‘Mack’ of Mack Amps on EL84s and Tone Controls

April 7, 2010 | By | Reply More
It looks so innocent...but is dirty!

It looks so innocent...but is dirty!

Part 2

Here’s the second part of the EL84-focused interview with Don Mackrill of Mack Amps, which is based in Ontario, Canada.

WoodyTone: What tonal properties can you get from EL84s that you can’t get from other power tubes?

Don: In my opinion, EL84s and EL34s are very similar. 6L6s and 6V6s are too, but are noticeably different from 84s and 34s. To my ears, 84s produce tone that is different than L6s and V6s. Chimey vs. creamy cleans, respectively. Aggressive, upper-mid range emphasized overdrive/distortion vs. thicker, darker OD/distortion.

Marshalls are known for that upper-mid tone shape – can you really get that tone out of the Heatseeker?

Heatseekers were not designed to specifically emulate Marshall tone. I was after a combination of Marshall and Vox tonalities. That said, the upper-midrange Marshall aggressiveness and ‘crush’ is definitely present in the Heatseeker’s tone.

You mention on your website the simplicity of your circuit as being tone-enhancing, or maybe ‘tone-preserving’ is better. Can you explain that a little?

I truly believe that less is more. The best tone is achieved by designing a signal path that is as uncluttered as possible. Think about Trainwreck amps for example. They are revered as iconic tone machines, and they’re very simple designs with few controls.

One thing I think really contributes to opening up an amp’s tone is to NOT use typical treble-middle-bass tone controls – commonly referred to as a ‘TMB tone stacks’ – because passive tone controls reduce gain and alter the frequency response of the circuit, regardless of their settings. [In 2007 Don wrote a post on his website about this.]

Our amps only have a treble control. It’s useful for rolling off high frequencies to remove the ‘ice pickiness’ from a Tele or to tame bright-sounding guitars. But when it’s on 10 it’s out of the circuit. At that point you hear what your guitar really sounds like – no tone-shaping controls are there cutting gain and altering the frequency response. So it’s pure electric guitar tone. You may be surprised at what that sounds like. I think it sounds great.

The only other tone-shaping control on our Heatseeker and Skyraider amps is a switch that boosts gain and bass frequencies. That’s helpful for adjusting the amp’s voicing for different guitars and producing more bottom-end grind. One thing to note is that this control alters the preamp tube’s response – it does not add components in the signal path. In other words, while this does affect tone and gain, it’s not adding more components in the actual signal path.

The other thing that a simple signal path produces is sensitivity. An amp that responds quickly to picking dynamics and changes in guitar volume is said to be sensitive. It’s a lot of fun to alter the gain response of an amp simply by changing your picking attack and also by making small changes to your guitar volume. Playing a ‘fast’ amp does reveal imperfections in your playing technique, but it opens up another universe of tone and performance possibilities.
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And there you have it – some insight on EL84s and amp construction. Bearing in mind that people can hear things differently and manufacturers often have different philosophies – which is partly why all amps sound different – I definitely learned a couple things. Hopefully you did too.

I want to play a Heatseeker now!

Here’s a vid. Not the greatest demo, but you can get a feel for the amp. I like what I’m hearing at about 0:55 and 1:09.

- End of Part 2 (of 2) -

Category: EL84s, Mack Amps

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