• Ryan

Inside & Analysis of a REAL John Mayer Two-Rock Signature Amplifier

Updated: Sep 14


Ah so excited to finally see the inside of one of these bad boys and learn about the features that make up the tone of John's Signature Two-Rock amps! As a reminder, I publish these insights and thoughts for educational purposes and not to undermine, destroy, or promote in any sort of way. The information is to guide someone someone to learn to build this amazing, out of production, amplifier.


On the Dumble amp clones and D-style pedals Facebook group, a generous forum member who was working on a JM Sig for a customer (it kept blowing a fuse) provided some really nice gut shots. Because of my own quest for information, as well as a few other members on My Stupid Mouth forum, these pics help with reference points. There were a few prototype and post production "signature" amps that were let out into the wild which did not flip the preamp section and did have pictures taken of the inside to help the information flow along.

Some of my notes that I cover in the YouTube video

  • The Wonderland layout as provided by Amplified Nation component values seems to be very accurate compared to the production amp.

  • The amp that Amplified Nation had included 100R resistors in the power section that is not present on the production amp.

  • The power caps on the AN amp are Illinois (IC) which is different than the production units.

  • The treble pot measures ~262k Ohm and marked with an "H" to indicate it's a high value.

Component lists

Some of this information is hard to say it's 100% accurate without seeing the components with my own eyes, however, I'm fairly certain the production unit uses the following components.

  • 1/2 watt (Draloric?) carbon film resistors mostly used throughout the circuit. Interestingly, they are E-26 decade values which I've never seen before.

  • 1/2 Watt carbon film 10M and 22M resistors are used on the local negative feedback side of things.

  • 100k Ohm Dale RN65D Military precision resistors used on voltage drop sections on the preamp board.

  • 1.54k Dale RN60D metal film cathode resistors on V1.

  • 1.82k Dale RN60D bass floor resistor.

  • 1 Watt metal film resistor used for the global negative feedback resistor.

  • Vishay 1kv ceramic disc capacitors used on the bright, mid, reverb, and other parts of the circuit where the yellow caps are used. I believe they are X5F dielectric type (yellow) and I suspect the red disc on the reverb might be a different tolerance or dielectric type.

  • I'm pretty sure the brown local negative feedback .047uF resistors are JB 473k metalized polyester based on Two Rock using them for a while throughout their amps. You can buy these capacitors from Cables & Connectors as an "NTE" brand.

  • Belton octal and 9 pins.

  • General Cable/Carol 18 ga hookup wire C2064 series.

  • Likely General Cable/Carol coax white wire or RG188.

  • Power Transformer: ClassicTone 40-16932 (about 10% lower voltage than a standard Fender Twin Reverb PT)

  • Choke: M1529C1 (replacement p/n is 40-18003)

  • Reverb Driver: M1529A1 (replacement p/n is 40-18034)

  • Output Transformer: ClassicTone 40-16852 (replacement p/n is 40-18013)

  • 20uf 500v supply capacitors are Sprague Atom

  • 220uf 350v supply capacitors are likely Ruby since Two-Rock used Ruby around this time period.

  • 9AB3C1B reverb pan - 3 spring long decay

As I learn more about the amp and other parts, I'll publish findings. If YouTube videos are your style, I made one with the same info as above :-) If you have any information to add, please contact me or comment on the YouTube video and I'd love to learn more!


#johnmayer #amplifier #analysis

2,580 views

© 2020 by  The Tone Geek.  Donations are appreciated via Amazon wish list. (Thank you in advance!!)