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Author Topic: vox ad 100vt  (Read 9639 times)

adv

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Re: vox ad 100vt
« Reply #15 on: September 25, 2012, 01:22:57 PM »
Hello Roly, Thanks for the response.

http://www.youtube.com/watch?v=loSllHtY9q0    This is close to what mine is doing but just the opposite in sound noise. Mine is the helocopter 1st and then a slight siren noise not as prominent as this amp on y/t. P.s. Turn your sound down this guitar player will rattle your brains. Thanks adv

adv

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Re: vox ad 100vt
« Reply #16 on: September 25, 2012, 09:41:00 PM »
http://www.youtube.com/watch?v=loSllHtY9q0  Hello Roly this is similar to what my amp is acting like, the hellocopter sound first then a slight siren noise not as prominent as in this vid though. ADV

Roly

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Re: vox ad 100vt
« Reply #17 on: September 26, 2012, 02:27:01 PM »
Hoooo Boy, that's the worst case of whatever it is I've ever heard.   :duh

Seriously 'tho, that's not analogue so forget the suggestions written below the vid about cleaning connectors and broken valves - that has one serious digital headache.  It's not two sounds but one, a software loop that starts off short and gets longer, sliding rapidly down in frequency until you get the "helicopter" putt-putt.  Even if I had the circuit of the digital effects area it would still be mainly guesswork, and it's not just out of your class, it's out of ours too.

What I can say is that it seems to be a generic failure, a common failure in older Vox's, but it could be anything from a surface mounted device coming unsoldered to an internal silicon failure.  I am certainly not advising you do this, but if I really had to try and fix this one thing to try would be removing the whole Fx PCB and putting it through a solder reflow oven, but this is almost certainly not going to be practical.

It could be as simple as requiring new electrolytic caps in the power supply, but that's a pretty long shot.

As a generic I expect that Vox knows all about it, 'tho they may not admit it, but if you talk to their service department, reference the vid, you may get lucky and get a definite answer and a proposed fix (like buy a whole new PCB costing lebenty-leben dollars).  Sorry to be pessimistic, but I've been watching this one coming down the turnpike for a couple of decades now.

All I can suggest is that you e-mail Vox's service department and see what they have to say.  :(
If you say theory and practice don't agree you haven't applied enough theory.

Enzo

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Re: vox ad 100vt
« Reply #18 on: September 26, 2012, 06:52:12 PM »
Go for it.   But I have to say about generic faults, they may be aware that some 100-pin LSI chip has weak solder, but each of those 100 pins will have a different effect upon the operation of the amp.   It won;t be like pin 47 is always what comes loose.   And a lot of problems are caused by lead-free solder.  It grows "tin whiskers" which can cause shorts to adjacent parts, and they can be ANYWHERE, so knowing you may have tin whiskers doesn;t really help narrow down the location.   Wish I had better news.

adv

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Re: vox ad 100vt
« Reply #19 on: September 28, 2012, 10:10:37 PM »
Hello, Thanks be to all with your in put. Man that robot was 21st century.LOL!After reading that I should build my own pre-amp. Sounds like a plan.Would it be possible to gut this ss amp and build a good tube amp out of that chassis and cab? What could I salvage off of it that would interact with atube amp? I think i will do some home work and investigate another alternative. Once again I do thank you all for your experience and advice. ADV :dbtu:

J M Fahey

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Re: vox ad 100vt
« Reply #20 on: September 29, 2012, 12:39:03 AM »
I'd keep the SS amp if possible, or build a simple new one fed from its salvaged PSU and if possible attached to its heatsink.
I mean, that thing is *optimized* for SS !!!
And would feel *very* free to experiment with the preamp.
Post a couple gut pictures.

Frank

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Re: vox ad 100vt
« Reply #21 on: October 04, 2012, 04:23:19 PM »
Voxman almost lynched me over on the Valvetronix site for raising the same concern about digital amps and digital equipment in general some years ago. But the longevity of digital circuits really is their main problem. Once it goes, it goes. We can prolong their life by hoarding amps, and swap circuit boards and that will keep us going for a while, but eventually we will run out of functional boards. This is also a major concern in respect to digital synthesizers. I own an Ensoniq TS-12 packed with specialized chips, and I know that one will go too eventually. In the synth area, things started to get problematic about the time the DX7 was launched.

This is really a shame, because my AD120VTH head sounds incredibly good. Vox did a really good job on the models in this amp.

But my trusty 1964 AC30 will live forever. So will my 1967 Vox Conqueror solid state. And my MiniMoog. And my Hammond organs.

J M Fahey

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Re: vox ad 100vt
« Reply #22 on: October 04, 2012, 05:16:35 PM »
Or any 100/150 years old piano  :dbtu:

Roly

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Re: vox ad 100vt
« Reply #23 on: October 05, 2012, 01:17:25 AM »
A DX-7 is "my main man", so I'm keeping my fingers crossed.  My general experience with Yammy electronics is that they are pretty solid.

A friend has an Ensoniq ESQ-1 sampling synth which was a lovely instrument but has a pretty crappy 3.5 inch 360kB disk drive, and when you couldn't buy 360kb disks any more...

If I could get my claws on it today I'd consider trying to knock up something like an Arduino as a fake FDD-to-SD card, or similar.  I think it was Z-80 based, while my E-MU Proteus/1 has a 68000 inside, so you at least have some idea of what you are dealing with; but when it's an in-house anono-chip...   :-\
If you say theory and practice don't agree you haven't applied enough theory.

DrGonz78

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Re: vox ad 100vt
« Reply #24 on: October 05, 2012, 06:30:29 AM »
Maybe that amp is trying to send a fax somewhere?? I recently had an AD30VT amp where luckily the speaker was the only thing bad. I decided to look in the amp just out of curiosity and pulling off the knobs loosened/cracked a couple pots. So I now have to take the whole thing apart...  :trouble

The stems pulled right out of the pots and I had to replace them, but they had legs that bent around. Very proprietary pots and so I clipped off the legs. I soldered the legs onto replacement pots, and that was actually fun. Like a MacGyver repair technique that this amp really deserves. So I got the thing all patched up and working. Sold that amp and now I don't think I will ever touch one ever again.

Playing the amp the decay of the strings was vibrating in some sort DSP way that just kills my heart. For loud playing the amp is ok. If you have any level of dynamics to your music then these amps do not do justice at lower dynamic playing level.
« Last Edit: October 05, 2012, 08:41:51 AM by DrGonz78 »
“A person who never made a mistake never tried anything new.” -Albert Einstein

Frank

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Re: vox ad 100vt
« Reply #25 on: October 05, 2012, 03:58:02 PM »
A DX-7 is "my main man", so I'm keeping my fingers crossed.  My general experience with Yammy electronics is that they are pretty solid.
Me too. I have two original DX7, and a TX802. I once had a TX7, but it literally went up in smoke at a gig.
A friend has an Ensoniq ESQ-1 sampling synth which was a lovely instrument but has a pretty crappy 3.5 inch 360kB disk drive, and when you couldn't buy 360kb disks any more...
Ensoniq were particularly fond of custom chips, making them particularly hard to repair. Floppy drives don't make things easier.
If I could get my claws on it today I'd consider trying to knock up something like an Arduino as a fake FDD-to-SD card, or similar.  I think it was Z-80 based, while my E-MU Proteus/1 has a 68000 inside, so you at least have some idea of what you are dealing with; but when it's an in-house anono-chip...   :-\
Actually a really good idea! While I still had a functioning floppy drive, I took all my old Macintosh OS7-8-9 floppies and transferred the contents into images on my present HD. You can have a lot of floppies on a modern HD! The idea is to make them available to a virtual OS9 machine some day.
A similar thing could be done with the Ensoniq floppies. But as far as I remember, you need a special DOS-program to even read those discs and control the drive. But, if you overcome that problem, then using something like Arduino to present the machine with a virtualisation of the floppies is a really good idea.

So why do I hijack the thread to talk about this? Because, maybe a similar hi-tech type approach is the future of rescuing our DSP-based amps. If we can get a future electronic device - similar to the Arduino, but likely more powerful of course - to simulate the software running the Vox amp simulations, then maybe we would be able to virtualise the Vox software, and repair these amps with replacement boards made of such general purpose template boards. A good idea in fact!

/Frank

Roly

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Re: vox ad 100vt
« Reply #26 on: October 06, 2012, 07:36:21 AM »
Quote from: Frank
Playing the amp the decay of the strings was vibrating in some sort DSP way that just kills my heart. For loud playing the amp is ok. If you have any level of dynamics to your music then these amps do not do justice at lower dynamic playing level.

A kind of step-wise granularity?  This reminds me of a project I did with the original AY-series "toot-bang-whistle" chip that only had 8-bit amplitude control.  Sounded okay up high, but at the tail of a decay it sounded like it was falling down a flight of stairs - bumpbump  bump    bump       bump ...

Spotted a TX-7 in a junk shop a while back and was sorely tempted, but they were asking far too much for it, even if the cassette interface is still a proposition.  Left it a couple of months and went back to make them an offer they would be silly to refuse, but it had gone.

I've just bought a little Arduino-based thing called a LeoStick, and while I once did a truckload of F-8, 6800, Z-80, and CP/M, I'm not quite sure why (apart from the fact that they are only $A30).

I wouldn't be afraid of trying to reverse engineer the OS ROM's from an ESQ-1 if I had one, but unless it turns up scratching at the door (which is possible but pretty damn unlikely) then it's all a bit theoretical.  But as a general concept for gear that is up the beach due to unobtainium (e.g. Boss DM-1 with a dead Reticon CCD/BBD) it's certainly an approach worth keeping in mind.
If you say theory and practice don't agree you haven't applied enough theory.