Vox AC15

[Blille]

The name of the engineer/designer of the AC15 and AC30 escapes me. I have read he was hard of hearing. Employees at VOX would have to yell at him to communicate. People think his hearing loss is what made him design the amp so bright. He had problems hearing high frequencies and dialed the amp in to compensate for his ears.

Dick Denney?

[Securb]

Dick Denney?

Yep, that is who I was thinking about.

The man who many regard as the UK’s most important guitar amp designer was actually deaf in one ear, but Dick Denney’s perforated eardrum may have been the making of him. As a result of his affliction, he was exempted from military service during World War Two and seconded to the Vickers munitions factory – something that would permanently alter the trajectory of his life.

During the pre-war years, Dick had become infatuated with both jazz music and radio electronics. Early experiments resulted in the inevitable destruction of the family radio, but Dick’s skills improved and his wages from the factory enabled him to buy components. His work at Vickers also meant that Dick was freed from an unwanted apprenticeship in his father’s barber shop, and perhaps most importantly of all, it introduced him to a man named Tom Jennings.

During the war, amateur radio activity was prohibited so, as a guitarist, Dick turned his electronic skills to amplifier building. His goal was to develop an amplifier that was loud, but also small and light – and he had ample opportunity to test them out.

[Ewizard]

I had read that bands such as The Beatles wanted the amp to be even brighter and were bugging him to make it as such so they could hear it clearly over all the noise of the fans ( screaming women ). This led to the Top Boost implementation which was eventually a standard option. The Celestion Blue is already a bright speaker and by the time it was used in conjunction with the Top Boost, made for an ungodly bright sound.

The top boost is more or less an up to +30db boost at frequencies over 10khz and the bass is more or less a bass cut to thin the sound out or thicken it a little as needed. The amp's original brilliant channel was already pretty bright, the introduction of the " blue " speaker made it a little brighter still, and by the time the Top Boost was implemented, it was VERY bright. A sound I don't care for. The Vox AC30 is a very polarizing amp, you either love it or you hate it. I will be honest in saying that it sounds amazing in the right hands. With 20+ years of doing sound for nearly a thousand different bands, I have more than a few land on my stage. I can only say that it is a 50/50 shot that it is going to be decent sounding or I can't get enough people and other sound-absorbing material between me and that amp... It is so polarizing, I will say that I have never ever played one in my 30+ years as a performing guitarist.

All that being said, you can't deny that it is an amp that has stood the test of time at least in fame, and has shaped the sound of MANY artists.

[Mincer]

I love when a good player uses an AC30 or 15. I've never been able to get that kind of sound out of them, but I appreciate the hell out of other people that make them sound great.

[JB_From_Hell]

Oz really knows how to tame one. We sat maybe 20 feet from him, just offset from the amps. At no point did he sound ice picky or noticeably bright. I’m sure that had to do with his three pedal boards, but still, he rides the Strat’s bridge pickup at least half the set, and it was awesome.

[Securb]

I love when a good player uses an AC30 or 15. I've never been able to get that kind of sound out of them, but I appreciate the hell out of other people that make them sound great.

The same with me and Orange amps. I can't pull a sound out of them that works for me. I hear other people playing them and they sound great.

[beaubrummels]

I had read that bands such as The Beatles wanted the amp to be even brighter and were bugging him to make it as such so they could hear it clearly over all the noise of the fans ( screaming women ). This led to the Top Boost implementation which was eventually a standard option. The Celestion Blue is already a bright speaker and by the time it was used in conjunction with the Top Boost, made for an ungodly bright sound.

The top boost is more or less an up to +30db boost at frequencies over 10khz and the bass is more or less a bass cut to thin the sound out or thicken it a little as needed. The amp's original brilliant channel was already pretty bright, the introduction of the " blue " speaker made it a little brighter still, and by the time the Top Boost was implemented, it was VERY bright. A sound I don't care for. The Vox AC30 is a very polarizing amp, you either love it or you hate it. I will be honest in saying that it sounds amazing in the right hands. With 20+ years of doing sound for nearly a thousand different bands, I have more than a few land on my stage. I can only say that it is a 50/50 shot that it is going to be decent sounding or I can't get enough people and other sound-absorbing material between me and that amp... It is so polarizing, I will say that I have never ever played one in my 30+ years as a performing guitarist.

All that being said, you can't deny that it is an amp that has stood the test of time at least in fame, and has shaped the sound of MANY artists.

Not only did they implement the Top Boost for the Beatles, but they added a horn to the cabinet!

I have an AC30 and have played AC15s live. They don't sound the same to me. The AC15 sounds clean and even and breaks up at a lower volume, almost more like my Champion 600 with more power. My AC30 has it's own characteristic response curve. I also don't find any AC's bright though. I've actually had trouble getting any 'presence' out of them. They do have a high mid spike that is characteristic for getting chimy sounds, but the top end drops off after that IME.

[Blille]

I love when a good player uses an AC30 or 15. I've never been able to get that kind of sound out of them, but I appreciate the hell out of other people that make them sound great.

As a worship player, Voxes are pretty standard as backline or as expected tone. I grew up playing Marshall and then my go to became Fender Blackface and Deluxes. So I had to learn to use Vox about 10 years ago when I started doing worship.

For me the key was the speaker. It’s amazing how important it is to have a broken in darker speaker like a Blue. (Edit: not dark,-full bodied- like wizard put it) Now with my helix I got the best results in the mix with a lo pass at 3.5k (vs my usual 8k or so). I know it feels like a waste but it still sounds clearly Voxy.

[jeremy]

i dont find the blue to be a dark speaker at all actually

[Ewizard]

The blue is definitely not dark. It has a full-bodied sound with an emphasized high-frequency response. That is to say, it is relatively linear in the lows and mids, but has a pretty substantial bump in the highs. Not a bad thing, just a thing.

[Blille]

The blue is definitely not dark. It has a full-bodied sound with an emphasized high-frequency response. That is to say, it is relatively linear in the lows and mids, but has a pretty substantial bump in the highs. Not a bad thing, just a thing.

i dont find the blue to be a dark speaker at all actually

You’re right. It’s not dark as in it has no highs. Not sure how to explain it, it is flatter in terms of frequencies (including more lows) and has more high mids.

[beaubrummels]

I hear what Jeremy and Ewizard are saying. This might not make sense, but the only way I can describe my hearing of Celestion Blues in a Vox is that to my ears it is to the amp world like the Brobucker or Whole Lotta Humbucker is to the 59 or Pearly Gates in the pickup world. It's got high-mid chime that will poke your ears or bite when it needs to, but the highest top end is rolled off a bit, compared to like the highest fizzy top end I am able to get out of a Celestion 25/30/75 in a Marshall with a presence control.

I also wonder if what I consider high-mids is considered 'bright' to other people?

[LLL]

2-3-4-5-6kHz (roughly high-mids) can poke a hole right through your brain and the people behind you if cranked. Painful.

Anything above 6kHz is "air".

[Ewizard]

Well, according to the spec sheet, it is pretty linear between 100hz up to about 1.6khz where it has a dip ( a phenomenon caused by the size of the speaker ) and then from 2khz up to 4khz, it has a roughly +6 to +7db boost. by 6khz the frequency response is linear again ( equal in output to the lows ) but it falls off sharply to pretty much useless output by 7khz.

The sound of a Blue is bright to my ears, although it is even and full in the lows and mids. The spike it has is right in that area, with the even response in the lows and mids, punches out at you.

The Blue was initially designed as a PA or Radio speaker, hence why it is rather linear in the lows and mids. Speakers that size have NEVER done well in the top end. Historically 1.2khz to around 1.6khz is where a crossover was set to transition into a horn, tweeter, or other high frequency reproducing device. The blue was designed to try and do away with needing a HF device and be an all-in-one solution. Hence the boost around the last of a 12" speakers usable frequency response.

Denny's idea was to use EQ to emphasize frequencies 10khz and up in order to further even out the frequency response of the speaker. With a corner frequency of 10khz, there was likely a generation of output down to around 5khz. With the natural response of the speaker and the added output of the Top Boost circuit, the resultant sound of the output ( at the speaker ) was essentially linear enough to be a PA speaker.

If you have ever plugged your guitar amp into a PA speaker, it would have nearly the same effect. That is what Denny was trying to produce with the top boost circuit, but utilizing a regular speaker.

The original bright channel of an AC30 was pretty bright, while the normal channel was actually rather muddy and dark. The Bright channel utilizes a 500pf coupling cap, which is very small, cutting off lots of bass and even some mid frequencies. It also utilized 220k plate resistors which kind of makes the stage seem compressed, punchy, and abrupt, which adds to that chime and stacatto-like sound it has. I.E. It doesn't bloom and sound bubbly like a Fender does. With no feedback loop in the power section, the amp is allowed to sound the way it does, which is why the cut control exists. Without it, the amp would be very brash. Even with the cut turned all the way down ( least amount of cut ) it still has quite the effect on the output stage. If you were to remove the cut control altogether, it would get VERY VERY bright.

[Securb]

I love when you post. I always learn something.