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Post by RandomHero on Mar 22, 2006 23:02:22 GMT -5
I've been heavily rethinking my $750 purchase of the Vox Valvetronix. The reason is that I found a $500 all-tube 100 watt 2x12 that I like the sound of a lot... and it's called the B-52.
Anyone else had any experience with these amps? At this point I'm sold on them (two of my co-workers rely on the half-stack models for their touring band,) but I'm curious to see if anyone else has any input.
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Post by RandomHero on Mar 23, 2006 11:11:25 GMT -5
More testing with the amp makes me like it more. I realized that all I would do with that 3/4s of a $grand Vox would be to find a clean channel I like, a slightly dirty channel I like, and an over-the-top distortion I like. The B-52 has all those, and footswitchable, with built-in reverb and a low-res control. Also included much to my <3 is
a line out,
a tri-mode rectifier (Tube A, Tube AB, or Solid State operation),
a serial effects loop with level adjustments,
and external speaker outs.
Seems like it's got everything to be the foundation for some awesome tones...
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Post by UnklMickey on Mar 23, 2006 12:27:13 GMT -5
a low-res control?
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Post by ChrisK on Mar 23, 2006 12:41:23 GMT -5
Resonance, methinks.
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Post by RandomHero on Mar 23, 2006 12:41:57 GMT -5
Basically adds that much more bass to the sound. It's in the Master control section, along with volume and reverb.
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Post by sumgai on Mar 23, 2006 16:03:13 GMT -5
Unk,
The opposite of Fender's Presence control. Well, the opposite end of the timbral range. Like RH said, affects the lows and low-mids more than the highs.
Chris, do you have a VG-8/88, or only a GR-33? A VG user would be very likely to know all about that "resonance" thing. ;D
sumgai
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Post by sumgai on Mar 23, 2006 16:16:13 GMT -5
All,
Before I go off on a tangent, does anyone want to enlighten an old duffer? I'm just flabbergasted to learn that in all the time I've been fixing tube stuff, I have never before heard of a "tube rectifier class". Half-wave versus full-wave, even voltage multipliers, yes, but Class A or AB, nope, haven't seen it.
There seems to be nothing on Google that isn't marketing hype (or repeats of the same from reviewers/hawkers/etc.). Anyone, please?
BTW, RH, B-52 is an amp manufacturing company. Which model are you specifically looking at?
sumgai
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Post by UnklMickey on Mar 23, 2006 17:24:57 GMT -5
my guess, and it's only a guess!
this might refer to using a single, rectifier tube (tube A),
two tubes (in parallel for less sag?) (tube AB) or (tube A+ tube B),
or a pair of silicon rectifiers.
the tubes likely are both dual plate, in a full wave, center-tapped configuration.
i think the description just confuses the issue, and it suggests, incorrectly a class of operation for the rectifier similar to amplifier classifications.
again this is only a guess. don't bust my ..........well you know, if i'm wrong!
unk
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Post by UnklMickey on Mar 23, 2006 18:55:16 GMT -5
hey guys,
forget what i just said!
i went to the B-52 site and this uses a single 5AR4 rectifier.
they claim to switch between class A and class AB1 modes.
i've never heard of a rectifier changing class of operation.
and push-pull outputs either run class AB1 or AB2, not class A
(i don't care what hype you've heard about the Vox AC-30, it's not class A.)
yes, you could bias the output tubes so that both sides would always be conducting (class A) but you would severely sacrifice power output.
the rectifier operation class might just be something they made up.
just sounds like some tater-head claims to me.
unk
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Post by sumgai on Mar 24, 2006 4:54:36 GMT -5
unk,
Agreed. Your second analysis is spot-on, IMHO.
Still, B-52 makes some fine stuff, and should be considered a value leader. They don't get the respect I think they should, and hype like this doesn't help their cause.
Remind me to tell you sometime about what Soichiro Honda said about Harvard MBA's.
sumgai
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Post by RandomHero on Mar 24, 2006 8:45:29 GMT -5
The B-52 AT100 in the 212 combo version.
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Post by sumgai on Mar 24, 2006 17:42:38 GMT -5
RH, Ah yes, that's a very nice package, a good alternative for those who can't swing a Twin Reverb. Some manufacturers that make a Twin-clone want even more money than Fender, and then scratch their heads as they see the balance sheet going deeper and deeper into the Red Ink Zone.  BTW, I just noticed your sig, very nice. Somewhere around here I've got stashed away a Hetfield smilie.... it swings either the left arm or the right one, as needed. Should I dig it out for you? ;D sumgai |
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Post by ChrisK on Mar 24, 2006 22:31:46 GMT -5
sumgai,
I'd have to dig out the manual, but I do have the VG-88 and it did have a "body resonance" parameter for building virtual guitars a la the Line6 Workbench (now, if I could just remember where I put the Workbench).
I get real confused about tube classes. Back in the 60's I knew all about them. Now I don't.
I suspect that Class A operation (conduction beyond 180 degrees) may be possible in push-pull. I may also be on drugs. However, push-pull "cleans up" things by eliminating some popular harmonic distortion.
A single-ended tube PA that humans are willing to listen to will always be Class A(and "dirty").
I suspect that the rectifier "Classifying" may be a reduction in effective biasing just enough to change things a tad.
But, I'm so confused. The Stellartone ad indicates that the "steep roll-off curves enhance the tube amp's even-order harmonics". Has anyone bot one of these and traced the circuit? I don't (much) believe in magic.
Did I mention that I'm confused?
I'm still liking the VOX AD50 fer the Celestion speaker and the 1 Watt out mode (I like the Korg amp modeler, I carry one to eval guitars).
unklmickey,
Why not, by using tube amps we've already sacrificed efficiency and fidelity!
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Post by sumgai on Mar 25, 2006 6:58:03 GMT -5
Chris, The problem I have here is with the marketing hype of "tri-mode rectification". Any English speaking person is going to take that as "there are three different modes or ways that this recitifies AC into DC for the tubes". And as I pointed out, and mickey agreed (and you appear to be agreeing), there are indeed only two modes of recification on that amp - solid state and tube. (In the strictest vernacular, both devices use the same mode, full wave, but we'll let that go for the sake of this discussion.) My claim here is simply stated: if you are going to be monkeying with the bias, then say so, don't try to BS the customer. Not a small handful of those customers actually know something about amps and what goes on under the hood! When you bias each tube in a push-pull setup to turn on more than 180 deg. of the waveform, you are in Class AB 1 or AB 2. Merely a difference in degree between the two. But yes, you are wasting power, see the next paragraph. Switch to Unk, It's not the power output that's going to be reduced by forcing both tube to conduct a full 360 deg., it's the fact that each tube will be attempting to impress the complete waveform on the transformer's primary. Since it's happening twice, said transformer is going to be suffering from a helluva lot of magnetic saturation. (All other design parameters being equal to normal push-pull operation). The net result is a loss of power efficiency. You put in twice the normal amperage in driving the tubes to full saturation, but you only get the one waveform out the secondary (at full power). A classic example of wasting power, if there ever was one. Back to Chris, Unk's right, the aforementioned circuit will be dirty for the stated reasons. But let's agree on the definition of a term first, shall we? Fidelity is defined in any dictionary as "a faithful reproduction of an original". The key word there is reproduction. In your answer to Unk, you make the common mistake (I'm sure you don't do this often!  ) of confusing the fidelity of a reproductive amplifier (hopefully it's high) with the desired sound qualities of an amplifier that's part and parcel of the original sound source. Musicians can argue about what order of harmonics are most desirable and all that, but the fact is, if it sounds "good", "better" or "best" to our ears as we create the music, that's what we're gonna use. ;D Unless one were to get picky about the fidelity of exactly reproducing the string's vibrations, then the word fidelity should be stricken from this part of the equation. What the amp adds to the sound of the strings, and the overall sound in general, is a desired end product. Here, fidelity should not be confused with "clean", or so it seems to me. sumgai |
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Post by RandomHero on Mar 25, 2006 9:24:07 GMT -5
Hehehe. This is very informative and cool to watch pan out, but all I know is I get three -very- different sounds from the little knob on the back. Maybe descriptions would help?
A is warm, full, and squishy.
AB is slightly more precise with a harder attack.
Solid State is, of course, to the letter; sterile clean and exact overdrive.
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Post by sumgai on Mar 25, 2006 22:39:35 GMT -5
RH, Makes me wonder if there really is any rectification switching going on - I can think of 10 or a dozen amplifiers that can get those exact same difference tones, but without having to "switch rectifier circuits". Sophisticated tone-shaping and channel switching can do the job, as can most of the better amp modelers. Looks like we'll have to open 'er up to see just what's going on. Or can you perhaps get your hands on a schematic? ;D Although come to think of it, it really doesn't matter how the do whatever they do, so long as you like the end results.  sumgai |
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Post by ChrisK on Mar 25, 2006 23:33:35 GMT -5
Check out the mavenpeal.com site.
Cool is! (Apparently around $3k).
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Post by sumgai on Mar 26, 2006 22:13:48 GMT -5
Chris,
Some pretty bold claims. ;D I can think of at least two, maybe three amp builders that won't take kindly to claims of holding patents on such things as variable power supplies and sag controlling circuits.
And speaking as a repairman, what happens if this thing comes into a shop for repairs, or just a checkup, a re-tube, whatever. Are the circuits in question so obtuse as to make repairs all but impossible unless the thing is returned to the maker? Or will the maker supply schematics? Be nice to know before plunking down any kind of cash.
And I couldn't find any price schedule, where'd you see it?
sumgai
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Post by UnklMickey on Mar 27, 2006 13:53:47 GMT -5
...I get real confused about tube classes. Back in the 60's I knew all about them. Now I don't.... Amplifier Classifications: Class A: device conducts for 360 o of input cycle Class A 2: device conducts for 360 o of input cycle, grid current flows on part of cycle Class AB 1: device conducts for less than 360 o but more than 180 o of input cycle, grid current never occurs Class AB 2: device conducts for less than 360 o but more than 180 o of input cycle, grid current flows on part of cycle Class B: device conducts for exactly 180 o of input cycle Class C: device conducts for less than 180 o of input cycle ...Switch to Unk, It's not the power output that's going to be reduced by forcing both tube to conduct a full 360 deg., it's the fact that each tube will be attempting to impress the complete waveform on the transformer's primary. Since it's happening twice, said transformer is going to be suffering from a helluva lot of magnetic saturation. (All other design parameters being equal to normal push-pull operation). The net result is a loss of power efficiency. You put in twice the normal amperage in driving the tubes to full saturation, but you only get the one waveform out the secondary (at full power). A classic example of wasting power, if there ever was one.... if you bias a push-pull amp to run class A without reducing the power supply voltage, the average power dissipation in each tube (which will now occur at idle) will far exceed the absolute maximum. you won't have to wonder if the tubes are on, that bright red glow of the plates will tell you. in addition, you may be running at a higher current than the output transformer can tolerate. so, to use the same output transformer and tube complement, and run Class A, you would need to run at reduced power. unk |
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Post by JohnH on Mar 27, 2006 21:04:48 GMT -5
Check out the mavenpeal.com site. Cool is! (Apparently around $3k). I had a look at that, then came across this: www.londonpower.com/pssc.htmIt seems there is some interesting controversy here. Any comments on this from our own tube experts? John |
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Post by UnklMickey on Mar 27, 2006 21:21:20 GMT -5
Well John " I'm not a tube expert, but i play one on the Internet."
(inside joke, variation on an american commercial)
i haven't bought any of Kevin O'Connor's books, but the buzz around these parts is,
his series: "The Ultimate Tone" are considered to be almost "tube-amp bibles"
so i'd be inclined to take anything he says, to merit serious consideration.
of course, if you can find a quote from Randall Aiken that supports any of his statements,
consider it Gospel.
unk
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Post by RandomHero on Mar 27, 2006 23:28:26 GMT -5
Where's a crash course on what any of these terms you guys are using means?
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Post by UnklMickey on Mar 27, 2006 23:48:49 GMT -5
Where's a crash course on what any of these terms you guys are using means? Oooooh, that phrase don't feel so good after last weekend's IRL incident. nothing on the web is a real replacement for a good electronics textbook, but there is some good stuff on the internet. start with these: www.aikenamps.com (go to tech info page) www.angelfire.com/electronic/funwithtubes/ (lots of tube basics, you can sort out from the radio oriented sections) |
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Post by ChrisK on Mar 30, 2006 0:16:31 GMT -5
Re: mavenpeal.com
I found a price reference in a review.
18watt.com
I'm still liking the VOX AD50 fer the 1 Watt and the Celestion.
RandomHero,
Was the Valveronix that you had the one w/ the NeoDog speaker(s)?. (And did you like them over the AD50 which I would assume that you also tried?)
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) of confusing the fidelity of a reproductive amplifier (hopefully it's high) with the desired sound qualities of an amplifier that's part and parcel of the original sound source. Musicians can argue about what order of harmonics are most desirable and all that, but the fact is, if it sounds "good", "better" or "best" to our ears as we create the music, that's what we're gonna use. ;D Unless one were to get picky about the fidelity of exactly reproducing the string's vibrations, then the word fidelity should be stricken from this part of the equation. What the amp adds to the sound of the strings, and the overall sound in general, is a desired end product. Here, fidelity should not be confused with "clean", or so it seems to me.
