BITMO BLUES J MOD KIT for the AMPEG J-20 GUITAR AMP

----------------- BitMo™Blues J Mod Kit ---------------

for theAmpeg J-20 Guitar amp

(Amp not included)

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This is a great and often over-looked new guitar amp.

· Hand wired with quality components (2nd picture shows stock circuit)

· Great bias tremolo

· Very cool looking - classic

· Resonant cabinet and light to carry

Specs from Ampeg - RMS Power Output: 20W, Fixed bias, Class AB
Speaker: 1 x 12" alnico
Preamp Tubes: Tubes (3 x 12AX7)
Power Amp Tubes: Tubes (2 x 6V6)
Rectifier: Tube (5AR4)
Controls: Volume, Tone
Effects: Tremolo
Footswitch: Tremolo On/Off
Output: Dual ¼" jacks
Dimensions (W x H x D inches): 20 x 17.5 x 9.75
Weight: 25 Pounds

These amps are going for very reasonable prices (less than $500 if you look around). Where else can you get a hand wired, 20 watt classic looking amp for these few $$$?

The stock amp does have a couple limitations – While the clean is full and beautiful, and the overdrive is classic tube, the in-between range can be a bit ragged. Voicing wise, it is kind of a “one trick pony” (it is a very good trick, however).

With the BitMo Blues J mods, this amp does not sound like other modern amps in my collection. (This is a good thing). It really fills out my tonal options for recording and gigging. I would say it is especially suited to blues (also sounds fabulous with harmonica), classic rock (killer for slide guitar), rock-a-billy, or jazz.

If you have any kind of arch-top guitar, you need to check this out!

This kit includes several modifications to the amp’s circuitry.

· The useless Bright channel is re-voiced ( the amp is too bright anyway, IMHO).

· The 2 input channels are ganged in parallel from one input jack

· The 2^nd input jack is removed and replaced with a version of the famous BitMo 3-way Voicing/Gain switch, (see switch near input jack in the 1st picture) specially configured to enhance the attributes of this amp. My descriptions of the settings are:

o Thick – great for jazz, emphasizes the “doink” of a Gretsch for rock-a-billy, woman tone at higher gain settings

o Crispy – a kind of hyper tweed, very much like a tweed Deluxe – fat and crispy as pan-fried chicken!

o Punch – great for a bluesy crunch or full-on overdrive

· The 2^nd preamp gain stage bias is changed

· The bias is changed on the output tubes (I recommend that you have the amp professionally re-biased for your favorite set of output tubes, but I think the bias resister included with the kit is a better default than the stock one – it seems to make the crossover to distortion range much smoother, especially with the tremolo engaged.)

· Tweakage suggestions for tubes, speakers, etc.

Roll your own J-20!

Assumptions, warnings, etc:

·

· These amps contain potentially lethal voltages. You must discharge the capacitors. They are not “self-discharging” like some more modern amps. I include a discharging probe.

· Tools you will need – screwdriver, soldering iron, rosin core solder, wire stripper, needle nose pliers.

I do not recommend this kit for complete novices.

** Check out my other mod kits, feedback rating and comments from hundreds of satisfied customers. **

Several people have suggested changing the speaker. I prefer Weber ceramic Blue Dogs.