(29 votes, average: 4.07 out of 5)
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Electro-Harmonix has released a low noise, low microphonic version of the 12AX7 that meets all specifications required for the tube to be designated 7025. The original 7025 tube was a 12AX7 that was tested and selected for the lowest noise and microphonics for use in the critical first preamp stages of amplifiers where noise and microphonics could be an issue. In order to ensure that the 7025 specification is consistently met, Electro-Harmonix has redesigned the structure of the 12AX7 and has implemented construction techniques to ensure the absolute lowest noise and microphonics possible. In all samples tested, noise and microphonics could not be detected.
The Electro-Harmonix 7025EH has a mid-range that gives clarity and definition to the sound and a smooth top end for warmth and balance. With these characteristics, along with the exceptionally low noise and low microphonics, the Electro-Harmonix 7025EH will work equally well in vintage and modern high-gain guitar amplifiers, as well as sensitive phono preamps.
The Electro-Harmonix 7025/12AX7 arrives with a completely new plate structure for this line, though it is clearly derived from their 6922 design and shares a striking resemblance to the legendary Frame Grid tubes from Telefunken and Tesla.
In terms of technical performance, I am thoroughly impressed. This tube clocked in at -89dB of noise, which is exceptional compared to the typical 12AX7 average of -86dB. Furthermore, it is practically immune to microphonics. Even under a hard physical strike, feedback only reached -84dB, whereas standard tubes often crash down to -70dB. When compared to a vintage Amperex Bugle Boy 7025, the Electro-Harmonix was surprisingly quieter and more stable, as the vintage Holland-made tube exhibited significantly more noise and microphonics.
The sonic profile is transparent and dynamic, offering an expansive soundstage that mirrors the characteristics of a high-quality 6922. While it may not be quite as “involving” or lush as the Genalex Gold Lion B759, it remains a top-tier performer. The only real caveat is the gain: rather than the standard 100 typical of a 12AX7, these measure between 80-90. This puts them in a middle ground—hotter than a 5751, but slightly lower than a spec-standard 12AX7.
Final Verdict: An outstanding modern production tube that outperforms many vintage counterparts in noise floor and stability. It is a must-buy for high-gain applications where silence and clarity are paramount, provided you don’t mind a slightly lower gain factor.
Bought it from your store and tried it in my Nobsound 12AX7 preamp. The tube is very transparent and very quiet.
This is becoming the hottest seller of all new production tubes. Not only that, it ‘s the highest-rated tube of all new production/reissue tubes listed on the site.