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The Fender Blues Junior III and IV use a trio of 12AX7 preamp tubes and a matched EL84 output pair; Fender’s published IV specification confirms that complement, and the III manual identifies a 12AX7 plus a matched EL84 pair. Order by tube position and generation, not by a generic “Fender tube” label. Power tubes should be a matched EL84 pair; a complete retube covers every preamp position plus that pair. Tube amplifiers contain hazardous voltages after unplugging: do not open the chassis or change bias-related components unless qualified to service valve equipment.
| # | Product | Price | Where to buy |
|---|---|---|---|
| 1 | Fender Groove Tubes EL84 Duet | $45-$65 | Amazon · eBay |
| 2 | Fender Groove Tubes 12AX7 | $20-$35 | Amazon · eBay |
| 3 | JJ Electronics EL84 Matched Pair | $35-$55 | Amazon · eBay |
| 4 | JJ ECC83S / 12AX7 | $18-$30 | Amazon · eBay |
| 5 | Tung-Sol 12AX7 | $25-$40 | Amazon · eBay |
| 6 | Electro-Harmonix EL84 Matched Pair | $35-$55 | Amazon · eBay |
| 7 | Electro-Harmonix 12AX7EH | $20-$35 | Amazon · eBay |
| 8 | Genalex Gold Lion EL84 Matched Pair | $60-$90 | Amazon · eBay |
| 9 | Ruby 12AX7ACZ HG | $20-$35 | Amazon · eBay |
The picks, in detail
Fender Groove Tubes EL84 Duet
Fender’s matched EL84 output pair, the factory-style format for the Blues Junior power section.
- matched pair
- EL84 output tubes
- Fender grading
- Correct two-tube output format
- direct factory-family replacement
- Does not replace three preamp tubes
Fender Groove Tubes 12AX7
A current-production 12AX7 preamp tube for one of the Blues Junior’s three small-signal positions.
- 12AX7 type
- preamp position
- current production
- Correct preamp family
- available singly
- Three are needed for a full preamp change
JJ Electronics EL84 Matched Pair
A current-production matched EL84 pair for the Blues Junior output stage.
- EL84 pair
- matched grading
- current manufacture
- Appropriate paired power-tube format
- widely stocked
- Have a technician assess any bias/service concern
JJ ECC83S / 12AX7
A current-production 12AX7/ECC83 option for a Blues Junior preamp position.
- ECC83/12AX7 designation
- preamp tube
- current manufacture
- Correct type
- easy individual replacement
- One tube is not a full amp set
Tung-Sol 12AX7
A current-production 12AX7 for one of the three preamp slots, not an EL84 substitute.
- 12AX7 type
- preamp use
- single tube
- Correct small-signal type
- available individually
- Does not replace output pair
Electro-Harmonix EL84 Matched Pair
A current-production matched EL84 pair for the two output positions.
- EL84 output tubes
- matched pair
- current production
- Correct output count
- common tube type
- Installation/service safety still applies
Electro-Harmonix 12AX7EH
A current-production 12AX7 preamp tube, supplied singly for the three-tube preamp complement.
- 12AX7 type
- preamp tube
- single tube
- Correct family for V1-V3-type positions
- current manufacture
- Buy quantity by the actual service plan
Genalex Gold Lion EL84 Matched Pair
A matched current-production EL84 pair for the output stage, sold as a premium alternative.
- EL84 pair
- matched
- current production
- Correct paired format
- clearly differentiated from preamp tubes
- Costs more than basic pairs
Ruby 12AX7ACZ HG
A current-production selected 12AX7 used in Blues Junior III/IV-oriented tube kits for a preamp position.
- 12AX7 type
- selected grade
- preamp tube
- Correct preamp specification
- kit-compatible format
- Selection does not eliminate amp-service needs
Buying tips
- The EL84s are the two power tubes; the 12AX7s are preamp tubes—do not confuse the counts.
- Matched means the pair is selected together; it does not certify an amplifier is safe or correctly serviced.
- Avoid unverified NOS listings if provenance, testing and return terms are unclear; current-production tubes are the predictable baseline.
As an Amazon Associate and eBay Partner, toptenpick.com earns from qualifying purchases. Prices and availability are subject to change.