Re: Competent Explanation Vox "Valve Reactor" Amp Circuit
claudel
George Orwell <nob...@mixmaster.it> wrote:
>There's a 60%-off sale on these amps this month at GC, so I
>bagged a VR30 (AKA VR30R) to put into a bookshelf next to my
>bed. It's OK -- a little NOISY like all the cheap Vox amps --
>but it fits the space (with room for convection cooling and
>sound reflection from the open back), survived burn-in and is
>nice looking. I have to say that Vox sure gets the look down if
>nothing else, right down to the "VOX by Wharfdale" sticker on
>the ack of the Chinese speaker. ;-)
>
>http://media.zzounds.com/media/brand,zzounds/VOXVR301-
>b5afc15b0b2ea3325c5fa763d11f45b7.jpg
>
>[That's a GIANT .JPG!]
>
>For the life of me, I can't quite make heads or tails of the
>"Valve Reactor" concept. As I gather it, contrary to usual
>"hybrid" amp circuits, this amp has pure solid-state preamps
>(two channels with two different overdrive circuits in the
>second) which go into an intermediate stage using the two halves
>of a 12AX7 dual pentode as a tiny power amp [Class-A? AB? What?]
>and then runs the output of this valve micro-power-amp into a
>_second_ power amp, a straight solid-state.
>
>Do I have this right so far?
>
>You wind up with a two-channel amp with no less than four (4)
>gain & volume knobs.
>
>I don't quite get the object of he exercise here, and I don't
>find it in any of the pages I've searched: Is the idea to be
>able to get the full tube amp power-stage breakup at any volume,
>or exactly what? That's all I can figure out.
>
>Thanks for any competent help with this question.
>
It's a reasonably successful attempt to warm up the modeller...
<http://www.voxamps.co.uk/products/valvetronix/vtoverview_inside_story.htm>
Claude
Amp U! Tator
> claudel wrote:
> warmup [chop]
> Claude
Dick Clot, you decripit old boy-hooking codger...you couldn't warm up a
toilet seat. You sit there with one ancient ball freezing up the the
bowl water and the other climbing old turkey sack to pollute your
blue-veined hairless, wrinkly gut. The sounds reverberating from that
bleeding hole you think with, brown spackle alt.guitar.amps with your
every odd and painful post.
Get back in the basement.
Anonymous
> It's a reasonably successful attempt to warm up the modeller...
The VR30 isn't a modeling amp.
claudel
Sorry, I didn't realize that Vox uses the Valve Reactor
in non-modelling gear.
read it as
"It's a reasonably successful attempt to warm up a solid-state
amp by adding a tube to the output circuit"
The URL you snipped contains Korg's explanation of how it works.
Claude`
The VG&L Railroad
...
> For the life of me, I can't quite make heads or tails of the
> "Valve Reactor" concept. As I gather it, contrary to usual
> "hybrid" amp circuits, this amp has pure solid-state preamps
> (two channels with two different overdrive circuits in the
> second) which go into an intermediate stage using the two halves
> of a 12AX7 dual pentode as a tiny power amp [Class-A? AB? What?]
> and then runs the output of this valve micro-power-amp into a
> _second_ power amp, a straight solid-state.
>
> Do I have this right so far?
Pretty much. The 12AX7 is a dual triode,
not a dual pentode. It's configured as a
low power push-pull power amp which is then
amplified by a solid state power amp. I
think the idea here is that this is more or
less what you do with a PA amp, anyway, except
the speaker and mic are missing. No idea how
it's biased; if I had to guess it would be for
Class A.
> You wind up with a two-channel amp with no less than four (4)
> gain & volume knobs.
A good start.
8^)
> I don't quite get the object of he exercise here, and I don't
> find it in any of the pages I've searched: Is the idea to be
> able to get the full tube amp power-stage breakup at any volume,
> or exactly what?
From what I have read, they are trying to get
"tube sound" out of an SS amp. By all accounts,
they do fairly well. One of the possibilities
is (theoretically) "full tube amp power-stage
breakup at any volume" but I don't think that's
*all* they wanted.
George Orwell
>> Do I have this right so far?
> Pretty much. The 12AX7 is a dual triode,
> not a dual pentode.
Of course. I know better than that...I was exhausted whe I
wrote that, but shame on me.
> It's configured as a low power push-pull power
> amp which is then amplified by a solid state power
> amp.
[...]
> No idea how it's biased; if I had to guess it
> would be for Class A.
It's AB. I eventually found that. In the stand-alone
Valvetronix modeler it's switchable, A/AB, but not in this amp.
Still, it seems like that with the (not inconsiderable)
exception of the coloration provided by the speaker, you could
then get a consistent user-adjusted level of power-stage
distortion at all volumes, which they never seem to come right
out and say -- but then they inject this seemingly contradictory
business about feedback "reaction," whatever that may actually
be. I'm stumped. It's gibberish, a technical explanation
written by an intern with a hangover in Marketing based on a
phone call to an admin-assist in Engineering.
> From what I have read, they are trying to get
> "tube sound" out of an SS amp.
Well, yeah, aren't they all? And they all do it just
_wonderfully_, too! 8-)
> By all accounts, they do fairly well. One of
> the possibilities is (theoretically) "full tube
> amp power-stage breakup at any volume" but I don't
> think that's *all* they wanted.
I dunno; I've read all their explanations and they don't seem to
get past the gee-whizness of it all into plain talk about what
it's specifically going to do on a practical level for me and
how I'm supposed to use it. Neither have the whoring, puff-
piece magazine "reviews" that seem to be little more than
rewrites of the manufacturer's promotional copy to please the
advertisers. You have to wonder if those people ever see the
product.
I suppose I'll just have to figure this thing out by trial and
error. 8-/
Guncho
The amp's got an attenuator which allows you to run the tube in the
power stage at full saturation while allowing you to run the amp at any
volume level.
That's what it does on a practical level.
What did you think it did?
Chris
boardjunkie
"power" stage.
Jim Anable
I don't think that is quite accurate. With the low output from the
12AX7, they need to AMPLIFY it before it gets to the speaker. So not
attenuator, but variable gain after the tube.
Guncho
How bout this:
"It allows you to crank the one tube in this amp, without cranking the
volume."
How's that?
Chris
George Orwell
>> The amp's got an attenuator which allows you to run the tube
in the
>> power stage at full saturation while allowing you to run the
amp at any
>> volume level.
> I don't think that is quite accurate. With the low output from the
> 12AX7, they need to AMPLIFY it before it gets to the speaker. So not
> attenuator, but variable gain after the tube.
No, there's no attenuator. As contradictory and incoherent as
Vox's explanations are, I'm at least clear on that much.
Guncho
See above.
Chris
Jim Anable
> One would think they would have used a 12au ot even a 12at for the p-p
> "power" stage.
I would've gone 12AU7 or 6n1p, because of the lower plate impedance.
Note that the "valve reactor" amp claims to have an output transformer,
but the ADxxVT series has a "virtual load." A real output transformer
sounds better to me, but I suppose the test is the ear of the player.
I've suggested the 30W model to my sister (for her to buy my nephew for
Christmas). I just bought my nephew a guitar and an RP200. So he's got
the modeling, already. The Vox ought to be a decent amp to learn on.
George Orwell
> Note that the "valve reactor" amp claims to have an output transformer,
> but the ADxxVT series has a "virtual load." A real output transformer
> sounds better to me, but I suppose the test is the ear of the player.
I'll eventually get around to popping this one open and looking,
but for the moment I think I'll leave well enough alone. I was
under the impression that it also had the "virtual load."
> I've suggested the 30W model to my sister (for her to buy my nephew for
> Christmas).
I suggest that Uncle Jim give it a good going over well before
Christmas. QC on these cheap Voxes is just nonexistent. The
first VR30 I got had a bad pot and almost no reverb right out of
the box. This one seems better, or at least doesn't have those
same defects. I've gotten other bad new Voxes as well. I don't
think the VR30 will be as failure-prone as the AD**VTs, though,
as it's a lot simpler analog amp.
It really is an attractive piece, though, if you get a good one.
Good luck!
The VG&L Railroad
>> No idea how it's biased; if I had to guess it
>> would be for Class A.
>
> It's AB. I eventually found that. In the stand-alone
> Valvetronix modeler it's switchable, A/AB, but not in this amp.
Ah. I'd have figured they'd have gone with Class
A for the mojo hype. I wonder why they went with
Class AB. Is it because they realized a lot of
folk would prefer the sound? Or did it just turn
out that way? We'll probably never know.
> Still, it seems like that with the (not inconsiderable)
> exception of the coloration provided by the speaker, you could
> then get a consistent user-adjusted level of power-stage
> distortion at all volumes, which they never seem to come right
> out and say --
Yes, you should be able to, and it's pretty amazing
that even the hype-boys don't realize what valuable
brownie points they would get for stating that clearly.
> but then they inject this seemingly contradictory
> business about feedback "reaction," whatever that may actually
> be.
Oh, no! A *reactor*! A *nuke*! We should sue!
Hey, it makes as much sense as anything *they* say about it.
> I'm stumped. It's gibberish, a technical explanation
> written by an intern with a hangover in Marketing based on a
> phone call to an admin-assist in Engineering.
No, no, no. I bet someone worked hard on that gibberish.
They're probably right proud of it. Probably got an award
in front of the whole company, with a paid vacation in Hawaii.
Gibberish sells in the mass market. 8^(
>> From what I have read, they are trying to get
>> "tube sound" out of an SS amp.
>
> Well, yeah, aren't they all? And they all do it just
> _wonderfully_, too! 8-)
Yeah. I would have given up on tube amps, but now
I'm working to get that SS buzz from the tubes. So
far I'm failing miserably, but somehow I like the
tone, anyway.
-Miles
George Orwell
>> Note that the "valve reactor" amp claims to have an output
transformer,
>> but the ADxxVT series has a "virtual load." A real output
transformer
>> sounds better to me, but I suppose the test is the ear of the
player.
> I'll eventually get around to popping this one open and looking,
> but for the moment I think I'll leave well enough alone. I was
> under the impression that it also had the "virtual load."
Yeah Jim, curiosity got the better of me and I popped it open
last night. The only transformer in there is in the power
supply.
George Orwell
this...]
The VG&L Railroad <m...@rru.com> wrote:
> I'd have figured they'd have gone with Class
> A for the mojo hype. I wonder why they went
> with Class AB.
I assume because of tube longevity. Just a guess.
>> you could then get a consistent user-adjusted level
>> of power-stage distortion at all volumes, which they
>> never seem to come right out and say --
> Yes, you should be able to, and it's pretty amazing
> that even the hype-boys don't realize what valuable
> brownie points they would get for stating that clearly.
So amazing, in fact, that I was fairly convinced I was
misunderstanding the whole technical issue, as I could not
conceive of them not making a big deal of this if it were the
case; it's so much more buyer-significant than the explanation
they do give.
> No, no, no. I bet someone worked hard on that gibberish.
> They're probably right proud of it. Probably got an award
> in front of the whole company, with a paid vacation in Hawaii.
> Gibberish sells in the mass market. 8^(
I know people get paid well to write it. I used to do technical
writing and documentation and the difficulties one faces in
getting lucid copy approved in the corporate setting is just
amazing. There are predictable reasons why everything you read
from a manufacturer is meaningless gibberish, but they're beyond
the purview of this thread.
> Yeah. I would have given up on tube amps, but now
> I'm working to get that SS buzz from the tubes.
A quality solid-state amp is dead quiet at idle, unlike this one.
I have also discovered that this thing has the most severe case
of reverb-circuit feedback that I have ever, ever encountered:
If you null all controls and remove input, then just turn the
master volume and reverb up halfway (twelve o'clock), it will
shortly go into full feedback, and that's just at halfway with
no input! Very severe...
[Later:] Turns out that this is apparently due to nothing worse
than an overtightened mounting flange on the reverb unit in the
chassis crushing the foam isolator strip which is supposed to
damp vibration. I can see the problem, but have to do some
desoldering and other warranty-wrecking moves to get to it, so
merely loosening the mounting screws holding the chassis to the
cab has greatly lessened the problem in the meantime. Weird,
huh?
A.Melon
this...]
The VG&L Railroad <m...@rru.com> wrote:
> I'd have figured they'd have gone with Class
> A for the mojo hype. I wonder why they went
> with Class AB.
I assume because of tube longevity. Just a guess.
>> you could then get a consistent user-adjusted level
>> of power-stage distortion at all volumes, which they
>> never seem to come right out and say --
> Yes, you should be able to, and it's pretty amazing
> that even the hype-boys don't realize what valuable
> brownie points they would get for stating that clearly.
So amazing, in fact, that I was fairly convinced I was
misunderstanding the whole technical issue, as I could not
conceive of them not making a big deal of this if it were the
case; it's so much more buyer-significant than the explanation
they do give.
> No, no, no. I bet someone worked hard on that gibberish.
> They're probably right proud of it. Probably got an award
> in front of the whole company, with a paid vacation in Hawaii.
> Gibberish sells in the mass market. 8^(
I know people get paid well to write it. I used to do technical
writing and documentation and the difficulties one faces in
getting lucid copy approved in the corporate setting is just
amazing. There are predictable reasons why everything you read
from a manufacturer is meaningless gibberish, but they're beyond
the purview of this thread.
> Yeah. I would have given up on tube amps, but now
> I'm working to get that SS buzz from the tubes.
A quality solid-state amp is dead quiet at idle, unlike this one.
The VG&L Railroad
> [ Well, it looks like the server's out to lunch, so I'll re-send
> this...]
Stupid servers. (I spend a great deal of my life
dealing with servers.)
> The VG&L Railroad <m...@rru.com> wrote:
>
>> I'd have figured they'd have gone with Class
>> A for the mojo hype. I wonder why they went
>> with Class AB.
>
> I assume because of tube longevity. Just a guess.
A 12AX7 will last a loooong time unless you really do something
screwy with it. Almost every 12AX7 ever used in a tube amp was
running Class A, unless it was biased to one side for distortion
purposes (or in ignorance). And then they still last 90% of
forever. Even as PIs, despite what Mr. Pittman suggests.
...
>> Yes, you should be able to, and it's pretty amazing
>> that even the hype-boys don't realize what valuable
>> brownie points they would get for stating that clearly.
>
> So amazing, in fact, that I was fairly convinced I was
> misunderstanding the whole technical issue, as I could not
> conceive of them not making a big deal of this if it were the
> case; it's so much more buyer-significant than the explanation
> they do give.
But we're talking about *marketing* here. And mass-market
marketing at that. The name of the game is obfuscation,
dumb it down, don't give out any real information (we could
be held liable!) You aren't their target audience. (Not that
they aren't happy for you to buy!) The target audience is a
clueless 12-16 year old with little to no science interest,
who goes, "Dood! It has tube,s but it's as cheap as these
solid state amps, and look at all the crap it does!" And they
get their parents to buy one. Parents are targeted, too. And
people who vaguely recall something called tubes.
>> No, no, no. I bet someone worked hard on that gibberish.
>> They're probably right proud of it. Probably got an award
>> in front of the whole company, with a paid vacation in Hawaii.
>
>> Gibberish sells in the mass market. 8^(
>
> I know people get paid well to write it. I used to do technical
> writing and documentation and the difficulties one faces in
> getting lucid copy approved in the corporate setting is just
> amazing. There are predictable reasons why everything you read
> from a manufacturer is meaningless gibberish, but they're beyond
> the purview of this thread.
Not any more.
8^)
>> Yeah. I would have given up on tube amps, but now
>> I'm working to get that SS buzz from the tubes.
>
> A quality solid-state amp is dead quiet at idle, unlike this one.
Heh. A quality amp of *any* sort should be dead quiet, or
awfully close to it. But a lot of them aren't.
> I have also discovered that this thing has the most severe case
> of reverb-circuit feedback that I have ever, ever encountered:
> If you null all controls and remove input, then just turn the
> master volume and reverb up halfway (twelve o'clock), it will
> shortly go into full feedback, and that's just at halfway with
> no input! Very severe...
Ouch. They need another slogan. ``The quality goes IN before
the feedback turns ON!'' It's meaningless, yet trite.
> [Later:] Turns out that this is apparently due to nothing worse
> than an overtightened mounting flange on the reverb unit in the
> chassis crushing the foam isolator strip which is supposed to
> damp vibration. I can see the problem, but have to do some
> desoldering and other warranty-wrecking moves to get to it, so
> merely loosening the mounting screws holding the chassis to the
> cab has greatly lessened the problem in the meantime. Weird,
> huh?
OK, maybe we'll need to modify that.
``The quality control goes IN with an impact wrench,
before the feedback turns ON!''
Cyberserf
The VG&L Railroad wrote:
> George Orwell, tied to the tracks, said:
> ...
> > written by an intern with a hangover in Marketing based on a
> > phone call to an admin-assist in Engineering.
>
> No, no, no. I bet someone worked hard on that gibberish.
> They're probably right proud of it. Probably got an award
> in front of the whole company, with a paid vacation in Hawaii.
>
> Gibberish sells in the mass market. 8^(
>
I like my gibberish in pink...with sparkles on top...and big hooters
;-)
I own an AD50VT. I chained it to my ceiling (the rep told me that would
be an official chain reaction). It run and external cab with a big
Jensen (P15N) and a horn. It is not noisy...the rep. told me the
ringing in my ears is perfectly normal...EVERYBODY hears it!
Then he gave me some yellow pills...
I like the grill...it's real shiny...
Cheers, C[Oh, Dementia, Dementia, where fore art thou Dementia?]S