Ef86 voltage. Plate voltage 250v 3.

Ef86 voltage Also check out our ClassicPedals! The tube tester probably puts the screen at some weird voltage, maybe not, but the best way to test is in the circuit. The power supply is solid state. I did try changing the plate, cathode and screen resistor as suggested and as dictated by the datasheet. The EF86 is a terrific voltage amplifier, but it can't drive loads. attenuate output with a voltage divider (you do not need 80-90V RMS do you?), say 10:1 or 20:1, say 1M:100k or 1M:47k , the attenuator lower leg may vary well be an Audio potentiometer, I have a mic preamp where the heater supply is powering 2 EF86 tubes and 2 12au7's. 6V/5W zener diode for filaments But instead of that, I would If the voltage across the cathode resistor is zero, the plate current is zero. 9k ohms Hence Ug2 voltage drop equals: 5600000 * 0. WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES. The EF86 is the standard early stage audio pre-amplifier valve. Pin 4 must be positive with respect to pin 5. 5 200+/- 10% Indi The specification for a NOS CV4085 (EF86) under conditions of an HT voltage of 250V and an anode load of 100kΩ is for an equivalent input noise voltage of 2µV (RMS) in the frequency range 25 to 10kHz. There are other factors, but I find these to be a good starting point. Why people call these 'mesh plates' is unclear. The EF86 tube adds a ton of character, clarity, and sparkle to any amp, and works amazing after other overdrives. This design uses an EF86 pentode as the preamp. The plot corresponds to a plate voltage of 250 volts, but it doesn't change much for other plate I don't have another ef86 but the one I have is a tested TAD one. The specification for a NOS CV4085 (EF86) under conditions of an HT voltage of 250V and an anode load of 100 kΩ is for an equivalent input noise voltage of 2µV (RMS) in the frequency The EF86 boasts low noise operation, effectively minimizing unwanted background noise and providing a clean and pristine audio experience. No The value of the maximum heater-cathode voltage rating when the cathode is positive may be different from that when the cathode is negative. 3rd edit regarding EF86 and spiral heaters. The EF86 is a low noise pentode intended for use as a RC coupled AF voltage amplifier, particularly in the early stages of high gain audio amplifiers, microphone pre-amplifiers and magnetic tape recorders. Building, troubleshooting and testing of these amplifiers should only be Good western EF86 will have twisted filaments, which, in turn might result in lower hum when AC heated. That part of the circuit is stock Akai/Roberts. But if you want a small, clean-to-crunchy-to-insane amp that is a lot of fun, and EF86 into some EL84 will be great (classic design is the Vox AC15). Note that the knee is well defined, and the input sensitiviy is lowest: If centre biased it would take roughly a 4Vp-p input signal to cause clipping. Base connection 5. Care in the design of the valve to ensure that the electrode structure and its mounting are as rigid as possible has reduced the microphony of the EF86 to a very low level. It is very similar electrically to the octal base EF37A and the Rimlock base EF40. The real Problem with EF86 pentode input is that the gain is much too high for any modern Pentode output to drive. 2015-02-05 12:48 pm #26 2015-02-05 12:48 pm Out of sheer curiosity, and love for the EF86 as a preamp tube, I recorded a comparison between the JJ EF806S (modern EF86 from JJ) and an RFT EF86 (NOS). Here are the transfer characteristics for an EF86 pentode, showing plate current versus grid voltage for several different screen voltages: Maximum plate voltage is at cutoff, where the plate current is zero. The screening mesh and below the bottom mica addditional screening. Assuming G2 winds up at 40V or 160V, then cathode voltage will be 0. Microphony. The JonesAmps is meant to work with a 125V PT, what is the ideal voltage to run the EF86?? I attached a revised Jonesamps Schematic adapted for an EF86 at V1 (mods in blue). Put in a handy 2. 00 Vout 1. Very few are quieter than this. The first stage of amplification is provided by the EF86 in a circuit giving a voltage gain of about 150 times. Noise and microphony The specification for a NOS CV4085 (EF86) under conditions of an HT voltage of 250V and an anode load of 100 kΩ is for an equivalent input noise voltage of 2µV (RMS) in the frequency range 25 to 10kHz. As a consequence I have only one Ei EF86, and tons of PF86 😉 PF86 are a complete equivalent and were often used in TV sets, so should be easy to find. The voltage of the EF86 has gone down a little with the addition of the source follower but it was only about 53V before. On the matchless clubman the plate load resistor for the EF86 is 220K. com Guitars / Amps / It actually has less gain but the gain you get is smoother than a 12AX7 in the same position. I just completed an amp design that involves 2 12AX7 stages in front of an EF86 pentode stage in the pre-amp. Today, with D/A conversion, the anticipated hum noise floor has got a min -90dB down. 1mA - 2mA) = 300v / 0. I will however repopulate the schematic, tweaking a few values and target voltages that should work well with more standard transformers (his design's starting point is repurposing an old Hammond amp transformers). The next grid must be DC-grounded, but you may use a resistor up-to 1 Meg so you don't short the signal. The HF-50 seems to have an 18Watt Technical Discussion. The input stage uses an EF86. It worked but not quite as well as the tube it replaced. Merge Mullard's 5-20 with EICO's HF89: EF86 voltage amplifier, 6CG7/6SN7/7N7 LTP, and "fixed" bias O/P tubes. 00m 5. But the circuit isn't real fussy. 00 0. Noise is the main problem with those tubes. Above left: The EF86 characteristics at a fixed screen voltage of 100V. That may change though after the plate voltage is lowered. A reasonable question to ask, then, is "Does the AC15 meet Philip's specification?" Add the 1/6th G2 current, 0. 0 Svetlana EF86 High-Performance Audio Small-Signal Pentode ELECTRON DEVICES Svetlana Typical operation, Class A Connection, Small-signal amplifier pentode triode DC plate Voltage 250 250 V Screen grid voltage 140 V Cathode bias resistor 1k 3. 9k ohms Ef86 - CF - TS - FX - PI - Cut - Type 2 MV - EL84 Concerned about gain from the Ef86, I might A/B different pentode tubes 5879s, think it might benefit voltage divider maybe. Low voltage EF86 tube preamp Hi! This is simple guitar preamp using EF86 tube. 1, page 189), I came across a new flavour. Plate voltage 250v 3. Building, troubleshooting and testing of these amplifiers should only be My EF86 tubes so far. It features an all enclosing, outer screen or shield around all electrodes (connected to pins 2 and 7), special measures for extra mechanical stability against microphony, and a bifilar wound heater element to reduce hum injection to the absolute minimum. 0-3. 89K. Here is a plot of plate current versus grid voltage for an EF86 pentode. The EF86 was used in many preamplifier designs during the last decades of vacuum tube hi-fi development. Of course, the voltages jumped way up when I went from EZ80 to SS from 260Vish to 300V. 3V AC/DC heater voltage and a maximum DC plate voltage of 300V - the Tube Amp Doctor EF86/6267 demonstrates the extraordinary balance between technical superiority and As for the JPS2, its specific power supply recreates a voltage for the module with a 80 Hz frequency in order to avoid problems that can occur due to the 50 or 60 Hz frequency from the mains supply. You get the most voltage output from the EF86 when the screen is 30% to 40% lower than the screen, and Signal Voltage Gain: The EF86 offers high voltage gain, allowing for amplification of weak audio signals to sufficient levels. 3 Volts / If 0. I am building a vox ac15 pentode chanel replica, 6n2p and 6p14p instead of ecc83 and el84. page 265 M. That Jakob may have a better idea how it should bias, but I'd aim for plate voltage about 1/2 to 2/3 of supply voltage. No, it is definitely not possible. Type Substitutes Base Diagram; EF86: 6267: Web References: EF86 (Philips) @ Franks Electron Tubes EF86 (Mazda-Belvu) @ Franks Electron Tubes EF86 (Philips) @ Franks Electron Tubes EF86 (La Radiotechnique) @ Franks Voltage at B+3 is now 202V. The Phædrus Audio CV4085 (Special EF86) Supertube™ measures <1. For the EF86 under normal conditions, I. 6J32P filements are of folded design. Look at the old Mullard circuits, they have much less input voltage. Thats why I've gone for a 47k Ra + 500k vol pot also debating the cut control, EF86 - Voltage Amplifier Pentode Aug 9, 2016 · 11 Hits Philips EF86 - 1956 Pentode Aug 9, 2016 · 9 Hits Tube Amp Doctor EF86 - Low Noise AF Pentode Aug 9, 2016 · 7 Hits tage Negative DC Grid Voltage Plate dissipation Grid 2 Dissipation Bulb temperature (surface hottest point) Cathode Current 6. 00 250 000 2. Building, According to the databook the EF83 was also intended for audio. Minimum plate voltage is at a grid For the EF86 under normal conditions, I. Page 7 of this EF86 data sheet shows a 2. You'll have a little less than half the gain, but that should be adequate with your sources. The Or you could add a resistor connecting C8 with R20 to build a voltage divider (which is similar to the shunted pot, just in a different place). Donations. Perhaps the screening then is not so good, The EF89 replaces the EF80 and EF85 for RF & IF work, the EF86 is a low noise part for Audio Preamps. 50 -5. 6, far-far short of the nominal Mu of 360. The screen is dimpled and not perforated. Initially the EF86 would then charge the 500 uF cathode capacitor as quickly as the anode and screen grid resistors allow, which means with several volts per second. You load a tube with a resistor to drop "about half" of the supply voltage, typically 50K-220K. Measurements taken at supply voltages of 100, 200 and 250 were in close agreement across 3 separate EF86 pentodes. 5uV. I have the parts December 27, 2024, 02:43:06 PM: Welcome, Guest The EF86 is type with minimised noise, only a little more noise than a Triode. If the screen voltage is 100V, the voltage drop The EF86 is a low noise pentode intended for use as a RC coupled AF voltage amplifier, particularly in the early stages of high gain audio amplifiers, microphone pre-amplifiers and magnetic tape recorders. 2K (as Mattitch did) and see where the plate voltage falls. The Lite IIb, EF86 Lite 2P and Trinity TC15 will be what I'll look to adopt from. The filament supply is regulated at 6. 5v gridline where plate current is 2mA at 100v plate, and increases to only a bit over 2. Member. However the EF86 preamp doesn't seem to be providing enough gain. It is similar to the EF86. Aim for around 90v screen and 115v plate as a center value, and go up or down from there by changing your screen resistor value and your dropping resistor value. Also, does running the screen at such a high voltage increase the gain even further? Seems you could end up with a screen voltage higher than the plate voltage if you made the dropping resistors equal. 2K 3W resistors in series with the 10Ks and that helped. If you run the plate ate say, 250 volts B +, try running the =screen way down at Does anyone know the expected voltage output from the single EF86 RIAA stage? I am torn between Quad22 single EF86 and standard Mckintosh C220 ECC83 twin triode. There may also be a maximum value quoted for the resistance The 5879 is a very low noise voltage amplifier pentode that is used in audio amplification. B+2 = 234V and B+1 = 275. The voltages on the preamp components are very important in the reduction of noise and microphonics. Building, troubleshooting and testing of these amplifiers should only be performed by someone who is thoroughly familiar with The EF86 has no place in a For the EF86 under normal conditions, I. Is that normal? VOLTAGES: 12ax7 145 & 158 ef86 280 12ax7 167 & 254 el34 plates 379 el34 screens 375 gz34 rectifier 391 Try your EF86 then. i swapped out ef86 tubes and the same. Building, troubleshooting and testing of these amplifiers should only be When running an EF86 in triode mode, is there any advantage to be gained by inserting, say, a 100e resistor between the Cathode & G3, An EF86 was famously used as the input stage for the early Vox AC30s, but it acheived such high gain (about 200) and was used in such a sensitive position that microphonincs was a major problem. So it is the luck of the draw. Don't bother listening. you'd have to lower the dropping resistor to that section, as well as substantially increase the cathode resistor/lower the plate resistor and use like a 4. B+ Voltage Reduction Amplifier Tools & Parts Info Web Design: DolceVittoria. Edwind. EF86 (209 HT) Plate = 92 VDC Screen = 69 VDC Cathode = 0. The voltages and currents are very much lower than normally. However when the Anode voltage drops much below the g2 voltage (usually fixed at 1/2 HT, HT or via a resistor to HT WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES. Above right: Using the same screen voltage but inserting a 100k Vf 6. A+" "Got to say I have been enjoying the pedal quite a bit. 2 Ampere / Indirect / Specified voltage AND current AC/DC: Description: Lineare 91 Tube prices (visible for members only) EF86: Courtesy Bureau Belper (De Muiderkring, Bussum), Scan Frank Philipse Karel De Reus † EF86: RTT 1974 (Franzis) 13. Low noise pentode intended for use as R. Grid3 voltage 0V 5. Cathode positive: 100 V TAD EF86 / 6267 Premium Select Low Noise AF Pentode The TAD™ EF86 / 6267: is a glass envelope miniature pentode for high- Grid Voltage Svetlana EF86 Typical Plate Charicteristics-1. Resistance in grid1 circuit, 3 MOhm 7 It was based on a Matchless DC-30. With an appropriate operating point, the EF 86 will have at least double the output impedance, so you should calculate the The 12AX7 seems to tame the EF86 down a lttle but you get lots of gain. 00m 3. You do need a low plate resistance. EF86 voltage amplifier, particularly in the early stages of high-gain audio amplifiers, microphone pre-amplifiers and magnetic tape For the EF86 under normal conditions, I. Mullard describe the EF86 as a low noise pentode intended for use as a RC coupled AF voltage amplifier, particularly in the early stages of high gain audio amplifiers, microphone pre-amplifiers and magnetic tape recorders. 2 kilohm, R a =220 kilohm, R g1 =1 megohm, Vout<44 V RMS; Special precautions have been taken in the design to reduce the: The input pentode circuitry for the VOX AC15 and other similar guitar amps was lifted straight from the back of a tube catalog. 79VAC Rectifier – 5. Each channel of the preamplifier circuit is a C4S isolated EF86 voltage amplifier direct coupled to 1/2 of a The EF86 is a low noise, AF voltage amplifying pentode specifically for very small signal preamplifier applications. I'd like to use a pentode/triode switch Equivalent to tubes: EF86, 6267, 6CF8. Is it common to put resistors in series with the transformer heater windings? I'm guessing I'd need a pretty high wattage (and perhaps well matched WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES. The trouble is, the schematic in the catalog was designed to extract the maximum possible voltage gain from the EF86, for use in microphone preamps, tape recorder playback preamps, record player magnetic cartridge preamps, et cetera. I am planning to build an EL34 amp based on the Eico HF-89 or HF-50 designs. But reading the Merlin's book on amplifiers (the hifi version, section 4. 0-1. Voltage on the Plate of the EF86 is 155V for the Left and 148V for the Right. 9 volts Gain around 120. Input Impedance: The input impedance of the EF86 is an essential The EF86 is a high transconductance sharp cutoff pentode vacuum tube with Noval (B9A) base for audio-frequency applications. This is simple and inexpensive build, but good quality NOS tube is recommended. if it is more than 5 %, you may parallel the higher voltage heater with a properly calculated resistor. It works well with 12V power supply, but it gets even better with 24 volts. The controls are straight forward: Volume and Tone. Tim C. Very pedalboard friendly, as each unit draws 200mA or less power supply current. I swapped in the SS rectifier, and the buzz disappeared. If you indeed observe a voltage difference between your series connected EF86 heaters, and if it is of any concern, i. of course finding the balance between performance and price is the restraining factor. Gm is 600 microMhos or 1667 ohms. This signal pentode became the standard early stage audio pre-amplifier valve after it replaced the EF37A octal as a low noise pentode intended for use as a RC coupled AF voltage amplifier, particularly in the early stages of high gain audio amplifiers, microphone pre-amplifiers and magnetic tape recorders. The regulation of the high voltage is assured by two tubes: 1 X EF86 and 1 X EL84. The figure below shows this being done for an EF86 with a screen voltage of 100V. Without a doubt i 'm enjoying the pentode tone, it's got a lot more life than the standard triode preamp! I'm just looking at the ceriatone ef86 18 watt voltage chart and one of his has plate at 83v and screen at 98v. I'm rebuilding the amps in an Akai/Roberts tube R2R for mic/line/guitar use. Voltage gain seems to be 24. The description you provided a link to indicates that the HF-35 uses DC coupling between the EF86 and the 6SN7 phase splitter. That could be your problem if you are running AC heaters. I would describe the tone as thick and meaty for an open back combo. Reply. Auflage Martin Renz More Just Qvigstad: EF86: Valvo Dietrich In my opinion, the EF86 in that circuit is starved for voltage and starved for current. I know what you mean about preferring triodes but many people have reported success with pentode voltage amp stages in SE. There is another plate load resistor after this and before the tube plate. The tube line up includes an EF86 pentode fronted by a 12AX7 twin-triode. 27VAC Loaded 5Y3GT, 6V6S (8K Pr Z), 12AX7, EF86 HT voltages B+ = 415 VDC at reservoir cap (470 peak at startup) 10k node = 343 VDC (436 peak at startup) 22k node = 280 VDC EF86 Vacuum Pentode. J. I will let you guys know how it sounds after I lower the plate voltage on the EF86. The stage is capacitively coupled to the phase splitter. Resistance in cathode circuit, 500 Ohm 6. but the PT seems fine now, and I don't think its running hot. ) For new builds I find more justification in keeping the EF86 stage as pentode as originally, with rather a lower µ tube as driver/phase inverter, say ECC82 or ECC81 - but that is a longer fzfwyv wrote:Hey, I just finished building the same amp (the AC30/4 scematic) with a few tweaks. 00m 4. Of course, lamps voltages and current were changed: 150v/1. NOS small signal tubes are gradually diminishing and many were designed to work on AC heater supplies with the hum and noise in the 1960's spec i. The both amps have cleaner gain and louder volume now. In the case of the EF86, for a line voltage of 250V and an anode load of 100 k, the equivalent noise voltage is approximately 2 uV for the frequency range 25-10,000 Hz. . It was introduced by the Mullard company in 1953 and was produced by Philips, Mullard, Telefunken, Valvo, and GEC among others. The EF86 BOOSTER is a boutique all-analog vacuum tube pedal using a pentode to deliver warm, clean gain for overdriving amplifier inputs or other pedals. Then to get from the plate at high DC voltage to grid at zero DC voltage, you use a capacitor. Tons of headroom! Dial in your desired amount of tubey The EF86 is the standard early stage audio pre-amplifier valve. 3V using a LT1085 voltage regulator. Before I swapped the Dropping Resistor I was getting 94V at the Plate. Phase Splitter The phase splitter uses the triode sections of two ECL86 in a 'long-tailed' pair. Love the complexity of the ef86. regarding the buzz, any thoughts? the 32uf and voltages seems within the specs of the EZ80. I'm getting 245v b+ for the ef86. EF86 Mu is 38. Since the EF86 operates at such low currents and in grid leak bias it will be difficult, if not impossible, to get anything of value from the typical published plate curves without knowing the operating voltages. I'd like to lower it to preserve my tube life a little more. the only thing i didn't do is replace the socket in case pin 6 insn't making contact . One of those was a direct coupled EF86-to-6DJ8 circuit, a very simple design with a unique passive RIAA eq and a very basic power supply. Steer clear of the 12AX7/ECC83 Mullard used as the LTP. This exhibit was made by Mullard who designed the EF86 as a development of the EF40. Even the wimpy EF86 has no problem driving the tiny capacitances of the Adjust the EF86/6267 plate resistor downward. Because I hate tube rectifiers and other “museum exponents” (like paper-in-oil capacitors and germanium transistors) the mosfet voltage regulator (Q1) was implemented. Mullard describe the EF86 as a low noise pentode intended for use as a RC coupled AF voltage amplifier, particularly in the early stages of high gain audio amplifiers, microphone pre-amplifiers and magnetic tape recorders. Hi all, I really enjoyed building a simple valve phono stage using a low voltage design by Karsten and very pleased with the results. 7 volts though. Joined 2011. Stacked capacitors are used (C1,C2 and C3/C4) to give plenty of voltage rating. line voltage of 250 V and an anode load of 100 kΩ, the equivalent noise voltage is approximately 2 μV for the frequency range 25-10,000 Hz. They amplify a Wanted to share my tube phono stage that I recently finished, along with a vintage turntable overhaul to match. In the preamp the single supply line feeds the plate resistor and screen resistor. The reason for starving the EF86 plate voltage was to 'easily' get the grid voltage of the EL84 not be too high (a disadvantage of DC coupling, just what I do not like, woopty do) Therefore, as Essay observed, the voltages on one EF86 was far different. 00 Ug2 45 Igl -26,8uA PVT2 EF806S VMI -843,98mV PVTI EF806S AMI -124,06uA PVT2 EF806S . This controls the current through the EF86, a relatively small amount of which causes a big voltage drop across the 1 meg plate resistor. 8% and 4. Now I'm ready for a possible new project. Schematic has 5. waltube. A different screen voltage changes the gain of the EF86. 5µV (RMS) under the same conditions. In fact my current iteration is a standard Marshall 18-watt style pre-amp preceded by an EF86 with a 500K gain control followed by a 500k/500k voltage divider and 500pF bypass cap. I remember now that I had similar trouble when using it as V1 in another pentode design. The voltages to the PI and preamp are still high, but not anything that will start a fire. Grid2 voltage 140V 4. 5-3. 0003 = 5600 * 0. The tube behaves differently when using standard EF86 values I will try to find a proper values for making this tube behave more like an EF86. Let's also assume the preamp drives a 1M gain control, which is a relatively light load, even for a pentode. I was told it is actually an EF86 with a different control grid to give it remote cut-off characteristics. Use it mostly as a boost/slight OD and it performs beautifully. 3V using a WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES. not too noisy and sufficiently linear: as good as an EF86, in fact, with all that lovely pentode gain! One may then expect some 2V signal at the anode in an R. Stamp of technical control department of the manufacturer ” ОТК “ Technical specifications 6J32P: Heater voltage: 6,3 ± 0,6V; filament current: 0,2 ± 0,015A; Anode Rated voltage (DC): 250V; Anode Ei apparently did make an EF86, and it definitely did make LOTS of PF86. 27v. I suppose input transformers would get around the voltage gain problem of a 6dj8. The AC heater voltage is up at 6. Buffer the pentodes with ZVN0545A source followers DC coupled to the plates and your matched complementary FET pairs will do fine. 7meg or greater My cathode voltage is up to 1. 5uV and 1. Maximum Output Voltage Swing: The EF86 can deliver a significant output voltage swing, allowing for sufficient volume levels in audio amplifiers. Heater Voltage (AC or DC) in Volts 6. Building, troubleshooting and testing of these amplifiers should only be but you still have high level of noise due to large amplification ( EF86 plus 12AX7 ) and due to partition noise of the EF86 in pentode mode amplifier . The 6267 is Tungsram's special quality implementation of the EF86. 0-2. The phenomenon is common enough among high R P /low gm types; look at the 12AX7. 3+/-0. C circuit (say EF86 voltage amplifier). You will have to find an operating point for the 'X7 that puts the same voltage on its plate as the EF86 has on its plate. The voltage gain of the stage is approximately 120 times. The RIAA stage is essentially an inverting op-amp stage with the op-amp replaced with the EF86, but there is nothing in the feedback network that levels off the gain below 50 Hz: if the EF86 had nullor/ideal op-amp properties, the gain would just keep rising as frequency decreases. I had intended that the screen voltage be about 10 volts lower than the plate voltage. 5) Heater – 6. As to your ideas about driver and voltage amp, I would think EL34 in triode-connected CF operation as a driver would be good and an EF86 voltage amp would also be good. And given pentode vacuum tubes allow appreciable amounts of negative feedback to be used without triggering instability and high-frequency rolloff due to the Miller Effect, they merely paved the way for the development of the solid state transistor power EL34 Single-Ended (SE) Tube Amplifier Schematic (EF86 input) Single-Ended (SE) EL34 Tube Amplifier Schematic with EF86 input stage. 5µV (RMS) under the While pentodes like the EF86 are sometimes seen in guitar amplifier preamps, triodes like the 12AX7 are the overwhelming favorite for voltage amplification duties. nevertheless, did you actually measure the ef86 voltages in the 65 amp---i've never seen such a disparity between plate and screen in the normal type guitar amps we've seen. Close manufacturing specification tolerances and improved processing Above left: The EF86 characteristics at a fixed screen voltage of 100V. The EF86 [1] is a high transconductance sharp cutoff pentode vacuum tube with Noval Voltage gain: 185 (45dB) at V supply =250 V, I k =0. The effect is subtle yet effective at adjusting the amount of The original Mullard 5-20 uses an EF86 as the voltage amplifier and that meshes with your thinking. 4. For almost any practical case, R29 is the dropping resistor that sets the voltage value at the filter capacitor (AC ground). 2% (100V), 4. any oyther ideas There's a loud hum, possibly a ground loop or bad ground scheme. R6 is the dropper resistor for the EF86 stage, this voltage is bypassed by C5. First, the EF86 BOOSTER and the 12AX7 OVERDRIVER are tube-based (as there still is high voltage (2V input and 140V tube supply) for optimal tube operation with a lot of headroom. Output Capabilities. 8mA through it, 41,000 ohms. NewYorkDave Well-known member. 00m Vin 2. oom. So the voltage gain of a pentode preamp is roughly these two extremes divided by the grid voltage swing needed to create them. but, ef86 and the russian 6j32p - not that easy to find. The high voltage is regulated by two tubes: 1 x EF86 and 1 x EL84. Same with the Klangfilm. 7% (200V and 250V respectively). The cathode voltage will be something near half of G2 voltage divided by Mu. line voltage of 250 V and an anode load of 100 k, the equivalent noise voltage is approximately 2 μV for the frequency range 25-10,000 Hz. The pedal runs on 120 volts via a fused IEC socket mounted at the top of the pedal. 53mA, is 1. For lowest distortion the screen grid voltage should be 30% to 40% of the plate voltage. 9k ohms I put in some 8. Could the gurus check that?? Thanks in advance! (The lower gain designed in by a Mr. 5V to 2V. E. The Phӕdrus Audio CV4085 (Special EF86) SupertubeTM measures <1. Above right: Using the same screen voltage but inserting a 100k One of those was a direct coupled EF86-to-6DJ8 circuit, Each channel of the preamplifier circuit is a C 4 S isolated EF86 voltage amplifier direct coupled to 1/2 of a C 4 S isolated 6DJ8 voltage amplifier, with the passive RIAA equalization network positioned between the two gain stages. My cathode voltage is up to 1. 3 = 3360 V Does that mean that the EF86 is almost always abused in this amp? At least, from the link to the online plotter linked above, it seems that the 220k resistor is a real overload for the plate of the EF86 The voltage divider changes the screen voltage. High-stability, cracked-carbon resistors are used in the anode, screen-grid and cathode circuits, and they give an appreciable improvement in the measured level of background noise compared with ordinary carbon resistors. 9k ohms Audio CV4085 (Special EF86) device. The schematic is from the book "Build your own Audio Valve Amplifiers" by Rainer zur Linde. The heaters should be elevated in any event, as this degrades the heater insulation and eventually cause an early failure. With the 5R4 I'm getting anywhere between 460-490 VDC to the EL34 plates depending on the time of day, around 340 to the PI and 160ish to the plate & screen of the EF86. Maximum output is obtainable with the arrangement shown above, and the output voltage developed is sufficient to drive the 20 W circuit described in 5-20 Amplifier. RCA say that pins 2 and 6 should be connected to ground in all applications to shield the control grid and anode from any AC on the heater. Leave the screen resistor where it is unless you loose too much gain. e equipment noise floor capable of -60dB down. Building, troubleshooting and testing of these amplifiers should only be The EF86 just senses the diffrence between a divided down portion of the output volatge and the 122V reference, amplifies it, and controls the triode-connected EL84, making the EL84 pass greater of These pedals are not copies or clones, but entirely authentic, original designs. 52mA and 0V, 0mA. At a high level, it is a balanced input MC phono with Lundahl LL9226XL MC step-up transformers, CCS loaded LED biased triode-strapped D3a first gain stage, all-in-one passive RIAA EQ, CCS loaded LED biased triode-strapped EF86 second gain It's a bit of a mixed specification (voltage at the input, power at the output), but once the speaker impedance is chosen, it's basically a specification of the maximum voltage gain that's acceptable (voltage gain from pentode input to loudspeaker terminals). This unique design minimizes current consumption while still providing high voltage for proper tube operation. Hello!!, I have a question regarding to the triode connection of an EF86. Hagerman Amplification knocked the ball out of the park on these two pedals, and for several reasons. But if you still want to bias up the filament voltage and stay away from the maximum for the EF86 of 100V, +40 to +50V (even 20V may be beter!) would be just about ideal and as an added benefit you would be biasing off the cathode/heater diode of the EF86 and It isn’t 0V. It drops the voltage quite a bit. 5v vs the 0. Probably more than you need but you can throw some away. You need additional voltage gain between the cartridge and the EF86. 0001A The EF86 has a very low heater-to-cathode leakage voltage, about 50 V. maybe I was over drawing it, or the PT. You find a quiet one and 6 months later, the popcorn starts popping. coupled A. :confused: Wondering which will give the highest yield for a valve front end. Over the audio-frequency band, the EF86 in pentode mode has an equivalent input noise voltage of around 2uV, which would be an R eq of 12k ohms! The equivalent input noise voltage of most triodes will fall between 0. EF86 is intended to be used as an instrument amplifier tube with exceptional high gain or as phono preamp tube. Links EF806S /EF86, 6BK8, Input voltage (V) 7500 100. I know the usual way to connect the screen grid to plate. When probing to check voltages and bias I found that when I probe the plate of the EF86 I get a loud CRACK at the speakers, louder than anywhere else. 5-2. The signal hits an EF86 first (originally used to amplify signals off the tape head) before going to a 12AD7 for further amplification. I've found turning the Amplitude control to max brings the screen to up to ~70v, pulls the plate down to ~70v, and gives the most grit & gain. Stamp of technical control department of the manufacturer ” ОТК “ Technical specifications 6J32P: Heater voltage: 6,3 ± 0,6V; filament current: 0,2 ± 0,015A; Anode Rated voltage (DC): 250V; Anode voltage limit (constant): 300V; Current anode: 3 ± 1mA; Cathode current limit: 6mA vangogh-hk In the Mullard circuit(s) the cathode/heater voltage is within the rating for the ECC83. That was the usual way EF86 microphone input stages in consumer gear were The EF86 in the voltage-amplifying stage is used under conditions approaching those of starvation operation, 20 V anode and 0,21 mA. Wonderful, my tele sounds like a Les Paul. 1960 Mullard EF86 mesh plate, 1970 Mullard EF86 solid plate, Tesla EF806S (not JJ), Hoffman Amplifiers Tube Amp Forum, EF86 vs 5879 - What do you think about an AC15 with 5879 tube instead ef86 ? Welcome To So 250V-135V= 115V across the resistor, 2. 3v 2. The negative-feedback voltage from the secondary winding of the output transformer is introduced across the 100Ω resistor R3 in the cathode circuit. For first test, assume 1V, at 0. I have a switch between a 220k (stock value) and a 330k (actually just a 100k in seried with the 220k) going to the EF86 plate. With the Drive all the way down (and volume I'm using the 6AU6 successfully at present as a pentode CCS in the tail of a 6SL7 LTP splitter, with a neg voltage rail of 110v. Other readings I am getting for the EF86 are: At pin3 I am getting 1V on both. One now applies 20dB (x 10) of GNFB to the cathode, thus an input signal of 100mV is now necessary for the same 2V output, 90mV of which is 'cancelled' at the cathode. 5-5. R7 is a bleeder to keep the voltage on C5 down during the switch on surge. Pentodes are tweaky, but mostly worth the effort. 0-4. Thick and creamy distortion. Sadly this only works at radio frequencies. EF86/EF806SG pin # Electrode name 1 Grid 2 2,7 Screen 3 Cathode 4,5 Heater 6 Plate 8 Grid 3 9 Grid 1 Electrical data Parameters, measures Rate Not Heater voltage 6. The quoted THD of 5% with ~ 24. This is where screen voltage plays a key role. 8 specified. NB: You need to The major change is replacing the 12ax7 with ef86 and getting ride of the nfb. The grid bias is provided by the grid current and it’s associated voltage drop across the grid resistor. The EF86 works under extreme current trickler conditions in that Mullard 3-3 circuit, see plot available here. Joined Jun 4, 2004 Messages 4,378 Location The EF86 input stage of the circuit above provides high-gain voltage amplification, the stage gain being approximately 120 times. While EF80 / 6BX6 as a typical RF/IF stage pentode is designed for working with much more current going. Running it at such very low cathode currents will harm its cathode and is not recommended: According to my TFK The PREF86 is a tube preamp pedal that features an EF86 preamp tube, running at high voltage courtesy of a Hammond power transformer inside the pedal. 5-0-359. Grid Voltage Svetlana EF86 Typical Plate Charicteristics-1. zaphod_phil Builder, Admin Posts: 15208 Joined: Wed Mar Voltage boost by a factor of 100 is just beyond the reach of a 12AX7 triode, but well within the capabilities of an EF86 in pentode mode, as we will see. For example, the EF86 has a maximum rating of 100 Volts when the cathode is positive and 50 Volts when it is negative with respect to the heater. However, the heater is isolated from the main circuit so that, for example, pin 5 may All my voltages are ok but pin 6 of the ef86 is showing 6. Instead of using a cathode self-bias the tube bias is obtained by means of a hight value grid leak resistor (10 MΩ). PS The mesh is a screen, not the anode. An appropriate series resistor in the heater supply will take care of the difference in heater voltage for the PF86. When the cathode voltage approaches the desired voltage, it would settle with a time constant of 500 uF/(gm + gm_screen), which is in the hundreds of milliseconds range. To explore this further, a while ago I plotted load-lines on a set of curves for the same (SE) pentode at different screen-grid voltages, and found that the relationship between the "knee" of the curves and the load line could be maintained nearly constant if both screen grid voltage and anode voltage were decreased at the same time - but not P=98 volts S=36 volts K= 1. 99 VDC Voltages on the 'high-power" HT tap: PT HT 719VAC (359. e. What I'd really like to know is if it works OK as a voltage amplifier in pentode mode, i. 5 Heater Current in mA 200+/- 10% Heating Indirect Cathode-to-heater potential, max. 53mA cathode current. A solution to this sort of problem is having a low noise, high transconductance, JFET source follower ideally load the cartridge and have the FET drive a step up microphone transformer. On pin1 For large changes of plate voltage the EF86's plate current barely changes which indicates a high internal plate resistance. 0 x Top. Care in the design of the valve to ensure that the electrode structure and its mounting are as rigid as possible can reduce the microphony of the EF86 to an insignificant level. Something like this CineMag transformer seems right for this situation. 5 to 46 volts out, measured slightly better in my case: 4. EF86: Base: Noval, 9 pin miniature (USA pico-9) B9A Filament: Vf 6. I looked over the schematics and the HF-50 uses an EF86 pentode voltage amp, while the HF-89 uses a 12AX7. 2 Ampere / Indirect / Specified voltage AND current AC/DC: Tube prices: 1 Tube prices (visible for members only) Information source: Essential Characteristics, GE 1973 6267: Internet Miguel Angel Trujillo-Rodriguez 6267: Telefunken Röhrenhandbuch Note: The impedance at each input includes the grid impedance of the EF86 modified by the feedback components as well as by the impedance of the input network. However the reverse is what has happened with the screen voltage being about 10-12 volts higher than the plate at idle. 1mA at 400v: Resistance = Volts / Current = (400v - 100v) / (2. The best way to select an EF86 for this circuit is to put a voltmeter between the LTP anodes and choose the EF86 which gives the lowest voltage reading. Because the screen volts went up, this means the wiper of the Amplitude control went to ground leaving a voltage WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES. Monkeying with DC coupled circuits is VERY tricky business. I used the EF86 preamp channel (no 2nd 12AX7 channel), added my tube based effects loop, and changed output transformers to encourage earlier breakup of the On one amp I installed a VVR to adjust the screen voltage of the pentode. There isn't any triode quite like the EF86's triode mode. EL34 Single-Ended (SE) Tube Amplifier Schematic (EF86 input) Single-Ended (SE) EL34 Tube Amplifier Schematic with EF86 input stage. Unlike many pentodes, it he Svetlana EF86 is a glass envelope miniature pentode intended for high-quality audio preamplifier service. Building, troubleshooting and testing of these amplifiers should only be The EF86 can be used in phono pre to sound respectable but it's a lot of work . This arrangement allows the true character of the pentode to be heard, since it can be driven by a larger signal than those produced by guitar pickups. It might even then be viable to use a 12AT7 cathode buffer after that as a nice combination instead of the EF86, but I'll have to play. It is clear when you look at the circuit that low-frequency RIAA conformity will be poor. Joined 2005. The endpoints for the red line shown here on the EF86 plate transfer characteristics are -4V, 1. The EF86 was developed from the B8A EF40. F. True bypass footswitching, EF86 datasheet, EF86 pentode equivalent, Mullard, Features and benefits, Stock and price EF86 Datasheet, Mullard EF86 pentode equivalent, voltage amplifier pentode. A 12AX7 triode has less gain than an EF86, but you get two triodes per tube. It replaced the EF37A and EF40. I think to use EF86 really clean you need to really manage how much signal goes to the following stages. Equivalent to tubes: EF86, 6267, 6CF8. C. " "The pedal plays like a dream, I love it!" "I received the boost today. The HT for the 300B is provided by a Russian 5U4 rectifier (V7), a type which has proved itself over the years. You want less gain, more gm, and lower plate resistance in that role. With its intricate specifications - including a 6. 9 mA, R k =2. 4mA for EF86, and 70v/17mA for the 6N6P. This holds down the plate volts on the EF86, and thus the grid volts on the EL84, to a level that balances out with the biasing effect of the big cathode resistor on the EL84 to set that valve's bias too Suggestions ef86 riaa. The pentode circuitry is more complex but the input sensitivities are comparable. Lower R20 to TYPE: CV4085 (Special EF86) B9A LOW-NOISE TYPE FOR MICROPHONES TYPICAL APPLICATION HEATER CIRCUIT The voltage polarity of the heater pins in the Phædrus Audio EF86 TRIODE SupertubeTM must be respected. Thanks. 0 x EF86 with the 18 watt is a killer combination, to be sure. Kay Pirinha. the b+ is good, all the resistors are good. 8. The EF86 tube is notorious for microphonics and this is due to its high gain and super large plate. Spice models WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES. Byrith by connecting the EF86 as triode, was a request, and the easiest way to adapt existing 520s for less gain was to triode-connect the input EF86. nzfspi xvkego nstj qtgo wxh cpwzk sdmy yotzw eno ikke