JJ 5751 Tube Review
As some of you may know, the 5751 is similar to the very common 12AX7 aka 7025 and ECC83 but with a bit less gain. In this review, I’ve compared the new 5751 with the JJ ECC83S (12AX7) which has been my standard workhorse guitar preamp tube for several years.
A casual visual inspection would give the impression that it’s the same as the JJ ECC83S and some have even suggested that the factory may have re-labeled the ECC83s tubes that measured a little less gain than average. This is not the case. A closer inspection reveals that the new tube’s inner construction more closely resembles their ECC81 (12AT7) but some of the materials are obviously different. It is indeed a totally new tube.
In our test, we used a vintage Fender Vibrolux Reverb and installed the tube in the V2 slot which is the first gain stage for the tremolo/reverb channel of the amp and is critical for good tone and low noise.
Tonally, the tube is smooth and balanced but lacks some of the harmonic complexity of the ECC83S. It also produces just a bit less shimmer and sparkle in the treble ranges. It is however a good sounding tube with no harsh overtones, low noise and low microphonics. It can be very useful for amps that need a little taming in the treble and gain. Gain wise, it does make a noticeable difference, allowing for at least another number on the volume control to reach similar breakup of a 12AX7.
Does it give you more clean headroom? Well, maybe just a touch if you have hot pickups but headroom in these amps is limited by the output power and speaker efficiency. It will however give you a wider range of adjustment within the clean zone of your volume control setting. It will break up at about the same actual sound pressure level as any other preamp tube but you might find it easier to adjust your settings when playing at lower volume.
Overall, we like the new 5751 and we expect it to eventually find a place in a lot of different amps. You can plug it into any tube socket that calls for a 12AX7, 12AY7 and most 12AT7 applications.