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Vox AD50VT amp pretty slick!

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11/15/2005 1:02 AM

Vox AD50VT amp pretty slick!

At risk of being burned at the stake for rank heresy, I checked out this amp at the store and ended up taking it home. Like I need another amp...

I was looking for something small to haul to clubs, and really wanted to like the 30 watt version of this amp with 1-10" (at ~26 pounds), but it sounded like a transistor radio. The 50 amp version with a Celestion 12" speaker sounded much better (at ~45 pounds). The amp has a variable power control on the rear panel so it can be turned down for smaller rooms if necessary- although there is a master volume control, too.

This is the first modelling amp I've tried that actually sounds great playing blues; the ones from Line 6 are very bland once you turn off the effects and turn down the gain.

The amp has 11 different preamps and 11 effects and combinations. The gain, volume, treble, middle and bass controls are all programmable, although there are only 2 save slots. For certain modelled amps, there are extra controls not on the original. In those cases you can set the extra controls to 12:00 and it will be neutral, just like the original amp. Or you can adjust it to tweak the sound.

It was here that I read about this amp, so to whoever it was that recommended it, I must say "thanks a lot" because I'm not a big fan of modelling amps and I doubt if I would have tried it.

Steve Ahola

11/18/2005 7:52 AM

Question about speakers in SS amps

One common complaint about this amp in the user reviews at H-C is that the internal speaker (a Celestion 70/80 - 12 inch 8 ohms) is automatically disconnected when an external speaker is plugged into the ext spkr jack.

It should be simple enough to defeat the switching at the jack, but what kind of loads would a SS amp want to see if it is rated for 8 ohms? I don't want to burn it up...

--Thanks!

Steve Ahola

11/18/2005 8:43 AM

I would keep it at 8-ohms.

IIRC, Unlike a tube amp, the SS amp will try to deliver the power based basically on ohms law. You halve the load, the power should double - and the problem there of course is the heat that will have to be dissipated to pull that off. Eg: a 100W amp into 8 ohms will want to be a 200W amp into 4 ohms. Same idea as a short circuit - lower load = more curent flow = more heat = dead amp.
So I would go higher, but not lower.

jm2c, icbw, ianal, and the usual disclaimers apply

11/18/2005 5:36 PM
Enzo	In addition to heat, the poor output devices would be asked to conduct twice the current. of course I suppose that is the source of the heat in the first place, so maybe it is the same thing.

11/18/2005 6:41 PM

quote:
"so maybe it is the same thing."

Yup.

The short version is this -
Tube amps are happy with lower-than-spec loads.
SS amps are happy with higher-than-spec loads.
Reverse at your own risk.

11/20/2005 11:58 PM

I took the amp to a gig at a restaurant/bar tonight and it worked just fine, using the Blackface, Vox AC15 and AC30 models. I had tried out 6 different 12AX7 tubes, ending up using a NOS Phillips 12AX7WA, which sounds very "blah" as a preamp tube, but seemed to work great with the application here. Perhaps someone can fill me in as to how the tube is used. The manual suggests that it is connected to a small output transformer, with the signal sampled and then amplified by a solid state amp. In any case the amp sounds very different when the tube is changed from the stock Sovtek 12AX7EH to a Groove Tube 12AX7M(ullard) to old stock Teles and Mullards and finally the Phillips. I figured it was a good use for the Phillips...

Steve Ahola

P.S. As for the speaker issue, I think that the ext speaker jack could be rewired to put an external 8 ohm load in series with the 8 ohm internal speaker, which would bring it up to 16 ohms. I would then add a switch to bypass the internal speaker- maybe rotary since it would be harder to accidentally turn it off.

11/21/2005 4:57 PM
Enzo	Check your email, the tube is on page 3.

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