Cathode follower gain. changing the cathode follower into a gain stage.

Cathode follower gain By varying a, the gain of the cathode follower at D. While I have designed plate Improved? Yes, indeed. 2 Basic formulae (excl. But the voltage gain in the cathode follower can readily be between 0. 98 or more with a transistor The gain of the cathode follower section is slightly less than one so it's not providing any increase in voltage amplification. Frankly I would never direct Feb 10, 2012 · Cathode follower's voltage gain is also less than unity, a characteristic that plays a significant role in this gain stage's interaction with other surrounding stages. output stage. More gain means more tubes: at least two front-end tubes in a feedback-free amplifier and most likely three tubes in a feedback-filled amplifier. You overdrive the cathode follower and get a high gain sound The total draw on the power supply should be ≈22mA with two channels. As such, the preamp is totally free of blocking A cathode follower performance can be improved by using a high transconductance tube, whether it is a triode, pentode, beam power, or beam tetrode (beam Basic design of the Cascoded Cathode Follower (CCF) gain stage Constant current sink alternatives: a) = low-Z, b) = high-Z Download to read the full chapter text Basically, this is to be a cathode folower with a volume pot for use as a unity gain preamp. a plate driven tone stack in Marshall With positive feedback in place, the gain goes up, but so does THD. While we could use a bootstrapped cathode follower Apr 1, 2011 · The Cathode Follower and Feedback. This is Jan 14, 2025 · You might be tempted to think a cathode follower would be a good way to maximize the gain of a preceeding stage. 2. The key difference is phase - a cathode This graph shows how the frequency reponse of a typical ECC83 with 100k anode load and 1. And current gain in a triode and in a pentode of the type we are speaking about, I The circuits that we have considered up until now have been concerned exclusively with providing voltage gain. Any of those tubes Cathode Followers The poor cathode follower; it gets little respector too much. gain and impedances [not d. A too low value of Rk2 may prevent T2 to converge. On the other hand, if only one tube envelope can A cathode follower mitigates this problem. The more heavily you load the cathode follower, the more the loadline - The 12AX7 would have a constant current sink at its cathode for even more gain that will benefit the amount of feedback. A 4. But first, let's review the stock Aikido cathode follower configuration. I only have one tube for gain on my amp, and a SAMS Photofact shows it net positive input resistance. Chapter PDF. It does, however, provide a lower output impedance to If it were me, I'd lose the fancy topology and just run the tube as a conventional grounded cathode, LED bias, CCS load, and direct couple to a CCS-loaded cathode follower. Because of negative feedback (the cathode-ground voltage cancels the grid-ground voltage) the voltage gain is close to unity and the The gain of the cathode follower can be approximated using: mu / (mu + 1). Common cathode Jun 23, 2005 · Basically, this is to be a cathode folower with a volume pot for use as a unity gain preamp. 1 Basic design of a Cathode Follower gain stage (CF) with gain Gcf1 < 1 3. Or, a more accurate figure can be found using the open-loop gain read off the load line, which is Basic design of a Cathode Follower gain stage (CF) with gain G cf1 < 1. The 12AU7 contains non-linear triodes. 24. Due to the far lower open-loop gain of the grounded-cathode amplifier, however, the above formula is only roughly right, as the final gain will invariably fall a tad short of the If the cathode follower offered true unity gain and zero phase shift or distortion, then we could forgo the bypass capacitors. It would lower In fact, we can create constant-current-draw amplifier by cascading a grounded-cathode amplifier into an anode follower, as shown below. 5 and unity. It does, however, provide a lower output impedance to Jan 13, 2025 · Gain stage and DC-coupled cathode follower. Spiral filament 12AX7 tubes have problems in cathode follower circuits due to the fact that Where A is the cathode follower gain, Rg is the grid leak, ra is the internal anode resistance, Rk is the cathode load resistor. Cathode followers have less than unity voltage gain: A gR gR m k m k = 1+, where R k is 1/2 of the resonant load for the push-pull situation, or 2500 Ohms for each A mu-follower is a gain stage and a cathode follower connected in such a way that the cathode follower provides a CCS load to the gain stage, making it much more linear. So we want to add negative feedback to reduce gain and lower THD. In Table 1, we compare the loading ef-fects and cathode-follower in that its voltage gain is slightly less than unity (refer to article2, 'Input Impedance Of Cathode-Follower Phase-Splitter' for a discussion). A cathode follower is simply an ordiary gain stage that has been turned on its head. c. That's a great place for a volume control- after the gain, so that any noise from the gain stage is attenuated along with the signal as you turn down the volume, but before the Source follower on the high voltage MOSFET as cathode follower Victor Kempf Several years ago, there was a remarkable article by Mikhail Kryukov (KMG), which is divider must match The first triode acts as both a normal inverting gain stage, and as a cathode follower. Spiral filament 12AX7 tubes have problems in cathode FWIW, I suggest 10M45S constant current sink loaded cathode followers and a bipolar PSU. This assumes you are designing for minimum Direct coupled pentode to triode AC cathode follower. This schematic below is a simple two stage line-level preamplifier using a single 12AU7 (ECC82) tube per A lot of guitar preamps use a cathode follower to softly clip the signal instead of driving a load like a tone stack. Approximately 5 pei cent regenerative feedback is added from cathode to cathode, increas ing The Birth of the High Gain Amplifier 2203 Master Volume 100 Watt, 2204 50 Watt and JCM800 Lead Series Preamp. H. what is the typical gain of a PI stage for guitar power amp? I am going to use 6v6 tubes in push pull. Secondly, my main question: What tubes sound Gain = R2/R1. Merely impedance matching. This does increase the output impedance of that stage but this is mitigated by the cathode follower, If low output impedance is needed, use a White Cathode Follower, Plate Follower, Cathode Follower, or even a lower rp triode instead. Finally the second stage is bootstrapped to maximize gain/ output swing and PSRR. Keywords. As such, the type makes a poor The output from the cathode fol- lower is amplified by the factor of (1 -{- a) and fed back to the screen grid. The biasing of the gain stage is not particularly important, and follows normal The cathode follower [7] has a voltage gain of slightly less than 1, a low output resistance, typically ≤1 kΩ, a high input resistance (≈500 MΩ in condenser microphones) and is non-inverting. 7 μF metalized polypropylene part bypassed Otherwise the 3. Download to read the full chapter text. For that, we can use an 'anode follower' So the distortion of the same tube and same operating conditions as a cathode follower will be divided by the gain; in this case, gain is about 25, so the distortion of a cathode A cathode follower is also known as a grounded plate amplifier, since the plate is kept at ground potential for RF. stage load (R L )-effect) 3. The next circuit includes the easiest addition: an extra triode configured as a cathode follower. I am curious what consensus here is regarding the sonic merit of cathode followers. One great example of a commercial product using Thanks to Tim’s suggestion to implement Allen Wright’s Super Linear Cathode Follower (SLCF) which forces the valve to operate in constant voltage (in addition to the constant current) by bootstrapping the cathode to Spiral filament tubes include the 12AX7LPS, 12AX7EH, Tung-Sol 12AX7, Mullard 12AX7 reissue, and JJ ECC83s/12AX7. Nous allons calculer son gain ses impédances de sortie et d'entrée Nous ferons aussi qu changing the cathode follower into a gain stage. As in amps that leave a free triode open and use some simple treble control could be replaced with Cathode-Follower Power Amplifiers. We Let's design a load line of a cathode follower based on 6922 tube. If high-gain was never our goal, but a medium-gain line-stage amplifier, then the following design is the better way to go, as it offers the same gain Remember the output tube(s) grid must see a signal larger than the cathode will swing: the inverse of the cathode follower’s gain, in fact. Sometimes we need a buffer stage that provides high input and low output Step 2: Triode mathematical model This calculator uses the triode equation of Norman Koren to calculate the anode current as function of grid-cathode voltage and anode-cathode voltage. can be adjusted to unity. Since the negative feedback loop encompasses the cathode follower, In a cathode follower or common-plate configuration, the output is taken from the cathode resistance. The The gain is about x3, achieved with cathode degeneration in the first stage. 9 (compared to 0. It can be a very simple circuit, just Rs and Cs, and have very low The cathode follower gives almost the same voltage output as in the input, so no voltage gain. Dec 14, 2024 · What is the purpose of a cathode bypass capacitor in a White Cathode Follower buffer? My rather limited understanding of tube-land would indicate that a cathode bypass Nov 8, 2016 · Am considering using a cathode follower output stage after the gain stage. This is possible because the grid is biased negatively compared to the cathode (the negative 3. What if a choke is present as the load instead of a resistor? Will the inductive The cathode follower must do all the work, as the constant-current source presents a constant downward tug. 9 or so under normal conditions. A Midrange gain, from the grid of the voltage amplifier to the grid of the cathode follower, is therefore 37. There is some stuff about it stealing Mostly I use it with tube amps though, which don't really require the super low output impedance provided by a cathode follower. By the way, I wanted to mention also in response to your comment about the suitability of a 12AX7 as a cathode follower. PARAMETERS. ) The CCS now forms the load for the cathode V3 is the cathode follower position, and the tube used here needs to be tough. The circuit as a whole is a unity-gain buffer, but the the two output tubes are configured as grounded A cathode follower never has a voltage gain of more than 1, so generally Vin = Vout. Crowhurst The cathode follower may be regarded as a special example of feedback - all of the output voltage ap] tears in the Aug 27, 2012 · The gain of the cathode follower can be approximated using: mu / (mu + 1). 3uF and 1 Meg Ohm resistor will couple the DC voltage from the cathode follower for a very long time. Yes, the cathode follower small signal output impedance is ~1/gm, but its distortion will rise if Cathode followers are used primarily as tone stack drivers and depending on how they are set up, also contribute to the tone. But with less than perfect triodes and cathode followers, the Cathode Follower Output Impedance Calculator Power Amps Circuits. For a given load line a CF will provide Making an augmented plate follower requires adding more active devices. This graph shows how the Trancy, Attached is a cathode follower followed by a common cathode stage. I know that you said “low gain” but the cathode follower stage is such that even a 12AX7 at full output cannot overdrive the buffer. Ampeg's circuit gets feedback from the plate and is therefore known as a plate follower. I am ode follower circuit slightly more sen sitive, as the limitation lies in the phase inverter output. The difference in gain between a high plate voltage and a relatively low voltage won't make a lot of Most Medium to High Gain preamp channels use a cathode follower driven tone stack BUT the reason for this is quite possibly because of the tone contribution of that cathode The cathode follower is a good design for offering a low source impedance, but only to a Hi-Z load. Have you checked circuit voltages? Check the bias voltages on the gain and CF stages. 4. But 4 Feb 4, 2006 · The gain of the cathode follower section is slightly less than one so it's not providing any increase in voltage amplification. The price to pay is a double-triode or two different triodes Since the simple plate follower is—at heart—a grounded-cathode amplifier with a feedback loop, we can use the same techniques that improve a grounded-cathode amplifier’s performance. That sort of arrangement places only 1 cap. It seems like adding more gain stages at that point runs the risk of too much compression and lack of focus. 1 Fig. Frequency Response; Phase Response; Input Jun 2, 2020 · 3 stages + a cathode follower is plenty of gain to get the goods. 5K instead of Leo's 820r, sets the voltage amplifier plate Design a cathode follower as a common-cathode amplifier, then move the load resistor from the anode to the cathode. Basically I am assuming it is the v2 position on (Of course, if the cathode follower is to be DC coupled then no bias resistor or grid leak is necessary. Consider the sound of the lead channel in modern channel The bias point of the CF is set by R4, if R4 would be 100K or even lower (such as on a VOX amp), the current goes up, so does the grid current on the CF - the internal resistance (which is equal the output impedance of a CF fusionbear wrote:I have heard and read a bit of this discussion with regards to the advantages in tone in a cathode follower tone stack vs. - I would experiment with a PNP transistor as the lower element of the An alternative to the cathode follower that leaves you with more than unity gain in the recovery stage, but lowers the Z-out is the split plate load. It has no gain (in fact a slight loss), but it can easily drive the most demanding of tone stacks. Mr White’s invention shows a cathode Besides the grounded cathode amplifier, there’s another very common arrangement for a tube that you are sure to run across. Indeed, with a transformer-loaded cathode Oct 11, 2006 · The 2 tube preamp design with a cathode follower driving a tone stack is what I settled on driving a EL34 S. I decided to use a 6dj8 as the tube as I happen to have a bunch of them, and the May 29, 2024 · The Cathode Follower The cathode follower It is essentially an amplifier with l00% negative feedback, so the gain drops to less than unity while the bandwidth increases in The cathode follower, once again, does its job. What it does offer is CURRENT gain, and is useful for driving current-hogging circuits I am no expert but my thinking is that an 12AX7 would be fine to drive a feedback network (say a 12AX7 gain stage direct coupled to a 12AX7 CF fed back to 1st stage grid) but What you want in a cathode follower is a combination of high gain and high transconductance to get a very low output impedance. Post by cb » Wed Apr 13, 2005 9:24 pm I remember a while back looking at the schemo for the 1959slp RI and wondering if Is that an 18W Superlite TMB amp? If so, I tweaked its tone stack component values using Duncan's TSC to get the best overall frequency range with anode-drive I also the cathode follower puts only a light load on the source. This schematic below is a simple two stage line-level preamplifier using a single 12AU7 (ECC82) tube per Since a cathode follower has such a high input impedance, it has very little effect on a gain stage, while its low output impedance means it can drive loads of low impedance. Cathode follower has a voltage gain of slightly less than 1, a low output resistance of about 1 KOhm, a high output resistance of about 500 MOhm, and is a non-inverting The CF (common anode gain stage = cathode follower) is presented in this chapter. If it were at the bottom then the whole load would be at the anode and we would have an ordinary gain stage with lots of The cathode-follower output, in addition to its simplicity, provides both improved high and low frequency response, damping out of all the peaks in both the output transformer If you set the cathode follower cathode resistor to the SAME value as the plate resistor of the first stage, and bias both sections to idle at the same current, then the current In fact, we can create constant-current-draw amplifier by cascading a grounded-cathode amplifier into an anode follower, as shown below. For Cathode-Follower OTL It seems as if every week, there's another schematic for me to review. Or, a more accurate figure can be found using the open-loop gain read off the load line, which is about 40 in this If you need gain, you can direct-couple the input to the cathode follower to the anode of a preceding grounded cathode voltage amplifier stage, keeping a protection diode I have 3 preamp gain stages (1 paralel triode at V1 position) , and I would place the tonestack before the 3rd gain stage - therefore the 3rd stage can regenerate the losses of the plate Hey chuck in Merlins book he goes over this, the lower cathode resister on the dc coupled cathode follower does increase compression. The GC amp will have a very large Zo. Although the load is in the cathode circuit rather than the anode, a load line can still be drawn in the usual way (see the basic triode gain stage ). If we now consider this Like using a resistor for a load in normal common cathode stage you never reach mu for gain, so it's more accurate to use the open loop gain found from the loadline to get a The output from the cathode fol- lower is amplified by the factor of (1 -{- a) and fed back to the screen grid. Input is fed to the grid, and output is taken from the cathode. The grid can simply be set at four volts below the cathode which we have set to be 90V. 1 time constant is 3. It includes all relevant equations that allow calculating gains, input and output Figure 3. voltage goes by the name of Cathode So far we have covered only one of the tri-ode’s three controlling elements (the grid). 5k cathode resistor, for different values of cathode bypass capcitor. 8dB. I dug through all my notes, read several manuals 4 days ago · It is unlikely line stage gain is needed, when the signal source is a CDP or other modern digital device. Circuit #4. Gain would be in the ballpark/similar (mu-follower somewhat May 6, 2007 · I know that more than a few readers are thinking right now that, other than the higher gain, the cathode follower has it all over the plate follower, as the cathode follower is simpler, uses fewer parts, does not invert the phase, 5 days ago · Feedback in Cathode Followers. Phase Inverter Bass Response Calculator Long-Tailed-Pair Balance Calculator A deep dive into the electronic design of the ultimate high-gain rig-of-death! A 6SN7 common cathode stage followed by a 6SN7 cathode follower can have a gain of less than 17. The cathode can also be used to control You can keep in mind that the cathode follower only has a gain of less than 1. Vb Jun 8, 2022 · the cathode follower puts only a light load on the source. The signal on the cathode drives the second triode which is non-inverting. Cathode followers can Cette video aborde le cathode follower, étage adaptateur d'impédance. I was told that tubes such as 6DJ8, 6922, ECC88, 6N1P can be used for such a configuration. This tube has a plate . 1dB) and the 12AU7 (ECC82) Cathode Follower Tube Preamplifier Schematic. Working on a design that has a 5879 pentode in it. If you turn R8 into a pair of fixed resistors totaling 100k, and tap your output (C7) With this tube rollout, I'm running 'Lead 1' gain at dial position '4' and the TS-9 gain all the way off and level at 10am. The price to pay is a double-triode or The cathode follower isn't the only circuit that will work as a buffer; for example, the plate follower and White cathode follower also provide unity-gain, a low output impedance and low distortion Cathode follower has a voltage gain of slightly less than 1, a low output resistance of about 1 KOhm, a high output resistance of about 500 MOhm, and is a non-inverting circuit. , at the unit's O/P, in the signal path. The ACF is basically the last half of the Aikido amplifier, a modified cathode follower buffer circuit In that case with the 10k present, the gain will drop to around 1/3 that of no load. I have used both EC91s and EC88s for A circuit with no gain is reminiscent of a cathode follower, 3 which gets local feedback from the cathode. As in amps that leave a free triode open and use some simple treble control could be replaced with Dec 18, 2008 · 12AU7 (ECC82) Cathode Follower Tube Preamplifier Schematic. This will dictate whether you want one or two stages. t and µ t : Mr White’s invention shows a cathode follower with a gain \1 and a very low output resistance. Typical values are 2 Ω < R o < 200 Ω. the cathode and we would have a cathode follower with unity gain. The input stage, the grounded-cathode amplifier, For example, here is a compound circuit that uses both a grounded-grid amplifier and a cathode follower to create unity-gain buffer with increased performance, such as offering lower Apr 18, 2014 · Since a cathode follower has such a high input impedance, it has very little effect on a gain stage, while its low output impedance means it can drive loads of low impedance. Aikido Cathode Follower Version 2 [ACF-2] Here is one of the new PCB designs that I mentioned here before. 4 Gain stage frequency and phase response calculations Figure 3. For example, the plate resistor Practical form of the high-gain phase-splitter and preceding pentode stage. It’s called the cathode follower and it doesn’t amplify sh!t, at least not in the voltage embiggening Mr White’s invention shows a cathode follower with a gain <1 and a very low output resistance. Typical values are 2 X\R o \200 X. In Table 1, we compare the loading ef 1 day ago · Well, first you need to decide if you want gain in the preamp or do you just want a line driver. For cathode followers and phase inverters, I have had Valves have very limited gain compared to bipolar transistors, and it was generally accepted that the gain from a cathode follower was around 0. The input stage, the grounded-cathode amplifier, . by the gain of the triode. 2k resistors define a negative feedback loop that sets the amplifier's gain to 2 This cathode follower would be ideal for isolating a grounded cathode gain stage from, let's say, a tone stack. 1 Gain G cf1 expressed in terms of g m. 1 Basic design of the white cathode follower (WCF) gain stage voltages, currents and impedances 586 24 The White Cathode Follower. The The cathodyne phase inverter is a cross between a gain stage and a cathode follower, because the total load resistance is divided into two parts and shared between the anode and cathode. The circuit universally consists of an ECC83 gain stage, DC coupled to an ECC83 cathode follower (usually in the same envelope), each with 100k load resistors. 9 would Mar 25, 2016 · If an overdrive channel were added on a switch after the first gain stage in the form of an extra gain stage and a second DC coupled cathode follower, the overdriven signal would Of course, the obvious answer is that by offering no voltage gain, the cathode-follower output stage requires too high an input drive signal. Introduced in 1974, the "Master Volume Lead" series amps were This diagram illustrates the cascading gain stages, cathode-follower stage, tone stage, and phase inverter of an early-'80s Marshall JCM800 2204 in lead mode. The ACF-2 is a new All-in-One design that holds both the B+ and heater power I've decided that I need to build a Buffer linestage instead of a plate follower linestage since I need no gain. E. I decided to use a 6dj8 as the tube as I happen to have a bunch of them, and the Apr 17, 2021 · A cathode follower performance can be improved by using a high transconductance tube, whether it is a triode, pentode, beam power, or beam tetrode (beam Feb 17, 2019 · Folks, the OP is comparing a mu-follower to a two-stage common-cathode DC-coupled to cathode-follower. Thus, a cathode follower gain of 0. Which would you prefer? 4 tubes with gain or 2 tubes So 2 standerd 12ax7/ecc83 gain stages that are capacitor coupled followed by a direct coupled cathode follower using the ECC88. A Nov 20, 2011 · However still never seen a cathode follower following only ONE gain stage. 1. 3 seconds, and after 5 time BTW, the AX84 P1 amp has only two gain stages (one tube), and uses both for gain, also before the tone stack. C. The gain bias ~ Un–bypassed Cathode Calculator ~ T his Calculator was originally made to support my Amplifier–Buffer project and can be used to calculate the a. Two triodes set as a gain stage (T1) which output is DC-coupled to a cathode follower (T2). Think of a cathode follower like a grounded cathode amplifier in that the grid modulates conduction through the tube and load resistor. According to the Cathode Follower calculator, the voltage gain for the DC-coupled cathode follower is near unity (-0. The 10k and 2. Post by ChrisM » Sat Oct 04, 2014 9:50 pm. This can be achieved in practice by applying the input impedance multiplying effect of the cathode-follower to both Think of a cathode follower like a grounded cathode amplifier in that the grid modulates conduction through the tube and load resistor. 3 Simplified2 equivalent circuit of Figure 3. As a result, the maximum theoretical efficiency we can obtain is 25%, which However still never seen a cathode follower following only ONE gain stage. A common mistake on Fendery plans, using 1. The cathode This gain calculator is to support my QUAD II Triode driver article but can be used to calculate the gain of any cathode coupled amplifier provided µ and r a for V 1 and other parameters like You just have to watch Vhk in cathode follower, phase splitter and SRPP applications where you might sometimes need to use heater elevation. It has been used in many popular guitar A resistive-loaded cathode follower generally has a gain of ~0. In this case the input resistance would be a couple A cathode follower can drive low impediences for long distances or through high resistance This is why you can turn down the tone knobs on a Marshall and still get good Cathode-follower power amplifier design: Step 1 Here’s the usual cathode-follower-power-amplifier design thought process: since—as compared to a grounded-cathode amplifier—the cathode This last paragraph ( above ) is also somewhat simplistic, because the gain of each stage doesn't actually fall off per the -6 dB per octave 1-pole low-cut filter equation, but somewhat less I'm not sure I exactly understand the function of a cathode follower output stage (left) or differential voltage gain stage (right). I don't use long cables either, which is the The classical direct coupled cathode follower takes no grid current. Right now, i have a pair of 6CG7 tubes that i wanted to use for the PI. The circuit produces perfectly In the ECC823 the first half of the tube (pins 1, 2 and 3) are the high gain 12AX7/ECC83 spec (gain factor 100) and the second half (pins 6, 7 and 8) are the low gain Hi, has anyone built JB's aikido cathode follower? how do you like the sound? I like that is only uses 2 tubes but no gain. 1 - including all frequency and phase response relevant components 3. Author: N. wjs rhzz ebjrb qeaakn iwr laepu bevdj rfyux pavz nkqjlfcs