JSX Class

[Praetorian]

Hey guys, I was wondering, what class amp is the JSX? I keep hearing most guitar amps are class A/B which doesn't make sense to me becuse Class A/B only gives a partial replica of the input signal wheras class A is the whole signal. I know there are some class A amps out there, though most of them are boutique amps, but then what about the most popular ones? Such as, are all the Marshalls class A/B? I know Mesas are almost all A/B besides the Lone Star special, and then what about Fenders? And the Legacy and JSX? I've just spent about a month learning about amplifiers in my Apprenticeship class but it wasn't focused on musical applications and they don't use tubes anymore. Anybody have a clue?

[jt93]

Originally Posted by Praetorian

Hey guys, I was wondering, what class amp is the JSX? I keep hearing most guitar amps are class A/B which doesn't make sense to me becuse Class A/B only gives a partial replica of the input signal wheras class A is the whole signal. I know there are some class A amps out there, though most of them are boutique amps, but then what about the most popular ones? Such as, are all the Marshalls class A/B? I know Mesas are almost all A/B besides the Lone Star special, and then what about Fenders? And the Legacy and JSX? I've just spent about a month learning about amplifiers in my Apprenticeship class but it wasn't focused on musical applications and they don't use tubes anymore. Anybody have a clue?

im about 99% sure it's an a/b amp. most class a's i have seen (not a lot by any means) are low output (30-50w), and expensive (2-3k). a high wattage pure a would be (i would think) very expensive. i did a google for 'class a guitar amp' and found http://www.classahighperformance.com/
lots of expensive stuff there

[rgr]

Definitely A/B, even a 50W class A amp would require quite a few output tubes and generate alot of heat.

Roger

[red5]

I can guarantee you it is not a Class A. Most likely A/B but it could be B as well.

Vox AC15 and AC30s are Class A, as well as most Bad Cats, Laneys and Soldano makes a Class A. There are a couple I am forgetting too. I found a company that makes handwired class A amps that run at 5 watts on just a single power tube!

[Praetorian]

yeah, thanks guys. I'm looking into AC30's now. I don't know, why is it that most guitar amps are A/B when it doesn't give the full output signal? It's like cutting a quarter off your pickups. I guess it must be OK because from what I hear the JSX is a wondeful amp, but I guess this is the reason everyone loves the SLO100. A high gain 100 watt Class A amp, it's a beautiful thing!

[Drew]

Originally Posted by Praetorian

...but I guess this is the reason everyone loves the SLO100. A high gain 100 watt Class A amp, it's a beautiful thing!

The SLO's A/B too.

There's a LOT of debate on this, naturally, but A/B is actually fairly well suited for guitar - it'll give a bit of extra definition in relation to a true A. B is generally held to overdrive too abruptly (all or nothing) for a guitar amp, but A/B is totally workable.

Also, apparently most "Class A" guitar amps aren't actually true class A. I don't understand the exact differences, but do a Jemsite search and a few links to some interesting articles should turn up.

Basically, finding a transformer that can handle more than 50 or so watts in Class A is prohibitive.

-D

[old_metal_head]

http://www.mesaboogie.com/US/Smith/ClassA.htm

[rgr]

SLO's are definitely A/B, as well as most Laneys. I think they make an AC30 type amp that may be "class A" although, as Drew said, "true class A" in guitar amps is debateable. As far as class A being more efficient that A/B, it's quite the other way around, A is considerably less efficient, hence why you don't see class A amps over 30 or so watts.

The reader's digest version of the way class A works is that the power amp is biased so the zero line of the sine wave is right in the middle of the tube(s)'s amplification range and as the wave swings positive or negative, the same tube(s) amplify the signal both ways, so the tube is always "on" even when there is no signal. The creates a nice "vintage" tone, warm and smooth, and usually "spongy". Class A/B amps use at least 2 (or some other even number) power tubes and are biased (you'll see why biasing is so important now) so that the zero line is "between" the tubes (or pairs, triplets, etc..., you need an equal number of opposing tubes). When a signal is applied, one set (or side) of power tubes amplifies the positive side, then when the sine wave crosses the zero line, that set turns "off" and the other set of tubes amplifies the negative side. Class A/B amps are usually louder, cleaner, and tighter than A amps.

So you can see, class A/B can use the full power of a tube for each side of the wave, while class A can only use half (or less) of a tube's power for each side of a wave. Also, since tubes in class A are always "on", they generate more heat that class A/B amps.

Please note, before I get hammered, this is quite a simplification and doesn't try to explain all the nuances, or possibly be 100% correctly stated, but is supplied more to help as a visualization of how the different types of power amps work.

Roger

[Drew]

"Reader's Digest version" - awesome!

And that's a very clear explanation that corresponds pretty well to my vague udnerstanding of the subject, so props for that too. Myself, I tend to like a very spongy response for lead playing - this is part of the reason I like lower wattage (even A/B) amps. I'd probably love a low-wattage two- or three-channel high gain class A head if someone would just build one, but for now my "simul-class" (whatever that means) 45-watt Nomad is working out pretty well...

[vaijem777]

I tend to like my older Matchless Chieftain for cleans, but have really fallen in love with the lead sounds I'm getting from my Bogner Shiva. Definitely the nicest all-around A/B amp I've played through.

There is definitely a lot to be said for a nice, low-wattage single-channel Class A amp though. The nuances and personality of that type of amp can be a lot of fun to play with

[Drew]

Originally Posted by vaijem777

I tend to like my older Matchless Chieftain for cleans, but have really fallen in love with the lead sounds I'm getting from my Bogner Shiva. Definitely the nicest all-around A/B amp I've played through.

Why is it, whenever you post, I have near-unbearable attacks of G.A.S? Man... It's probably a good thing I've never gotten a chance to play a Shiva, because I'd probably fall for it pretty hard.

[vaijem777]

Originally Posted by Drew

Why is it, whenever you post, I have near-unbearable attacks of G.A.S? Man... It's probably a good thing I've never gotten a chance to play a Shiva, because I'd probably fall for it pretty hard.

LOL I've pruned my gear collection a LOT, but kept most of the good stuff

The Shiva is the closest I've come to the "perfect" amp. I'd definitely take the EL34 version over the 6L6 though. MUCH more "organic" sounding. It just seems to breathe more (definitely has the nice, warm Jerry Cantrell tone!)
Plus, it's been road-tested and pulled through like a champ (even after being dropped and getting knocked over a couple of times) The thing is built like a rock!

[red5]

Originally Posted by Drew

The SLO's A/B too.

I say Soldano makes A Class A amp, and people assume it's the SLO... that says a lot!

[red5]

Originally Posted by Praetorian

yeah, thanks guys. I'm looking into AC30's now. I don't know, why is it that most guitar amps are A/B when it doesn't give the full output signal? It's like cutting a quarter off your pickups. I guess it must be OK because from what I hear the JSX is a wondeful amp, but I guess this is the reason everyone loves the SLO100. A high gain 100 watt Class A amp, it's a beautiful thing!

You are completely not understanding Class A. Class A does not necessarily/always/ever sound better than Class A/B or B, it's just different. It's not like taking a class A/B amp and running your tubes hot or boosting your input more for more power tube OD. Usually it's pretty warm and have lots of highs.

And I must add most Class A amps are cathode based which means they are auto biasing.

Listen to rgr and be forwarned that Class A amps eat tubes in a way that puts the Marshall Major to shame (ie really fast!).

[rgr]

If Soldano makes a Class A amp, it would be the Astro head or the AstroVerb combo. Both are small 20W amps but their website doesn't say if they are class A or not (at least that I saw on a quick look). It is possible to make low wattage A/B amps too, a pair of EL84s or 6V6s will put out 20 - 30W in A/B. Red5, it was Drew that thought the SLO was class A, so those comments weren't directed at you. I did have a HR50+ head, probably the best sounding amp I've owned, never had the $ for a SLO, I would only assume that they are awesome!

Roger