Vacuum Tube - 7025, Electro-Harmonix
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." -EHX
Accessory Items:
| Base | Noval | ||
| Base to Shoulder Height | 40mm ±2.5mm | ||
| Diameter | 22.5mm | ||
| Envelope Height | 49.5mm | ||
| Max Amplification Factor (filament 6.3V, plate 250V, grid -2V, grid resistance 1MΩ) | 110 | ||
| Max Cathode Current | 10mA | ||
| Max Cathodes-Heater Voltage | ±200V | ||
| Max Filament Voltage Parallel | 6.6V | ||
| Max Filament Voltage Series | 13.2V | ||
| Max Grid Back Current (filament 6.3V, plate 250V, grid -2V, grid resistance 1MΩ) | 0.2mA | ||
| Max Grid Resistance per Triode Fixed Bias | 1MΩ | ||
| Max Grid Resistance per Triode Self Bias | 2.2MΩ | ||
| Max Heater Current 6.3V | 370mA | ||
| Max Heater Current 12.6V | 185mA | ||
| Max Plate Current (filament 6.3V, plate 250V, grid -2V, grid resistance 1MΩ) | 2mA | ||
| Max Plate Current Difference between triodes (filament 6.3V, plate 250V, grid -2V, grid resistance 1MΩ) | ±40% | ||
| Max Plate Dissipation per triode | 1W | ||
| Max Plate Voltage | 300V | ||
| Max Temperature at most heated part of envelope | 368 | ||
| Min Amplification Factor (filament 6.3V, plate 250V, grid -2V, grid resistance 1MΩ) | 81 | ||
| Min Cathode-Heater insulation resistance (filament 6.3V, cathode-heater voltage ±200V) | 20MΩ | ||
| Min Heater Current 6.3V | 325mA | ||
| Min Heater Current 12.6V | 162mA | ||
| Min Plate Current (filament 6.3V, plate 250V, grid -2V, grid resistance 1MΩ) | 0.75mA | ||
| Min Slope of characteristic (filament 6.3V, plate 250V, grid -2V, grid resistance 1MΩ) | 1.1mA/V | ||
| Nominal Heater Current 6.3V | 347mA | ||
| Nominal Heater Current 12.6V | 173mA | ||
| Total Height | 56.5mm | ||
| Packaging Dimensions | 2.815 in. × 1.025 in. × 1.025 in. | ||
| Weight (Packaging) | 0.0375 lbs. | ||
 Datasheet | All Models |
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Product Reviews
Not impressed on at least two counts. First, one of the (4) 7025 tubes I got added a huge amount of hum to the amp. Obviously something wrong with the tube but it does say something (not good) about their quality control. Second, it was no quieter than the JJ 12AX7 that it replaced (which was the first tube, most sensitive in the audio chain). Same hum and hiss levels. So why does this cost 50% more? I'm sticking with JJ.
I put these in V1, V2 and the PI slots of my early 1990s Fender Vibroverb reissue - very nice warm sound and no discernable noise or hiss - certainly a noticeable reduction in noise from the previous tubes, which were the 'blue lettered' Philips JAN 12AX7 (although I put those in ten years ago, so maybe they had worn out). After using the 7025EH I don't think I will bother buying NOS tubes anymore as these fit all my requirements.
Great tube!
First, no cross-talk between triodes (thanks to shield between triodes), so when I turn the volume knob on my blfc Vibrolux amp all the way down, no sound from guitar comes thru the speakers. With Tung Sol 12AX7 reissue (which sounds brighter, but also very good, built more traditionaly, so has NO shield between triodes) I still could hear a bit of my guitar from the speakers with volume on the amp down thanks to crosstalk between triodes.
Second, GREAT sound! Warm and round, but still great articulation. If JJ ECC83s sounds mufled to you, try this new 7025EH there. If Tung Sol 12AX7 reissue sounds too sharp, try EH7025 there. It has very well balanced sound.No hard and piercing highs.
Third, I bought 4 pieces and no problems with microfonny, hiss and hum at all. Super. With Tung Sol 12AX7 sometimes I get a bad one with too much hiss.
Also to me, EH7025 sounds richer than Shuguang variants of 12AX7/ECC83/7025.
Thanks to EHX for new great tube.
Excellent for V1 and V2. Very quiet with great tone.