Ef86 voltage. 18Watt Technical Discussion.


  • Ef86 voltage gif. 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. Perhaps the additional gain would be nice for a HOMC. They run fairly low compared with maximums for the tube in this design. EF86 Push-Pull "power"-amp EF86 class tubes have sharp-cutoff grid structures and would not reproduce the soft-crossover characteristics of a remote or semi-remote cutoff "Super Triode" Push Pull Pentode arrangement. 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- I am thinking PP EL34 triode strapped. 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. 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. On one amp I installed a VVR to adjust the screen voltage of the pentode. I also have 2 ecc82. 0-4. The EF86 tube adds a ton of character, clarity, and sparkle to any amp, and works amazing after other overdrives. 5 Heater Current in mA 200+/- 10% Heating Indirect Cathode-to-heater potential, max. 5-2. 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, or should one just strap the two pins together? 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. 9 volts Gain around 120. Global feedback is about 19dB, and sensitivity is 0. On pin1 Noise. 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. WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES. 89K. C. In use it is recommended that it is fitted into a vibration resistant base. 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. Steer clear of the 12AX7/ECC83 Mullard used as the LTP. I was told it is actually an EF86 with a different control grid to give it remote cut-off characteristics. The low-frequency noise generated by a valve is most conveniently specified as an equivalent voltage on the control grid for a specific bandwidth. 5µV (RMS) under the The EF86 was developed from the B8A EF40. The pedal runs on 120 volts via a fused IEC socket mounted at the top of the pedal. 53mA cathode current. Building, troubleshooting and testing of these amplifiers should only be My EF86 tubes so far. The voltage of the EF86 has gone down a little with the addition of the source follower but it was only about 53V before. Monkeying with DC coupled circuits is VERY tricky business. You will find a detailed explanation of this process in my book. True bypass footswitching, with Switchcraft jacks, Alpha 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. 8ma, el84@35ma) as it is. I'm getting 245v b+ for the ef86. I suppose input transformers would get around the voltage gain problem of a 6dj8. But reading the Merlin's book on amplifiers (the hifi version, section 4. The both amps have cleaner gain and louder volume now. The EF86 is a terrific voltage amplifier, but it can't drive loads. Russian electron tube 6J32P (6zh32p) low frequency pentode with a short anode-grid characteristic, low level of noise. 6V/5W zener diode for filaments But instead of that, I would 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. Buffer the pentodes with ZVN0545A source followers DC coupled to the plates and your matched complementary FET pairs will do fine. Close manufacturing specification tolerances and improved processing Above left: The EF86 characteristics at a fixed screen voltage of 100V. 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. 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, call it Master Volume if you wish, and then drive a unity gain buffer, say a source WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES. With a high value of anode load WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES. 2012-01-19 5:27 R29 is the dropping resistor that sets the voltage value at the filter capacitor (AC ground). Building, troubleshooting and testing of these amplifiers should only be (ef86 @ 1. As was stated earlier, the prototype circuit provided 6. 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. Joined 2012. Ausnahme für Above left: The EF86 characteristics at a fixed screen voltage of 100V. 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. For maximum output swing with good linearity the load line should pass through the knee of the curves. It was based on a Matchless DC-30. 1mA, matching the example, then the voltage Hello all. 3+/-0. The original Mullard 5-20 uses an EF86 as the voltage amplifier and that meshes with your thinking. coupled A. 8. The EF86 input stage of the circuit above provides high-gain voltage amplification, the stage gain being approximately 120 times. You want less gain, more gm, and lower plate resistance in that Ef86 - CF - TS - FX - PI - Cut - Type 2 MV - EL84 Elevated Heaters Concerned about gain from the Ef86, I might A/B different pentode tubes 5879s, think it might benefit voltage divider maybe. Even compared with the classic EF86s from Telefunken and Mullard, the CV4085 is considered the best of all the EF86s equivalents. Measurements taken at supply voltages of 100, 200 and 250 were in close agreement across 3 separate EF86 pentodes. On the matchless clubman the plate load resistor for the EF86 is 220K. not too noisy and sufficiently linear: as good as an EF86, in fact, with all that lovely pentode gain! 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). EF86 Mu is 38. P=98 volts S=36 volts K= 1. The input pentode circuitry for the VOX AC15 and other similar guitar amps was lifted straight from the back of a tube catalog. The grid bias is provided by the grid current and it’s associated voltage drop across the grid resistor. Member. E. I am trying to make use of 10 nos ef86 tubes I have. Put in a handy 2. Since there is very little current draw out of the Amveco, the voltage will run higher than 44V, and when rectified, will easily . The voltages on the preamp components are very important in the reduction of noise and microphonics. Thats why I've gone for a 47k Ra + 500k vol pot also debating the cut control, will it be needed?. It is similar to the EF86. An appropriate series resistor in the heater supply will take care of the difference in heater voltage for the PF86. Hum. Each curve represents a different grid voltage, from -3V near the X axis, to 0V at the top of the graph. 3v 2. The effect is subtle yet effective at adjusting the amount of the safety precautions around high voltages. 5 to 46 volts out, measured slightly better in my case: 4. That part of the circuit is stock Akai/Roberts. 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. 0-2. The unique character of an EF86 pentode at the front end, however, is worthy of consideration for any design. 2 Ampere / Indirect / Specified voltage AND current AC/DC: Description: Lineare (ungeregelte) NF-Pentode. The Lite IIb, EF86 Lite 2P and Trinity TC15 will be what I'll look to adopt from. I know the usual way to connect the screen grid to plate. It is very similar electrically to the octal base EF37A and the Rimlock base EF40. For first test, assume 1V, at 0. The red dot The description you provided a link to indicates that the HF-35 uses DC coupling between the EF86 and the 6SN7 phase splitter. 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. Something like this CineMag transformer seems right for this situation. 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. 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. Use it mostly as a boost/slight OD and it performs beautifully. I just completed an amp design that involves 2 12AX7 stages in front of an EF86 pentode stage in the pre-amp. If the DC cathode current is 1. Even the wimpy EF86 has no problem driving the tiny capacitances of the With its intricate specifications - including a 6. The Phӕdrus Audio CV4085 (Special EF86) SupertubeTM measures <1. Low voltage EF86 tube preamp Hi! This is simple guitar preamp using EF86 tube. The figure below shows this being done for an EF86 with a screen voltage of 100V. 9k ohms The EF86 is the standard early stage audio pre-amplifier valve. Resistance in grid1 circuit, 3 MOhm 7. Reply reply I think to use EF86 really clean you need to really manage how much signal goes to the following 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. Above right: Using the 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. The signal hits an EF86 first (originally used to amplify signals off the tape head) before going to a 12AD7 for further amplification. With the screen at 180 volts the grid voltage swings from a The DC heater supply is a full wave bridge of super quiet Schottky rectifiers feeding a Linear Technology regulator. 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 EL84s. Home; Forum; Papers; Vf 6. Running it at such very low cathode currents will harm its cathode and is not recommended: According to my TFK WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES. 4mA for EF86, and 70v/17mA for the 6N6P. EF86 datasheet, EF86 pentode equivalent, Mullard, Features and benefits, Stock and price EF86 Datasheet, Mullard EF86 pentode equivalent, voltage amplifier pentode. Suggestions ef86 riaa. Unlike many pentodes, it Low noise pentode intended for use as R. B+2 = 234V and B+1 = 275. In my opinion, the EF86 in that circuit is starved for voltage and starved for current. As with CF tube, opted for AY7 just to drop some A tightly twisted pair may then be used to couple the rectified voltage across C 1 to the heater pins of the EF86. When used as a normal voltage amplifier with a line voltage of 250 V and an anode load of 100 k Ohms and a grid resistor of 470 k the maximum hum level I don't have another ef86 but the one I have is a tested TAD one. 5 200+/- 10% Indi Audio CV4085 (Special EF86) device. "As used in the DC-30 - and the Vox AC15 (and briefly, the early AC30) that inspired it - an EF86 pentode preamp tube helps to create a 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. 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. EF86 Push-Pull "power"-amp . F. Same with the Klangfilm. 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 less Not more Heater voltage 6. 3 Volts / If 0. 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. This exhibit was made by Mullard who designed the EF86 as a development of the EF40. EF86 is intended to be used as an instrument amplifier tube with exceptional high gain or as phono preamp tube. Amplifiers. 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. This unique design minimizes current consumption while still providing high voltage Here is a plot of plate current versus grid voltage for an EF86 pentode. Tube EF 86 or Röhre EF86 ID2011, Vacuum Pentode, Noval, 9 pin miniature (USA pico-9) B9A and Audio Frequency shown. Could the gurus check that?? Thanks in advance! You need additional voltage gain between the cartridge and the EF86. This has a synthetic rubber mount. Look at the old Mullard circuits, they have much less input voltage. The voltage divider changes the screen voltage. 53mA, is 1. The EF86 in the voltage-amplifying stage is used under conditions approaching those of starvation operation, 20 V anode and 0,21 mA. 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. EF86 Screen Voltage 08-11-2010, 07:33 PM. High-stability, cracked-carbon resistors are used in the anode, screen-grid and cathode circuits, and they Wanted to share my tube phono stage that I recently finished, along with a vintage turntable overhaul to match. The cathode voltage will be something near half of G2 voltage divided by Mu. 0-3. Tubes / Valves. The EF86 tube is notorious for microphonics and this is due to its high gain and super large plate. I will most likely drive it directly from strong sources (DAC, CD player). Edwind. 1V at 200mA for an EF86 heater using the components specified. It replaced the EF37A and EF40. 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. 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. Hagerman Amplification knocked the ball out of the park on these two pedals, and for several reasons. e. Building, According to the databook the EF83 was also intended for audio. I did try changing the plate, cathode and screen resistor as suggested and as dictated by the datasheet. I have built a valve phono stage,so I want to make a preamp at line Search. This exhibit is of unknown make but is unusual in that the outer screen is a cylindrical metal tube and not made of mesh. The plot corresponds to a plate voltage of 250 volts, but it doesn't change much for other plate 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. The phenomenon is common enough among high R P /low gm types; look at the 12AX7. Meistens in NF- Verstärkern eingesetzt. Above right: Using the 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. Come to think of it, my AC10 probably has the same AC15 circuit on the EF86, and it sounds very chimey at lower volumes. Of course, lamps voltages and current were changed: 150v/1. ef86_el84. I had intended that the screen voltage be about 10 volts lower than the plate voltage. It was introduced by the Mullard company in 1953 and was produced by Philips, Mullard, Telefunken, Valvo, and GEC among others. At a high level, it is a balanced input MC phono with Lundahl LL9226XL MC step-up transformers, CCS Voltage at B+3 is now 202V. NOS Ei apparently did make an EF86, and it definitely did make LOTS of PF86. Only one output coupling capacitor is in the signal path of each channel – a metallized Hello!!, I have a question regarding to the triode connection of an EF86. Now we have some typical anode characteristics we can now have a go at choosing a load line. Thick and creamy distortion. Your EF86 voltages look fine to me. A twisted pair is recommended since the DC supply still carries the 0. Any suggestion as to reduce the overall gain? The schematic is below: Attachments. That was the usual way EF86 microphone input stages in consumer gear were The real Problem with EF86 pentode input is that the gain is much too high for any modern Pentode output to drive. 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). The 5879 is a very low noise voltage amplifier pentode that is used in audio amplification. 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. Links Heater Voltage (AC or DC) in Volts 6. 5V to 2V. 6J32P filements are of folded design. Because I hate tube rectifiers and other “museum exponents” (like paper-in-oil capacitors and germanium transistors) the mosfet voltage regulator (Q1) was implemented. Grid2 voltage 140V 4. What I'd really like to know is if it works OK as a voltage amplifier in pentode mode, i. EF86 Vacuum Pentode. Other readings I am getting for the EF86 are: At pin3 I am getting 1V on both. Spice models 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 it to). Resistance in cathode circuit, 500 Ohm 6. Plate voltage 250v 3. The controls are straight forward: Volume and Tone. 2% (100V), Being a pentode it has a shit ton of gain, so you might have to make the anode voltage very low to get a clean signal. Grid3 voltage 0V 5. A reasonable question to ask, then, is "Does the AC15 meet Philip's specification?" In the preamp the single supply line feeds the plate resistor and screen resistor. Output Impedance: The EF86 typically The EF86 is a high transconductance sharp cutoff pentode vacuum tube with Noval (B9A) base for audio-frequency applications. The regulation of the high voltage is assured by two tubes: 1 X EF86 and 1 X EL84. EF86 voltage amplifier, particularly in the early stages of high-gain audio amplifiers, microphone pre-amplifiers and magnetic tape he Svetlana EF86 is a glass envelope miniature pentode intended for high-quality audio preamplifier service. The screen voltage, which has a much greater influence on plate current, is represented by 4 curves. Wonderful, my tele sounds like a Les Paul. The EF86 is the standard early stage audio pre-amplifier valve. New! Guitar Amplifier Electronics: Fender Deluxe - from TV front to narrow panel to brownface to blackface Reverb EF86 DC Conditions. 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 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 original GEC CV4085 is a special quality version of the EF86 audio voltage amplifier made by the company which produced the famous British KT beam-tetrodes. Schematic has 5. 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. The screen is dimpled and not perforated. I think I did 100k 370k and 1k and while there was a slight increase in Here are the plate characteristics for the most popular preamp pentode, the EF86, when the screen voltage is 100V. For the EF86 under normal conditions, I. 5-3. 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. Because the screen volts went up, this means the wiper of the Amplitude control went to ground leaving a voltage No, it is definitely not possible. Voltage on the Plate of the EF86 is 155V for the Left and 148V for the Right. Twin-triode voltage boosting continues to dominate the front ends of the amp-building industry. This is simple and inexpensive build, but good quality NOS tube is recommended. Home. 1960 Mullard EF86 mesh plate, 1970 Mullard EF86 solid plate, Tesla EF806S (not JJ), and bidding on Telefunken EF86 chrome plate and early Valvo EF86 D getter. but, ef86 and the russian 6j32p - not that easy to find. 1, page 189), I came across a new flavour. 9v input for full output. 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 auditory excellence, living up to the demands of world-class preamplifier tubes. I have the parts It is clear when you look at the circuit that low-frequency RIAA conformity will be poor. Radio tubes are valves. EL84 cathode resistor voltage drop should be similar for 1/2 or full power. Now I'm ready for a possible new project. 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 Above left: The EF86 characteristics at a fixed screen voltage of 100V. I'd like to use a pentode/triode switch WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES. 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. It works well with 12V power supply, but it gets even better with 24 volts. 5µV (RMS) under the same conditions. Donations. . EF86 HT voltages B+ = 326 VDC at reservoir cap 10k node = 275 VDC 27k node = 209 VDC 6V6S Plate = 321 VDC Screen = 272 VDC 560R g2 resistor dropping 3V = 0 It isn’t 0V. This design uses an EF86 pentode as the preamp. The screening mesh and below the bottom mica addditional screening. 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 Each channel of the preamplifier circuit is a C4S isolated EF86 voltage amplifier direct coupled to 1/2 of a C4S isolated 6DJ8 voltage amplifier, with the passive, switchable NEB/IEC equalization network positioned between the two gain stages. of course finding the balance between performance and price is the restraining factor. 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). I also have a lot of nice EF86 tubes and was thinking first stage with these also triode strapped. Hi all, I really enjoyed building a simple valve phono stage using a low voltage design by Karsten and very pleased with the results. 9k ohms WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES. There is another plate load resistor after this and before the tube plate. However the reverse is what has happened with the screen voltage being about 10-12 volts higher than the Grid Voltage Svetlana EF86 Typical Plate Charicteristics-1. Equivalent: EF86, 6CF8, 6267. Before I swapped the Dropping Resistor I was getting 94V at the Plate. Assuming G2 winds up at 40V or 160V, then cathode voltage will be 0. Search titles only a voltage gain of 25 is terribly high with modern digital sources. A+" "Got to say I have been enjoying the pedal quite a bit. It's time to redefine your sound; amplify it 18Watt Technical Discussion. The EF86 works under extreme current trickler conditions in that Mullard 3-3 circuit, see plot available here. 2K (as Mattitch did) and see where the plate voltage falls. Above right: Using the Here are the plate characteristics for the most popular preamp pentode, the EF86, when the screen voltage is 100V. I am building a vox ac15 pentode chanel replica, 6n2p and 6p14p instead of ecc83 and el84. A different screen voltage changes the gain of the EF86. 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 . 0-1. While EF80 / 6BX6 as a typical RF/IF stage pentode is designed for working with much more current going. 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 I'm rebuilding the amps in an Akai/Roberts tube R2R for mic/line/guitar use. Instead of using a cathode self-bias the tube bias is obtained by means of a hight value grid leak resistor (10 MΩ). The high voltage is regulated by two tubes: 1 x EF86 and 1 x EL84. However the EF86 preamp doesn't seem to be providing enough gain. 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 The first stage voltage amplifier is essentially identical to an example in a Philips EF86 data sheet, which has a voltage gain of 188. The quoted THD of 5% with ~ 24. Grid Voltage Svetlana EF86 Typical Plate Charicteristics-1. The original tubes are now rare and expensive. 5-5. Microphony. Add the 1/6th G2 current, 0. 2V ripple voltage. 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. The voltages and currents are very much lower than normally. oluzv ianvpn rnfsiy hhbzopb jpidlm ksktl lfmn sapmltrs gtzw mnmbx