These are commonly used as phase inverters in McIntosh Hi-Fi amps, some Ampeg amps, and will yield the most clean headroom in many amps.

In the latest Fender Pro Series amps such as the Pro Reverb, Concert, and Twin, this tube in V2 (or a 12AY7), will drop the gain of the gain channel where some feel the tone is of a less intense or “buzzy” character. This will then allow a much wider range in the sweep of the volume and gain controls of this channel.

The Groove Tubes 12AX7M is a dual-triode vacuum tube based on the highly sought after Mullard 12AX7, which went out of production in the late 60's. Its unique triple mica design reduces tube hum and microphonics, and gives performance stability under the most demanding conditions, such as high gain tube guitar amps sitting on 4x12 cabs. This tube delivers rich, harmonically complex tone and midrange warmth that is just not available in any other currently manufactured tube today. It is also the only 12AX7 type tube on the market today that meets (or exceeds) 100% of the critical performance specs of a textbook 12AX7 such as transconductance (1600 mU) and current (1.2mA). The new 12AX7M is an excellent choice as a replacement tube for any amplifier design using a 12AX7, ECC83, or 7025 preamp tube. “Of course, the real test is how it sounds,” continued Pittman. “Our new 12AX7M will really ‘wake up' an old (or new) Fender, Ampeg. or Marshall tube amp!”

IF YOU DO PRE ORDER THESE, PLEASE DO NOT INCLUDE THEM ON ANY ORDER WITH OTHER ITEMS OR THIS MAY DELAY THE ENTIRE ORDER.

This tube is closest in specification to a 12AX7 and can be exchanged with a slight drop in gain.  Most companies changed over to the 12AX7 as it became more common. 

This tube can be tried in later Marshall amplifiers in the first gain position, where the owner of these amps would like to drop the background noise and lower the gain level to plexi or early 70's vintage gain levels with its returned wider frequency response.

This tube is selected for low microphonics and hum, and for high gain so as to produce a strong signal to noise ratio when placed in critical audio paths. Specially selected for low noise for use in tube mics and recording gear. This tube is a pentode and is not interchangable with a common 12AX7 type tube.

This tube is used in some early Vox AC-10, 15, 30/4 amps, Matchless DC-30 amps, some Bad Cat amps, Victoria Sovereign, and the Doctor Z amps; Z-28, Route 66, KT-45, and 6545. EF86 / 6267 tubes made today are very inconsistent. Their transconductance and current capabilities are quite far ranging from tubes of this type from the sixties.

GT puts each and every one of these tubes though a battery of tests to ascertain a tube that will stand up to the rigors of a first gain stage position. The first gain stage of the amps above are where these are used, and proper characteristics are critical.

This tube is the most common type used in the music world. It's a direct replacement for the 12AX7, although the GT-7025 will produce its own special sound when compared to the stock GT-12AX7. It has a little more gain than the GT-12AX7 and more edge (or high frequency response). This tube will give a stock Fender more bite and crunch. It makes a Marshall even brighter, and perhaps too much so for the all-around guitarist. The GT-7025s are usually the choice of most Fender owners and the Marshall owners who like the "metal" sound.

Our GT-7025s are tested extensively under actual listening conditions and are guaranteed to be free of excess microphonic ring and noise, even in the high gain "boogie-type" amps made today. A trick for "4 input" Marshall amps, and JCM 800/900 users that have pedals plugged into their amp input is to use a 7025 in V1. Pedals change the input load, and when using pedals, especially less expensive ones, the mid highs and highs may be diminished and your amp may lack a little of its sparkle. By using a 7025, which is brighter in these Marshalls, you regain some of the lost sparkle and artculation that was lost.

For those that change first stage gain preamp tubes to change the taste and character of their amps (remember, this can be done in less than a minute without tools, adjustments, or a "tech"). This is one tube that should be in your basic toolbox. The basic tube sets generally are the 12AX7C, ECC83, and 7025 to cover a wide range of styles and tastes for most amplifiers.