Not sure, but I have heard he used a Kasha QuikMod, which is basically a quick way of adding another 12AX7 gain stage to your tube preamp.
They're still selling them (latest version is III)
https://www.kashaamplifiers.com/product-page/quikmod3
Big Crunch Sound:
The 2017 models just arrived and I have many of them to sell. If you want a little more out of your amp or if you want to hear what two tube gain stages will do to your Fender, Marshall, Vox or even a Valve Jr, you should get this thing. Jake E. Lee used them with Badlands on tours and studios across the globe. Many professional recording studios use them to hot rod amps instantly without ever touching the electronics inside. Producers and mixing engineers like Keith Olsen, Tom Werman, Rhett Laurence and Mike Plotnikoff used them to create tone with many classic amps and bands of the 80s, 90s and current.
The best thing about it is that it can be moved to any amp. It's like you are creating new tone with an amp you have used thousands of times. It's safe, simple install and the results are mind blowing. You can't get this type of tone or gain from a pedal.
QUIKMOD® is the ultimate DIY mod for your amp. In less than 5 minutes, you will have a professional mod from a well-known amp designer without ever sending it in.
The QUIKMOD modifies amplifiers producing a HUGE amount of musical gain, more than enough for even the most gain enthusiasts. Converts a one channel tube amp into a two channel or a two channel into a three channel with a powerhouse of tone and versatility. The QM3 2017 is the latest model, and now includes easy access to your tubes and tube Boost for even more gain since you never have enough of it.
Installing the QUICKMOD is easy... The QUIKMOD cable plugs into the first tube or V1 of most tube amplifiers. Power for the QUIKMOD comes from the QUIKMOD cable included with every QUIKMOD. It is safe and easy to install, just like replacing a tube. Once installed, it can instantly switch between normal and QUIKMOD sound via the rear manual switch or any standard single channel footswitch (not included). The QUIKMOD comes with one 12AX7 pre-amp tube and a slot you put the tube taken out of the amp. The QUIKMOD is a single channel preamp designed to run in standard Marshall®, Fender®, or Vox® architectures. For the most part, these are manufacturers that have provided the bench mark designs for most of the high-end boutique and custom designed amplifiers to date.
You can experiment with different tube types such as 12AT7, 12AY7 and 12AU7 for a plethera of options for gain and tone.
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I had a Whiteface reissue for a while and I can attest to the grindy/crunch effect like what you hear in Nuno Bettencourts tone and it's cool I just never connected that with Jake's tone. I love rabbit holes like this though................................ 