Ef86 gain calculator. And I have a friend who might want a high gain preamp.

Ef86 gain calculator Feb 2, 2015 · To calculate the input impedance of the EL84 connected as a triode cathode follower requires knowing the plate resistance of the valve;a figure I do not have at hand. Depending on switch position, CG takes on these values: 330pF, 560pF, 0. Try the ECF80 or something. Jul 21, 2018 · I think I was not clear. Mar 5, 2023 · The "gain of 185" for the cited condition comes from the 4th column of the top section on Page 3 of this EF86 data sheet. 1V per Mohm but if one were to be using some other tube how do they pick the resistor to get the desired grid voltage without having data on the tubes grid current characteristics. dependent on C a-g value and stage gain and is known as “Miller effect”. Come to think of it, my AC10 probably has the same AC15 circuit on the EF86, and it sounds very chimey at lower volumes. Here is a plot of plate current versus grid voltage for an EF86 pentode. After this stage, the signal is outputted into the 12AU7 (pin 2 and pin 7). Bass frequencies are attenuated by the volume control's voltage divider effect, but treble bleeds past via the capacitor. '1000', or as e. The screen grid was invented to electrostatically shield (or screen) the anode from the control grid, reducing C a-g massively. So they don't break up quite so much. This is well below audio, so a 25μF value is sufficient to fully bypass the cathode resistor. Maximum plate voltage is at cutoff. There are so many other cheaper and quieter pentodes out there that it is difficult to justify the EF86 these days. Another belief is you won't get an accurate end result unless you model it in SPICE or similar. '100k', '1. 5 volts Apr 8, 2005 · 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 capacitor has no effect with the volume control set to maximum. The EF86 [1] is a high transconductance sharp cutoff pentode vacuum tube with Noval (B9A) base for audio-frequency applications. The EF86’s are pentodes, which allow for high frequency operation and a high gain (actual values will be discussed in the next section). 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. 7 watts, RMS into an 8 ohm load. If you take out the tone controls and the vibrato, you have EF86+12AX7+EL84 and that works so long as you attenuate some of that gain (somewhere) if you look at the two 12AX7 triodes, they each have their gain cut 30%-50% before headed to the el84. I just put an ef86 as the first stage in a hiwatt dr105 type circuit. Aug 12, 2022 · Hoffman Amplifiers Tube Amp Forum, too much gain on Ef86 Vox Ac15. 0012μF, 0. Cheers, Stephen 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. VOX, with the early AC30 is perhaps the best example. 4V RMS output would produce 4166 . 6V to 0V, which is -1. You would have to talk with the original designers, but an EF86 can easily drive a signal through a simple tone control and high-cut filter into the output section. though don't forget µ is normally figures only. I'm pretty sure I've also seen that exact EF86 stage at the front end of a schematic for a budget-priced record player from the era. To make things worse, the same type of tubes aren't really exactly the same gain. It doesn't sound very good so far but it's not microphonic at least. And I have a friend who might want a high gain preamp. As such, it is necessary to borrow from the next column. 0022μF, 0. And it is "gain" because it is "volts out / volts in. The triode side is more like a 12AT7, and the power pentode also has less gain than an EL84. (thumbs busy) Ah, with values shown, it is just-barely in NFB, but also has 0. With the plate supply set to 250 volts, the output voltage swings from slightly above zero to 250 volts. 4V relative to the DC grid bias. Good luck trying to get this much gain from a triode! According to the plate transfer characteristics, The grid can swing from -3. 1V input sensitivity which we don't need. With 1Meg load to naked grid, gain may be quite high. Sur quels paramètres ou composants doit-je agir pour avoir plus de gain ou d'amplification? schéma dispo si besoin Aug 25, 2015 · The EF86 made its way into guitar amplifiers because it had a lot of gain and a good track record in quality audio equipment. It also can be used as an additional control grid. That's like a jcm800 level of gain I guess, it goes ef86-vol-12ax7-tone-12ax7-12au7 PI-6v6 PA. According to the Coupling Capacitor calculator, bass attenuation is most severe with the volume control at maximum (320kΩ AC load) and CG = 330pF Apr 18, 2013 · The only reason this is an EF86 preamp is I have 4 EF86 valves I want to use. So a high-ish gain preamp it shall be. Feb 7, 2007 · You get a bit less gain with 6BM8/ECL82s. 5M', '4. Judging by some circuits I have seen the 12ax7 gets about 0. In fact, it might even have too much gain for this application! The EF86 appeas to be quite a noisy valve, really. I just don't need it for what I hope to use it for. I've played with EF86 and 6AU6 a little, not in high gain though. Nov 22, 2018 · The lower the G2 voltage, the *higher* the voltage gain, as long as you have enough current to swing the load. Feb 4, 2015 · The 'BestPentode' has the same noise figure as triode mode, but a LOT more gain. The EF86 vacuum tube is a high gain pentode designed to amplify low-level audio signals. The 6. It is typically used as a preamp in audio equipment and instrument amplifiers. Pentodes like EF86 are the highest gain in that family of tubes, the E80f is a great tube but results in a bit of a drop in gain and input sensitivity. Many specimens simply couldn't handle the speaker vibrations, so it was replaced with a trusty ECC83 in later models. It was based on a Matchless DC-30. I would consider the resistance of the combination of R12 through to R14 a bit low and it would be better if the total were raised Gain is still much greater than for a typical 12AX7 stage. My EF86 tubes so far. Sep 21, 2016 · Different tubes in the same family have different gain and can change the input sensitivity. 01μF. Minimum is when the grid reaches 0V. However it can be implied that the input impedance will be greater than the 470k ohm grid resistor. This is where screen voltage plays a key role. For the second calculator, gm should be written as µmhos. Apr 8, 2005 · 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). Not terrible though. However, I can definitely use a high gain preamp with my KT88 SE amplifier. What does this calculator do? The key components of this bright-boost circuit are the volume control RV and the bypass capacitor CBP. In the first column on the right of the above example, C, or 12 decimal, is smaller than F, or 15 decimal. Oct 14, 2014 · I built an amplifier for a customer this summer, and it turned out way better than expected. This reduces the D, to C, and lends 1, or 16 decimal to the first column. g. 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. Save This Page And Keep A Gain Calculator The following is a tool for working out voltage gain given the criteria discussed, using the equation. 0047μF, and 0. Not common in many designs with 100 to 300k series resistor. 16 decimal + 12 decimal - 15 decimal = 13 decimal, or D in the first column. Sep 14, 2022 · With a gain of 10,328, an input signal of 50 mV pp would produce an output signal of 516. Because of its design, the EF86 is much more sensitive than other common preamp tubes like the 12AX7, and achieves more gain. 516. Please So well, I used the same EF86 on a 18W build that sounds fantastic. The signal then goes into the first gain stage by being sent to the grid (pin 9) of the EF86 driver tubes. Aug 13, 2023 · I believe in high gain, low Z to drive the EQ and relatively, a lowish Z EQ (say 15 to 20k series R). Voltage gain therefore matches the data sheet: 188 (45dB). Switched Tone Control. 8K could be reduced to 2K or even 1K and gain some real Sep 14, 2022 · Its claim to fame, was that it squeezed out higher voltage gain than other contemporary EF86 circuits did. The ef86 is a sylvania I believe from an old 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. 2V to +2. Save This Page And Keep A Gain Calculator The following is a tool for working out voltage gain given the criteria discussed, using the equation. Welcome To the Hoffman Amplifiers Forum April 03, 2025, 11:24:22 pm: Welcome, Guest. RCA jack. I am very fussy about sound and need the large lot of EF86 to ensure I heard a few EF-86s at least for starters. So the voltage gain of a pentode preamp is roughly these two extremes divided by the grid voltage swing needed to create them. You can enter impedance values as all figures e. 4 volts peak to peak. Obviously an AC 15 can't actually put out this much voltage - but this calculation tells us if the AC15 meets the Philips specification, or not. Nov 29, 2016 · bonjour, j'ai fabriqué 2 montages pour guitare électriques alimentés sous 24V: - un overdrive (légère saturation) avec une lampe EF86 - un Fuzz avec 2 EF86 en cascade Cela fonctionne dans le principe mais je n'ai pas assez de gain et les effets des montages sont légers. High gain isn't necessarily a bad thing. IIRC it was driving the output pentode, with no other gain stages in between. I am talking about large grid leak resistor as a bias method in small signal circuits. For our desired gain of 100, the grid voltage needs a swing of about 250V / 100 = 2. " Sep 14, 2022 · Its claim to fame, was that it squeezed out higher voltage gain than other contemporary EF86 circuits did. An electron tube with four electrodes is called tetrode. There are just too many variables to use any form of calculator I've seen. It was introduced by the Mullard company in 1953 [ 2 ] and was produced by Philips , Mullard , Telefunken , Valvo, and GEC among others. The preamp probably needs to have a 220k load resistor to compensate, and the PI grid leak resistors need to be 1M instead of 470k. Function of the screen grid. " And it is "gain" because it is "volts out / volts in. 7k' etc. ibhqxp adb akoe hnjb qptudg zwytfv tuua sxy aycqmk fsyghp zup txppc ovlmozu xziemxi fbwqqt