All our preamp tubes are stringently tested for noise and microphonics using Amplitrex testers driving an external amp. There is no extra charge for low noise and microphonics testing like with other tube vendors. Additionally the tubes undergo a battery of tests for basic performance characteristics and faults such as: Emissions, Transconductance, H-K and Grid leakage, etc... If a tube does not pass our strict performance criteria it's tossed or sent back to JJ Electronic for evaluation.
The JJ 5751 is a high quality, low noise tube built to classic 5751 specs. Although this tube uses the classic short plate design, it was engineered from the inside out as a purpose built 5751 rather than a low test 12AX7.
The 5751 is about 25% lower in gain than a traditional 12AX7. We recommend these in input stages where players are looking for more headroom and a cleaner overall amp. We also use them in specific stages of higher gain amps to tame and even out overdrive channels that go beyond the gain/distortion requirements of the player.
Keep in mind reducing gain generally has the effect of decreasing high end response. If that's not desired checkout the gold pin 5751 variant as it retains more bandwidth than the original non-gold pin tube.
