Rightly or wrongly, I believe there are benefits to circuit designs that are simple. Thus, having a signal path, with as few components in it to strangle or color the ultimate sonic results. Sometimes, less, is more & this product significantly performs greater than the sum of it's parts.
With this in mind I was drawn to the Zephyr & certainly in this case it has confirmed my beliefs.
After four weeks of much knob twiddling, I agree with the statement in the website description, that the EQ controls are not intuitive. However, as hard as I tried, I could not get an unusable, bad sound out of it, which has not been the case with all of my previous amps ! In fact nearly every setting had something interesting to offer.
This, I believe is down to the unique 'James Tonestack' coupled with the superbly useful 'Range Control'. A full description can be accessed on the Arkham website.
I do not intend to repeat all of the other users glowing comments, but, can only add that sonically it is unusually smooth & balanced, with a full bodied realistic immediacy & presence, rounded off with pleasant articulate harmonics producing that sort of 'organic' type of texture. My Lakland & Sire basses have never sounded better.
To aid in understanding what the EQ can do, I have attached some Frequency Response plots, illustrating some of the possible changes. Please take into account that these plots are produced by my bass speaker cab. which, undoubtably, will be different than your cabs. But the relative changes are a fair reflection of what to expect.
There is more that I could illustrate with plots, that can reveal the interesting interaction & the symbiotic relationship between the tone controls, but, it would take too much space to cover it all. Another time perhaps. This is just a primer.
Whilst there are other outstanding pre amps that I have not had the chance to try, the Zephyr should certainly be number One on your list to try. The price is a bargain & absolutely belies it's superb sound quality.
1. Red line Controls, including Gain,Pre Out & Range set at 12o'clock
boost switches off. This is a accurate plot of the
woofers' factory spec confirming the
flat response of the mid position controls
Blue line Adjustment of Treble & Bass
2. Red line Range control turned fully counter clockwise
3. Red line Range control fully clockwise
4. Red line Hi switch on
5. Red line Mid switch on
6. Red line Lo switch on
7. Red line HPF on
The knobs & boosts interact with each other for more permutations.