12ax7 Operating Point

Triode Amplifier Operating Points Article By Paul Joppa From VALVE Volume 2 Number 5 May 1995 How do you choose a good operating point (supply voltage, current, and load impedance) for a vacuum tube? For ordinary tubes, used in an ordinary way, it's simple -- you just look it up in your RCA handbook. Bugera V22INFINIUM Tube Guitar Combo Amp Building on the original VINTAGE V22, which has become a modern classic and inspired combo amp design, the impressive and hand-built, 22-Watt, 2-Channel VINTAGE V22 INFINIUM exudes vintage tone and style, plus possesses modern features that will launch your sound into the sonic stratosphere. For example, suppose a 12AX7 were chosen, with a plate supply voltage of 300V, and a 100K load line was drawn on the curves, and the desired operating point was the intersection of the -1. Contents :-Some history of triodes and basic tube operation of cathodes, anodes and grids. info, and posts from various Z-Talk Members, that I found valuable to me as I was learning about my amp. The operating point of a vacuum tube is the position on the loadline, corresponding to the voltage and current measured at the anode in the quiescent status, that is when no signal is applied to the grid. in the application circuit. Well, the Marshall DSL5C just isn't for them. 12 vdc in instantaneous values. From the factory, it came with a 12AU7 for phase inverter, which I switched out to a 12AY7 for a little more drive on the output tubes. Greater capacitance values are not recommended, as they can make the circuit operate as a relaxation oscillator for high regeneration levels. R3 (1K Plate Resistor) - The plate resistor drops the voltage and limits the current to the anode of the first triode of the 12AX7. P a: Anode power dissipation at. There is a biasing system in place to ensure that happens. The reason that the Ab763-amps have less preamp gain is the use of only one half/triode (V4 12ax7) in the second gain stage vs both halfs/triodes (V2 12ax7) in the the Bassman AB165. Please write the serial number and purchase details of your Genesis. That leaves plate voltage and grid-cathode bias as the remaining interdependent variables. because the 12AX7 is a dual, it is a great opportunity to cascade two identical stages like this for extra sick weirdness. Fig 2, 5AR4 diode Ra curve for one of its diodes. primary of the trans- former measures 55 ohms, so an addi- tional 205 ohms per tube is needed. Using the same operating point and load, things improve considerably at a higher supply voltage. The exponent actually shifts from 2. So that's one reason why the Matchless might seem to have different gain characteristics than a typical BF/SF fender type, because it does have different signal gain and input signal overload characteristics. We strive to provide service to our customers that exceeds their expectations and maintain an atmosphere that is clean, comfortable and relaxing. Tube Amps: Why Fixed Bias Amps Cannot Self-Bias September 08, 2016 18 Comments In response to our recent article about replacing tubes in your amplifier, we received the following question from a Carvin Audio enthusiast. Back to Triode USA. The restriction on this method is the requirement for a low impedance microphone. B+ is 320V, regulated. 6N2P, 6N2PEV, 6H2n, 6H2n-EB, Hi-Fi Audio. Changing the bias effects the location on the operating point of the load line. Enjoy the same deals at our retail showroom! Save on shipping and additional charges!. Hickok used the published operating point of +100V plate and -1. Mit Flexionstabellen der verschiedenen Fälle und Zeiten Aussprache und relevante Diskussionen Kostenloser Vokabeltrainer. The cathode floats about 150 volts. from this central point on the grid characteristics will give us suitable amplification. Buy your Bugera V55HD Infinium 55-Watt Tube Guitar Amplifier Head from Sam Ash and receive the guaranteed lowest price. Amplification factor (g) at : this operating point is 42, and dynamic plate resistance (rp) is 2kQ. Search the history of over 381 billion web pages on the Internet. The hand-selected 12AX7 preamp tubes in VINTAGE V55HD INFINIUM's classic '60s-era preamp provide everything from sweetly-purring blues to mind-blowing crunch. There are several other ways of doin this that I know of but the practicality of this approach also allows continuous variation (tuning) of the relative position of the Quiescent Bias point inside the curve and at the same time. The Bugera V5 Infinium amplifier uses 1 x ECC83 (also called 12AX7) preamp valve and 1 x EL84 power valve. This puts the cathode positive of the grid and everything works, but the actual operating point is imprecise since it is dependent on the individual tube current. Its two input jacks give me two choices: a single 1/2 12AX7 triode, or both halves in parallel. russian 12AX7WAs are perfect. The overall gain of this pre-amplifier is around +39dB or about 90 times. 7) determines the operating point of the first tube but the individual tube data also have significant influence. This is hugely important, as the previous circuit (with a 12AU7- and 12AX7-based cathode-coupled amplifier) is a perfect example of a circuit that can function flawlessly in SPICE but fall on. At the conservative operating point these tubes should last many many hundreds of hours. Larry Carlton and Santana used the venerable Boogie Mark I. The size of the cathode resistor sets the operating point (intersection of the plate and cathode load lines detailed in the next section) along the red plate load line which affects headroom. In non techspeak, bias is what controls the operating point of the tube. To do so, specify initial conditions for the simulation that are near the desired steady-state operating point. The primary reason tube guitar amplifiers are favored over solid state amps is their overdrive tone. The restriction on this method is the requirement for a low impedance microphone. using a typical operating point and load, or have you made it up yourself? 120k seems very low for an ECC83. Plate load resistor (RI) is 22kQ, selected to be more than ten times the plate resis- tance for excellent linearity and high. Swapping 12ax with 12at and other 12 variants will affect the sound because if a circuit is deigned for a 12ax7 it will not be operating a 12at7 at it's optimal operating point. Some sound will be made but you will throw the operating point of the 6080 into the unknown. After that the signal is fed to a 1/2 12AT7 as cathode follower. 12AX7 Voltage Amp. This is a good match for any dynamic microphone having an impedance's between 200 and 600 ohms. Anode voltage at operating point. The 12AX7 has the highest gain at 100, the 12AT7 is lightly lower and the 12AU7 is the lowest gain of the group. The 12AY7 and 6072 are the tube designations for a dual triode with medium gain that shares the same pin-out configuration as the 12AX7 and its variants. 6550 / KT88 / KT90 / KT120 tubes. 1) Replace cathode caps from pin 8 of the 12AX7 to gnd with a 220uf 35v electrolytic and 1uf 35v tantalum. The hand-built 5-watt amplifier is driven by a 12AX7 tube in the front-end preamplifier stage, an EL84 tube in the output stage, and powers an 8" Turbosound. Pretty boring as a description goes. By Rob Robinette. R i: Plate (internal) resistance at operating point. 12 vdc in instantaneous values. How to find Ra for a given working point and plot loadlines in steps 1 to19. A 12AT7 can replace a 12AX7 at the phase inverter (actually drives the power tubes harder), but shouldn't be used as a replacement gain stage. 216% (depends on where the drive, mix and detail controls are set too, but just choose a fixed setting for those and proceed as it is all relative). defined at the operating point (the graph shows Gm and Rp calculated in different regions only for clarity). And when you increase the input to around 0. 8V and Vp=350V are used to determine the parameter values of r p and gm and µ from the 12AX7 average transfer characteristics graph (note that Eb is Vp). in the application circuit. "Remember, any point along the load line is an operating point for the tube under the voltage and resistance conditions you set up. In the two years since the Fetzer Valve was first published in the midst of our adaptation of tube amps for use as distortion pedals, the circuit has enjoyed popularity as a standalone booster and as a building block in larger circuits. 0V grid bias for these tubes. In contrast, upright operating point was distant from the centering point of the reset curve and fell. Loaded with three 12AX7 preamp tubes and a pair of 6L6 power tubes, this amazing handbuilt, boutique-style powerhouse is primed for action whether you're onstage, in the studio, or in your practice room. Russian EL84 operating in pentode mode with 12AX7 driver. the tube compliment is 2X E80CF (6BL8), 2X 5703WB submini (under the hood), 1X 6CG7 and 2X 211. Rather than a traditional push-pull configuration, the S6 employs three EL34 tubes per side, in parallel, driven in single-ended, Class-A triode mode. The rear panel consists of two speaker outputs with an impedance selector. The 6X4 also has the sandblasted white dots which means - you'll guess The last tube with the anode cap probably has something written under those yellow labels - need more information to identify them. Well, at the conclusion of several hours of work, we were able to bias the amp for a reasonable operating point @ 515V DC anode supply. Korg matches its comparators with unrivalled sound and design technology. 12AX7 + 6H30 / Point to Point Complete Hand-wired Driver Stage on Copper (Clear-coated) Platform. The Bassman sounds “browner” than the AB763-amps, particularly the AB165 model, and it has more preamp distortion and mids when the volume is turned up. Single point matching can be inadequate. The total current is 17 ma on dynamic swing, or 18 ma in quiescent condition, and we require. The various Chinese 12AX7 tubes sound very small, thin and harsh by comparison in my experience. After completion of all the changes , the preamp sounds much richer , clearer and more detailed to my ears. I tried comparing the gain of the pass tubes as a cathode follower which yielded only a small percent difference. 8V and Vp=350V are used to determine the parameter values of r p and gm and µ from the 12AX7 average transfer characteristics graph (note that Eb is Vp). In an amplifier with high input impedance, increasing the gain will introduce a DC offset which affects the operating point of the circuit (changes the balance of the amplifier). the 6N2P or 12AX7 have WAYYYYY too much gain for a line pre. The single line with the positive slope represents the 1. The amp is clean and tested for many hours. Search the history of over 380 billion web pages on the Internet. The hand-built 5-watt amplifier is driven by a 12AX7 tube in the front-end preamplifier stage, an EL84 tube in the output stage, and powers an 8" Turbosound. His math (confirmed by TCA) shows a 3/2 law but only AT the half-way operating point. While it is not quite as linear as for example the 6SN7 or 12AX7, the plate curves still look quite good, especially if you pick a good operating point and a linear region. The long plate 12ax7 would be better served in a high fidelity tube amp than a guitar amp. ECC35 has another operating point, but it will fit in normal 6SL7 circuits, since this is a high gain tube and auto bias is functioning very nice with high gain tubes. 5dB per gain stage, a very small number. This enables precise current measurements over a 1:1000 operating current range - 12AX7 to 6C33C, with 700V plate/screen and -150V control grid scale. Noise had a greater spread of about 6dB between tubes of the same type. You can use this bias system to set an operating point for the output tubes… to a point. Loaded with three 12AX7 preamp and two 6L6 power tubes, this incredible boutique-style powerhouse gives you the flexibility of two independent channels and selectable reverb, both switchable via the included heavy-duty footswitch. 2) Replace 510pf coupling cap between pin 6 of the 12AX7 and the volume control with a. Most excellent Russian version of ECC83, but different pin connection. The 12AX7 is a very high mu (gain) tube that is best suited as all or part of the input voltage amplifier in a phono stage. 5/gm at the chosen operating point. Download datasheet for this tubes here. If you wanted to drop the output power then a bias supply or cathode resistor would probably need to be added to keep the tube at a reasonable DC operating point with low or no drive. The VINTAGE V22 INFINIUM features true Class-A technology with a 3 x 12AX7 front-end and 2 x EL84 power stage. 12 vdc in instantaneous values. Plate load resistor (RI) is 22kQ, selected to be more than ten times the plate resis- tance for excellent linearity and high. Looking at the D3a datasheet, we see that both plate resistance and mu vary rather steeply with current at low currents. Cheap vacuum tube integrated amplifier, Buy Quality tube integrated amplifier directly from China integrated amplifier Suppliers: Nobsound Handmade HiFi 6P1 Vacuum Tube Integrated Amplifier Stereo Single-ended Class A Headphone Amp Black Enjoy Free Shipping Worldwide! Limited Time Sale Easy Return. Without it I can't be absolutely sure, but I very much doubt that swapping a 12AX7 for a 12AT7 would make any difference to the operating point of the el84. Another point is that for a high power tube like a 6L6 or other power amplifier tubes, the curve tracer may well test at the higher voltage and. 1) Replace cathode caps from pin 8 of the 12AX7 to gnd with a 220uf 35v electrolytic and 1uf 35v tantalum. Pictures below are LTspice simulation results. Both are usable sounds, the parallel-triode mode is thicker, with a bit more drive and oomph. However there is an important difference, a 1k "stopper" resistor is added at each grid input. In Multisim 7 and 14 the tube models seem to be much the same, but I get no sensible results from simulation. operating-point current with respect to power supply variations. Note that a tube such as 12AX7 will test low since the operating parameters (100vdc plate, approx -1. Of course you can always replace a 12AU7 with an ECC82 and vice versa, because these are just different names for the same type of tube. unlimited resources must satisfy scarce desires. I am building a simple single ended 12AX7 driven EL34. This clearly seems to mean that much of the original point of the SRPP topologogy is lost. Also a multiplex take-off point is provided at low impedance which will not affect the regular operation Of the tuner. They just don’t see the point in low watt amps, and frankly look down on anyone who doesn’t play a 100w Marshall stack. 7 vdc bias) are a poor operating point for this tube, and the Gm number on the setup chart should be taken with a grain of salt. cent operating point, because each tube passes 7. Here's a better loadline and bias0-point for the 6922. Thus with an input signal of 1V RMS, I could expect about 25V RMS (~ 35V peak to peak) on the grid of the output tube which is just below the maximum for the operating point that I selected for my output tube. A masterfully crafted all-tube combo amplifier, the V5 provides sweetly-balanced harmonics and natural tube compression, resulting in the warm distortion and break-up you’ve come to appreciate from those vintage megaliths of yesteryear – only in a much more portable and attractive package. I know this has been discussed before, if not here, then plenty times. The long answer is: Maybe. Some of this material is general and applies as much to hifi circuits as to guitar amps, but some of it is very. All three of these tubes is virtually identical. I have been using this phono circuit since the early 90s starting with a PAS chassis with Telefunken ECC83/12AX7. Often times the distinction between Design Point and Operating Point is unclear during the pump selection process. Both are usable sounds, the parallel-triode mode is thicker, with a bit more drive and oomph. Probably why I liked it so much as the primary of the clean channel in the RA100. , the V-60, K-35 works with an automatic bias control unit. So you will get more distortion and easier clipping on that side of the signal. The noise resistance is approximately 2. Three different plate resistors were tested: 100k, 220k, and 330k. The coupling capacitor also stores the average voltage generated by the grid current. Negative feedback might not need re-calibration since a lower gain tube will generate less NFB. A tube needs a proper operating point for it to function correctly and to live long. And has been pointed out, most testers check the "gain" at only one point on the curve - which could be totally different from the circuit you are using it in. (Adjust the cathode resistor to give each section anywhere from 16 to 20mA of quiescent current, depending on personal taste, and the sonics of your favorite tube and your favorite operating point. Your treasured tubes will provide extended, robust sound and high gain to accommodate medium output phono cartridges. Also pick a time for the simulation, in this case 15 seconds. For industrial use, instrumentation applications, and other critical uses, the 5751 was used which served the same function but to much higher standard. If it pleases your ears it is good tone. Sound I traced the SC26's initial hum problems to a faulty ECC83, which Woodside replaced with a Golden Dragon 12AX7. 5) at one point. This puts the cathode positive of the grid and everything works, but the actual operating point is imprecise since it is dependent on the individual tube current. What was the operating point of the tube? One can easily change the sound of a tube in a circuit from clean and precise to vague and warm simply by changing the operating point. Lernen Sie die Übersetzung für 'operating point' in LEOs Englisch ⇔ Deutsch Wörterbuch. Now, looking at the curve we see that not only is it set to an O. Looking at the D3a datasheet, we see that both plate resistance and mu vary rather steeply with current at low currents. The nominal operating point levels of Vgk=-2. Let’s choose the operating point. Guitar Amplifier Electronics: Basic Theory - a modern approach to understanding tube amp design. 12″ speaker and V-Front 2×10″ cabinets available. Further details on materials and methods: The paralleled 12AX7 and the 1/2 12AX7 both have 68K grid resistors. Here is the load line and DC operating point for the 12AX7 differential amplifier when the cathode potentiometer is set to minimum: With the control set to minimum the preamp runs very clean. LUXMAN CL36. Without doing a proper design-check, I'd expect the 12AV7 to exhibit slightly more gain when plugged in the same socket, albeit with the possibility of being biased to a poor operating point for the tube. From the menu, Simulate|Edit Simulation Cmd, and make sure that Start external DC supply voltages at 0V and also Skip initial operating point solution are checked. The ECC83 / 12AX7 is a weakling in this regard, although for guitar applications it is often 'good enough'. DC voltages are locked to the voltage of the reference tube to ensure a stable operating point. The design is almost the same as the 12AX7 preamp, it is a single gain stage triode tube with cathode follower. 5k setup on a 12AX7 preamp. Cheers![/quote] This is where my inexperience comes in, I thought that the 6n2p with a mu=97. The idea here is that tubes that match at two different points on their operating curves are likely to remain reasonably matched at higher plate voltages, or other changed operating conditions, as well. This is not one of them so needless to say we will not be stocking this one. I did not use tube manual numbers but picked values from the graphs as close as possible to the actual operating point. From the factory, it came with a 12AU7 for phase inverter, which I switched out to a 12AY7 for a little more drive on the output tubes. GoGo uses 2x 12AX7 tubes operating at +300 Volt internal och cames with an adaptor Gogo has two fotswitches, true bypass-switch and a switch som toggling crunch- and overdrive-mode GoGo has also a speaker out to be used as a practice amp with 0,5 Watt output. 7) determines the operating point of the first tube but the individual tube data also have significant influence. 's endeavor to continuously improve the functionality of its PUMP-FLO branded pump selection software, an improvement has been made to the calculated Operating Point in the PUMP-FLO Premium product. 5V, always measured with respect to the cathode. Hans tells me that the next production will include a few updates, improved cooling by better circulation around the output tubes, and an even better stabilized operating point to further reduce bias current drift. An extreme case of this is the 12AX7 in the Moscode Minuette. If you use a high impedance source, the a low noise active preamplifier stage is still required. Home / FAQ / News Classifieds / Events: Tubes Asylum: 12AX7 operating point with low supply voltage. In some tubes, maximum µ can be obtained at a modest negative bias. Orange Box Ceo 6,570,211 views. A Comparison of Current Production 6L6GC Tubes. Often employed in British-style amplifiers, the EL84 output tube is known for its crisp and chiming tonal quality when pushed to the max, and the V22 INFINIUM harnesses every ounce of that. Thus with an input signal of 1V RMS, I could expect about 25V RMS (~ 35V peak to peak) on the grid of the output tube which is just below the maximum for the operating point that I selected for my output tube. Orange Box Ceo 6,570,211 views. 08mA; this is where the -lV curve crosses the load line. 252ma with a bias voltage of -2. I am moving this thread over from the electronics and components section. Price From $129 Contact iZotope. They don't need to be adjusted so long as they are roughly the same type, like a 5751 and a 12ax7, however when switching to one of a different type, especially one with a much higher transconductance like a 12at7, the same values used for a 12ax7 do not reflect the same bias point or where the load sits in the grid curves. I used two 100K plate plate resistors and two 1. Approximate power available per channel at "clipping" (both CH. Now, looking at the curve we see that not only is it set to an O. DC voltages are locked to the voltage of the reference tube to ensure a stable operating point. I strongly recommend choosing a capacitor with a voltage rating well in excess of the expected operating voltage, so as to handle unexpected voltage surges or any other event that may tax the capacitor. We would pick an operating point (plate voltage, bias voltage) and plot a tangent to the grid voltage curve at the operating point. In an amplifier with high input impedance, increasing the gain will introduce a DC offset which affects the operating point of the circuit (changes the balance of the amplifier). The DC voltage on the output is restored by a chain of Zener diodes and the DC operating point is controlled by adjusting the cathode resistor of the. The Heathkit TT-1 estimates Gm by applying an AC signal Vg (at about 5 kHz) to grid and exciting an AC ammeter response to measure variation in plate current. If your power transformer has a 5V, 3A rectifier winding, you can experiment with rectifiers. The exclamation point triangular symbol is intended to alert the user to the presence of important operating and maintenance (servicing) instructions in the user manual accompanying this amplifier!. The idea here is that tubes that match at two different points on their operating curves are likely to remain reasonably matched at higher plate voltages, or other changed operating conditions, as well. Mit Flexionstabellen der verschiedenen Fälle und Zeiten Aussprache und relevante Diskussionen Kostenloser Vokabeltrainer. EEVblog #516 - LTSPICE Tutorial - DC Operating Point Analysis - Duration: (12ax7) tube Spice. Maximum µ point can be found experimentally by achieving minimum distortion of an unloaded cathode follower at high signal level. ECC83 (12AX7) Microphone needed to set the dc operating point of the valve, it must be bypassed for ac signals by Ck to connect this input to signal ground. If the valve sound converter is inserted between a preamplifier and the power amplifier, it should be before the volume control potentiometer as otherwise the sound will change. However, the Mark V is design to enhance the gain structure by shifting the operating point of the triodes for different channel selection. The total current is 17 ma on dynamic swing, or 18 ma in quiescent condition, and we require. That would be the operating-point +/- 2. They just don't see the point in low watt amps, and frankly look down on anyone who doesn't play a 100w Marshall stack. In some tubes, maximum µ can be obtained at a modest negative bias. A shorted filter will cause smoke and blow the fuse; an open or intermittent-open filter cap will cause hum, distortion and weak tone. The complete datasheet for the 6v6. Sears 1465 Silvertone (Chassis 185. Home / FAQ / News Classifieds / Events: Tubes Asylum: 12AX7 operating point with low supply voltage. The Heathkit TT-1 estimates Gm by applying an AC signal Vg (at about 5 kHz) to grid and exciting an AC ammeter response to measure variation in plate current. It had a metal envelope which was popular at that time for use in radio sets since it was less likely to break than a glass envelope. Not the best tube operating point but nonetheless a real tube. The LM-845 Premium uses Shuguang 300B tubes in drivers, the 310A for amplifier and Shuguang 12AX7 in pre-amplification. Maximum µ point can be found experimentally by achieving minimum distortion of an unloaded cathode follower at high signal level. Victoria Ivy League The new Ivy League is a loving recreation of the classic 5F10 Fender Harvard style amplifier. Requires 4 triode per channel to work, & the common practice is to use dual triode envelope valve, such as 12AX7, ECC88, 6N1P, ECC81, 6SN7 etc etc. A Comparison of Current Production 6L6GC Tubes. You can express such operating specifications as requirements on the system state x and inputs u. (Adjust the cathode resistor to give each section anywhere from 16 to 20mA of quiescent current, depending on personal taste, and the sonics of your favorite tube and your favorite operating point. 7, we see the results of measurements taken from several 12AX7 (Siemens, Valvo, Brimar, Mazda, Ultron, TAD). Quiescent Point. the tube may not establish its correct operating point. Ironically, 'better' valves with lower leakage current would run hotter, but the point is the configuration doesn't suggest predictability IMO, and operating point seems likely to much depend on the 12AX7 fitted. For purchase is (1) Tung Sol 12AX7 Cryo Preamp Vacuum Tube. If the valve sound converter is inserted between a preamplifier and the power amplifier, it should be before the volume control potentiometer as otherwise the sound will change. A reasonable bias point (which we will call Q) corresponds to a plate current of i d =10. We’re glad you’re here. If the adjustment failed, check and vary the cathode resistors of the voltage-feedback-valve and the final stage valve. The mighty 6L6 power tube is known for its crisp and driving tonal quality when pushed to the max, and the V55HD harnesses every ounce of that power to awesome effect. The nominal operating point levels of Vgk=-2. It is usually the case that two different testers will give substantially different values for Gm on the same tube. I know this has been discussed before, if not here, then plenty times. Get a low price and free shipping on thousands of. No, it's viewing a representation of the definite location of the DC operating point (Q point) of the load line where one tube is being driven out of cutoff while the other tube is biased into cutoff (due to phase inverter action). from this central point on the grid characteristics will give us suitable amplification. In an amplifier with high input impedance, increasing the gain will introduce a DC offset which affects the operating point of the circuit (changes the balance of the amplifier). Well the ALLEN was designed for 12ax7 as u can see it stamped on the back of the amp in my video. 3 volt operation - twice that of a 12AX7 and the plate resistance is half that of the 12AX7. After completion of all the changes , the preamp sounds much richer , clearer and more detailed to my ears. The only 12AX7 alternative I've had success with is the 5751, but I still prefer a NOS 12AX7 over all. The green color line plot is the output voltage wave form and the blue color line plot is the input voltage wave form. The SC26 was then as quiet as my solid-state preamplifiers—at least on casual listen. To get operating points back where they should be I'll simply remove the wire link across to the 12AX7 and bias it separately. The hand-built 5-watt amplifier is driven by a 12AX7 tube in the front-end preamplifier stage, an EL84 tube in the output stage, and powers an 8" Turbosound. 12AX7 load line associated with driver stage The load line above is the result of the decision to use a +HT = +300V power supply, recommended by [1], and a 183 kOhm load resistance, which lies within a range recommended by [1] [2] [3]. The original 'Point' was on the south side of the Neuse River east of Hancock Creek, and the word 'Cherry' came from cherry trees that at one time grew on the point. The result of this analysis is generally referred as the bias point or quiescent point, Q-point. Fortunately, the 6SL7 driver I'm using has a high transconductance and yields about 25x gain even without a bypass cap. We have had a lot of time to test these and have found that they have proved consistant and reliable. 2mA of current, 4000ohm resistance, transconductance of 1600 and gain of 100. will shift the operating point of the Fetron. By 20mA, they are beginning to level off, so let's use that as a starting point. It looked the same on the tube curve tracer, sounded the same, worked the same, as a 12AX7. If you leave them open the simulation engine will try. triode such as a 12AX7 as a grounded cathode amplifier, coupled to another triode acting as a cathode follower. P a: Anode power dissipation at. In that context, removing the capacitors and inductors (setting them to 0) makes sense because you are trying to find the DC steady state solution. 5K cathode resistors in parallel to assure the values are truly halved relative to the single triode comparison stage (same resistor stock for both). in the application circuit. The Bugera V22HD Infinium 2-Channel Tube Amplifier Head with Infinium Tube Life Multiplier and Reverb exudes tone and style, plus possesses modern features that will launch your sound into the sonic stratosphere. High gain, ultra-low microphonics, and superb linearity with a dynamic 3-D sound. This is not to suggest that you cannot test those tubes with this tester. R4 should be changed to 100 Ω, and R8 to 680 Ω. I only got the Sovtec for use as a PI. By means of the load line you can read off current, voltage, and bias conditions without any further calculations. The RC timeconstant between resistor and capacitor determines which frequencies are carried by the +B to cathode capacitor and which will flow through the powersupply and cathode capacitor (it is basically a highpass). Product Description for the Bugera V22 Infinium. Bias Conditions and Operating Point: The first stage, Q1 was designed to operate with a collector current of 200 uA. The grid bias is -45V. DC voltages are locked to the voltage of the reference tube to ensure a stable operating point. Hickok 600A Microomha Tube Tester - $150 This allows you to check the tube tester at any random operating point you choose. The 2K on the pentode should be about right. So, I have guitar direct in to a single-ended class A (12AX7 and 6V6) Champ-style amp. You want to know why these tubes sound clean? It's because running a 12AU7 or 12AT7 in a circuit designed for a 12AX7 biases them cold, damn near sterile. If you REALLY want to mix soup with nuts, build a mu-amp with a high-voltage MOSFET working the plate load. From a practical point of view, at least as far as audio is concerned, the moral of all this is to operate tubes at as high a standing current and as low a bias level (i. Power tubes. From the graph, the red dot is the picked operation point, you can see the grid voltage is at -1V, plate voltage is about 130V, plate current is at 0. Do you need the 100k? If so, could you use a lower fixed resistance multiplied by feedback, and could that arrangement alleviate the grid current problem? The only mention I found of grid current in datasheets is on page two in this:. A masterfully crafted all-tube combo amplifier, the V5 provides sweetly-balanced harmonics and natural tube compression, resulting in the warm distortion and break-up you™ve come to appreciate from those vintage megaliths of yesteryear “ only in a much more portable and attractive package. Well then, you have the trong tube to begin with. 8V (shown in green above). I see a lot of schematics using, for example 12AX7/12AU7 or 6SN7/6SL7 in the same amp. Fig 5 plots this for the entire range. As a result many good 12AX7’s test low on the Cardmatic. Its two input jacks give me two choices: a single 1/2 12AX7 triode, or both halves in parallel. And when you increase the input to around 0. that is off the chart - it is swept by the drive signal to places that one would normally not bring this tube into in actual service, and which includes non-linearities like crazy. Pictures below are LTspice simulation results. The VINTAGE V22 INFINIUM features true Class-A technology with a 3 x 12AX7 front-end and 2 x EL84 power stage. Product Description for the Bugera V22 Infinium. Exuding vintage sound and style, the Bugera V55HD Infinium guitar amp head gives you 55 watts of phenomenal all-tube tone. Without doing a proper design-check, I'd expect the 12AV7 to exhibit slightly more gain when plugged in the same socket, albeit with the possibility of being biased to a poor operating point for the tube. Well, the Marshall DSL5C just isn’t for them. 5V grid line and the 1. R3 (1K Plate Resistor) - The plate resistor drops the voltage and limits the current to the anode of the first triode of the 12AX7. Of course you can always replace a 12AU7 with an ECC82 and vice versa, because these are just different names for the same type of tube. A 12AT7 can replace a 12AX7 at the phase inverter (actually drives the power tubes harder), but shouldn't be used as a replacement gain stage. The following figure shows the starved 12AX7 frequency response between 10 Hz and 20 kHz with anode load potentiometer varying from 0 to 1. It was felt that this gave lower distortion than for a pair of tubes pushed to their limit. You can also have the 3/2 law for any value of the operating point such that k takes the value k=1/2*z^(-3/4) where z is the normalized input voltage. My favorites are the 5V4G and 5Y3, but have also used GZ34/5AR4 and 5U4. The purpose of the regulator is twofold: to reduce residual AC hum from the AC smoothing filter, and to maintain a constant DC voltage (within limits) as the load demand and AC power line vary. The VINTAGE V22 INFINIUM features true Class-A technology with a 3 x 12AX7 front-end and 2 x EL84 power stage. I know this has been discussed before, if not here, then plenty times. Generic Part Number. The input voltage signal is added to the grid bias voltage and is amplified. Is there a known problem with the models or am I doing something wrong?. I get preamp tubes in a preamp, but I've 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. Looking at the D3a datasheet, we see that both plate resistance and mu vary rather steeply with current at low currents. (Which means it is definitely operating in SE mode, and not push-pull. In that context, removing the capacitors and inductors (setting them to 0) makes sense because you are trying to find the DC steady state solution. A fantastic, medium-powered, highly portable 1x12" tube combo. This is certainly the best 12AX7 that Sovtek have.