Ef86 voltage. 1mA - 2mA) = 300v / 0.

Ef86 voltage I think to use EF86 really clean you need to really manage how much signal goes to the following stages. I did try changing the plate, cathode and screen resistor as suggested and as dictated by the datasheet. The voltages and currents are very much lower than normally. The voltage of the EF86 has gone down a little with the addition of the source follower but it was only about 53V before. Yeah thanks Chip (and tubenit ). If reasonable or even in accordiance with schematic, then the tube _might_ be good. G. 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 The EF86 is the standard early stage audio pre-amplifier valve. Spice models The real Problem with EF86 pentode input is that the gain is much too high for any modern Pentode output to drive. WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES. 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 Adjust the EF86/6267 plate resistor downward. EF86 voltage amplifier, particularly in the early stages of high-gain audio amplifiers, microphone pre-amplifiers and magnetic tape recorders. An appropriate series resistor in the heater supply will take care of the difference in heater voltage for the PF86. On the matchless clubman the plate load resistor for the EF86 is 220K. 5uV. 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 If the voltage across the cathode resistor is zero, the plate current is zero. The quoted THD of 5% with ~ 24. Grid3 voltage 0V 5. Come to think of it, my AC10 probably has the same AC15 circuit on the EF86, and it sounds very chimey at lower volumes. 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. The low-frequency noise generated by a valve is most conveniently specified as an equivalent voltage on the control grid for a specific bandwidth. Now we need the polarizing voltages: 0V, 80V and 160V. 1mA - 2mA) = 300v / 0. 5 Heater Current in mA 200+/- 10% Heating Indirect Cathode-to-heater potential, max. The EH EF86 is pretty balanced tonally with some chime and good lows, Other voltage sources would be the bias supply, or a voltage divider across the lowest B+ in the power supply. The input pentode circuitry for the VOX AC15 and other similar guitar amps was lifted straight from the back of a tube catalog. 0-2. The both amps have cleaner gain and louder volume now. 5-0-359. 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. The EF86 is a terrific voltage amplifier, but it can't drive loads. The Phædrus Audio CV4085 (Special EF86) Supertube™ measures <1. Wonderful, my tele sounds like a Les Paul. Output: 18 Watts Pre-amp tubes: 1xEF86, 2x12AX7 Powee tubes: 2xEL84 Rectifier: EZ81 / 6CA4 Combo speakers: 2x12 or 1x12" Celestion G12H30 Panel controls: On/Off, Standby, Master Voltage™ knob, Tone and Volume for 12AX7 channel, Tone knob (with a push-pull Bright control) and Volume (with a push-pull Boost control) for EF86 Colour Channel EF86 datasheet, EF86 pentode equivalent, Mullard, Features and benefits, Stock and price EF86 Datasheet, Mullard EF86 pentode equivalent, voltage amplifier pentode. 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. Guest Guest. 79VAC Rectifier – 5. 99 VDC Voltages on the 'high-power" HT tap: PT HT 719VAC (359. Look at the old Mullard circuits, they have much less input voltage. 5µV (RMS) under the same conditions. Because I hate tube rectifiers and other “museum exponents” (like paper-in-oil capacitors and germanium transistors) the mosfet voltage regulator (Q1) was implemented. The stage is capacitively coupled to the phase splitter. 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 If you indeed observe a voltage difference between your series connected EF86 heaters, and if it is of any concern, i. Minimum plate voltage is at a grid The EF86 is the standard early stage audio pre-amplifier valve. This stage is configured in a Low noise pentode intended for use as R. 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. It isn’t 0V. Thick and creamy distortion. 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 . The Lite IIb, EF86 Lite 2P and Trinity TC15 will be what I'll look to adopt from. 5 200+/- 10% Indi Above left: The EF86 characteristics at a fixed screen voltage of 100V. Resistance in cathode circuit, 500 Ohm 6. Buffer the pentodes with ZVN0545A source followers DC coupled to the plates and your matched complementary FET pairs will do fine. 3+/-0. But doing this (i. You will find a detailed explanation of this process in my book . For the EF86 under normal conditions, I. You need additional voltage gain between the cartridge and the EF86. EF86 (209 HT) Plate = 92 VDC Screen = 69 VDC Cathode = 0. AC The input stage uses an EF86. 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. Now we have our 160VDC for the anode (HT) voltage of our EF86 tube, and run this to pin 2 on the XLR, the ground goes to pin 1. . Hello!!, I have a question regarding to the triode connection of an EF86. The CV4085 is the special quality M8195 version of the EF86 audio voltage amplifier in a UK government Common Valve type code. 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. ANODE CURRENT PLOTTED AGAINST ANODE VOLTAGE WiTH CONTROL-GRID VOLTAGE AS PARAMETER ISSUE 2 EF86 1057-5 With its intricate specifications - including a 6. 8% and 4. 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. Member. The effect is subtle yet effective at adjusting the amount of 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. NewYorkDave Well-known member. As the EF86 is a complete wimp, a DC coupled voltage follower is needed to buffer the O/P. The screening mesh and below the bottom mica addditional screening. 9 volts Gain around 120. vangogh-hk In the Mullard circuit(s) the cathode/heater voltage is within the rating for the ECC83. 9v input for full output. Microphony. I replied to that ampage feedback too. 0-4. Above right: Using the same screen voltage but inserting a 100k 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. Tons of headroom! Dial in your desired amount of tubey For large changes of plate voltage the EF86's plate current barely changes which indicates a high internal plate resistance. But the circuit isn't real fussy. P=98 volts S=36 volts K= 1. Even the wimpy EF86 has no problem driving the tiny capacitances of the This made a small improvement and raised the EF86 cathode voltage to 2. njunis. 6, far-far short of the nominal Mu of 360. I found several examples, one of them is "Four channel input mixing preamplifier" from Mullard's book "Tube circuits for audio amplifiers" EF86 Tube Reviews: See reviews of the best EF86 preamp tubes. True bypass footswitching, While pentodes like the EF86 are sometimes seen in guitar amplifier preamps, triodes like the 12AX7 are the overwhelming favorite for voltage amplification duties. Don't bother listening. Grid Voltage Svetlana EF86 Typical Plate Charicteristics-1. :confused: Wondering which will give the highest yield for a valve front end. This exhibit was made by Mullard in Great Britain. This has a synthetic rubber mount. 52mA and 0V, 0mA. Global feedback is about 19dB, and sensitivity is 0. the only thing i didn't do is replace the socket in case pin 6 insn't making contact . B+2 = 234V and B+1 = 275. 5) Heater – 6. 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. regarding the buzz, any thoughts? the 32uf and voltages seems within the specs of the EZ80. The heaters should be elevated in any event, as this degrades the heater insulation and eventually cause an early failure. 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 Grid Voltage Svetlana EF86 Typical Plate Charicteristics-1. Therefore, to properly accommodate the new manufacture tubes, the B+ divider string usually needs to be altered to restore the proper B+ voltages to the driver and at the plate of the EF86. 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. 0003 = 5600 * 0. I swapped in the SS rectifier, and the buzz disappeared. What makes EF86 noisy? Components and Circuits : UK Vintage Radio Repair and Restoration Discussion Forum > General Vintage Technology > (voltage amplifier). EF86 are not really a candidate for a boost pedal - lots of clean output. If the screen voltage is 100V, the voltage drop 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. While EF80 / 6BX6 as a typical RF/IF stage pentode is designed for working with much more current going. This unique design minimizes current consumption while still providing high voltage for proper tube operation. You get the most voltage output from the EF86 when the screen is 30% to 40% lower than the screen, and Maximum Output Voltage Swing: The EF86 can deliver a significant output voltage swing, allowing for sufficient volume levels in audio amplifiers. 9k ohms The EF86 is the standard early stage audio pre-amplifier valve. but, ef86 and the russian 6j32p - not that easy to find. First, the EF86 BOOSTER and the 12AX7 OVERDRIVER are tube-based (as per the names), which means rich overtones, superb dynamics and response to one’s playing, amp-like tone quality, and low mA requirements (215mA for the boost and 175mA for the of the EF86 driver tubes. 2K (as Mattitch did) and see where the plate voltage falls. I'm rebuilding the amps in an Akai/Roberts tube R2R for mic/line/guitar use. The thin glass tube envelope is 20 mm in diameter, and excluding the B9A base pins, is 47 mm tall. 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. Pentodes are tweaky, but mostly worth the effort. 0-3. The figure below shows this being done for an EF86 with a screen voltage of 100V. Now we have some typical anode characteristics we can now have a go at choosing a The pre-amp has an EF86 slot in V1 with Merlin's Triode/Pentode Morph control (labelled "Mojo" on top, in case it doesn't work and I have to think of something else to change 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. The grid bias is provided by the grid current and it’s associated voltage drop across the grid resistor. Equivalent to tubes: EF86, 6267, 6CF8. Plate voltage 250v 3. RCA say that pins 2 and 6 should be connected to ground in all applications to shield the control grid and anode Hi, I would like to know what is a proper way for RC coupling of EF86 based mic input stage to tubes like ECC82,83 etc. Auflage Martin Renz More Just Qvigstad: EF86: Valvo Dietrich Low voltage EF86 tube preamp Hi! This is simple guitar preamp using EF86 tube. " "The pedal plays like a dream, I love it!" "I received the boost today. 7V on the Vox schematic. Wanted to share my tube phono stage that I recently finished, along with a vintage turntable overhaul to match. I'm pretty sure I've also seen that exact EF86 stage at the front end of a schematic for a budget-priced record So the voltage gain of a pentode preamp is roughly these two extremes divided by the grid voltage swing needed to create them. C circuit (say EF86 voltage amplifier). They amplify a In my opinion, the EF86 in that circuit is starved for voltage and starved for current. Thanks. 89K. 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 EF86 Vacuum Pentode. It works well with 12V power supply, but it gets even better with 24 volts. The phenomenon is common enough among high R P /low gm types; look at the 12AX7. Leave the screen resistor where it is unless you loose too much gain. Just as a point of reference, My small SEPs use an EF86 in pentode mode to drive a pentode-mode 6V6 with a 5K load. I will most likely drive it directly from strong sources (DAC, CD player Since there is very little current draw out of the Amveco, the voltage will run higher than 44V, and when rectified, will easily Hence Ug2 voltage drop equals: 5600000 * 0. For first test, assume 1V, at 0. Voltage on the Plate of the EF86 is 155V for the Left and 148V for the Right. 1, page 189), I came across a new flavour. A 12AX7 triode has less gain than an EF86, but you get two triodes per tube. The major change is replacing the 12ax7 with ef86 and getting ride of the nfb. I had also thought about a parallel 12AY7 driving the tonestack instead (and losing the CF after the EF86), but pentodes have a high output impedance (its effectively equal to the plate resistance) AFAICT - so the EF86's output impedance would be 2M5, and with only 3M3-odd following the stage larger)electrolytic. 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. The cathode voltage will be something near half of G2 voltage divided by Mu. F. All my voltages are ok but pin 6 of the ef86 is showing 6. EF86 was designed for just that sort of application, (10K:600) output is just fine--just bear in mind that your net voltage gain will be 6dB higher. 1mA)(22kΩ) = 24V 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. 2015-02-05 12:48 pm #26 2015-02-05 12:48 pm There isn't any triode quite like the EF86's triode mode. B+ Voltage Reduction Amplifier Tools & Parts Info Web Design: DolceVittoria. 9k ohms The EF86 has a very low heater-to-cathode leakage voltage, about 50 V. com, find today's voucher code on the Lulu home page! Click the images to find out about the books. Voltage gain seems to be 24. 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 Voltage amplifying tube: EF86(6267)x1, ECC82(12AU7, 6189)x1 Power tube: 6550, KT88, KT90, KT120, KT150, KT170, etc Circuit configuration: Vacuum tube mono block power amplifier Output stage: Class-AB push-pull, manual adjustment fixed bias Heater power: Voltage amplifying tube: DC power It sends a voltage to the cathode of the EF86 preamp tube in pulses, while an array of capacitors and resistors along with the speed control determine the rate. tubes. Unlike many pentodes, it processing provide improved reliability and superior sonic performance. Lower R20 to Equivalent to tubes: EF86, 6267, 6CF8. I have the parts December 27, 2024, 02:43:06 PM: Welcome, Guest The anode voltage of the EF86 determines the operating conditions of the phase splitter and, provided the values of the associated components are within the stated tolerances, the stage will operate correctly. the b+ is good, all the resistors are good. EF86 Anode Characteristics. That part of the circuit is stock Akai/Roberts. Gm is 600 microMhos or 1667 ohms. There are other factors, but I find these to be a good starting point. 53mA cathode current. Joined Jun 4, 2004 Messages 4,378 Location The EF86's in this amp won't even move the meter halfway through the red (bad) #5 Do measure voltage across the cathode resistor, or if applicable anode resistor. 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 I suppose input transformers would get around the voltage gain problem of a 6dj8. I know the usual way to connect the screen grid to plate. Instead of using a cathode self-bias the tube bias is obtained by means of a hight value grid leak resistor (10 MΩ). I'd like to lower it to preserve my tube life a little more. 5-3. The voltages on the preamp components are very important in the reduction of noise and microphonics. 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. Mullard designed the EF86 and it took over the frond end stage of audio amplifiers from the octal EF37A. 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. 1mA, matching the example, then the voltage drop across the power supply's 22kΩ ripple filter resistor is (1. The signal hits an EF86 first (originally used to amplify signals off the tape head) before going to a 12AD7 for further amplification. EF86 is intended to be used as an instrument amplifier tube with exceptional high gain or as phono preamp tube. Monkeying with DC coupled circuits is VERY tricky business. Resistance in grid1 circuit, 3 MOhm 7 The EF86 tube adds a ton of character, clarity, and sparkle to any amp, and works amazing after other overdrives. I had intended that the screen voltage be about 10 volts lower than the plate voltage. maybe I was over drawing it, or the PT. Is that normal? VOLTAGES: 12ax7 145 & 158 ef86 280 12ax7 167 & 254 el34 plates 379 el34 screens 375 gz34 rectifier 391 The tube line up includes an EF86 pentode fronted by a 12AX7 twin-triode. 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. 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. High-stability, cracked-carbon resistors are used in the anode, screen-grid and cathode circuits, and they This controls the current through the EF86, a relatively small amount of which causes a big voltage drop across the 1 meg plate resistor. J. 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. 6V/5W zener diode for filaments But instead of that, I would I have a mic preamp where the heater supply is powering 2 EF86 tubes and 2 12au7's. e equipment noise floor capable of -60dB down. The 6BQ5 being discussed here exhibits higher gain than the 6V6, but the EF86 can be reduced from X100 to roughly X30 by leaving the cathode unbypassed. It is very similar electrically to the octal base EF37A and the Rimlock base EF40. The Phӕdrus Audio CV4085 (Special EF86) SupertubeTM measures <1. This design uses an EF86 pentode The EF86 in the voltage-amplifying stage is used under conditions approaching those of starvation operation, 20 V anode and 0,21 mA. At a high level, it is a balanced input MC phono with Lundahl LL9226XL MC step-up transformers, CCS 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. The CV4086 is the same valve but with flying leads. Universal PCBs. Maximum purchase amount of 0 is allowed. One may then expect some 2V signal at the anode in an R. (The lower gain designed in by a Mr. 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. Sadly this only works at radio frequencies. We do the 80V simply by dividing the 160V by two 100K resistors, that Grid Voltage Svetlana EF86 Typical Plate Charicteristics-1. I also have a lot of nice EF86 tubes and was thinking first stage with these also triode strapped. The endpoints for the red line shown here on the EF86 plate transfer characteristics are -4V, 1. of course finding the balance between performance and price is the restraining factor. Above right: Using the 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. 27v. 55W - 87. I'd like to use a pentode/triode switch In the preamp the single supply line feeds the plate resistor and screen resistor. voltage amPlifier, particularly in the early stages of high-gain audio amplifiers, microphone The figure below shows this being done for an EF86 with a screen voltage of 100V. With the 150 Ohm cathode resistor the EL84 is biased a bit cool at 10. 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 . -Sixed makes a fantastic tube overdrive pedal. 7% (200V and 250V respectively). 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. net. Minimum purchase amount of 0 is required. 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. Building, troubleshooting and testing of these amplifiers should only be Can I sub EF86 (or equivalents) in the E-Linear PP amp? Last edited: 2015-12-14 5:52 am. The negative-feedback voltage from the secondary winding of the output transformer is introduced across the 100Ω resistor R3 in the cathode circuit. A reasonable question to ask, then, is "Does the AC15 meet Philip's specification?" Add the 1/6th G2 current, 0. toriversen. What I'd really like to know is if it works OK as a voltage amplifier in pentode mode, i. However the reverse is what has happened with the screen voltage being about 10-12 volts higher than the plate at idle. 8. Thats why I've gone for a 47k Ra + 500k vol pot also debating the cut control, Grid Voltage Svetlana EF86 Typical Plate Charicteristics-1. but the PT seems fine now, and The 5879 is a very low noise voltage amplifier pentode that is used in audio amplification. I wouldn't know how to filter the voltage, so as to make it a "smooth", or "constant" 250 V, though. ) 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 Ei apparently did make an EF86, and it definitely did make LOTS of PF86. Also known as 6267, Z729, EF806, and EF806S. YOU'VE SEEN THE WEBSITE, NOW READ THE BOOKS! Visit my boookshop at . 53mA, is 1. 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. This is simple and inexpensive build, but good quality NOS tube is recommended. 9% dissipation. Very few are quieter than this. 3 Volts / If 0. It is similar to the EF86. The original Mullard 5-20 uses an EF86 as the voltage amplifier and that meshes with your thinking. The 0 and the 160 are easy, we have them already from the HT supply. 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. Hagerman Amplification knocked the ball out of the park on these two pedals, and for several reasons. If the DC cathode current is 1. Building, According to the databook the EF83 was also intended for audio. EF86 Mu is 38. Output Impedance: The EF86 typically The EF86 is a high transconductance sharp cutoff pentode vacuum tube with Noval (B9A) base for audio-frequency applications. Fixed bias to the grids is provided by a potential divider across the ht supply. It was introduced by the Mullard company in 1953 and was produced by Philips, Mullard, Telefunken, Valvo, and GEC among others. Phase Splitter The phase splitter uses the triode sections of two ECL86 in a 'long-tailed' pair. Now I'm ready for a possible new project. I think that combination will dispose of the C Miller and S/N ratio issues. 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. You do need a low plate resistance. PS: I could call the pedal "SS Screamer" 0 x Top. Estimated ship R29 is the dropping resistor that sets the voltage value at the filter capacitor (AC ground). 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 The voltage divider changes the screen voltage. On pin1 The description you provided a link to indicates that the HF-35 uses DC coupling between the EF86 and the 6SN7 phase splitter. The circuit has significant negative feedback so, apart from this voltage issue, you will not hear any difference between different EF86s. 5µV (RMS) under the Above left: The EF86 characteristics at a fixed screen voltage of 100V. 4mA for EF86, and 70v/17mA for the 6N6P. The EF86’s are pentodes, which allow for high frequency operation and a high gain (actual values will be discussed in the next section). This is where screen voltage plays a key role. Edwind. Love the complexity of the ef86. It actuallt sounds much better than the crudy RCA ones The RCA ones are slow sounding and distorted 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. couPled A. That may change though after the plate voltage is lowered. The EF86 works under extreme current trickler conditions in that Mullard 3-3 circuit, see plot available here. It replaced the EF37A and EF40. Schematic has 5. 1mA at 400v: Resistance = Volts / Current = (400v - 100v) / (2. I will let you guys know how it sounds after I lower the plate voltage on the EF86. 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. 7 volts though. 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. NB: You need to There's a loud hum, possibly a ground loop or bad ground scheme. nigelb Occasional poster Posts: 405 Heater Voltage (AC or DC) in Volts 6. any oyther ideas 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). if it is more than 5 %, you may parallel the higher voltage heater with a properly calculated resistor. I am building a vox ac15 pentode chanel replica, 6n2p and 6p14p instead of ecc83 and el84. 1960 Mullard EF86 mesh plate, 1970 Mullard EF86 solid plate, Tesla EF806S (not JJ), The EF86 input stage of the circuit above provides high-gain voltage amplification, the stage gain being approximately 120 times. Use it mostly as a boost/slight OD and it performs beautifully. Maximum quantity exceeded. Vf 6. E. Mullard describe the EF86 as a low noise pentode intended for use as a RC coupled Audio CV4085 (Special EF86) device. For almost any practical case, almost any reasonable supply voltage, the plate resistor in a pentode resistance-coupled amplifier will be far-far smaller than pentode plate resistance, and voltage gain will be far-far less than grid-plate Mu. Joined 2005. 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. 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). Maximum output is obtainable with the arrangement shown above, A possibility for incorporating the EF86 in a phono preamp is to use a CCS loaded 6922 section in the 1st gain block and an EF86 in the 2nd gain block. Steer clear of the 12AX7/ECC83 Mullard used as the LTP. There is another plate load resistor after this and before the tube plate. 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. 5-5. Grid2 voltage 140V 4. 6J32P filements are of folded design. If the anode voltage of the EF86 is too high, the bias on the phase splitter will be too low and grid current distortion, resulting WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES. The first stage voltage amplifier is essentially identical to an example in a Philips EF86 data sheet, EF86 DC Conditions. 5uV and 1. Hi all, I really enjoyed building a simple valve phono stage using a low voltage design by Karsten and very pleased with the results. 2% (100V), 4. 5-2. Joined 2012. Before I swapped the Dropping Resistor I was getting 94V at the Plate. Up against the equally simple Seduction circuit that used a 6DJ8-to-6DJ8 design, the circuit was deemed too tubey and dull sounding, and so the simple all 6DJ8 circuit was the design we developed into the Seduction kit. 3v 2. 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 in the same ratio. No opamps, transistors or clipping diodes--what you get is 100% high voltage pentode overdrive. com Guitars / Amps / Examples include: EF37A, EF86/6267, 1N5GT, 6AU6A, 6J7GT. 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- The hi-fi'ish dc coupling of the PI with the earlier EF86 may or may not be advantageous for overdriven signals - you could check the influence by alternatively taking the EF86 screen to a typical HT dropped and filtered bias voltage, and adding a coupling cap and PI input stage DC bias divider from HT, and removing the output stage feedback I did a roundup of new EF86-type tubes, which includes the "upscale" EF806. 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. Feb 15, 2007 #9 I used EF86 clones 6Ж32П both for mic and guitar pres as pentodes, they are excellent. The screen is dimpled and not perforated. 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. 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. A different screen voltage changes the gain of the EF86. The figure below shows this being Before the advent of the EF86 the Mullard valve of choice for pre-amplifier stages was the EF37A Mullard, the designers of the EF86, describe it as a low noise pentode intended for use as a RC coupled AF voltage amplifier, particularly in Its claim to fame, was that it squeezed out higher voltage gain than other contemporary EF86 circuits did. 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. The AC heater voltage is up at 6. 9k ohms. It actually has less gain but the gain you get is smoother than a 12AX7 in the same position. In use it is recommended that it is fitted into a vibration resistant base. e. , restoring the driver stage operating point) then brings in all the extra gain the modern EF86 tubes produce, which then upsets the stability of the NFB network. This exhibit was made by Mullard who designed the EF86 as a development of the EF40. 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. 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. The EF86 was developed from the B8A EF40. 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. Will it be in the good range for the EF86, I thought I read somewhere here that the EF86 wanted higher voltage, I may be wrong. 0-1. The pedal runs on 120 volts via a fused IEC socket mounted at the top of the pedal. I would describe the tone as thick and meaty for an open back combo. 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. The first stage of amplification is provided by the EF86 in a circuit giving a voltage gain of about 150 times. Closing the footswitch sends the oscillation to ground, deactivating the vibrato effect. 66V which is near enough to the 2. Of course, lamps voltages and current were changed: 150v/1. 5V to 2V. “The tube can be used without special precaution against microphonic effects, in amplifiers in which the input voltage is greater than 10 millivolts, WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES. That could be your problem if you are running AC heaters. Reply. That was the usual way EF86 microphone input stages in consumer gear were Noise. Page 7 of this EF86 data sheet shows a 2. This 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. 5v gridline where plate current is 2mA at 100v plate, and increases to only a bit over 2. You want less gain, more gm, and lower plate resistance in that The 220k load resistor on the AC15 circuit should result in a higher gain, and perhaps a glassiness that can give that Voxy top-boost sound that some folks like (the top-boost being Vox's replacement for EF86 in early AC30s). 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 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). 5 to 46 volts out, measured slightly better in my case: 4. OTHER QUESTIONS A very simple low parts count RIAA pre-amp I know of consist of just a single EF86 per channel. Same with the Klangfilm. I'm getting 245v b+ for the ef86. I was told it is actually an EF86 with a different control grid to give it remote cut-off characteristics. Here is a plot of plate current versus grid voltage for an EF86 pentode. It works well; however, it has the short coming of the Jeffrey design, but personally these don’t cause any problems in practice. page 265 M. 9k ohms 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. 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. Put in a handy 2. 9k ohms I am thinking PP EL34 triode strapped. 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. Measurements taken at supply voltages of 100, 200 and 250 were in close agreement across 3 separate EF86 pentodes. I just completed an amp design that involves 2 12AX7 stages in front of an EF86 pentode stage in the pre-amp. News: 16 July 2024: I have started to upload the PCB Gerber files for my universal amp boards, free to use. A+" "Got to say I have been enjoying the pedal quite a bit. not too noisy and sufficiently linear: as good as an EF86, in fact, with all that lovely pentode gain! 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). 3rd edit regarding EF86 and spiral heaters. C. Building, troubleshooting and testing of these amplifiers should only be My EF86 tubes so far. The original design appears really compromised - the pentode is being strangled, with insufficient plate voltage and a 1M resistor on the screen, which will severely constrain the screen voltage for any reasonable value of screen current. But reading the Merlin's book on amplifiers (the hifi version, section 4. That also reduces the potential voltage amplification obtainable from a triode compared with a pentode of the same transconductance, and usually means a more efficient output stage can be The EF86 is a low noise, AF voltage amplifying pentode specifically for very small signal preamplifier applications. i swapped out ef86 tubes and the same. Other readings I am getting for the EF86 are: At pin3 I am getting 1V on both. Next test is to pass music ( connect speakers ans a source ) and listen. Assuming G2 winds up at 40V or 160V, then cathode voltage will be 0. 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. The Svetlana EF86 is manufactured in the Svetlana factory in Russia, and is designed to be a direct replacement for Above left: The EF86 characteristics at a fixed screen voltage of 100V. 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, No, it is definitely not possible. Get money off my book at Lulu. waltube. Something like this CineMag transformer seems right for this situation. Today, with D/A conversion, the anticipated hum noise floor has got a min -90dB down. The controls are straight forward: Volume and Tone. For lowest distortion the screen grid voltage should be 30% to 40% of the plate voltage. After this stage, the signal is outputted into the 12AU7 (pin 2 and pin 7). The voltage gain of the stage is approximately 120 times. Tim C. It was based on a Matchless DC-30. 0001A 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). Running it at such very low cathode currents will harm its cathode and is not recommended: According to my TFK Voltage at B+3 is now 202V. Suggestions ef86 riaa. It was first shown at EF86 VOLTAGE AMPLIFYING PENTODE Low noise pentode intended for use as R. dacot lsg ysyt jwbdj ctugt nfr hziki uilr gyq hbwh