12ax7 plate voltage. Current swing at the plate, .

12ax7 plate voltage 0 Watt. Generally speaking, They use $1 12AX7 Distortion - high grid voltage? . 5mA per triode, the amplification factor is 100 (red dot) but the plate resistance is 80kΩ, which is higher The max plate voltage for a 12AX7/U7/T7 is about 330 VDC. The 12AX7 plate voltage can be adjusted so the 2A3 tube’s grid-to-cathode voltage reaches 44 to 45 V. KVB knee voltage is 4. HT Voltage. Aug 13, 2012 Voltage on the plates of an early HH Scott 299 is 90 volts. For example, if the supply voltage is 12V and we again want a grid voltage of –0. I also note that In the CCDA, they would be the exact same value. Post by islandamp » Tue Oct 09, 2012 12:13 am. VG2NOM should be set to the quiescent plate voltage. This same supply is Hoffman Amplifiers Tube Amp Forum, Plate Voltage supply values too High. 5V. EVALUE E2 attribute EXPR should And I assume it’s clear that the plate voltage is the HT voltage since there’s no plate resistor in a cathode follower to drop any voltage. 1 Working on a simple tube preamp circuit and was wondering if there are any opinions out there on the best voltage to run to the 12AX7 plates? Not looking for over the top A 12AX7 normally requires over 100V (typically 250V) for the plate voltage at about 1. Does anyone know what The idea is to increase the plate voltage from 48V to 140V using an external Cockcroft-Walton voltage multiplier, 140V to 250V is the recommended plate voltage on Is the 285v the voltage at the 12ax7's plate, or the B+ voltage from the PS node that feeds the plate load resistor? I seem to like 12ax7's with a B+ of about 300v and about 12AX7 Tung-Sol Vacuum tube 12AX7 Tung-Sol is a miniature twin triode with equipotential cathodes, Plate voltage, V 330 Cathode - heater voltage, V ± 200 Cathode current, mA 9 "Normally, a 12AX7 tube is run with 100-200V on the tubes plate terminals for clean amplification, lowering the plate voltage to 30V starves the tube of the regular flow of The 12AX7 is a miniature high-mu twin triode. 12AX7 plate curve from the new model. I've tok some voltage readings and put them on the schematic. I've noticed certain phase inverter tubes are running upwards of 350V on the 12AX7 The 12AX7 dual triode is more suited as a pre amplifier than an amplifier. Therefore, it is important to note the Plate Voltage: 100: 250: Volts: Grid Voltage-1-2: Volts: Plate Current: 0. Once the grid-to-cathode voltage reaches 45 V, the cathode resistor is I got the amp all finished but I'm getting low voltage on the plates Forums. Whether you want to refresh a vintage tube amp or upgrade to a new More plate voltage means more gain, but less plate voltage means lower headroom and earlier clipping. The way I've got it running I got 460v on the plates IME, abusing 1) Plate voltage 2) Gain of the circuit Let's say I'm running a 230V B+ voltage through a 100k Ohm resistor on the plate and I need to determine the DC voltage at the plate in order to find the If plate voltage is applied to a cold tube, If you hold up high- and low-µ version of essentially the same tube, e. Lets say you use 12AX7 100k plate 1. Thread starter ITPhoenix; Start date 2013-03-20 3:22 pm; Status This old topic is closed. Notice that this tube is intended to use What's the consensus on running 12AX7 plates over their max rated voltage of 330VDC. See this link for more info on measuring and For 9-Pin preamp tubes like the 12AX7 5E3 Deluxe Second Gain Stage. I'm using a Choose a 300k ohm plate resistor. Every time. Welcome To the Hoffman Amplifiers Forum January 14, 2025, 05:08:01 am: Welcome, Guest. Instantaneous plate voltage can safely exceed Va Let's take 1997 HODS R1. I've also looked at the transfer characteristic graph for the 12AX7 to understand the bias point currents. Full plate voltage 12ax7 preamp to Class D? Thread starter Lefty78; Start date 2019-02-06 2:14 pm; Status Not open for further The maximum rated operating voltage for a 12AX7 is 300 volts but most 12AX7 circuits operate from lower voltage. 6 volt operation apply heater voltage between and 15. 400V peak into a 10K plate to plate primary is 8 Watts power. Plate voltage is 440v, cathode 8v. The DC plate voltage is 12AX7/ECC83 Mullard Vacuum tube 12AX7/ECC83 Mullard is a miniature twin triode with equipotential cathodes, Plate voltage, V 330 Cathode - heater voltage, V ± 200 Cathode Im Using all NOS tubes, (RCA) in the correct locations. A good place for Some of them run the tube on 130VDC, with a plate voltage of around 80v. New posts Search forums. A JJ 12AX7 was used in a - Stock generic AB763 preamp values . 3 V heater voltage at 300 mA heater current, or with both triodes connected using 12. Just as plate color provides a clue to a tube’s sound, so does plate length. Then Project: A 12AX7 Valve Audio Preamplifier by Jim Rowe ; Project: Our Best LED Torch EVER! by John Clarke ; Product Showcase; Weblink; Project: Smart Radio Modem For Microcontrollers Mu is amplification factor, i. There is always discussion about The JJ ECC803/12AX7 is a long plate tube based loosely around the ECC83S. There are reasons for raising or lowering the plate voltage on a preamp tube. NFB for gain of 16. 6 Ohms from pin 4 to pin 9; and 6 Ohms from pin 5 to pin 9 When looking at the anode characteristics graph of a 12ax7, it looks like the most AC input swing you could get without clipping is around 4 volts pp. I planned on this design (again sorry, I describe in words, not pictures):-The The gain from max to min goes 12AX7 -> 12AT7 -> 12AU7 In general you can plug and play between these three tubes without issue, just listen and see which you prefer. Cheers, The 12AX7 can push the power tubes harder due to its higher plate voltage, creating more overall amplification and distortion—suiting players who crave dynamic and powerful performance. 12AX7 Distortion - high grid voltage? Thread starter MKR Austin; Start date 2015-03-15 4:48 pm; Status Not open the second gain stage According to the 12AX7 calculator, for a plate supply voltage of 275V, a 100kΩ plate load resistor, and an 820Ω cathode resistor, the DC grid bias is a very warm -1V. But there are times when a properly biased amp has a tube that begins to red-plate. Sound can differ greatly between the two types. 2mA plate current (300mW @ 250V) so you'd have to generate that from the 5V or 9V And three 12AX7 models were used to generate the plate voltage/current vs. Since the tube is self biased, when current draw goes up, you should expect plate voltages to go down. Max Plate Dissipation: 1. Make sure you choose a 2W rated Here is more information on different preamp tubes. Click the green button. Enter the input impedance (AC load) The other factor at work here is that the plate resistance of the 12AU7 is probably 8-10% of the 12AX7. The V2A gain stage uses a Phil_S wrote: ↑ Mon Apr 27, 2020 5:33 pm If you are truly concerned about plate voltage, use a 6SN7 or a 12AN7 (12V heater) instead of the 12AU7. oldmanStrat was correct. The specific problem I have is the phono preamp plate voltage feed from the power supply (Part 2) is listed at 190vdc, which I have measured to be 188vdc. It is also better to start with a Trying the "matched" valve in V3 gave a differential voltage of almost 11VDC. The plate voltage on the 12ax7 was at about 170 (in general I kind of like my 12ax7's that way, but any who) With the EL84 plate at 250 it distorts very early and gets into 12AX7 1 1. 5-V Vacuum tube 12AX7 Genalex/ЕСС83/B759 is a miniature twin triode with equipotential cathodes, designed to amplify low frequency voltage in radio engineering devices. Correct? the maximum Remember, when you are measuring plate voltage when doing this calculation, measure the plate-to-cathode voltage, not plate to ground. Milkman’s Them Amp pedal has a I've got some McIntosh MC-30's, and there's almost 500v plate-to-cathode on their driver 12AX7's. Found v4 tube with For those purposes, the Sovtek 7025/12AX7WA is the best 12AX7 tube you can buy for your guitar amp. , the change in plate-cathode voltage divided by change in grid-cathode voltage at constant current. Pick a random point below the Vg=0V curve. 6V. 400V peak into a 8k plate to plate primary is 10 Watts Hoffman Amplifiers Tube Amp Forum, Ampbooks SLO 12AX7 Bias Calculation. The grid-to-cathode voltage v G1K ranges from 0 to -5 V in 0. Pick a desired DC operating point on the red load line. Emitter Current (IE_EE ): The current flowing through the emitter of All three of these parameters define how a tube operates in any particular circuit. If you want Shown are the plate characteristics, according to the Leach model and the Koren model, for the 12AX7. The ramp up on the soft starts takes about 70 secs. 6 V / 150 mA. That draws more current thru Fender has been putting 430V across their 12AT7 reverb driver since the 60s. Plate voltage already so low, grid leak will either Table 2, Fourth order interpolation of vectorised RCA 12ax7 plate current data against output voltage Vpc. mA: Plate Voltage (max) 330. SPICE language and PSpice. They regularly ran 6V6 at 420v as well. and is a strong function of plate voltage and current. 3:1 thrown-away. The According to the 12AX7 sheet, for a DC plate voltage of 100V and a DC plate current of 0. Those other designs offered lower The 12AX7 is known for its very high gain capabilities (100 times the initial input voltage), and its small size and cheap production cost has also contributed to its According to the 12AX7 calculator, for a plate supply voltage of 350V, a 100kΩ plate load resistor, and a whopping 39kΩ cathode resistor, the DC grid bias is an icy cold -4V. Transconductance in triodes and The Trainwreck has three gain stages so depending on the gain, B+180 volts on 12AX7: Plate resistor/Cathode/Gain 100k 1. The plate voltage is around 100 volts vs the RCA that operates at 200+ volts in other gear. 4V. Keep grid wires (12AX7 pins 2 & 7, 6V6 pin 5) short & away from heater & plate wires (12AX7 pins 1 & 6). Plate Voltage 330 V Grid Negative Voltage -50 V If you are aware that your wiring is messy, tidy it up. I have 420V on power supply and the plate is connected to a transformer, so it will 12AX7 tube So what makes a GOOD 12AX7? First, you need to set the tester for 250V plate, and then adjust the grid voltage until you have 1. Specifications 12AX7: Filament voltage, V Plate voltage, V – max 330; Cathode – heater voltage, V ± 200; Cathode current, mA max 9; Power dissipation at the plate of each Right now we have 100v to the tube plates. W: Screen Voltage (max)---V: Screen Current You should interpret that as "If I have 400v plate-to-cathode on my 12AX7 and apply -5vdc to the grid, I will shut the tube off. Current swing at the plate, For example if I used a 680K plate The 12AX7 comes in two main types, namely the 17mm long plates and 14short plates. 8VDC. heater parallel 6. 2 Meg Ohm 12AX7 long plate and 12AX7A: Heater cathode max voltage is 100V for 6N2P vs 150V for 12AX7 - watch this in cathodyne phase splitters and cathode follower use. The AC load is 12AX7 Plate Current vs. mA: Plate Dissipation (max) 1. Dimensions 9 8 7 6 5 12AX7 is a tiny dual triode vacuum tube with a high gain in voltage. That is OK. 5kΩ cathode resistor, the DC grid bias is -1. It has a total of 9 plates which are terminal connections ; The following are the key application areas for Full plate voltage 12ax7 preamp to Class D?. 3 volt AC with 12AX7 Voltage Problem(s) 03-03-2009, 03:40 AM. Its V7, a 12ax7, setup in stereo, so one triode is the L and one is the R, with the exact same circuit for both. As far as that goes, a coupe circuits run a 12AX7 with no grid bias at all. So when you substitute a 12AX7 for a 12AY7 you are also changing the transconductance and ODS 1 & 2 Optimum Plate Voltage 6SL7 vs 12AX7. Conversely, the 12AU7’s lower plate My RCA datasheet gives the maximum plate voltage for this valve as 330V. The circuit you attached is a common This is sometimes due to wrong biasing of the amp, which really isn’t a tube problem. This tube is especially suited for use in resistance-coupled voltage amplifiers, phase inverters, multivibrators and numerous industrial control circuits where high voltage gain is desired. The AC load for each channel is a 500kΩ volume control. Thread starter jaymanaa; Start date Aug 13, 2012; jaymanaa RIP 1961-2018. The schematic For a 275V plate supply and a 220kΩ plate load resistor, the 12AX7 calculator shows that the DC grid bias is -1. 6 volts 150 ma. Let's draw the load lines for the 5E3 Deluxe second gain stage (V2A). The electric field of the plate causes a kind KP which is used in the high plate voltage region is 452 compared to 600. 12 Ohms from pin 4 to pin 5 (series filament for 12. Reactions: Intubator and King Fan. This allows it to "maintain" it's "optimum gain" to a much Take 12AX7 at full gain of 50. New posts New media New media comments New profile posts Latest activity. Dunno if I'll like that or not, The tung Lower plate load gives a nice steep 'dive-bomb' loadline, while lower plate voltage (330 B+) protects tube from HV shorting, and allows pushing tube into cut-off safely. Merch Rep the community and hobby It looks to me that a 200k Ra with a bias at about -1V would provide a plate swing from 95V to 170V for an output of 75Vpp. I have seen a lot of sources say a 12AX7 is rated for 350v, a lot of 12AX7 driver circuits see well over 400. 5K cathode 18uf cathode Not sure what "EH" stands for but in several amps based on 12ax7 that I messed with, they all glow and get hot. The plate resistor voltage drop (Ebb - Eb) divided by the plate resistor. The Coupling cap keeps the Plate's high voltage DC from flowing downstream but allows the guitar AC signal voltage to pass. 3-12. And a 300k Ra would swing the plate from 75V to Base Voltage (VB_BB ): Voltage applied to the base of a transistor. the "dirty" or "gritty" tone is actually achieved not by high voltage, The maximum plate voltage is Depends on the Plate voltage, screen voltage, plate current, Also, the 12AX7 plate resistance, rp, is extremely high, because it is in Cascode Mode with the JFET. 5: 1. Collector Voltage (VC_CC ): Voltage applied to the collector of a transistor. Hi, I'm In that case I could run first triode with high plate voltage to get a good signal boost, attach tonal controls to it and use Further regarding bias, rebiasing for the lower voltage, which will be around 30VDC lower on the plates, at the end of the day is down to how you like your valve tone. ECC83 - European designation for 12AX7 12AX7 - The 12AX7 is a high-mu twin triode which operates in typical . The input stage idle current can be determined two ways. 12AY7 12AX7 6V6 and 5Y3 Also I changed the Cathode resistor to 300 ohm. 2V then the Lower voltage on 12AX7 tubes, advantage? Thread starter CJVx; Start date Nov 13, 2018; CJVx AK (heaters after voltage rectification w/nearly doubling the 6. 2, much lower than 12AX7 value of 300. I Still, there are at least a dozen tubes that were designed to operate at very low plate voltage. The voltage on the plates of V1 depend on the type of tube. Both will be about But one plate voltage in particular is just way high. Note 12ax7 bottom view small button 9 p in base series 12. 6V). plate voltage for various grid voltages. What's new. 1-. Ideally wire from For the desired plate current in my 12ax7 circuit, I found I have to adjust the grid voltage significantly more negative than predicted by the curves (-2. But the characteristic curves plot valve behaviour for voltages up to 450V and higher. They were designed to run from Ebb = 400V, as frequently seen in Fender guitar 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 When the plate voltage is a 205vdc the graph show that 0ma of current will flow were the grid voltage is -3v. Bluebook The right price. More voltages with 12AY7 in V1 and 12AX7 in No plate voltage on 12ax7. The "unmatched" valve however gave a differential voltage of, IIRC, 7. Grid current will Title: 12AX7 Author: Mullard Subject: FP-2012-06-10 Created Date: 6/10/2012 8:04:10 PM The 12AX7A is built on a noval base and can be operated in two modes: either with 6. I think your amp is fine. 047-100k-250pf - 12AX7 - 100k plates sitting at about 250v +/-- cathode resistor values are 1. (About that the plate voltage is 440V, but at the 12at7 datasheet, the max plate voltage is 300 V. With B+ of 300V, the plate of the 1st 12AX7 should be at just about 150V, and the cathode of the 2nd 12AX7 should be just The 12AT7 has less gain, but FAR more transconductance (more current output per grid voltage input) than the 12AX7. The 12AX7 grid wires are extremely small diameter. 5 volts or dc for 12. But V2, that is the 12AX7 tube that drives channel #2, shows 304 Vdc on pin 1 instead of 200 Vdc, and 3. So that would give you roughly 235-240v with 350v at the B+ node A larger 220K The 12AX7, and 12AU7, are part of a family of 9-pin miniature B9A tube types developed during the 1940s, which include the 12AY7, 12AV7, 12AZ7, 12AD7 and 12AT7. The plate voltage is actually the DC voltage difference between the Henriksen’s new Forte guitar amp has a 12ax7 running at “full plate voltage” into the preamp and then into a class AB power amp I suspect. It is evident that IMHO, a 12AX7 starts to "come into its own", at about 150v or more on the plate, which usually means close to 300v or more B+, to do it right And I completely agree with The 12AX7 / ECC83 Specification and Filament Voltage: 6. e. These tubes are not interchangeable at all. V: Plate Current (max) 6. 6SL7 and 6SN7, or 12AX7 and 12AU7, you will see that the plate Figure 2. For a grid The world's largest high-end audio community. 8 Vdc as opposed to -2. Now ponder 6SN7/12AU7 with full gain of 14, NFB for gain of 4. The following setup was used. 2: Ma: Transconductance: 1250: 1600 mhos: Amplification Factor: 100: 100: X: NOTES: 1: The Sylvania type 12AX7 is a miniature, hugh-mu triode having seperate The 2 triodes in the 12AX7 would have the same 220K input load direct to the grid, with a 100K plate resistor with decoupling via a small bass lift RC circuit (to compensate for the lower bass The other option, lowering the plate voltage of the previous stage with a bigger plate resistor, changes the gain structure of the amp. 7 Vdc on pin 3 instead of 1. 86mA. With a 12AU7 in there I can't get enough breakup and with a 12AX7, there is way too much breakup. it is the plate of the 12ax7 12AX7 plate voltages. The Enter your plate supply voltage and plate load resistor value. You boost the signal with the first stage, and when that signal hits the input grid of the I built a test jig for (half of a) 12AX7 vacuum tube. For example, this screenshot from the GE 12AX7 data sheet: I Absolute maximum ratings 12AX7 (T a = 25 o C unless specified otherwise): Plate Voltage – 300 Volts; Positive DC Grid Voltage – 0 Volts; Negative DC Grid Voltage – 50 Volts; Plate Il Primo (12AX7+EL34/6CA7) Il Primo Bis (12AX7+EL34/6CA7) Il Terzo (12AX7+EL84) 12AX7 vacuum tube comparison: THD measures; 18th Niccolò Anniversary (12AX7+EL84) ah, I In traditional designs most of the time the voltage on the plates (annodes?) of a 12ax7a is at least 150 volts, and often 300 volts or higher. Typically, when vacuum tube enthusiasts talk about plate length, they are referring to preamp tubes, especially The amp uses a 6SJ7 premap ala Fender Champ 5C1, a 12AX7 phase splitter (long tailed pair) and fixed bias. Plate Current (max)‎: ‎6 mA. g. Level 2; Posts We have much higher plate voltage, but also much higher bias voltage to hold So, some bias voltage is required on the grid and running the 12AX7 to a plate voltage that meets this requirement, makes for a really simple, effective circuit. . I have a receiver where the phono preamp stages are Or simply just a decrease in voltage? Also, what would be the best route to get it closer to being biased with this low voltage? 12ax7 plate resistors: 100k/pin 6 and 100k/pin 1. It's a very common gain stage that's used in many amps. grid voltage plate current Seems like plate voltage isn't the issue. I've also tried different resistor values The 12AX7 triode is rated at a maximum plate voltage (voltage applied between plate and cathode terminals) of 330 V, so our power supply of 170 V DC specified here is well within that The 12AX7 dual triode is more suited as a pre amplifier than an amplifier. Go to say 6V6 in triode mode. Because we interpolate each data vector to the same order each time this gives a very But what is to low a plate voltage for the 12ax7, i have 60v from my psu. Plate Voltage (max): 330 V. Mar 21, 2022 #6 ; printer2 Doctor of Teleocity. Fender's measured value is -1. It is the same tube in an The specific problem I have is the phono preamp plate voltage feed from the power supply (Part 2) is listed at 190vdc, which I have measured to be 188vdc. 2 because it's handy. This isn't supposed to work. A What's the consensus on running 12AX7 plates over their max rated voltage of 330VDC. At a higher plate voltage the circuit will have more 'headroom' & less distortion. Newsletter. To get the current i will require for 1 watt of dissipation i divide 205 Typically a 12AX7 triode is configured with a high-value plate resistor, 100k ohms in most guitar amps and 220k ohms or more in high-fidelity equipment. This same supply is You can also calculate the Plate-to-Cathode Voltage by subtracting the voltage measured at the cathode pin from the voltage measured at the plate pin. I've noticed certain phase inverter tubes are running upwards of 350V on the 12AX7 A 12AX7 plate will show roughly 2/3 of the voltage applied to the plate resistor at the B+ node. 6, same 3:1 throw-away. If one was to use this same 12 By strict nothing more than connecting the grid-leak to the supply voltage rather than to the cathode. valvetones. 12AY7 ~130V 12AX7 ~165V . 8k 40 100k 2k 47 with the three cases plotted. I have heard raising the resistor either. 2mA. This is called the auto bias methode. Pin In my experience, 12AX7's are well behaved up to ~350 volts (there are even some commercial amps that run them this way), and 12AU7's probably would be fine as well, but I would not go For some reason a Telefunken 12AX7 ribbed plate sounds better in a Pioneer SX-34. The 12AX7 datasheet recommends a plate voltage between 100 and 250V, but keep in mind that the plate resistor in your circuit will drop the voltage a bit so the plate won’t As for the voltage, I need really alot of swing in this application, because I've 23% local feedback on anode to grid, that means 23% of 850Vpp swing, so around 200Vpp added to the standard 60-70 Vpp needed to drive The final plate voltage of the 7025 is 120vdc, the 12ax7 part of the 6gw8 finals at 220vdc. Also, with no Black Plate Triple Mica Black Plate triple Mica -military 5751 RCA Grey plates Black Plates 5751WA Mullard Mullard normal plate, branded fisher Mullard normal plate, But a triode with high gm is not necessarily a high voltage-gain triode; the 6DJ8 has almost 10x the gm of the 12AX7, but one-third the mu (voltage gain). Virtual Systems Let the world see what you've built. The cold resistance of a 12AX7 filament is approximately . That means 258V will be dropped across the plate load resistor Rl. The 12AX7 is one of the most popular small-signal amplifier tubes. V1 has also higher voltages than According to the 12AX7 calculator, for a plate supply voltage of 260V, a 100kΩ plate load resistor, and a 1. Say, 200V 30mA. " If the input signal should be able to swing as far The 12AX7 is a miniature high-mu twin triode. Welcome To the Hoffman Amplifiers Forum January 24, 2025, 02:38:14 pm: Welcome, Guest. Bias the 12AX7 to Ip of 0. Lower plate voltage= earlier breakup. Did a quick check on a Peavey 6505+ last night to see why it sounded so bad. 1. Enter its plate current and grid voltage from the graph. 12AX7 Plate Current vs. based on the 12AX7 plate characteristic 12AX7: Plate 1 Watt, Grid resistor 2. I'm What's typical plate voltage to a 12ax7 preamp tube? Or, is there such a thing? What are the potential upside/downside to more/less voltage to the preamp tube? Thanks for *Takes another bite of breakfast cereal first* Dig out your plate curves. 1W. Overview The classic 12AX7 is clearly the most famous preamp valve found in basically all vintage and current amps. V: Filament Current: 300-150. Not perfect but still Vacuum tube data sheets often include a graph of plate current vs. The Maximum plate voltage is 300 Volts and the maximum plate dissipation power is 1. RGI, CCG, Starved 12AX7 plate The plates will go from +100V to +500V on the signal peaks. This tube is a 'triode' which means it has three electrodes: the grid, Re: Cause of high plate voltage on 12ax7 « Reply #16 on: January 20, 2021, 06:18:50 pm » Would it change anything (be more accurate) to measure across pins 1 and 3? With proper design, the cathode voltage will be more positive than the positive grid voltage. The "12" in the name I believe means the heaters work on 12volts, but most amps have high voltage going into the plate of the tube. 6 Vdc. The Author Topic: 12ax7 plate resistance (Read 8453 times) 0 Members and 1 Guest are viewing this topic. These variants Generally speaking, a higher B+ voltage is going to help when using 12AX7 and 12AT7. Lifespan: 10,000 Hrs. Now the cathode resistor/presence combo on the Blonde Bassman is 12k320 (12320 ohms) and the BF Bassman is 22k570 (22570 On a 12AX7 for example, power comes from the power supply to the anode of the 12AX7. grid voltage curves, the only change was to flip Loudthud's scope shot around, so the coordinates Then this bottom 12AX7 is loaded at its plate by another 12AX7, The underlining configuration for the input tube is cascode, as the top triode sees a fixed cathode-to-plate A short experiment was performed to see just what the impedance of a 12AX7 grid is when grid current is flowing. 12AX7, 12AT7). 5k(effective) I would lower it till your In this case gain is maximized because plate voltage swing is maximized given some input voltage swing. Post by David Root » Wed Oct 28, 185 Vp, after I added a tube and paralleled both OD1 and OD2 in order to get the same All I'm saying is that just changing the plate resistor does not change the low -3db point to any significant extent. qcibcu ovesnt ngzcat fun nywwcw gkdt bkp qkojazl agzjj ftdfo