General tech questions

The VOX tone

1

Maybe a silly question and I'm no electrician or amp expert, but I just got an AC15 2x12 and the tone is addicting! Just what I've always heard in my head; what makes that unique sound that differs it from fender/Marshall etc? It seems to be much the same ingredients as many other amps, but the sound seems to distort and fuzz out from the top down, meaning that fuzzy jangle high end but relatively clean lows, which I like and is very different from my old fender and Marshall where the low end would break up and get muddy before the highs had any power. Feel free to get technical with any answers, I'll catch up haha

4

Class-A circuit. Link

– audept

Thanks! That pretty clearly summed up what I was looking for and suspected, my amp fits that Class A description to a tee, I love it! So going forward, can I expect to enjoy most "Class A" amps or will they vary as much as anything else?

5

It's magic.

– wabash slim

It is magic !

7

EF86.

– Strummerson

Not in the standard reissue, Strum.

8

Not in the standard reissue, Strum.

– sascha

Thought Class A with an EF86 in the pre-amp was the special sauce recipe.

9

It is worth noting that the Vox amps are not really Class A designs, though they are often marketed as such. While they're maybe closer to Class A than your typical Bassman or AB763 circuit, I think it's fair to say that the cathode bias--and lack of negative feedback--is responsible for their "chime" and smoothness of clipping (though the full truth is it's a lot of small things combined). As such, there are a few Fender and Marshall designs (such as the venerable 5E3 and 1974x, respectively) which I think will get you into a similar ballpark. Of course, through the years Vox has offered a few "quirks" like the top boost and the aforementioned EF86 that set it apart from the more "by the book" circuits Leo was using. There are also some tone stack differences, which I would encourage you to explore using this nifty piece of software.

Here are a few more readings if you're into that kind of thing (each of these sites contains a veritable gold mine of information, so feel free to poke around):

Push-pull

Class A

Top boost

Voxiness

Myths

Note: many--but not all--things that can be said about the AC30 can be said about the AC15. There's just a lot more articles about the AC30 out there.

10

I just bought this. Any discussion on blue alnico over greenback?

11

I just bought this. Any discussion on blue alnico over greenback?

– Threadkiller

Beware!! Before I bought my new vox brand new, I ordered a used one from the Chicago guitar center and the whole experience turned into a nightmare. I didn't get what was pictured, and when I looked in the back the speakers had been replaced with cheap fenders, the reverb tank and tubes weren't original, a lot of wires were not even hooked up inside and it was a 2012. Tolex torn and peeling to shit. When I called they told me the condition was great and that youd barely know it was used.

12

I have no problems returning items to GC. If it's not what I believe it to be (a more expensive amp at a great price), it will become a out of the box new ac15 with greenbacks.I have received things that were not as advertised before. Thanks for the heads up though!

13

I don't know what it is, but I like it! I had that amp for a while, and loved it....you will too. I downsized to an AC10 only due to it being too much stage volume since there's no drummer.

14

I've built some non-trem AC15's with an EF86 preamp. The power section is biased the same as a lot of other 2xEL84 amps but the original EF86 circuit was on steroids, possibly why so many are microphonic as hell. If you follow Blencoe and build a "proper" EF86 preamp, its less prone to microphonic noise but also much tamer. Needs to be followed by a triode punch. But jeez.....what a sound!

15

Oh, and on a personal note, my favorite speaker set up for the AC15 is a 10" alnico Blue Pup paired with a 10" ceramic Silver Bell (Webers). So much sonic territory covered. That's my 2 cents worth.

16

Thanks Otter for clearing up the "Class A" nonsense. I think it was Matchless who started all that up. Vox AC30s have of course never been class A, but are cathode biased with no NFB, and i agree that those things, along with the EL84 tubes and possibly the top-boost tone stack are where these amps get their tone.

EL84s just happen to work well being cathode biased. I have built a few Fender and Marshall style amps cathode biased and sometimes it sounds great, sometimes less so. My main amp right now is a cathode-biased 5F4 Super. It also runs KT77 tubes and a single 12" Celestion Gold. It sounds amazing with a Gretsch. Using fixed bias makes it sound a little tougher but I like the cathode bias because it lowers the B+ a little and sounds warmer and the breakup is a little smoother.

The Vox tonestacks are quite different from Fender too. The treble and bass are very interactive. Want more mids? Lower bass and treble. Raise treble and the bass disappears. And vice-versa. I have a blonde Bassman head I built with the regular normal channel but the "bass" channel is a top-boost preamp. Once I raised the B+ on the top-boost channel to match Vox voltages it sounded great - and VERY Vox-like! And the break-up is so smooth... I like it a lot more than the Fender channel.


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