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Fractal Audio AMP models: AC-20 (Morgan AC20 Deluxe)

yek

Moderator
Moderator
* EDIT: Up-to-date information is available in Yek's Guide to the Fractal Audio Amplifier Models *


AC-20: based on Morgan AC20 Deluxe

The AC-20 models are based on a Morgan AC20 Deluxe. This is a very popular EL-84 equipped 20 watts boutique amplifier that looks like a mini Plexi. It’s based on a Vox, and according to many: far superior.

Morgan:

"The Morgan AC20 Deluxe is a deceptively simple amplifier that is capable of producing a myriad of early 60s British tones but that is just the beginning. The switchable EF86 tube helps to make the range of tones from the cleanest of EL84 chime to ferocious high gain growl. The power level control allows you to dial in just the right amount of volume without sacrificing your tone the way some master volumes do. The AC20 Deluxe was created to solve modern guitar player amplifier issues with the ability to stay true to vintage tonality. It is equally at home in the studio or on the stage. It can be seen on the stages of superstars like Jeff Tweedy, Tim McGraw, The Band Perry, Taio Cruz and with Toshi Yanagi on Jimmy Kimmel Live. Plug into the AC20 Deluxe and you will instantly notice the familiar chime and compression of the Class A EL84 driven output section. The amplifier’s extreme touch-sensitivity will allow you to coax clean tones even at the highest of gain settings. To quote Keith Armstrong (Chief Engineer at Mix LA) “It is impossible to get a bad sound out of this amp!” (…) The AC20 Deluxe uses 3 separate switches to give you all of the original early 60’s EL84 tonalities, Normal, Brilliant and EF86. Never has such a deceptively simple amp had so many tonal options. Handwired in the USA."​

To my ears it’s a delicate tone. The AC20 sounds intimate and “small” in a good way.

It doesn’t have tone controls, apart from Cut (model: Hi-Cut) which attenuates highs, a Bright switch, a Brilliant switch (cuts bass) and a 12AX7/EF86 switch. For authenticity, keep all tone controls in the models except Hi-Cut at default.

The models have the Bright switch enabled. If that’s too bright for you, turn it off or adjust Hi-Cut. Cliff:

"As with the real amp I dial in quite a bit of Hi-Cut."​

Use Input Drive to dial in the desired amount of gain. Don’t hesitate to use low settings for a really clean tone.

The modes are represented by the separate Bass and Treble (Brilliant mode) models, and EF86 preamp and 12AX7 preamp models.

The 12AX7 preamp tube sounds more glassy and has more sparkle. The EF86 is more full-bodied and fat. Increase Input Drive and the EF86 gets a lot more distorted than the 12AX7. Some players use the EF86 setting with single coils pickups and the 12AX7 setting with humbuckers, for matched response and output.

The original AC20 Deluxe also features power scaling. Cliff:

"The AC-20 model is based on the amp with the power scaling at maximum power which effectively disables it (and sounds best IMO)."​

The Morgan pairs well with a G12H or AlNiCo Gold speaker. The Gold sounds like an AlNiCo Blue speaker that has been “well played-in”. Use this page to see which AC-20 cabs stock cabs are available.

Additional AC-20 IRs are available in Cab Pack 4: Universal Noise Storage - UltraRes.​

A selection of YouTube videos:



 
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yek

Moderator
Moderator
Adding a personal note:

I started using the AC-20 model for my main clean tones, when I needed an amp model with fat clean tones. Cliff had written that Tube Bias is a relevant parameter for a thick clean tone, and the AC-20 stood out (high Tube Bias value). I’ve moved on in the meantime, but when I need a Vox type of tone, I always choose the AC-20 (or Ruby Rocket). To me this is one of the gems in the amp collection.
 
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Rocket Brother

Power User
I've never been a big Vox fan - don't get me wrong they sound great when others play them but I've never really been able to bond with them myself.
I guess I've just never found my Vox sound or thought that I sounded good playing a Vox.
I've been slowly getting there lately though (somewhat at least), and credit for that goes to the Morgan AC-20, the Matchles DC-30 model and the Ruby Rocket - those amps sounds really great and for Voxy tones I always pick one of these three amps.

A friend of mine has a real Morgan AC-20 on order - been waiting a couple of years for that amp now, and judging from the blurp on TGP it seems he'll have to wait forever - litterally.
I've told him to stop dicking around and just get an Axe Fx - fastest way to get an AC-20 ....plus a lot of other other really great amps
 

pima1234

Fractal Fanatic
I owned this amp in a combo for a while. Mine had power scaling. Wonderful, marvelous amp. It remains one of my favorites. I'm so pleased to have the various settings available in my Axe FX. We are very fortunate.
 

Zelja

Inspired
My favorite "Class A" model.
Mine too!
So if the actual amp hasn't got a tone stack as such (which I guess is why it can overdrive quickly, little or no attenuation through the tone stack circuit), what does the Axe use - an "Active" tone stack?

Also, how do they get 20W out of 2 x EL84s, especially in anything approaching Class A operation (& I assume cathode bias config)?
 

chucma

Power User
Still the amp I always end up going back to! Love the AC-20! And it's funny because it doesn't look like much in the flesh.

You used to have to pull back on the Treble and Presence quite a lot on the 12AX7, until the new amps were introduced to the AFX with the EF86 preamp; these new ones are very well balanced.
 

Hotplate

Power User
I've been using this model since it was added.. it's one of my main go-to amps in the Axe, especially with my Les Paul.
Thanks for the summary yek!
 

brokenvail

Fractal Fanatic
This and the TripTik has been my amp's for a long time. I remember seeing guys using Morgan's and think what are those amps they look cool. I looked them up and I was drawn to the no tone stack. I really struggle with clean tones so was looking at our roster of amps that had less tone knobs ie no mid knob and then stumbled on the AC20 and thought Holy crap this is that Morgan amp. I tried it and have never left it since.

In case anyone is wondering I use the AC30 Blue and AC30 Silver stock IR's in a stereo cab panned center. Wish we had some "Gold" IR's to try as I head they are killer
 
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