JPB-24 - Mahasha


Specifications

Input impedance:

1 Megohm

Output impedance:

8 Ohms

Preamp tubes:

One 12AU7, one 12AX7,

Power tubes:

Two 5881

High voltage:

402 Volts

Filament heaters:

6.3V A/C

Output power:

24W RMS into 8 ohms

Operation voltage

115V A/C 60Hz

Internal speaker:

Weber 8F150 8"

Internal speaker impedance:

8 Ohms

Internal speaker power handling:

25W

External speakers:

None

Height:

13”

Width:

12”

Depth:

9”

Weight:

26 pounds

Covering:

Green Tolex *

Cabinet cleaning:

Moist cloth, dish-washing liquid


 Portability, simplicity, power, and tone…These were the design criteria for Mahasha.
My approach to amp design/construction is pretty simple: I build what I want to use myself, one amp at a time. That way, if nobody ever buys one, who cares? I have my ideal amp for my own use. If/when I sell one, then I’ll build another.

Since starting to design my own amps in 2009, I’ve assembled numerous successful prototypes, embodying dozens of unique features and topologies. When it came time to choose just one as my premier model offering, there was little doubt that would be the JPB-24 because it is the design which, if I never sell a single unit, I will be perfectly happy to have as my only amp.

Three goals underlie this design.

First, foremost, and almost requiring no mention, it had to sound great, for a multitude of styles and usages, and had to pack adequate cojones to hang with a full band, including an acoustic drummer.

Second, it had to be compact: something I can easily stow in the tiny trunk of a modern car, along with my guitar case.  With my knees not what they once were, and many venues located atop flights of stairs, I wanted to be able to grab my amp in one hand, my guitar case in the other, and arrive ready to play with just a single trip.

Third, it had to be simple. With 40 years experience as a Computer Systems Engineer, I am anything but a technophobe; nevertheless, when it comes time to make music, I prefer to leave my pocket protector at home and shift fully into music making mode. Moreover, after a couple of beers a/o a toke or two, the last thing with which I care to contend is a control panel that resembles a jumbo jet console! 

Despite its diminutive size, Mahasha packs a 24W punch, courtesy of a pair of 5881 output tubes, cathode biased. (A 45-watt version, with the same size cabinet but a 10” speaker, will be available shortly.)

The speaker is a remarkable little Weber Vintage Series 8F150. 

Weber describes this little giant as follows:

8”, 30oz Ceramic magnet, 25 watts, 1-1/2” voice coil, ribbed cone. Big, strong, well controlled low end. Detailed, later breakup. Very loud and aggressive with a lot of punch and dynamics for an 8” speaker. 

I would disagree only to say it has a lot of punch and dynamics ... period!

Despite advances in relevant technologies, old mind-sets persist, and people automatically associate an eight-inch speaker with wimpy little practice amps, but this can be a mistake. We don’t question the punishing bass levels available in some car sound systems, even though they are often produced by speakers as small as four inches or even less. Many state-of-the-art home entertainment speakers and even PA-systems employ arrays of small transducers. One simply doesn’t need a massive cone to move a lot of air these days.

Weber will provide this same speaker in a 50W version on a custom basis, so for my 45-Watt version, I will be shrinking the cabinet slightly for the 8” version, or putting a 10” model in the existing Mahasha cabinet. I have side-by-sided this amp with the internal speaker and with an external 1X15” (Eminence Legend 1518)  cabinet, and the internal speaker acquits itself admirably. The amp is easily capable of pushing a 4X12 half stack if more volume is required.

The chassis is extra-heavy 12-gauge aluminum. 

My goal of maximizing simplicity and portability meant foregoing such extraneous features as multiple channels,foot switching, and effects. My view is that while these features may be nice to have (particularly if size and weight are of no concern), they are inherently extraneous to the essential function of a tube amplifier. Don’t misunderstand; I’m a big fan of reverb, but the quality of today's reverb pedals makes implementing this function with tubes something of an anachronism. If I was willing to allow additional space and transformer capability for one or two additional tubes, there other functions to which I would apply them--additional switchable gain stages, for example. As it stands, I simply pack 2 small pedals into my guitar case: a Boss FRV-1 ‘63 Fender Reverb and a Danelectro Transparent Overdrive and I have everything I need.

Another consideration is that the more circuitry you pour into a given space, the more there is to go wrong, and the more your signal is apt to be compromised/degraded. 

Finally, this amp is designed to offer maximum clean headroom until you reach the point of everything being ‘dimed’. This was a deliberate decision. If you NEVER need to be loud and clear, then a roaring metal machine may be for you. On the other hand, there are myriad ways to create a great dirty sound, regardless of your tastes, but if the clean headroom isn’t there, there’s no way to create it after the fact. Again, these are simply my priorities, not a critique of the priorities of others. If this is what you want, then this is an amp that does it exceedingly well.

You can find out more about what's inside here: The Cascodyne Architecture.

Price: $1,495.00





Subpages (3): Demos Pictures User Manual
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