Ampeg SVT4PRO tube swap (with pictures)

[BrianVengeance]

Recently swapped out the preamp tubes on my SVT4PRO and took a few pictures, thought I'd post them up for anyone interested. Ridiculously simple process

The Ruby tubes are a lot cleaner sounding overall than the stock GTs (which at at least 6 years old at this point, maybe 7-8 depending on when the previous owner bought the head). Bass is tight and mids are solid, and the highs are clear but aren't quite shimmery or glassy. The preamp now has an ungodly amount of headroom before even tripping the input light... as in, crank the gain and get a running start and maybe you'll get a faint glow of recognition for your efforts.

RBI is a lot more expressive with the ability to crank the gain and get a hotter signal in, with all knobs feeling much more responsive. Its EQ simply outperforms the Ampeg EQ knobs at every turn (even more), and in turn the graphical EQ on the head is now quite useful for working with the curve. Low end overdrive is far more present and musical, but can still mud out and lose attack like any other OD / distortion if overdone.

Pups are still stock in the Fender MIA Jazz, and it feels like they're coming into their own with this upgrade. The parallel position is dark and approaching forceful, and switching to series really brings out a thick growl reminiscent of the P.

It basically took all of $50 and 30 minutes to fall back in love with my setup.


Amp racked up prior to operation:


Ruby 12AX7AC HG+ x1, HG x2:


Head unracked:


With top removed:


Top removed aerial, preamp board is in the bottom, tubes bottom left:


Closeup of tubes and stabilizer bar:


Closeup of stabilizer bar screws (inside):


Closeup of stabilizer bar screws (outside):


Closeup of stabilizer bar removed:


Closeup of preamp board with tubes removed (LTR = V1 V3 V2):


New glass installed!:



EDIT: now with working pictures!

[JimmyM]

Cool detail pics. Regarding the EQ of the 4 Pro vs the RBI...the RBI is designed to have a lot of range in tones that simply aren't available in most amps, from clean to super dirty, from big fat low end to painfully biting treble. The knobs in Sansamp stuff, however, are a lot more sensitive, which for me, while I love my VT Deluxe, makes it kind of difficult to dial in tones on the fly, and creates a fairly steep learning curve for a preamp. The 4 Pro may not quite have that much range, but is infinitely easier IMHO to dial up useful tones quickly.

[BrianVengeance]

Thanks Jimmy, that's probably a much better way of putting it. The Sansamp is a cruel mistress in that she'll happily let you dial in some less than ideal tones if you're just twisting knobs. The narrower EQ on the head itself makes it much more forgiving for dialing in something on the fly.