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.
We recommend these for long tail phase inverter stages or anywhere that symmetrical performance between triodes is sought. It also gives you the plate current and transconductance spec for each triode which is nice if you're trying to keep records or maintain exact consistency from tube to tube. If you need multiple matched tubes please see our "Balanced and Matched" option.
The Gold Pin JJ 5751 is based on the same construction as the original JJ 5751. The internal components go through additional selection and processing during assembly. After working with these tubes for several years we can confirm they do test more consistently and sound noticeably different than the original JJ 5751.
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.
The gold pin variant will retain more highs compared to the original 5751 when used as a 12AX7 substitute.
