This line drawing by David Szabados, originally published at legendarytones.com, shows how EVH achieved the signature brown sound in the studio. Now that you have the setup, all you need is the technique.
1. MXR e.q. set up as midboost (* only occasionally used depending on the guitar)
2. Marshall plexi Super Lead, unmodified, although simple modifications such as a cascaded input stage or added gain through capacitor/resistor exchanges may have been made.
3. Ohmite VARIAC set to approximately 90 Volts A/C
4. Dummy Load
5. MXR Flanger
6. MXR Phase 90 (** This was sometimes put in front of the amp instead of after the dummy load)
7. Echoplex EP3
8. (***Equalization sometimes added prior to power amp)
9. H & H power amp
10. Various Marshall cabinets (sometimes two, sometimes four) used with various Celestion and JBL speakers-via legendarytones.com