Тип: Guitar Tube Head (Модифицирана - описние по-долу)
Лампи: 5 x ECC83 + 4 x EL84
Мощност: 50 W
Брой канали: 2
Корекции: Volume, Master, Lead Master, 3-band EQ, Reverb, Presence
Входове/изходи: input, speaker outputs, footswitch in, effects loop, direct
Състояние: 8/10 (козметично)
Made in USA. Incl. footswith
List of mods and reasons:
1. Re-capped with high quality F&T capacitors - Self explanatory
2. Custom High-Quality 230V Power Transformer This removed the unpleasant sag and "buzz" after the note and quite considerably helped with cooling. The transformer itself is larger with more iron, so the amp sounds bolder and stronger. Also being a custom ordered unit I opted to lower the unreasonably high B+ voltages. EL84 can run on the stock B+ (440V) but they don't last more that 8-9 months (the JJ I had before fried in 8 months). Also running EL84 so hot - in layman's terms - chokes the amp,, reduces the headroom and kills the great responsiveness of a good EL84 tube. The reasoning Mesa use such high voltages on these and similar amps is to get closer to the "rated power". But this amp is definitely not pushing clean 50W.
Now the amp is running 395V on the plates - again considered high for EL84s by some. To compensate and prolong tube life I opted for using NOS Military Russian tubes that can withstand very harsh work conditions - the 6P14P-EVs. They sound tighter but rounder on the top end and don't mind being pushed on daily basis. Side note: The stock power transf. uses part of the HT secondary for the footswitch and Graphic EQ supply. Gregg from Garland Amps advised me to order the replacement power transformer with a separate 50V winding for the FSW/GEQ supply for cleaner work.
3. Changing preamp voltages. Getting lower B+ voltages (see point 2.) automatically means lower preamp voltages. In this amp the stock pre voltages are pretty low IMO. This reduces the 12AX7's voltage swing so it clips earlier. When you raise the plate voltage of preamp tubes you increase the headroom of the tube (more signal can pass trough). So I bumped the stock 240V to 340V. A big jump that brought the amp to life.
4. Added a 120mm cooling fan - Extracting heat from the chassis
5. V1 Lead Gain mod (the small knob below the input jack)-This mod is quite common for the Caliber series (.22, .50 and Studio Calibers). It's basically adding a separate gain knob on the lead channel so you can better balance the amount of gain in the who channels. It also gives a cool way to shape the lead gain structure - it can go from doom-y, sludgy dark tone, to fuzz-like old school to modern, tight sound. I used the Footswitch jack hole for the Lead Gain pot and moved the FSW jack on the back panel. It's a really clean way to do it. I covered the label but It's reversible.
6. Added a trim pot on the FX-Loop send stage. This amp in it's stock form LOVES to overdrive pedals in the loop, so I replaced a resistor-to-ground on the send stage with a Trim Pot so it can be easily manipulated. But lowering the send level meant the whole amp it's going to be quieter(not driving the output stages hard enough) so I revised the return stage as well. Also I removed a bight cap in the FX Loop stage to smooth out the whole preamp. Update 2019: 75pF on FX Loop added back
7. Slightly bigger Cathode Bypass Capacitors on V2B and V3A for deeper voice. Update 2021: Reverted to original.
8. Changed input and output capacitors on the Graphic EQ. - Many people complain the GEQ on some of these Calibers "eats tone". It's because the input of the GEQ is essentially a High-Pass filter centered around 50Hz in stock form. Graphic EQs in Mark series for instance are High-passed way lower.
9. Moved the Presence control in the FB loop - Way smoother and more useful in the output stage than in the preamp IMO. Update 2021: Reverted to original.
10. Not really a mod - Removing V4 (Reverb Tube). Removing this tube gets rid of some signal phasing issues the reverb circuit introduces. If you play blues/rock and hard rock its not an issue. But if you are going for high-gain metal tones it can really tighten the signal and maybe give you a little bit of a gain boost.
