal generator ( or an MP3 player, starting at low volumes ) to the effects return ( power amp in ) and/or connect the effect send ( preamp out ) to another amp, as per Enzo' s advice, either way way you should be able to ( approximately ) locate the problem.

Looking forward to hearing about your test results

Hope this helps

Best regards

Bob

[Steve Conner]

As far as I know, the Valvetronix amps are analog, so I'm not sure about stuck bits

Given that the original poster talks about letting a palm muted note ring, and muted things don't ring by definition, I think there may be some confusion over what the problem really is. Does the guitar volume affect it? the amp volume? Does it happen on both clean and dirty models?

[Enzo]

The Valvetronix series amps have a single tube floating in a sea of DSP crap. Tiny-lead-pitch LSIs and custom ICs abound. The things are laid out in some insane fashion that makes a PV Classic 30 seem downright convenient. I hate when they come in my shop.

I tried to post the schematics on the AMpix, but the file was too large. If you are interested, STeve, send me your email and I will forward the drawings to you. My PMs are off but my email is on.

[Steve Conner]

The Valvetronix series amps have a single tube floating in a sea of DSP crap.

Oh no! Silicooties! The guitarist in my old band had the Valvetronix combo and I honestly thought they were analog. My bad.

Try thumping it with your fist, and if that doesn't cure it, unload it on Ebay

[Robert M. Martinelli]

I own an AD120VT too, and I can only confirm that they' re very nice as long as they work.... when they don't....oh my God! I bought a GPS not to get lost while repairing mine , and it' s still out of order, maybe one of these days I' ll start a new thread about it, meanwhile, it gave me a good reason to go back home to my old AC30....

[Gunn_Slinger]

Thanks guys
the next sound you hear is me cocking the hammer on my s&w 357....bye bye valvetronics....lol
ok....i did all the tests Enzo suggested and the problem is before the power amp. The clean amp models are ok at low volume but at 6+ the noise is there on them also. The compression pedal setting really brings out the noise on all models. When you pick a note , the sound is great....if you let it ring and die ,here comes the noise ( sound is like s swoosh-ing noise ) stop the note....stops the noise.
In another post I read that the impedence switch ( 4-8-16 ) could corrode and cause noise..???
I bought this amp with a 400 watt 4x12 b52 8 ohm cab.
When i got it home i found that the former owner had used a guitar cable to hook the amp to the cab....aaarrrggggggg. + the cable has an intermittent short or open....double aaarrrgggggg.
The cab seems to be ok....put a marshall and a crate 100 watt head to it...ok
I love the sounds this head has and hope I/We/You guys can fix it...lol
or......cocking s&w 44 mag.
thanks for the replys
and........HHHEEELLLPPPPPPPPPPPPPPP

[Enzo]

You could also try reinitializing the thing, what is there to lose?

Initialization

Switch the amp off.

Switch the amp on while holding down the UP and DOWN BANK buttons, and TUNER/CANCEL button. If you've done this correctly, a "P" will be flashing in the BANK Display.

Press the WRITE Button and watch the BANK and the four CHANNEL LEDs do a little dance as they indicate each one of the 32 programs being reset to its factory preset. Once they both stop "dancing," you're done. The amp will automatically enter Program Select Mode with Program 1 - 1, "Flying High," selected.

[Enzo]

And there Steve is the evidence... The thing has a reinitializtion function.

[Gunn_Slinger]

wheee.....the light show was great...not as good as the 60's though...lol
But....it didnt help the problem.
I did notice that the higher string notes, when plucked and held, seem to wah slightly tone wise...or it could be volume wise....
Got to get a bigger gun...lol
Dump on ebay sounded good...but i cant sell anything thats not right...never could....soooo...where do i go next.....i have the chassis out of the box....

[Robert M. Martinelli]

The "power selector" too can oxidize and cause some problems, but the symptoms you' re describing make me think some signal gets lost before the A/D converter, I get ( uhm....well...used to get when the damn thing was working ) a similar sound on some presets when I turn(ed) down the volume knob on the guitar, and probably the signal getting to the A/D was no longer enough to be sampled properly..... I would check the signal path starting from the input jack, chances are some signal gets lost along its way to the A/D section.

I would not recommend anything less than a .460 Weatherby Mag. to get rid of the amp, but, if you don' t manage to fix it, it makes more sense to sell it on ebay "as is" for spare parts, or "cannibalize" it and sell the parts ( speakers, cab, handles, logo, knobs etc. ) separately to get the most out of them.

[Gunn_Slinger]

thanks mr vox
I figured i would be taking this thing apart. I like the sounds so much that im determined to fix this rascal....so im sure ill be screamin for help soon...lol
thanks again
Clay