were required, namely the addition of a fourth gain stage between the cathode follower and the tone stack. Sometimes a voltage gain stage is followed by a DC coupled cathode follower to drive a tone stack, as in the 5F6, and I understand that. This is a DC coupled cathode follower, taken from this page and in context of the page, its how the 5F6-A Bassman drove the tone stack. The tone stack file is setup for a cathode follower feeding the tone stack like in the 5F6-A. Eventually, we came back to the simplest criterion of all -- which one would you actually build? Shocki - I posted this to an Aussie Guitar Amp Forum where a similar question regarding teh cathode follower ahead of the tone stack was asked - haven't edited for applicability etc. Use them in noise critical positions such as V1 but avoid using them to drive a cathode follower tone stack (eq). If you want to simulate a tone stack fed by a normal gain stage as in the AB763 blackface then change the Zsrc (far left) from 1.3k to 38k. Cathode followers are used primarily as tone stack drivers and depending on how they are set up, also contribute to the tone. and put them on a terminal strip. The 6U8 has a pentode and triode in the same bottle so I’m using the pentode as the input and the triode as the cathode follower. As far as I'm concerned the jury is still out that the 12AX7 LPS can not tolerate the higher Cathode voltage from a Cathode Follower circuit. Joined Sep 22, 2008 Messages 8,829 Reaction score 4,852. We discussed many options, but the more scientific and objective we tried to be, the more complicated the task became. After the cathode follower is the tonestack. They also can be used as a type of cathodyne Phase inverter, typical on Orange amps and some of the Peavey Classic 50 designs. I know this is obvious to most of you, but I'm not sure. Basically Cathodes on preamp tubes see very low voltages, usually around 1.5volts or less. The “JP” Series The JP uses a different approach than the other amps. This gives the bass knob a greater range of control. Yes the V2 position on the MAZ is a Cathode Follower which drives the Tone Stack, like most Tweed and Marshall style amps do. Isolating the tone stack with a cathode follower representing an insignificant portion of the tone stack resistances will prevent this. And each tone stack sees the impedances of the other one. Cathode follower Cathodyne phase inverter What's more, you can implement this with: AC coupling Level shifting Cathode bias Fixed bias Direct coupling with a grid-cathode protection diode! With a common input resistance somehow mimicking the load of one single tone stack. my current circuit has 2 preamp stages preceding a tone stack, which can sound fizzy and harsh when driven too hard...not my thing. Ask vintage amp enthusiasts about the cathode follower at your own peril. Many will get a little gleam of love in their eyes, and start gushing about how it’s the pack mule among tube circuits, with a mean kick that’s perfect for driving tone stacks. … Schematic of pre-amp to tone-stack attached (original and modified). Top. The cathode follower would just grab the signal after the plate resistor (R16), be routed to the newly wired V1A, then fed by the cathode follower to C7 to enter the tone stack. This will be the output. The cathode follower basically acts like a buffer to prevent the passive tone stack from loading down the previous gain stage and losing too much signal. plexi, top boost, blah, blah). I tried changing the tone stack and other things but I eventually decided to try a different topology so I moved the 5725 to the input. One is used. i think i read that a … Any help is appreciated. Some F*nd*r amps use a100k value for their classic mid scoop, while Marshalls typically use a 39k value to get their stronger mids. Joined Jul 18, 2009 Messages 6,570 Reaction score In my amp though, I have a 1uF cathode cap at the first triode of the cathode follower. i do like the sound of circuits that use them (e.g. cathode follower, the grid resistor etc.) Jethro Rocker, Kelia, Matt_Krush and 1 other person like this. The weird part is that it crackles if i turn up the master volume even if the tone stack and gain control are set to 0. Of course, the 18 watt tonestack is not as robbing as a TMB. Its DC-coupled cathode follower and tone stack sit prominently in the signal path of the Soldano SLO, Traynor YBA-1, and Vox AC30 (without a middle control). I removed the original tone control (that is connected to the volume pot) from the circuit. So, that's the first step, taking all the preliminary stuff (i.e. The DC Coupled Cathode Follower. Cathode follower = classic tones. Cathode follower circuits are said to lend the tone a special flavor, as a number of classic guitar amps would go to show. The Bassman's gamma-network front end is the hands-down favorite of builders to this day. You can somewhat compensate the hardness of the plate driven stack by warm biasing the stage driving it. The output impedance probably won't stay put, and if it varies, the poles 'n' zeros of your tone stack will change with it. The 6V6 requires a lower cathode resistor value, but the other power tubes all use the same higher value and are easy to compare. The system is hardly overseeable. Then plate mode would just reconnect R16 to C7 as it is stock when the switch is flipped out of cathode follower mode. Aside from converting the V2 circuitry to the commonly used Marshall gain stage & cathode follower (slightly modified with a (V2a) cathode 22uf "fat cap" bypass & (V2b) cathode load 470pf bypass), then relocating the tone stack to be cathode follower driven, the rest pretty much has its origins in the often copied Josse mods. Keen’s MOSFET Follies . Top. Think of the output impedance of the preceding stage, and the impedance of the tone stack as a voltage divider. I'm not a silicootie hater or anything. The cathode follower tends to smooth the result a little more and with it's higher current, drive the tone stack more efficiently. Cathode Follower is irrelative to Cathode Biasing. This is fine, if bass isn't reduced prior to the tone stack. The cathode follower basically acts like a buffer to prevent the passive tone stack from loading down the previous gain stage and losing too much signal. I thought they had a cathode follower tone stack. An alternative to a switch in front of the stacks might be one or two JFET source followers after the cathode follower. I'm noticing that it's behaving strangely. So I wonder if there's some interaction with either the previous stage (cathode follower) or the next stage (master volume + power section) that could explain the difference. Cygnus X1 Senior Member. However, for some types of amps the soft clipping of an overdriven CF is an essential part of their tone, leaving aside the tone stack issues for a moment. The tone stack file is setup for a cathode follower feeding the tone stack like in the 5F6-A. MVC-003s.jpg. Lead channel, three gain stages with cathode follower, pre tone stack master, structure 3 position switch that changes stage two cathode values and bypass cap. Cathode Follower with Interactive Tone Stack One of the most significant elements of the circuit is the cathode follower tone stack. - cathode follower is generally a stage driving FX loops and the tone stack / EQ - long plates do not generally handle gain stages as well as … The tone stack can be connected either to the cathode or anode of V1b, or not used at all, and it can be configured either as: Basically Cathodes on preamp tubes see very low voltages, usually around 1.5volts or less. I replaced the 5725 and 1/2 6N2P cathode follower by using a 6U8 up front. The V4A Tone Stack Buffer Cathode Follower is used to prevent the tone stack from loading down the high impedance guitar signal coming off the FX Recovery V4B plate. The parts of the tone stack that I modified are shown schematically in Figure 4. The Valve Wizard. both interstage coupling caps can be changed to 22n to 2.2n independently. My question is do I need a coupling cap after the master volume? The plan is to follow Dumble lead dress and keep the 45/100 circuit intact (with exceptions for fine tuning). The tone stack goes into the fist half of a 6N2P and the second half is a. cathodyne PI. In Dumble lead dress, the first thing on the main board is the tone stack. The stock Class 5 circuit is gain stage > AC coupled cathode follower > tone stack > gain stage > gain stage > output. The plexi still had many significant elements that helped form the way the tweed Bassman did business, including the three-knob cathode-follower tone stack, Presence control, long-tailed-pair phase inverter, and a class AB output stage in fixed bias with a negative feedback loop to tighten up the performance. Tube compliment for maximum clean headroom with cathode follower mod v1 12AY7, V2 12DW7, v3 12AT7; For the Tone Stack Mod: Mouser part nums 75-715P1200V0.015 Orange Drop .015k capacitor. The cathode follower provides a very low source impedance that allows the tone stack to work as designed. The cathode follower would just grab the signal after the plate resistor (R16), be routed to the newly wired V1A, then fed by the cathode follower to C7 to enter the tone stack. Remember there is LOTS of BS posted on other forums . Apparently more people are getting this noise after the cathode follower mods The cathode follower tends to smooth the result a little more and with it's higher current, drive the tone stack more efficiently. Just my own preference. One is used. Below is a calculator for the cathode follower output impedance from Pentode Press. Just wondering how the winner will be judged in this challenge. For more, see Mike Donovan’s article on High Voltage Solid-State Circuits for Guitar Amplifiers , or R.G. The cathode follower provides a very low source impedance that allows the tone stack to work as designed. I need a full EQ tone stack (bass, mid and treble) to sculpt my tone. In this variation, the treble pin 2 (output) connects directly to grid of the next stage. You can somewhat compensate the hardness of the plate driven stack by warm biasing the stage driving it. They also can be used as a type of cathodyne Phase inverter, typical on Orange amps and some of the Peavey Classic 50 designs. The back end of the preamp is mostly normal, including the tone stack, but the front end has a cathode follower driving a Balance control that is controlled by footswitch (like the rare SAP amp does). And started after i turned the last stage into a cathode follower and changed the tone stack values. By nature of the design the cathode follower output is low impedance. I think the design "visually works better" when the output from the source is either direct to source or after the first source resistor (R33) - the waveform more closely replicates the wave of a 12AX7 cathode follower. In my recent build, I decided to drive the tone stack with a cathode follower. Just my own preference. cathodyne) phase inverter and a fixed-bias output stage with a negative feedback loop to tighten up the response. With a common input resistance somehow mimicking the load of one single tone stack. In my recent build, I decided to drive the tone stack with a cathode follower. … The load of the tone stack is fixed for any particular setting. Note both sides of the DC coupled CF are from a single 12ax7. Or, if this is a build as yet to happen, you could just feed the tone stack from a cathode follower. 0 x Nature abhors a clean tube amp. 75-715P600V0.1 Orange Drop .1k capacitor. He claims Violence mode engages a 4th gain stage, but there are only 3 12AX7s, so with a Cathode Follower, that only leaves 3 gain stages. 3 position voice switch that changes cathode follower 100k cathode bypass. The cathode follower driven tone stack tends to sound more compressed. The 0.0022μF capacitor at C16 was replaced with a 0.022 μF orange drop capacitor. Then plate mode would just reconnect R16 to C7 as it is stock when the switch is flipped out of cathode follower mode. The author begins with the 5F6-A's relatively simple triode preamps (bypassed cathode resistor, unbypassed cathode resistor, and cathode follower) and then progresses through the mathematically challenging tone stack, long-tailed-pair phase splitter, and push-pull power amp. Figure 3: Cathode follower schematic. The lowest prices in the industry. But it is prior to V2, so kind of but not in the way I thought. The cathode follower is DC coupled to the driving stage. According to the Cathode Follower calculator , this stage has an output impedance of only 615Ω, making it perfect for driving a frequency-dependent load that demands a lot of current. Attenuation is only 0.14dB. Transistor IRF820 N-Channel MOSFET 500 Volt 4 Amp TO-220 available at Jameco Electronics. They are most often found in amps that have post-gain tone stacks like Tweed Bassman, Plexi, … Nov 7, 2010 #5 But can you see what the voltages are? But wait, there's more! Kinkless Tetrode, Mar 24, 2020 #4. Ok no LPS for me then... But I do like the EH in v1 of my amp. Warm and balanced. I cannot speculate as to how it would sound in anyone else's amp... The Duncan tone calculator just substitutes an equivalent resistor value to take the place of the cathode follower circuit that drives the tone stack. In guitar amps a cathode follower is most often used in place of a gain stage, it gets its name because the signal is outputed through the cathode instead of the traditional plate output. LPV Senior Member. that too. I won't use these for anything. I've got an LPS in the PI. Why won't you use one? I've heard some bad things about these lately. Could yo... Nothing unusual. 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