JJ ECC803S / 12AX7 Long Plate Preamp Tube | Evatco
Equivalent to 5751, 7025 & ECC803
SKU code: 12ax7803jj
JJ Electronics 12AX7 / ECC803S Long Plate Preamp Tube
JJ Electronics has built a reputation for producing valves that genuinely meet the demands of tube and valve amplifiers, and the 12AX7 ECC803S long plate preamp tube is a standout example. It's sensational value for money and a tube we consistently recommend at Evatco.
JJ 12AX7 ECC803S Twin Triode — What Makes It Different
The JJ ECC803S (also correctly referred to as a 12AX7 — both names describe the same tube) is a long-plate version of the standard 12AX7. Its larger plates are specifically designed to bring more low-end and bass response through the signal, giving it a fuller low-frequency character than a standard-plate 12AX7.
Tonally, expect a rich, full sound with creamy distortion, along with the added low-frequency body the long plate design provides. A spiral filament construction helps reduce microphonics, making it a quieter, more stable performer.
Best suited to: Hi-Fi preamp applications, though it performs well in most 12AX7 circuits generally. It's less commonly reached for by guitarists chasing a brighter or tighter top end, but works well across the board.
Fitment note: Because the ECC803S is taller than a standard 12AX7, check available clearance if you're fitting it into a combo amp — some chassis have tight headroom and this tube may not clear.
Specifications
- Glass height: 49.2mm
- Pins to top of glass: 56.3mm (minimum clearance required)
- Width: 22mm
- Sold in retail quantities only
Not sure which valve suits your amp's V1 position? See our guide: Selecting the Right Tube for the V1 Position
For more on how preamp tubes differ from one another, read: Understanding Preamp Tube Differences
Browse the full range: 12AX7 / ECC83 Preamp Tubes
12AX7 vs ECC803S: What's the Difference?
Electrically, the JJ ECC803S and a standard JJ 12AX7 share the same gain structure and pin-out, so they're fully interchangeable in any 12AX7 socket. The difference comes down to construction: the ECC803S uses longer plates, which increases their surface area and shifts the tube's response toward more low-end and bass, giving it a fuller, rounder low-frequency character than the standard-plate 12AX7. The trade-off is physical size — the ECC803S is noticeably taller, so it needs more clearance above the socket, which can be an issue in combo amps with tight chassis space. In short: choose the standard 12AX7 for a tighter, more traditional response and easier fitment; choose the ECC803S when you want extra low-end body and have the vertical clearance to fit it, particularly in Hi-Fi preamp stages.
| SKU | 12ax7803jj |
| Brand | JJ Electronics |
| Shipping Weight | 0.1100kg |
| Shipping Width | 0.050m |
| Shipping Height | 0.050m |
| Shipping Length | 0.090m |
| Shipping Cubic | 0.000225000m3 |
| Unit Of Measure | ea |
| Assembled Length | 0.070m |
| Assembled Height | 0.020m |
| Assembled Width | 0.020m |
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