12ax7 cathode voltage

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. So, the gain is 80 x 0.9 x 0.9 = 64.8 Usually 12AX7's have a limitation on the heater voltage (heaters are inside the cathodes) and the voltage on the cathode. Step 2: Triode mathematical model This calculator uses the triode equation of Norman Koren to calculate the anode current as function of grid-cathode voltage and anode-cathode voltage. Plate voltage at the tube pins around 200v.' That seems to give me a very nice clean sound and OD sound. ECC832 (T-12DW7-JJ-X) TUBE/PIN. You're good. The lower gain of the 12AT7 and 12AU7 also allows them to have a higher headroom, which can provide a warmer . The tube's Cathode is the source of electrons. Double Triode Quick reference data • Anode current Ia=1,2mA • Transcoductance S=1,6mA/V • Amplification µ=100 Heating Heating is indirect by AC od DC, with serial or parallel supply. The 12AU7 has the smallest, at just 20. The first attempt to drive the 12AX7 used a cathode follower: The 6N3P triodes were paralleled, and connected as a cathode follower to drive the transformer. The cure ? The problem would seem to be the "maximum heater relative to Cathode, negative Voltage" in the case of the 12AX7, this is rated at, in many peoples eyes optomistic, 180Volts. Arrow points to the insertion index notch. If I feed the third gain stage with the signal right from the second plate, the sound cuts shortly after emitting crackling sound. Show activity on this post. high linearity over a wide range implies that we need a high output voltage, but given that the 12AX7 has limited gain, that also means the input voltage will be high too. I must mention that if the driver tubes are removed while the amplifier is . ECC83/12AX7 Page 1 of 4 ECC83 is A.F. Use a 24v or less zener. . Product Data. The elevation voltage should be decoupled/smoothed with an arbitrarily large capacitor (C1), say 10uF or more. Don't make the mistake of thinking solely in terms of voltage—current is equally important in a buffer's design. The 12AX7 tube is one of the pin-compatible tubes ( 5751, 12AT7, 12AY7, 12AV7, 12AU7) with differing gains. This capacitance-multiplication effect is called the Miller effect, and the extra 'phantom' capacitance is called the Miller capacitance. The optional Bypass capacitor boosts gain by acting as an electron reservoir. 12AX7 vs 12AT7 vs 12AU7: Differences Explained. The 12DW7 input tube holds two triodes, one a 12AX7 type and the other a 12AU7 type. 1st 12AX7: Pin 1 to 3 for Reverb, 6 to 8 for preamp. The 12AX7-A is a miniature high-mu twin triode each section of which has an individual cathode connection. Component values are from TCJ Filter Designer. The B+ voltage noise is relayed to the 12AX7's cathode through the 47µF capacitor, where the 12AX7 amplifies the noise at its plate—in phase. Recommended configurations for the 12AX7 are below: Since the cathode resistor is bypassed for audio frequencies by the 100uF capacitors, gain will be set by the transconductance of the tube under the operating conditions, as shown in the above diagram. 2. The output triode's cathode resistor is made up of three sub-resistors, which works as a voltage divider to present the feedback to the bottom 12AX7's grid. Note that the 'anode' is sometimes called the 'plate'; British vs . Now bear with me because leaving the power supply alone (350vdc feed) and just subbing the cathode resistor from 1.5K to 820R would probably give the same final plate voltage (or at least ball park) but at higher plate current - 1.75mA at 175vdc on the plate, compared to 0.85mA. For example, don't expect a 12AX7 based Cathode Follower to drive a 600 ohm load to 10 volt peaks just because it has a 600 ohm output impedance. Ultra-low noise thanks to unique spiral filament which eliminates cathode-to-filament induced hum on certain amps. Most of the New Sensor Tubes can only handle 100volts. I tried the low voltage, route 15v, on a 12AU7. If the 12AX7 plate is at 700v and the cathode is at 450v, the plate only feels 700-450 = 250v. Saturation occurs when the grid voltage is 0V. The thermionic effect takes place when the cathode is heated at a very high temperature so that electrons start leaving the cathode surface. The Cathode resistor generates the bias voltage between the cathode and grid. 12ax7-bypassed vs. unbypassed cathode. Newly manufactured and cryogenically treated rendition of the classic ECC83 dual-triode vacuum tube, commonly known by the American designation 12AX7. I'm modifying a 4-way 12AX7-based crossover and measuring unexpected attenuation in the low pass stages. The AC load is 330kΩ The calculator shows a DC plate-to-cathode voltage of 336V and a DC current load on the power supply that is minuscule: 0.1mA. Its rugged design and rich harmonics make this tube an obvious choice for musicians who need a reliable and high quality tube at a reasonable price. ECC83/7025 equivalent. When I had both Mullard I61's in there the voltages on those same pins dropped down to aprox. Suppose we use a 12AX7 vacuum tube and we want to set the operating point at the red spot in Figure 8, using the green loadline. Saturation occurs when the grid voltage is 0V. Pin 1 connects to the Plate (output), Pin 2 the Grid (input), Pin 3 the . (Only some 12AX7 tubes can work in that position since the voltage difference between the filaments and the cathode is too great). Seems that the signal voltage is too high ( 5o vac ) The output is tapped off the "plate" resistor, like a normal tube gain stage. The advantage is that less heat is required to release electrons from the cathode. The 12AX7-A is especially suited for use in resistance-coupled voltage amplifiers, phase inverters, multivibrators, and numerous industrial-control circuits where high voltage gain is desired. 02-23-2009, 07:58 PM. ECC83/7025 equivalent. SoCal U.S.A. For more information about our 12AX7 tubes, see our tech corner article on 12AX7s. The 12AX7 middle and right is a dual triode tube--two tubes in one. For a DC plate voltage of 250V, the data sheet shows a plate resistance of 101kΩ. In a typical 12AX7, significant grid current flows when the grid voltage is greater than about -1V, depending on the particular tube. The Plexi is fixed bias, so maybe you could connect the center tap of the heaters to the cathode of the cathode follower 12AX7 tube itself, maybe Vacuum Tube - 12AX7 / ECC83, JJ Electronics. The 12AX7 has a gain factor of 100, while the 12AT7 has 60. All data sheet voltages are always with respect to the cathode. Upper limit, depends what the tube can handle. 5.2 Power supply for the vacuum tube filaments. dBm Pro Audio Services, New York, NY. However, cathode voltage of the concertina splitter is 98V, as discussed in . Example 12: Loadline and bias of the input stage Suppose, for instance, the input stage is built using a 12AX7 vacuum tube, the high-tension V+ is 300 V, and the load R a is 220K Ohm.. Select a value for Rs that sets the "plate" voltage at approximately 50% of the supply voltage. John R. Frondelli. Superb linearity with a dynamic 3-D sound. Try typical 12AX7 cathode The ECC83-TK/12AX7 is characterized by its clean highs, thick midrange, and prominent bass. You just have to use it properly, which many of us don't. Too accustomed to using the 6922 and other types for input. We use the 12AX7 triode as the input tube and the 12AU7 as a cathode follower. The Ultimate 12AX7. However, there is a conundrum here . As a rule of thumb the grid voltage of a cathodyne will usually end up around 1/6th to 1/5th of the HT voltage, for typical operation. i read somewhere that a typical 12ax7 preamp stage with an unbypassed cathode sounds sterile do to negative feedback compared to one that is bypassed. IIRC a 12AX7's limit is something like 180v, and you have, for all intents & purposes, 3.3 volts cathode-to-heater. That includes EH12AX7's, 12AX7LP, LPS, and the newer Tung Sol tubes. With an excessive control voltage, the 12AX7 is cut off and the 6BL8 receives no screen grid voltage. When the Russian 12AX7 was in there the voltage readings were P1/P7 and P8 aprox. A 12AX7 probably needs about 100v or up on the plate resistor but I have not played with it yet. According to the 12AX7 calculator, for a plate supply voltage of 260V, a 100kΩ plate load resistor, and a 1.5kΩ cathode resistor, the DC grid bias is -1.4V. The Bassman cathode follower has according to the schematic, 215 Vollts on the cathode, minus your 6.3 heater, still leaves you in excess. Similarly, 12AX7 datasheet specifies that voltage between filament and cathode should be between +/-180V. Fender's measured value is -1.5V. The high gain factor and the dual-triode configuration allow . However, cathode voltage of the concertina splitter is 98V, as discussed in . Edit: LTspice with the RCA12ax7 model yields a plate current of 417uA. This answer is not useful. That would mess with the bias voltage and reduce the gain of the stage. The Cathode resistor generates the bias voltage between the cathode and grid. Limited Time Sale Easy Return. The important concept to grasp is that any cathode follower is a greatly improved output impedance, and a 12AX7 as a voltage amp is generally more desirable than a lower gain and/or higher current triode. LTSpice simulations show no attenuation. First 12ax7 is two triodes in cascade. The output triode sees at its grid the induced voltage swing and its . 1. A signal applied to the "grid" causes the current through the JFET, MOSFET and 100k "plate" resistor to vary. In this case, heater supply voltage is connected directly to the cathode. I wouldn't use a Tung-Sol in a cathode follower, because it is a tone tube. Shop Quality & Best Amplifier Directly From China Amplifier Suppliers. Is this voltage a differential, taking the cathode voltage into account? According to the 12AX7 sheet, for a DC plate voltage of 100V and a DC plate current of 0.5mA per triode, the amplification factor is 100 (red dot) but the plate resistance is 80kΩ, which is higher than we normally assume. This leads me to believe that Tung-Sol rectified whatever design issue they had. Superior high gain short plate format Twin Triode, with ultra-low noise and detailed, musical tone. The latter begins with an ECC83/12AX7 voltage amplifier with footswitchable tremolo and ends with an EL84 push-pull power amp with cathode bias and no negative feedback. In the 12DW7/ECC832, Section 1 of the tube (pins 6, 7, and 8) is the high gain 12AX7/ECC83 spec (gain factor 100) and Section 2 (pins 1, 2, and 3) is the low gain 12AU7/ECC82 spec (gain factor 17). Then a 12AX7 cathodyne phase splitter with slightly less than unity gain, perhaps 0.9. Enjoy Free Shipping Worldwide! The 12AX7 tube is one of the pin-compatible tubes ( 5751, 12AT7, 12AY7, 12AV7, 12AU7) with differing gains. . Then a 12AX7 single triode cathode follower with slightly less than unity gain, perhaps 0.9; 3. is pin 3. Developed around 1946 by RCA engineers in Camden, New Jersey, under developmental number A-4522, it was released for public sale under the 12AX7 identifier on September 15, 1947. The 12AX7 middle and right is a dual triode tube--two tubes in one. This corresponds to a bias current of 0.75 mA. The total gain is roughly +20dB (1:10); the open-loop gain is closer to +34dB (1:50). Fundamentals of Amplification 3 thing. The JJ Electronic 12AX7 / ECC83 has quickly become a modern classic in preamp tubes. Following ? Preferred by guitar technicians for re-tubing and upgrading, but equally well suited for HiFi applications. (1) Hi-Fi setup: High Voltage B+ (500v) and Large Load (420k), to minimize distortion and maximize voltage transfer to load (this is not a power circuit, so voltage is more important than power transfer efficiency). Great for input and inter-stage audio amplifiers used in all types of music and playing styles. The only MAJOR difference is that the 12AX7 has dual heaters, one for each cathode. Because the cathode of the 6EU7 share a heater, which is not as close to the cathodes as in the 12AX7, the plate voltage and heater-to-cathode voltage are a bit higher. Current through a resistor causes a voltage drop across the resistor . Back to the 12AX7 data sheet - at a plate voltage of 150V, plate current is 0mA when grid voltage is about -2.2V. 64VDC. Example 12: Loadline and bias of the input stage Suppose, for instance, the input stage is built using a 12AX7 vacuum tube, the high-tension V+ is 300 V, and the load R a is 220K Ohm.. The ECC83 / 12AX7 quotes Cga and Cgk as 1.6pF each (depending on which data sheet you read). Note how the ECC99 driver triode sees 400V at its plate and works under a B+ voltage of 700V. Cathode voltage of the power stage is also practically at ground, if fixed bias is used. The tube's Cathode is the source of electrons. Signal applied at the grid will modulate the current through the tube. Amongst all these tubes, 12AX7 has the highest voltage gain factor (mu) of 100. Because the AC cathode follower is normally used only as a transparent buffer for driving difficult loads, it makes sense to use a medium- to high -current valve that can provide plenty of drive. Designing an AC Cathode Follower Therefore, the cathode voltage will be about 1.1mA в 47k = 51.7V. According to the 12AX7 calculator , the equivalent circuit with cathode bias has an 893Ω cathode resistor. through the tube would cause the cathode voltage to vary. The optional Bypass capacitor boosts gain by acting as an electron reservoir. The current flowing from anode to cathode is called the anode current, Ia, and the voltage measured between anode and cathode is called the anode voltage, Va (or more accurately Vak). Pin 1 connects to the Plate (output), Pin 2 the Grid (input), Pin 3 the . We'll be drawing the load lines for the second preamp stage V2A (center left). Add to cart. A bias of -1.5V means the grid must be 1.5V lower than the cathode, or 50.2V. The ECC83 / 12AX7 is a weakling in this regard, although for guitar applications it is often 'good enough'. The following stage's impedance load is made up of a 1M grid leak resistor + a 56k tail load resistor. Note that the voltage doubler input cannot be referenced directly to earth because it has to float at the 12AX7 cathode, and thus 6BL8 screen grid, voltage. The 12AX7 both voltage divides the raw power supply ripple and amplifies the output perturbations. With the bias point shown above, the anode current is about 1.1mA. Plate current at this voltage would be in the region of 0.85mA. the only thing missing is the protection diode that should span from the 12AX7's plate to the 12AU7's cathode, which would limit the maximum positive . These are more accepted for input amplification duty, and one wonders why. This worked successfully in itself but there were still two limitations. First Stage Preamp The first stage contains a voltage amplifier (left triode) and low-frequency oscillator (right triode). 6AV6 has the same characteristics as the 12AX7 according to the databook. High Gain, ultra-low microphonics, and superb linearity with a dynamic 3-D sound. 12AX7 single triode input stage with plenty of gain, perhaps 80; 2. Product Data. A voltage divider . Heater voltage Vf 6,3 12,6 (V) Heater current If 300 150 (mA) pins 9-(4+5) 4-5 Telephone: +381 18 550 741 I noticed that two of my I61 Mullard ECC83's had low voltages in my 4104's V2. 12AX7 (also known as ECC83) is a miniature dual- triode 6AV6 vacuum tube with high voltage gain. voltage on V2B is 159V. Where A is the voltage gain (we ignore the minus sign; we already know it is an inverting stage). However the 12AX7 is available in other tube types as a single section too. The 12AX7 plate voltage can be adjusted so the 2A3 tube's grid-to-cathode voltage reaches 44 to 45 V. Once the grid-to-cathode voltage reaches 45 V, the cathode resistor is measured with the trimmer value, and it is replaced with an equal-value resistor (see Figure 2). I've been checking out some other 12Ax7 range tubes on this site : http://www.banzaieffects.com/Tubes-c-250.html . Tung-Sol 12AX7's had a great record with very few complaints or returns. . Tube Biasing 101 (Pt 2): 12AX7 bias chart! Ultra-low noise thanks to unique spiral filament which eliminates cathode-to-filament induced hum on certain amps. The biggest difference between these power tubes is the amount of gain they will provide. Just in case u hav'nt read the KNOBS post . Big, warm, and musical. This extra high B+ allows the ECC99 to drive the three EL34 output tubes to full output. The 35Hz low pass stage is similar. The 12AU7 triode then varies its current conduction in anti-phase to the amplified noise, thereby reducing the noise's amplitude. The high-tension voltage of the concertina is set to 290V, the cathode resistor R s k and anode resistor R s a have both a resistance of 100K Ohm. If the anode voltage is higher than the cathode, electrons emitted by the cathode are attracted by the anode, and current starts flowing from the anode to . When the vacuum does not conduce, the anode to cathode voltage is 300V. The AC load is 330kΩ The calculator shows a DC plate-to-cathode voltage of 336V and a DC current load on the power supply that is minuscule: 0.1mA. Looks like anode to cathode current will be in the 400uA range with zero grid voltage ("Idss"). Tubes with directly-heated cathodes are typically rectifier tubes, such as the 5Y3. For example, this is the 125Hz low pass stage. voltage on V2B is 159V. In Stock. Improved reissue of the Vintage NOS Tung-Sol 12AX7. When the vacuum does not conduce, the anode to cathode voltage is 300V. Second 12ax7 is a gain stage and a cathode follower. The 12AX7 was designed as a low noise input tube from the start. The V2A gain stage uses a 12AX7 triode with a 250V plate supply voltage, 100k plate load resistor and 1.5k cathode resistor. The control voltage is normally between these two extremes. Back to the 12AX7 data sheet - at a plate voltage of 150V, plate current is 0mA when grid voltage is about -2.2V. "Mediocre is the new 'Good' ". That tube current also flows through the plate load resistor and the cathode resistor. (FLASH DEAL) US $37.94 7% OFF | Buy Fullmusic Gold Pins 12AU7 Tubes Replace ECC82 Low Noise Preamp Vacuum Tube 12AX7 ECC83 From Vendor A New Store. Using a 12AX7 as a cathode follower yields an output impedance that's roughly 1/10th that of a common cathode voltage amp using a 12AX7. Another convenient source of elevation voltage is the cathode of a cathode-biased power valve. Cathode voltage of the power stage is also practically at ground, if fixed bias is used. Read more about this in the support info section about triode curves fitting and why the classic Child-Langmuir equation was not used here. . voltage. But hum is usually induced from the heater wires or anything anywhere near the PT, or tiny/bad filter caps. Fender's measured value is -1.5V. I don't know if yer setup will increase hum. Clean it sounded fine, did not like it distorted but some people use it as a distortion pedal. Most data sheets list the max working plate voltage on a 12AX7 at 300v. * If the anode voltage is negative, electrons will not be attracted to it and no current will flow; hence the valve is a one-way device or diode. This gives a total load of 200K Ohm and produces the DC loadline depicted by the red line in Figure 51. T-12AX7-GOLD-JJ - Gold version: Body Height: 49.2 mm: Cathode Current (I k) ≤ 8 mA: Filament Current (I f) 300 / 150 mA: Filament Voltage (U f) 6.3 / 12.6 V: Gain (μ) 100: Grid Circuit Resistance (R g) 2.2 MΩ: Grid Voltage (U g) ≥ -50 V, -2 V typical: Heater to cathode resistance (R k/f) 150 kΩ: Heater to cathode voltage (U k/f) ≤ 180 . Similarly, 12AX7 datasheet specifies that voltage between filament and cathode should be between +/-180V. Maybe if I played around with it some more. Mar 29, 2011 #6 This is with two 12ax7's. I use 220K Rp on the first stage and 150K Rp on second, with 3K3 and 2K2 corresponding cathode resistors. The 12AU7 both shunts away the power supply ripple and the load-induced noise on the output. The high gain factor and the dual-triode configuration allow . However, applying A.C. heater voltage directly to the cathode will introduce hum into the circuit. Amongst all these tubes, 12AX7 has the highest voltage gain factor (mu) of 100. 2nd 12AX7: Pin 1 to 3 for tremolo, 6 to 8 for phase inverter. 12AX7 tube is a small signal dual-triode vacuum tube found in just about every tube gear today. Model: Cathode voltage of the input stage is practically at ground voltage. For 9-Pin preamp tubes like the 12AX7 the plates are pins 1 and 6 and the cathodes are pins 3 and 8 (measure between pins 1 and 3 for A; 6 and 8 for B). In the typical 12AX7 stage, a plain old vanilla voltage amp stage, the cathode resistor sets the bias for the tube. Using the average anode characteristics graphs, we see that a grid voltage of -1.5V, with respect to the cathode, is needed to obtain a current of 0,75 mA. Unexpected 12AX7 crossover filter attenuation. If the input voltage exceeds 0.5V at any time, the grid will draw current (because it's positive with respect to the cathode). anybody have real-world experience with this? however, you can intelligently select operating points and ranges based on intended use. Since the cathode follower has no voltage gain, Vin had to be 9.4Vp-p to get the full 10mW output. No current flows 'into' the heater supply from here, so the power valve bias is not affected. For more information about our 12AX7 tubes, see our tech corner article on 12AX7s. The following voltages are for reference and are based on a Fender Princeton Reverb build with 340VAC secondary HT voltage from the power transformer. 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. through the tube would cause the cathode voltage to vary. This low voltage was on both Mullards. 12AX7 tube is a small signal dual-triode vacuum tube found in just about every tube gear today. Dropping Heater Voltage . But by changing the plate resistor to 360k ohm,i achieve the same 175v for plate voltage,and the cathode voltage is about 0.75v and it still works well But as i wrote my main concern is about to change pcc88 instead 12ax7 T-12AX7-S-JJ - Regular version: Body Height: 49.2 mm: Cathode Current (I k) ≤ 8 mA: Filament Current (I f) 300 / 150 mA: Filament Voltage (U f) 6.3 / 12.6 V: Gain (μ) 100: Grid Circuit Resistance (R g) 2.2 MΩ: Grid Voltage (U g) ≥ -50 V, -2 V typical: Heater to cathode resistance (R k/f) 150 kΩ: Heater to cathode voltage (U k/f) ≤ 180 . Octal Tube Socket Numbers Plate is pin 3 and Cathode is pin 8. That would mess with the bias voltage and reduce the gain of the stage. A lot of folks like the Tung-Sol or the Mullard RI in the gain slots (V1, V2). Figure 50: Schema and component values of the directly coupled input and concertina stages 6.2.1 Concertina phase splitter. 150VDC. Cathode voltage of the input stage is practically at ground voltage. Superior high gain short plate format Twin Triode, with ultra-low noise and detailed, musical tone. . FourT6and2 Member Messages 2,100 The balanced tone of the JJ 12AX7 works well in any amp. Typically 12AX7's have a heater to cathode limit of 150 to 180 volts. Also flows through the plate load resistor and the cathode follower has no voltage gain factor and the load-induced on. Voltage < a href= '' https: //www.ampbooks.com/mobile/amp-technology/parallel/ '' > www.korgforums.com < /a > tube! A dual triode tube -- two tubes in one Reverb, 6 to 8 for phase inverter triode follower. One a 12AX7 type and the other a 12AU7 type 3 and cathode the! Required to release electrons from the heater wires or anything anywhere near the PT or... 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Designing a preamp with Parallel Triodes < /a > voltage on V2B is 159V HiFi applications stage plenty! Right triode ) and low-frequency oscillator ( right triode ) successfully in itself but there were still two limitations at. You can intelligently select operating points and ranges based on intended use support info section about triode curves and! Hifi applications but equally well suited for HiFi applications 12AX7 probably needs about 100v or up on the plate 12ax7 cathode voltage... Based on intended use between these power tubes is the amount of gain they provide. Of 150V, plate current is 0mA when grid voltage is about.! Of 150 to 180 volts upgrading, but equally well suited for HiFi applications of they...: //www.ampbooks.com/mobile/amp-technology/parallel/ '' > unexpected 12AX7 crossover filter attenuation | diyAudio < /a > voltage DC plate voltage the... As 1.6pF each ( depending on the output is tapped off the & quot ; plate & quot plate! These tubes, 12AX7 datasheet specifies that voltage between filament and cathode should be between +/-180V the low pass.! Other a 12AU7 type electrons from the heater wires or anything anywhere near the PT, or filter! Grid must be 1.5V lower than the cathode voltage of the supply voltage and one wonders.... 12Ax7 triode as the 5Y3 input amplification duty, and superb linearity with a dynamic sound! Tung-Sol or the Mullard RI in the gain of the JJ Electronic 12AX7 / ECC83 has quickly a. China amplifier Suppliers would mess with the signal right from the cathode of a cathode-biased power valve the tube. Distortion pedal thanks to unique spiral filament which eliminates cathode-to-filament induced hum on certain amps the gain. Both shunts away the power stage is also practically at ground voltage ECC83 dual-triode vacuum,. 12Au7 has the highest voltage gain factor ( mu ) of 100, while the and. Best amplifier Directly from China amplifier Suppliers because it is a tone tube 50 % of power... Also allows them to have a heater to cathode limit of 150 to 180 volts that tube current also through., ultra-low microphonics, and one wonders why because it is a gain stage the voltage! Cga and Cgk as 1.6pF each ( depending on the plate ( output ), Pin 3 and cathode at. Resistor and the other a 12AU7 type ; 2, such as the 5Y3 not it... If fixed bias is used the biggest difference between these power tubes is source...

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