Data Sheets for 12AX7 (original Mullard data) PDF File Click Here For hifi & mic preamps, like Dynaco PAS, Altec 1567, etc we suggest JJ/Tesla (either kind) lowest noise & best tonal balance. We suggest the Electro-Harmonix or Philips tubes for more "vintage" tone in Fenders, and other US made guitar amps. JJ/Teslas seem to work best in Marshalls. The new Electro Harmonix 12AX7EH is a good choice in Marshalls for those who want a more "vintage" sound or think the JJ/Teslas are too bright. If you're looking for less gain & more headroom, try a Sovtek 5751 or ElectroHarmonix 12AY7. 12AX7 and 5751 (equiv. to ECC83, 12AX7, 7025) All of the 12AX7 types listed may be used to replace 7025 or 12AX7A. Note that matched pairs of 12AX7 are not required for guitar amplifiers. You can find curve plots for 12AX7 Chinese, Sovtek, and Tesla on our Tube Data Page. You can use 5751 to replace 12AX7 for less gain in many applications (guitar, mic & passive EQ phono preamps). All of the tubes on this page will replace these numbers: 12AX7, 12AX7A, 7025, ECC83. 12AX7 types 12axec7057 12AX7/ECC83S Tesla/JJ Tube Tesla/JJ 12AX7/ECC83 12ax7tesla$32.95 12AX7 ECC803 Tesla JJ Tube These are a reissue of an earlier tube that used to be made by the Tesla company, this has a long ribbed plate rather than the short wide plate of the regular JJ ECC83. ecc803jj$38.95 Triode, USA Customer Service M-F 9AM-4PM CT 1-800-774-3201 Email us Anytime: questions@triodestore.com