LunchBox Instrument Amplifier

I was using the Quark Minor amplifier a lot and with the ToneBack selector switch in the center which basically means no Tone control, only Volume. I was thinking of a Combo that would work more due to the stupid Covid Virus…. so low wattage, all in one combo that is smaller, but could do so much more if required.

The idea came to me of this design. Something you could use now and then use after you start to go out and play again. The requirements were as follows:
a) Volume Only, make the amp full range so it would work with any instrument.
b) Headphone ok let’s not wake the neighbors.
c) Optional transformer coupled DI would give you connection to your DAW or House PA system
d) 9V Stomp box supply to you can power a small analog board.
e) Light with a cover that has a pocket for cables.
f) All Tube design, YES even a tube rectifier. Typically not found in amps of this size.

Ok what tubes to use? I had this power transformer that looked awesome that was international (120/240Vac 50/60Hz) and had everything i needed. So starting with the 6072A my favorite gain tube, I then looked for an output tube. So many companies use the El84 for this job. Well there are these great 5686 tubes which are like a smaller version of an EL84 and you can get NOS ones that sound great ok. Oh the power transformer only has 0.4A of filament current left. I looked around and found the 6ZY5G rectifier. Wonder how it sounds and works. WOW this came together and it’s dead quiet and has 3W and the frequency response is stellar through this amazing speaker, wonder how the Warehouse 8” speaker would be in this design? Well it sounds incredible in both the Ceramic and Alnico versions.

Why a tube rectifier? Tubes like to be brought up to their high voltage slowly and you can do that with solid state. But think about this… Solid State rectifiers will pass everything onto the power supply: WIFI, DC DC switching noise, Ethernet POE, Cellular BS, Radio Station interference… you name it. A tube rectifier will not and even though all that garbage is way over our hearing, it still effects the performance.

I would classify this amp as an instrument amp. It would work great with any instrument, Harp, Guitar, Fiddle anything with a pickup. It is full range and wide open, nothing specific to guitar. But it really is killer for guitar!

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There is the standard version which uses Nichicon Audio Capacitors for the high voltage and bypass, Mial coupling capacitors and Mercury Magnetics output transformer.

The
TurboCharged model has the following upgrades:
1) MagneQuest custom over wound output transformer, limited quantities.
2) Black Gate capacitors for high voltage and bypass, look them up on eBay, current price there is $1122.00.
3) V-Cap ToneCap used for coupling.
4) Analysis Plus Speaker Harness cable.

Either version can be fitted with an optional transformer coupled DI. This version shipped with a TRS to XLR cable.

Tolex colors: Tweed, Red, Black, Black swirl, Carolina Blue, Pink, Dorthy Red Sparkle, Orange and Seafoam Green. Others available by request, see all the colors at MojoTone.com

Each amp is shipped with a 2.1mm extension cable and a 1->5 2.1mm splitter for the on board 9V/400ma stomp box supply. Also shipped is an IEC heavy duty power cord.

Prices $1000 and $1500 for TurboCharged version, DI + $250.00 all plus shipping.
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The main circuit board assembly:
Red capacitors are the Black Gate in the SuperCharged model.
Green is the transformer coupled DI.
Light Blue is the DC supply for the heater for the 6072A/12AY7A
Orange is the constant current source biasing used on the 5686
Dark Blue is the isolated 9V regulated supply with OSCONS and dedicated CMC inductor, with 9V regulator.
Purple you have never seen this in a guitar amplifier, we bias the input triode (6072A/12AY7A) with an LED, super quiet and fixes the input for really high head room.