This is actually two valves in one glass envelope. 12AT7s can be used in a pinch. Preferred Series 7025 and Tung-Sol 12AX7 are suitable, 5751 not recommended. However, it has a weaker plate current. Electro-Harmonix 12Ax7 Ehg Vacuum Tube Gold Pins. When in doubt, we start with Tung-Sol 12AX7.TungSol 12AX7 handles everything from vintage rock to a clean tone sound. Feb 28, 2011. It's also very common as a phase inverter in guitar amplifiers. So if you had your fave 12AX7 in V1, would you not also want that fave 12AX7 in the following stages? Ive attached a copy of the schematic for the Fender 5E3 circuit. To help us hear how the progressive decrease in PI-tube gain eases up on the output stage, I'm using the amp's rhythm channel (gain at 4, master at 5). The stock tubes are so-so. 12AT7s can be used in a pinch. Fender amps used 12AT7s for their phase inverter. this could save alot of headaches and cash. The Fender 5E3 circuit has a 12AX7 preamp and phase inverter and two 6V6 power tubes. I recently swapped the phase inverter on my bassman clone for a CV4024 (12AT7) instead of the 12AX7. Ive attached a copy of the schematic for the Fender 5E3 circuit. Subtle but noticeable as the tubes were pretty much opposites. This tube need not be low-noise or low-hum, nor does it need to be tested for microphony. To help us hear how the progressive decrease in PI-tube gain eases up on the output stage, I'm using the amp's rhythm channel (gain at 4, master at 5). Great tube at a great price. Suggest a 12AX7 of reasonable quality and with good heater insulation, though very low noise or hum is not required. So most amp designers design their stages around that. turns out there are new production tubes that use spiral filament instead of the regular one. Best 12AX7 For Guitar and Bass Amps TungSol 12AX7. Fourth tube is the phase inverter. I have a Metro GMP45 and I use 2 x Mullard 10M Gold Pins in v1 x v2 and a 57 Mullard Long Plate Sq Getter in phase inverter. Brents got Sylvanias GE, RCA, Westinghouse starting at $30. Fourth tube is the phase inverter. Preferred Series 7025 and Tung-Sol 12AX7 are suitable, 5751 not recommended. A Balanced ECC83 Valve for the phase splitter position. And for under $15, it's worth giving a try. 6681. I prefer to have an unbalanced tube in the PI, because it gives a little more character to the power amp. That is a Sovtek tube and doesn't sound anything like the 12AX7C in the phase inverter circuit. Some believe that having both sides of the tube matched, like matching power tubes, is best for the PI spot. Slight drop in volume but worth the sacrifice. I order a JJ 12AX7 MPI from a specialty tube shop, and the difference was superb. The perfect current production tube for the phase inverter slot in my Peavey Classic 30 amp. Power tubes are a pair of 6L6GC (5881s originally suggested). It's the tube I have in my Bassman right now for the phase inverter and it sounds good there. Answer (1 of 4): Hi, thanks for the A2A. The Split-Load is the simplest arrangement. I have a RCA long/black plate 12ax7 in the PI slot now, and it seems to be a happy medium between too detailed and too dark. These are what I would get if I wanted the arguably best tube for the money. In a split-phase PI, the gain is supposed to be 1 in some circuits, but in my experience one of the triodes does matter if it's used as a driver stage. "Going from a 12AX7 to a 12AT7 in the PI (phase inverter) will yield a change in output tube distortion, touch, and output dynamics in most amps. The Bugera vacuum tube has ultra-low audio and microphonic noise. The Sovtek 12AX7-LPS an entirely new design from Sovtek and a great step up in sound quality. (i.e gain stage 1, gain stage 2 are both on the same preamp tube) The PI combines both halves of the signal (after the gain stages) (again, depends on the amp, and how it was designed) but the premise is that you want a balanced tube so that . Page 2 of 2 < Prev 1 2. charveldan Well-Known Member. best way to do it is witha $3.00 pot, not a $30 tube that's. been dipped in snake oil. It is a nice quiet tube that is excellent for phono stage preamps and recording studio microphone preamps. If I have a very detailed tube in the phase inverter, it tends to be way too bright and ice-picky. You can also find it in hi-fi equipment. 4. Each 12ax7 has two parts. Preferred Series 7025 and Tung-Sol 12AX7 are suitable, 5751 not recommended. Beware though, because the phase inverter is a hard working valve, and some 12AX7s run very hot and might not last long in that position. Discussion in 'The Workbench' started by charveldan, Feb 28, 2015. The 12AX7WC has closely matched sections making it ideal for phase inverter circuits. Genalex Gold Lion 12Ax7 Tube (Balanced Triodes) Electro-Harmonix 12Ax7, Matched Pair. Logged. After hours and hours of analysis and deduction, we come to the decision that Tung-Sol 12AX7 Preamp Vacuum Tube, Single could be the best 12ax7 tube for phono preamp for your needs. Nov 5, 2012. The 2.2 meg resistor that goes to the second 12ax7 grid and the other end to "F" B+ section, might be the problem for some reason, its supposed to smooth out output distortion and add headroom slightly. The order of tubes in the '65 Princeton Reverb reissue that I have is described by Sweetwater as being "based" on the "blackface" circuit. The TAD 12AX7A-C BALANCED PHASE DRIVER can replace any 7025, 12AX7WA, 12AX7WB, 12AX7LPS, 12AX7EH, ECC83 or E83CC. I'm talking about the phase inverter or PI tube. Power tubes are a pair of 6L6GC (5881s originally suggested). It has been present on the market since the 1940s. Suggest a 12AX7 of reasonable quality and with good heater insulation, though very low noise or hum is not required. Is this because the gain is lower in the 12AT7? 12AX7 is your standard preamp tube. Like Marshall amplifiers, vintage Mullard tubes were hand made in Great Britain, and they are regarded as some of the best vacuum tubes ever made. Best 12AX7 Tube Comparisons and Reviews Our Recommended Tube Brands JJ ECC83S Microphonic Noise Response Tung-Sol 12AX7 Microphonic Noise Response Genalex 12AX7 Microphonic Noise Response Mullard 12AX7 Microphonic Noise Response Electro-Harmonix 12AX7 Microphonics Noise Response Groove Tube 12AX7 Microphonic Noise Response PSVANE 12AX7 Microphonic So is this one. The tube has a relatively high input voltage. However, the 12AU7 is frequently used in the guitar amp's phase inverter position owing to its excellent acoustic fidelity. Hopefully, this short article will explain what the phase splitter valve and clear up any questions about this . Should I consider replacing the phase inverter too? They tend to be microphonic anywhere but in phase-inverter postions, so just go with the regular JJ ECC83. The older "real" 5751's have extra thick mica spacers and extra support rods to minimize microphonics. Beware though, because the phase inverter is a hard working valve, and some 12AX7s run very hot and might not last long in that position. I heard that a 12ax7 will sound a little more aggressive than a 12at7. Also in a non-master amp, if you have a weak phase inverter tube, you'll have less preamp distortion at a given spot on the dial. Each 12AX7 is like two tubes in one, it has "two sides" inside, and can be split for various things. Best Overall Preamp Tube: The Mullard 12AX7 (vintage) The mighty Mullard tube is always the first tube one should consider when retubing a vintage Marshall amplifier. i thought it might be useful to share this information here. The Bugera 12AX7A is most likely the best of the modern day manufactured tubes. Remove the two. I see that the 12AY7 has a gain factor of 44 while the 12AX7 is 100. For my Hellcat, it had a JJ 12AX7 in the phase inverter stock. JJ 5751 with fully Balanced Triodes. 7025 specified. The 12AX7 isn't typically used in a push-pull PI, where a 12AT7 does the job it's supposed to do. 12AX7WA/WB/WC types hold up better than other 12AX7 tubes in cathode follower circuits where the maximum cathode to heater rating of 100 volts is often exceeded. I also like Chinese 12AX7 tubes in the phase inverter because the bright tonal character adds a nice bite. I did however read somewhere that long plates are not a good choice for cathodyne (high cathode voltage) PI circuits but good for long tail circuits (don't know . 2). Third tube is a 12AX7. It is a great all-rounder. It puts the cathode about 1-2V above the voltage of the tail resistor/each grid. The 12AX7WC has closely matched sections making it ideal for phase inverter circuits. "Going from a 12AX7 to a 12AT7 in the PI (phase inverter) will yield a change in output tube distortion, touch, and output dynamics in most amps. Second tube is a 12AX7. 12ax7 long tail pair phase inverter driving el84's. « on: April 20, 2013, 08:49:56 pm ». 12AT7s can be used in a pinch. 12AY7's will allow for a cleaner tone and a bigger sweep of the gain and volume controls on your amp. 10 Best 12ax7 Tubes. I will dig more into it. My current favorite is the JJ ECC803S because it gives a nice push and crunch and helps with sustain a bit. For a typical Fender PI stage, for instance, you use a 100K linear pot. Posted August 25, 2007. I was using a Tung Sol 12AX7 in v3 (phase inverter) of my reissue fender bassman and I found the sound overly bright and harsh - couldn't dial it out EQ wise. The 12AY7 valve versus the 12AX7 (ECC83) valve. An example is a phase inverter, which drives the power tubes. One is the "Cathodyne", also known as the "Split-Load" (Fig. Neither is better. The even balancing makes them a nice phase inverter and allows you push the front end of the amp a little harder. 10% yes perhaps. This vacuum tube is perfectly suited to this, as it offers exceptional headroom and crystal clear, high fidelity sonic qualities. The 12AT7 also has a gain factor of 70, but since its plate resistance is lower, it draws more plate current than the 5751 and 12AX7, making it less suitable for use in low current high gain stages. This JJ T-12AT7-JJ amp tube comes across as a seamless replacement for any 6201, ECC81, or 12AT7 tube. Recently I changed the stock 12ax7 to a NOS 5751 and the sound is pretty good but the output volume is a bit lower than before.So a. #1. there are current production 12AX7 that will die if you put them in a phase inverter position or in a cathode follower position. Likewise, for a 12AT7-designed PI, a swap to E180CC will give analogous gain drop (an E180CC is to a 12AT7 like a 5751 is to a 12AX7). The large plates make them more prone to . Top 10 Best 12ax7 Tubes. It's the tube I have in my Bassman right now for the phase inverter and it sounds good there. The lower gain is a factor but the larger factors are: 7025 specified. In these four soundclips, the Friedman Small Box's phase inverter is swapped from a 12AX7 (Clip 9) to a 5751 (Clip 10), 12AT7 (Clip 11), and 12AY7 (Clip 12). The key to choosing the best 12AX7 tubes is establishing the qualities that you require. The Paul C. phase inverter mod is supposed to be good, maybe I overlooked something. I think the "special" PI tube is a 12AX7 with a matched triode. Everything kept constan. You do not want a 12AX7 with two triodes that are wildly different from each other in this case. 12AY7's have less gain than a 12AX7, 5751, and 12AT7, but more than a 12AU7. Most amps use either a 12AX7 or 12AT7 for this purpose. I currently have a 12AX7 in my SCX2, but generally use a NOS Philips USA 12AT7 WC JAN mil tube, there. Power tubes are a pair of 6L6GC (5881s originally suggested). Both are quiet and clear. I got this to use as the phase inverter in a Bugera V22 Infinium Head. I seem to remember the Doc saying at a Z-Fest he likes long plate tubes in the phase inverter and indeed most (not all) of my Dr. Z amps have balanced Sovtek 12AX7LPS tubes for the PI. There are two designs that dominate guitar amps. It was originally designed as a low noise tube and was actually developed… The Fender 5E3 circuit has a 12AX7 preamp and phase inverter and two 6V6 power tubes. Current Tube lineup is V1 CV4024, V2 JJ 12AX7S, V3 CV4024. If you're . What a lovely warm tone. So I put a one of these Mullard 12AX7 in the phase inverter slot and it sounded great. These are what I would get if I wanted the arguably best tube for the money. The phase splitter valve in guitar amplifiers. Special selection BALANCED PHASE DRIVER tube for the use in phase driver / phase inverter circuits of guitar amps as well as for HiFi-Audio amplifiers. #3. Serving as an excellent choice for reverb speaker drivers, phase inverters, and all-purpose preamp use, the JJ T-12AT7 features solid construction for long-term functional life. 2,766. Of course, this is not just with 12AX7. I have a couple "theory" questions. I'm currently using this tube as a phase inverter on a Leak Stereo 50 HiFi amp, and the JJ is a great sounding tube. Power tubes are a pair of 6L6GC (5881s originally suggested). Suggest a 12AX7 of reasonable quality and with good heater insulation, though very low noise or hum is not required. In this application, you will get good gain with a warmer sound than the 12AT7. « Reply #1 on: May 08, 2010, 05:25:34 am ». JJs seem to make Ampegs sound *just* right. You can indeed try to swap your PI position tube for something else on most amps, particularly if like in this case you go for a. But, if you are still looking for something more cheaper and reliable, then you are free to go for Tung-Sol 12AX7 Preamp Vacuum Tube, Single. Re: 12ax7 Phase inverter voltages. Phase Inverter tubes can wear pretty quickly and if not replaced when they're ready to be it can affect your tone more than you think. I actually use a 12BH7 in my phase inverter to get a sweet clean amp that takes pedals extremely well. tube I tried was a 5751 (also JJ). Same pedal, same guitars, same settings etc. 10% yes perhaps. 12AY7 / 6072. Ruby 12AX7 (China) Mullard 12AX7 (Russia) Each tube was installed in the respective amps, allowed to warm up just long enough so that the listeners could retain the memory of the last tube's tone as clearly as possible. For less gain, you can substitute with a 12AV7. 12-04-2017, 05:12 PM. Should I consider replacing the phase inverter too? The harshness was gone, the EQ responded better and the mids were fatter. Another mullard in the PI is the worst, to me. It's commonly used as the phase inverter in some hi-fi amps, Ampeg and Fender amps. Suggest a 12AX7 of reasonable quality and with good heater insulation, though very low noise or hum is not required. So comparing and contrasting both the tubes, you may observe that the gain factor is inversely proportional to the current. It would have been helpful if you told us which amp we're talking about, as they certainly don't all respond to that equally. 2 x TAD 6L6GC-STR RCA Blackplate replicas. However, as seen from behind (above), left to right, the tube complement is: V7 5AR4 (rectifier tube); V6 6V6 (power tube #2); V5 6V6 (power tube #1); V4 12AX7 (1/2 vibrato & 1/2 phase inverter); V3 12AX7 (1 . I'm on my third Sovtek 12AX7LPS as I change out the PI tube whenever I change the power tubes. Electro-Harmonix 12Ax7 / Ecc83 Preamp Vacuum Tubes (Three Pack) Has anyone had good results replacing a 12AX7 in the preamp with a 12AY7? After all the tubes were heard, some participants requested to hear various pairs of tubes together for comparison. Fourth tube is the phase inverter. 3 Phase Inverter preamp tubes are compared in a 1977 Marshall JMP 2204 using a 2010 Gibson Les Paul Custom Black Beauty 1957 Reissue. If you have a push-pull circuit, an NOS 12AT7 can be had cheaply and will likely outlast you. It's a great choice. Swap the 12AX7 in driver section with a JJ and the 12AU7s with NOS JAN Philips (military grade). Using a 12AX7 in place of a 12AT7 in the PI will give a looser feel, and earlier breakup that may feel more lively. The PI is the tube that creates the push-pull waveform and it's the last tube the guitar signal sees before hitting the output tubes. Hi, I have a Koch Studiotone 20W tube amp, with 3 12AX7 preamp tubes and 2 EL84 output tubes.What kind of tube should I use in the phase-inverter to maximize output? #3. The stock power tubes in my Fender '65 Princeton Reverb reissue guitar amplifier were starting to sound ratty, so I thought I'd order some NOS vacuum tubes for it from Roy and Dale at Radio Electric Supply, my go-to guys for NOS USA vacuum tubes. In a phase inverter, one of the triodes drives one power tube, and the other triode drives the other power tube. 12AT7s can be used in a pinch. If you wish to use a 5751 in a 12AX7 position to reduce gain we recommend you use the JAN-Philips 5751 tube. I see that the 12AY7 has a gain factor of 44 while the 12AX7 is 100. The 12AU7 is also commonly used in a specific part of an amp, which is known as the phase inverter section. I have a Metro GMP45 and I use 2 x Mullard 10M Gold Pins in v1 x v2 and a 57 Mullard Long Plate Sq Getter in phase inverter. We recommend these for long tail phase inverter stages which are common in most push pull circuits (most all guitar amps), or anywhere that symmetrical sections are desired. 7025 specified. If you've already got a 12AX7 in there, I don't think there's anywere for you to go. Back to the Phase Inverter. It came highly recommended by trusted sources and did not disappoint. connect the pot's wiper to the B+ eyelet (where the two. The ECC82 (12AU7) is an excellent choice for a clean / bass amp. I've been studying schematics such as Vox style el84 and the Hoffman 18Watt Stout schematics. Puffer Fish, May 20 . This is the phase inverter tube. They have very large ribbed plates and great sound reproduction. Summary: Great choice for phase inverter position. The phase inverter tube plays a huge part in how this tone king sounds. Best Phase Inverter tewb for JMP 2203. Brents got Sylvanias GE, RCA, Westinghouse starting at $30. 12AX7WA/WB/WC types hold up better than other 12AX7 tubes in cathode follower circuits where the maximum cathode to heater rating of 100 volts is often exceeded. 7025 specified. A 12DW7 would give you that effect, because the two sides of the tube are something like 100 % gain and 20 % gain. I order a JJ 12AX7 MPI from a specialty tube shop, and the difference was superb. That is a Sovtek tube and doesn't sound anything like the 12AX7C in the phase inverter circuit. Anyone else tried this? The first replacement p.i. To get an unbalanced phase inverter effect that some people seek (like harp players) you would need to drop in a tube with a widely unbalanced value to over come the phase inverter correcting thing our amps do. We are often asked by customers "What is the phase splitter valve (or phase inverter valve) and is it special or different from the other valves in my valve guitar amplifier?". Re: Phase Inverter 12ax7 suggestions. Originally posted by misterwhizzy View Post. The ECC83 (12AX7) has the highest gain of course and will be the most easy to overdrive, but it has the least output signal swing, so is the best choice for amps which focus on preamp distortion. No complaints at all, and it stacks up very well compared to a Philips 7025 USA made tube when tested in the same position. I can see where maybe you might want different EQ . I found them very smooth and well balanced in terms of bass, mids and treble response. 1), and the other is the "Long-Tailed Pair", derived from a circuit called the Schmitt Inverter (Fig.
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