Like all jj tubes, it has a rugged construction that doesnt compromise the sound of your amp. Even then, a lot of people just prefer 12ax7 s in their pro audio tube gear based on sound files ive posted for blind listening tests in the past in other forums. Some 12at7s that will work just fine as phase inverters v6 will crackle and hiss in this position. Dwell, mixer and tone and includes a 12at7 tube as a preamplifier.
I used the proven circuit from the aa fender blackface princeton reverb and offer up layout diagrams for a simple reverb and a tremolo to add to an amp design. Because of the high demands placed on this tube by the fender reverb driver design, its important to get a good quality 12at7 for this slot. I did not know quiet what to expect tone wise from this tube and was pleasantly surprised. Because of their higher current you sometimes see them driving effects such as tube driven spring reverb in many guitar amps. Steve carr of carr amplifiers describes the characteristics of different preamp tube types and suggests some useful substitutions. The jj electronic 12at7 ecc81 is a good choice for phase inverters, reverb drivers, and general preamp use. In guitar amps, it is commonly use as a phase inverter. This is a punishing job for a 12at7, and the only one thats reportedly up to the job is the jan philips 12at7wc.
Fender 2 channel reverb amp preamp tube layout as seen from the back of the amp. I get preamp tubes in a preamp, but ive found it difficult to find a clear explanation of what the driver and input tubes are actually doing, and their relative importance to the sound of the amp. The reverb drive is basically a fourwatt output amplifier consisting of a 12at7 tube and a reverb driver transformer. For the reverb slot, you need a 12at7 there to meet specs.
This tube is only in use in the vibrato channel, but even so, it means nothing for the dry guitar tone of the vibrato channel or the normal channel. This little amp is a bit on the rowdy side still sounds great, but not as smooth as the anderson. Lets take a look at the less glamorous, but equally important type of amplifier tube the preamp tube. Fender amp preamp tube layout and recommendations kca. The 12at7 swap for the 12ax7impression talkin tubes. School me on 12ax7 vs 12at7 for reverb driver telecaster guitar. Its a useful tube when you want a little more ability to. The 12at7 tube is commonly used as a phase splitter and also as a reverb driver in many amps. The 12at7 is not normally used in guitar amps, the exception being as a reverb driver in some fenders. Its definitely at the higher end of the gain spectrum for the 12at7 genre, but thats what you want. This is used much less as a preamp tube because of the low gain, and more as a driver for the tube driven spring reverb. Example my epi bc30 uses both halves of an ecc83 12ax7 as the reverb driver, replacing it with a highercurrent lessgain genuine mullard ecc81 12at7 was. For use in the phase inverter position, we recommend the triode matched option. The eh 12at7 is a good choice for reverb driver, line stage, and phase inverter positions.
It was the first fender amplifier to incorporate onboard reverb which became a standard feature on many highend fender tube amps during the 1960s and 1970s. The reverb circuitry consists of two tube sections reverb driver v3 and reverb. I wouldnt recommend using a 12ax7 in place of a 12at7 in a reverb driver. Both channels will work fine without this tube just without reverb if youre using the vibrato channel. The 12ax7, 12at7, and 12au7 all belong to the same family of nine contact, twin triode tubes.
All 12at7 ecc81 valves come amplitrex at or maximatcher tested. Absolute sound quality of a tube itself isnt critical in this position so expensive nos isnt a must, its just a matter of degree of drive gain, how that makes the reverb tank sound both tonally and in terms of sproingyness, and how it affects the useful setting range of the reverb control knob. That being said, if you want to buy three or four 12ax7s by different makers. A good choice for phase inverters and reverb circuits calling for 12at7 tubes. I replaced the reverb driver with a janphillips 12at7 because i felt that the reverb was ringing a little too much. Better 12at7s notably, the mullard cv4024, mullard ecc81 or rca 12at7 s will also improve the tone of. Mullard ecc81 or rca 12at7s will also improve the tone of your reverb. We also offer low noise option to eliminate potential issues. Comparing 12ax7 vs 12at7 as the driver in the mcintosh mc40. We will take a look at why you might, or might not want to swap out the different types of tubes. Some earlier fender models used a 12ax7 or 12ax7 for the phase. Comparing 12ax7 vs 12at7 as the driver in the mcintosh.
The driver or phase inverter is the 12ax7 located nearest the power tubes. Reverb howls with 12at7 but not with a 12ax7 in the driver. A good choice for phase inverters, reverb drivers, and general preamp use. The 12at7 tube is often found in reverb stages or in the phase. The ecc81 tube type is equivalent to the north american 12at7 tube and can be used in any 12at7 or ecc81 circuit. Electroharmonix 12at7 ecc81 vacuum tube large plate format, superior dissipation over the originals. The 12at7 is rarely used in a tonegenerating stage, but rather in function stages, so our gt 12at7 is selected for durability. It was usually a 12at7, for the same reasons as the reverb driver above. This is a special and more expensive production run with a rugged construction. In many cases, these tubes are interchangeable and can easily be swapped. A 12ax7 has a gain factor of 100, whereas a 12at7 has a gain factor of 60. Musical details are very accurate with strong headroom dynamics.
Then theres the deluxe reverb ri with stock fenderbranded groove tubes 12ax7 s sovtek. Information on driving spring reverb using valves tubes seems to be rather sparse, so the following is presented as a guide to valve amp designers. Im not much of a rock fan and my first preference is jazz. I use only wet signal, so i send aux send tru mixing desk to a transformer first stage 12 12ax7 12v input in 12au7 parallel driver recovery channel 12 12ax7 too output other 12 12ax7 then i plug the output to a good direct box to m mixing desk via mic preamp. It all depends what the reverb driver was designed to use. I have a silkyn super 50 that uses a 12ax7 for the reverb circuit, that is typically weak. I know fender often used the 12at7 for reverb, and i think the much higher plate current is involved to drive the reverb transformer and send transducers a lot harder. You can plug it into any tube socket that calls for a 12ax7, 12ay7 and most 12at7 applications. And the noise floor is, well, theres no floor at all.
Buy the jj electronic 12at7 preamp valve, ecc816201. Can be also used as replacement for 12ax7 in many applications. The eh 12au7 replaced the v3 reverb driver 12at7 in my blackface super reverb with hammond tank. From the linear tube audio website description of the product in question. Internal construction provides mild microphonics resistance. This tube offers low noise, low microphonics, and warm smooth tones at a great price. I replaced the cathode resistor for this tube the triodes. I heard that using a 12ax7, which is a higher gain tube, would make the reverb strongerdeeperwetter but elsewhere i heard that it is current and not gain which would increase the reverb and that the 12at7 is higher in current than the 12ax7. What does matter is the current and transconductance. The jj ecc81 12at7 tube is a low noise and low microphonic preamp tube. Mesa 12at7 is a premium grade, classic low gain preamp tube most often used as a reverb driver andor phase inverter in older. What is the difference between the 12ax7, 12at7, and 12au7. I have seen no anomalies in parasitic or instabilities that the substitution of 12ax7 for 12at7. The 12at7 has more current gain than the 12ax7, maybe your amps reverb circuit is on the verdge of whining and the 12at7 is enough to put it over the edge.
The fender vibroverb was a 40watt combo guitar amplifier originally manufactured in 1963 and 1964. Same applies to the pi, swapping 12ax7 for 12at7 may work, or not. Lower gain, with more drive than a 12ax7, these feature in many hifi pre amps, power amps and guitar amps. If you for some peculiar reason own a vintage fender reverbamp and play strange. Here is a list of virtually every tube amp fender has ever made, and what tubes are inside of it. How to improve your amps tone with preamp tube reverb news. This tube does make a good reverb driver where tone is less important than ruggedness. The electroharmonix 12at7 preamp vacuum tube presents a clear, uncolored tonality with a very strong amount of signal gain. For reverb driver, we recommend smaller plate 12at7 such as electroharmonix 12at7ehwc.
I have a fender 63 reverb clone and a princeton reverb ii both of which use a 12at7 to power the reverb. In a reverb driver position undoubtedly what most people are buying 12at7s for, this is what you want, because it can so readily pick up ambient hiss from the springs. But, i will say this, the reverb driver is not a gain stage so the 12at vs. Most amps use either a 12ax7 or 12at7 for this purpose. Driverinput tubes i need somebody to either explain or steer me to an explanation of the 12ax7 12at7 tubes purpose in my jolida jd502p power amp. Mesa amps built before 1991 as a reverb driver stage, but the 12at7 can also be substituted in 12ax7 gain. Our tube will some times bear the number 6201 as well as 12at7. Ge 12at7 another nos tube that is still available this one will give you a little more upper mids and clarity while being slightly smoother in the treble frequencies. Even nicer than the mullard 12at7 that i found in the reverb driver stage of my pro reverb the one with no reverb tank in it top. Any 12axx tube is made as a 12ax7, then it is tested and rated as to how much gain it creates.
Unplug the reverb pan, and connect a speaker to the reverb jack labeled reverb. Remove the 6v6 or 6l6 output tubes to disable sound coming from the main speaker. Your amp tech or favourite tube vendor should be able to sort you out. The 12ax7 in that application will likely have a very short life. Reverb driver question12ax7 vs 12at7 a guitar forum. This article considers only the driver stage, and not the reverb recovery stage which is usually a simple triode gain stage, unfortunately. If you want less preamp gain out of this tube, insert the v1 tube and use 12au7 or 12at7 in the v2 slot in stead of the standard 12ax7. A 12ax7 and a 12at7 tube are directly compatible and can be swapped. Ecc81 is 12at7 medium gain preamplifying double triode. S early 60s seiman 12at7 that should sound very nice.