12au7 cathode follower schematic I noticed a mistake in all the schematics I saw. Give the value of resistors for current from 6mA? š Here arranged thy schematic with ECC82 š š Thanks and cheers! Am considering using a cathode follower output stage after the gain stage. 14 Feb 2024. 8 Meg cathode resistor, DIY Audio Schematics Tube Linestage Preamplifiers. There are better theoretical tube choices for a cathode follower for a lower output impedance, like the ECC99 or ECC88. Trio, LeeStereo, both great posts. These feed directly into single 12AU7 triodes running as cathode followers with 2N2222 current sinks set to 1mA. In that application, a 12AX7 will operate as a more efficient cathode follower, because it is the inherent gain of that tube coupled with the inherent 100% NFB of the Cathode Follower Calculator. But even when not Mar 22, 2024 - 12AU7 (ECC82) Cathode Follower Tube Preamplifier Schematic. (200 / 2 = 100V) for maximum headroom in the cathode follower. It is surely a better choice than SRPP from this point of view. In the 12AT7's are a popular choice for cathode followers because of their higher transconductance and plate current. Better yet would be a 5687 or 6N6P, since those have lower plate resistance, so can drive 10k with relative ease. In 12AU7 cathode followers, its more common to see 5mA Thank you very much for the helpful advice. My signal path is: DC coupled cathode follower 12AU7 Edcor 600:600 transformer pins 2-3 of the XLR Pin 1 goes to ground via a lift switch This is pretty much straight out of the Thunderfunk book. 12au7 cathode follower schematic Cathode follower again ;)no rocket science! Lm3886 gainclone supply cathode follower power application 56w note diy 90v 12au7 calculating using bridge schematics size recommend study also V2A - Cathode Follower V2B - AF Amp V3A - AF Amp V4 - Cathode Follower So should I focus my best tubes on the Pre Amp and Amp stages? Iām a bit new to all of this. However these tubes mainly date back to the days of mono so there is no reason that you cannot use a 12AT7 for the amplfier part of both channels and the 12AU7 for the cathode part of both channels. I don't like this tube but I have some nice NOS 12AU7's so I built this preamp. In the above schematic, the 6SN7 triode has a 600-volt window to operate within, allowing fairly large, say +/-250V, output swings. Is this what you plan to drive with 12AU7 cathode follower ? After reading Merlin's post on the sound of DC coupled cathode followers when they're set up to steal current from the previous stage, I'd like to toy with them in my next amp, which uses a solid state tonestack. So I built a "tubelab SSE" circuit a while back and fell in love with it. I suspect a schematic would answer most of these questions. It's just a little too powerful for the room it's in. By varying the trimpot the DC output of the opamp āand therefore the grid biasā can be altered to suit different valves, allowing the optimum working conditions to be found quite easily. but with 12AU7, this is not a problem. which then drives a bootstrapped 12AU7 cathode follower driver stage, which drives a UL connected 6550 output stage. separate heater wires to the switch and to the 12AU7 cathode follower ? Is the Allied 6K49VG power transformer suitable for the 4S - 460VCT at 50ma. First off I will start with the schematic by Tim Williams from which my project is based on. According to the Cathode Follower calculator, with a 220kĪ© cathode resistor the output impedance is only 617Ī©. During start up this value is actually 1/2 the full B+ (of about 275 V). I have some parts I'd like to turn into a preamp. I will try to calculate/measure the present bias current. Something like 6. Joined 2009. A few hundred Ohms between the output cathode and output jack helps to damp potentially resonant tanks that can form. Cathode follower with tube 12au7(ECC82) Schematic. Neither is it an aikido follower. have used the design as seen in the schematic with low impedance cans for quite a while and it performs pretty well. Level 3 Schematics library: Design a custom Eyelet or Turret Board: DIY Layout Creator File analyzer program: DIY Layout Creator File library: Transformer Wiring Diagrams: 12AU7 (ECC82) Cathode Follower Tube Preamplifier Schematic. A chart of these gains can be found on the 4S project page here. So with 215-225 V on the anode the cathode is over 100 V. The plate impedance of a The 73V output sets the DC voltage at the grids of the triodes forming the long-tailed-pair phase inverter. Jim Marshall crafted guitar amplifier masterpieces without the assistance of computers, software or the Internet In 1963 "graphical methods" meant drawing Bode plots with a pencil and ruler Times have changed. 6 or something. Some valve stages such as cathode followers require the heater supply to be elevated to avoid exceeding the valve's Vhk(max) rating. 12AU7's make fantastic PI's and cathode followers. 8VDC on the cathode. The actual gain will never be 20. I tried it with a ZVN0545 source follower, but the clipping was too sharp-edged. However- take a 12AU7 under the same load: Vout-max = 300 * 600/(12000 + 600) = 14. A PS-3 or PS-4 power supply would be perfect mate for the ACF. Dipping into Merlin Blencowe's "Designing Tube Guitar and Bass Preamps" I found the part about rounded clipping from a cathode follower drawing grid current. 28v, which equates to about 4. As such, the type makes a poor voltage amplifier. For example, since many tubes, such as the 6SN7 and 12AU7 the cathode resistor value is no longer a hair-trigger mess. anyway, there's one with a black mask for $10 and one with a blue mask for $12, the schematics (attached) seem similar. A global feedback loop will be a connection from the output of the circuit all the way back to the first stage, which is not a type of feedback we use in our products (except the Tode guitar amp we offered some years back). Otherwise, I want to make and the cathode followe with your ECC82 (12AU7) to hear how it sounds. The VA has plate load resistor of 120K and a cathode resistor of 1. k. The output This schematic shows a cathode follower circuit using a 12au7 vacuum tube with associated resistors and capacitors. In your example however i'm not following your derivation of the quiescent plate voltage on the tube. 5 Volts on the plate after the 100K plate load resistor. The 2 tube preamp The 12AU7 contains non-linear triodes. Another use for a second triode is as a cathode follower, The following unity-gain anode follower uses a 12DW7/ECC832 tube, which holds a 12AX7 triode and 12AU7 triode. I don't really know how complicated a 12au7 per channel preamp could be. although I bet that 6SN7s or 12AU7s would work just fine. The 12AU7 is a low gain, lo Z tube which in turn makes it capable of pushing more current. When we cascade the input stage and White cathode follower we get a PSRR of -29dB, As I surveyed the supplied schematic, I queried the use of a 1. Joined 2010. The CF stage has no plate resistor and has a 30K cathode resistor. Small signal pentodes usually have a lowish plate voltage, so there is no problem with DC coupling to a CF stage. Dear Sirs, I am using a line stage consisting in a pot followed by a 12AU7(ECC82) in a cathode-follower configuration. 12AU7 / ECC82 Cathode Follower Tube Preamp Schematic file. 12AU7 Preamp Schematic. Without knowing you have taken a conceptual discussion schematic from glassware and tries to implement it. The bottom of the pot would go to ground. It can be thought of as being half-way between an ordinary gain stage and a cathode follower, and provided the anode and cathode loads are exactly equal (including any external loads) we are guaranteed to get equal-but-opposite signal voltages developed across them, i. The ECC81 / 12AT7, ECC82 / 12AU7, and 12AY7, also have the same pinout. M. 96v RMS. Both of those exceed the design parameters of the 12AX7, which is 330v on the plate and 200V cathode to heater voltage, which also is affected by whether it's positive or negative. I've read lots of positive remarks from posters swapping 12BH7 for 12AU7/ECC82. I have been told that substituting my. do you think that since the schematic is made for 12AU7 will work directly or needs to be moded to fit in the 12AY7 output impedance, polarity) you can either make a single gain stage (hence inverting polarity), add a cathode follower for lower output impedance or cascade two stages for higher gain and non-inverting output. No. Only so many ways to get that done. 1. Schematic of the amplifier is here. cathode-coupled) amplifier I am a big fan of the common-cathode amplifier (also known as the ācathode-coupledā or āgrounded-gridā amplifierāno thanks to Bruce Rozenblit, whose taxonomic howler has made already murky waters murkier still). If one is a cathode follower, the other half has to be a voltage amp. Been searching the net for a foreplay schematic but can't find one except for a modified foreplay with 6N1P tubes. I've attached the load lines plus the roughly intended bias points. The idea is to take advantage of what I hear is a very linear EF86 triode mode inverted output is taken from the cathode. yes, you can also use bigger current in mosfet, from 2mA in the foreplay to about 10 in the IRF820 if you wish, but at that current you will need a small heatsink on the mosfet However in my travels online for a solution, I noticed that on this site the 12AX7's and other similar valves were used in linestage designs postedand that the 12AU7 (ECC82) Cathode Follower Tube Preamplifier Schematic - as listed in this site - appears to show promise in being able to be used/modified into the cathode follower stage of the JP200 preamp design. Looking at schematics for the OG rectifier, the V3B cathode follower is putting 415V on the plate and 216V on the cathode. Out Phono Preamp schematic here. I already have 2 paris of 12Au7 which is an excellent tube for buffers as it will be unity gain stage cathode follower. You aren't looking for gain, you want a current source so they are the obvious choice. Click to Note that V1's plate voltage biases the cathode follower! Tim . c. Over the last few weeks Iāve been delving into the confusing world of direct coupled post phase inverter cathode follower drivers for push pull The voltages are straight from the Ampeg schematic, and Ken, given that tube could sink more current than a 12ax7 or a 12au7. You should get around 1. 2022-01-13 4:55 pm #4 I employed a 12au7 triode as the reverb driver and thought to use the other half as the AC30 preamp type cathode follower. Second, your schematic indicates a 12AT7. I've attached a load line example of a 12AU7 cathode follower design with a 50kĪ© load resistor (RL), a NEW Matt presents bias and operation data for the 6V6 tube in SE operation - 6V6 Single-Ended (SE) Ultra Linear (UL) Bias Optimization. So Ra3 = 145 / 0. 4dB with a bypassed To make the 12AU7 CCDA with the positive feedback to V1 cathode and NFB from output to V1 grid, you have to arrange for V1 and V2 to draw the same plate current (Ip). A load line or schematic would help. Its design is based on one of my earliest microphone preamplifier designs hence the The drive problem is solved by changing the tube to a 6922. Pretty much everything in the preamp is standard tube amplifier construction. I use 100K ALPS log pot for volume control. Typically that tube swap is not a problem. Join Date: Aug 2006 06 May 2007. Some direct coupled experimental discussion schematic I would say. Aikido CF PCBs and kits are available now at the GlassWare-Yahoo store. The grid would be biased at -1V relative to the cathode, so looking at the plate curves, there would be about 2mA flowing through the tube and Ra3. But I'm trying to figure out if using a triode other than that of the same tube (like a typical CF in guitar amps) will require special consideration to get similar performance. Does anyone have anecdotal evidence to support his praise for their effect on the sound in an amp? I'm considering using them in two places in the amp - Hi, I mapped the schematic of this preamp with my resistor values. (12AU7 / ECC82 Cathode Follower Tube Preamplifier Schematic). . Two stage 12AU7 preamplifier with low impedance Cathode follower 1/2 of a 12AX7 or a 12AU7 can be used as a Cathode follower. I am wanting to use a cathode follower so that I can run both tube and ss power sections as I have read that using the CF drops the output impedance enough for solid state power to be happy. Nor a white follower. 2. If you are driving 600 ohms to Pro levels, the 12AU7 just won't do well. I intend to try something like that with a phono preamp that I have on the drawing board except I will be using 12AY7 for the bottom tube of the first stage. Hoffman Amplifiers Tube Amp Forum, Kagliostro 12AU7 push pull schematic. 2018-02-15 6:41 am #5 2018-02-15 6:41 am #5 Picture 12au7 cathode follower schematic. At least there was one in the original EAR834P I had. Here is the entire schematic. and 6. may even work for that with bigger output capacitors. D. Even at 150v i could not get the 12ax7 tubes to bias properly. Aikido Cathode Follower The second stage in the Aikido Cascode is an Aikido cathode follower. 5 amp - or is the voltage DIY Audio Schematics Tube Linestage Preamplifiers. of the 12AU7's cathode potential. Hi, Yes it ought to work, the gain will be more though. Well, Let's leave the Darkvoice 336SE behind and use a 12AU7-based cathode-coupled amplifier input stage. Schematic attached. EDIT: The wiper on the pot would connect to the grid, the top of the pot would connect to the node between C2 and R6. It was designed ONLY for a 12AU7. So, I'm working on step 1 of my plan outlined here to improve the sound of my Blackheart Killer Ant amplifier (2 x 12ax7 tubes, 1/4W, Class A) by replacing the 12ax7 "power" tube (V2) with a 12au7 for more clean headroom. Two stage 12AU7 preamplifier with low impedance output stage. 12AU7 I have 10s of yummy NOS treasures so I wanna use 12AU7 so to change colors. Not so much that they are alike, but frequently the settings work out the same. If you post up specific models of amps, I can search for the schematic and tell you. It sets the operating point of the tube and helps in achieving the desired gain and linearity. The circuit steps down a high positive voltage to a lower output voltage while providing current amplification. In this case at half HT (Va = 100V) and an anode Something that might be worth trying is using a mu-follower with 12AX7 on the bottom and 12AU7 on the top and eliminating the cathode followers. Is there anything I'm missing here in regards to "designing" (ripping off Schematic attached! Attached Files Comment. Logged Toxophilite. By the way, here are the values for the output transformer: Input impedance = 11. For example, the 5E8A Tweed Twin has a CF for valve 3. It appears capable of ~12VRMS or 30Vpp out before it starts to clip which is WAY more than enough to drive headphones, even high-impedance cans. -User I'm a Cathode Follower! Can we have everything louder than everything else? shooter. The overall voltage gain of the circuit is about 8. You cant trust dc output. Skip to main content. In the world of tubes you can often swap the 12AU7s with 12AT7s and the reverse. Or a triode strapped pentode, like Salas' 6V6 schematic Or a trioded EL84 Vincent77. DC coupling the cathode follower would only require 33K cathode resistor for about the same anode current, possibly slightly higher. 5V. There is no cathode resistor for biasing, whose "ground It was exactly what was on the JCM800 50/100 schematic - but apparently not the correct way to do it. But in reality, you could go anywhere from 250v to about 330v on the power supply without any issues. Make sure that is the tube in the cathode follower socket. I used 12au7 tubes and a b voltage of about 150v. Welcome To the Hoffman Amplifiers Forum December 26, 2024, 05:31:20 pm: Welcome, Guest. Check Details. You'll see that a 12AU7 without cathode bypass gives about 20dBv of gain. Schematic I was messing with. But for a cathode follower, R L from the anode to the HT is 0, so this equation is frequently approximated to 1/g m. ECC802S (12AU7 / ECC82) Tube SRPP Preamp Build Details. This ensures the cathode follower acts as a CCS for a long as possible before cutting off or saturating. 2023-01-06 5:43 pm #4 Here's a simple schematic with basic 12au7 cathode follower CCS check. I'm still working out the particulars of the power supply. 4mA plate current). 002 = 72. If youād like something with just a little more nerd sprinkled on top (and an extra 12AU7), try the following. Lets leave aside the silly topic about the source. 8uF to 10uF would be necessary with a 6SN7. EF86 triode + 6CG7 cath follower preamp. Sep 18, 2010 #20 Youāll note that I have the B+ listed at 300v. This will get rid of 1 coupling cap and 2 resistors. The Cathode follows the signal on the Post subject: Re: 4S Tube Preamp with 12AU7 Cathode-Follower Output Stage. Merlinb. The simple basic amplifier design that boutique builders favour uses 12AX7's in their preamps. This value exceeds the tube rating for heater to cathode voltage and will result in tube failure. I decided on the cathode follower mostly because of the simplicity of the circuit. Title: Cathode followerwith 12au7 Created Date: 8/28/2013 7:56:17 AM I know they exist, as I get email from its members all the time, asking if an Aikido or a White cathode follower can be transformed into an SRPP. Mike L. Power supply will be 90V. Grid stoppers are important to keep oscillations from occurring, especially for the cathode follower. This resistor is connected to the cathode of the vacuum tube and helps to provide the necessary biasing for the tube. e. Cathode-Follower OTL It seems as if every week, there's another schematic for me to review. Conceptual schematics takes some working usually irl. Exactly why that would be I don't know. Kind regards, beppe . I have been told that substituting my present Philips Miniwatt for a mil spec tube like the 5814A, others things remaining unchanged, I will get a more powerful and defined bass. Merlin's article on DC coupled cathode followers refers to the way a cathode follower is coupled at it's input, not output. cvanc. I used a 3V battery in the above schematic to bias triode T3, Yes, the SVT uses a cathode follower which is DC COUPLED to the output tubes. vinylkid58. You end up with lower gain from the tube, but otherwise things 'just work' more I have this old Ampex 1260, and found an old service manual, and it says ārecommended load impedance of 250k ohms or greater. Title: Cathode followerwith 12au7 Created Date: 8/28/2013 7:56:17 AM 12AU7 (ECC82) Cathode Follower Tube Preamplifier Schematic This schematic below is a simple two stage line-level preamplifier using a single 12AU7 (ECC82) tube per channel. Maybe ideally right at the cathode pin, but really anywhere will do the job better than nothing. Given 100% local current NFB, the 'U7 is OK in the cathode follower role. I cobbed this schematic together from this and this. cjalbum ģ”°ķ ģ: 35383, This schematic below is a simple two stage line-level preamplifier using. Hence, their popularity in the output circuits of many preamplifiers. At least at the low levels I'm using it. It requires a few extra resistors and caps and the heater reference voltage is tweaked just slightly so I can sleep better. The cathode follower is likely working with some grid current due to contact potential. First, the cathode follower was not designed for a 12AT7. Because the output stage in the 260 is operated in UL, A 12au7 gain stage followed by a pair of 6dj8 tubes as white cathode follower output buffers. 12AU7 (ECC82) Cathode Follower Tube Preamplifier Schematic from diyaudioprojects. Because the cathode follower itself has a low-ish impedance of about 500 ohms, the resistor right below the cathode needs to be no larger than maybe 2. Level 3; Posts: 1426; Re: EF 86 Microphone preamp circuit « Reply #3 on: December 23, 2023, 12:05:01 am 12AU7-Cathode-Follower This circuit is under:, circuits, 12AU7 (ECC82) Cathode Follower Tube Preamplifier Schematic l24634 12AU7 (ECC82) Cathode Follower Tube Preamplifier Schematic. Joined: 19 Oct 2018 9:30 pm The original 4S power supply diagram uses two 100R between the heaters and the Itās pretty tight where the tubes are, as it was built as a 4S Universal initially, and then the cathode follower was added, with not a lot of room available. The cathode follower then effectively multiplies or bootstraps the value of the lower anode resistor R2, making it look like a constant-current source. I am glad at least the Aikido PS1 is adequate for a PSU. From the anode characteristics, g m ā5 mA/V; this gives an output resistance of ā200 Ī©. If you need less gain, take a look Author Topic: 12AX7's like the tung sol RI that can't handle cathode follower voltage (Read 8186 times) 0 Members and 1 Guest are viewing this topic. In SPICE simulations, this circuit as novel circuits must be created, SPICE simulations must be run, schematics must be drawn, and thousands of words must be In the next days with the help of a friend I will try to draw out the buffer schematic in order to evaluate the possibility of using a ECC99. A line stage with a 12AU7 configured as common cathode + DC coupled cathode follower can easily give THD <1% for 18-20V output. As there is quite potential difference between the upper and lower cathode. Is there any issue to use both outputs (hi-Z and lo-Z) at the of course, but I think an SVT sounds pretty good, and the power tubes are driven by 12AU7 cathode followers. I think this is correct. Cathode grid valve follower tube bias loop effects auto ac triode negative come than output You look at the schematic to see if it has a cathode follower. Top . I could not find any ready made schematic of any tube buffer available which i could directly implement using the 12Au7 tubes. oh oh, Ive seen this schematic before, and he's driving the 6922 too hard: I suggested more tubes involved for example an input with a twin cascode or SRPP 12AU7 with a cathode follower 6DJ8 to lower the output impedance, total 5 tubes for a stereo preamp. This XL version uses a White Cathode Follower buffer for about half the output impedance of the vanilla version. However in my travels online for a solution, I noticed that on this site the 12AX7's and other similar valves were used in linestage designs postedand that the 12AU7 (ECC82) Cathode Follower Tube Preamplifier Schematic - as listed in this site - appears to show promise in being able to be used/modified into the cathode follower stage of the What is the purpose of a cathode bypass capacitor in a White Cathode Follower buffer? By the way. This is a high gain preamplifier that is suitable for use where a lot of gain is required - to drive a power amplifier that needs plenty of gain or perhaps for use with instruments, like a guitar or microphone. I've DC coupled a 5879 to a 12AU7 before (in a circuit using Merlin's morph control but with the triode coupling mode buffered from the CF) - schematic attached (with voltages. With respect to my voltages while using a 12AU7 in both positions, my B+ before the 100K plate load resistor is 266 Volts, and there is 68. Joined 2015. output all the way to ground, a cathode resistor is added so that the working cathode voltage will be about 3V, and the grid voltage just under this. 7. 2004-04-12 5:14 pm #6 2004-04-12 5:14 you will be able to figure out how to convert it to 12AU7, 6. If you need less gain, take a look at the RCA 12AU7 / ECC82 Cathode Follower Tube Preamp Schematic which has a gain of about 8. The White cathode follower by itself delivers a PSRR of -11dB (29% of the ripple leaks out), but the ripple is inverted relative to what appears at the B+ voltage. But, it's a great introduction to some of the issues involved in DC coupling which aren't a concern in an AC coupled stage. They make a sweet clean gain stage when looking for only a gain of 10. 5 amp - or is the voltage 12ax7 Cathode Follower Schematic. Master the basics Design your amp Know it works Amp Design for the 21st Century. 2013-02-05 1:01 pm This is done by splitting the previous stage's anode resistor into two equal parts and connecting a capacitor from the cathode follower's cathode, to the junction of the two resistors [see right]. Thats why I started with 12AU7, but then found ECC88 that I think is able to deliver output impedance Hi everyone, Need help calculating resistors for cathode follower. I finally decided to design my own cathode follower using the 12Au7 tubes with the following If the CF is cathode biased at 145V, then the voltage measured from the cathode to the plate would be 195V. 12au7 (ecc82) cathode follower tube preamplifier schematic. Take a look at the attached schematic and let me know what you think. 12AX7 has poor drive capability, a 12AU7 or 12AT7 would be more appropriate, FWIW: in the 'audio' range, the AX7 may be the most used cathode follower in serious gear, going back to the K2-W opamp. The 12AU7 has great potential as a classic rock tone tool, but if you like higher gain levels, it's not the right tube, IMHO. 3. The cathode follower therefore acts as a well-regulated voltage source to create a fixed DC grid bias for the LTP. Remember, the tube references everything to its own cathode. Joined 2006. BTW, schematic was recommended by Bruce Rozentblitz. This post has a file attachment. This is the Link to a side with my version. You may want to have more headroom at the input. Two-amplifier cascade part ii Follower cathode 12ax7 recommend cathod folks against why using schematic output plate follows looks Ef86 amplifier ac4 inspired 12ax7 some. Really reminds me of the morgan-jones headphone amplifier. 2012-05-04 11:00 pm Aikido Cathode Follower [ACF] 6H30, 12AU7, 12AT7, 12BH7, 5963, 5965, and ECC99. 2V grid bias (4. 12AU7 might not be the best linear triode but it is not as bad as many people tell. Finally, the cathode follower actually has a small loss (ā -1dBv). The Deluxe Reverb AB763 doesn't have a CF. The little PV Classic 50/50 stereo amp uses 12AT7 CFs to drive the EL84 power tubes. The BEST combo I have used yet is: V1: ECC823 V2: ECC83s V3: ECC83MG V4: JJ5751 Of course it is a follower and will follow the input voltage, but for a very short period it will draw grid current if the signal swings too fast and too high. Posted: 04 Dec 2018 2:19 pm . I've modeled 12AT7 and 12AU7 cathode followers into a 10k load, and they'll suffice. Frank is a regular here, I hope he spots the thread and will enlighten us. If you Discover a detailed 12au7 preamp schematic and learn how to build your own preamplifier for audio systems. The 5F6A Tweed Bassman has a CF for valve 2. Separately, it's always a good idea to include cathode stops for follower outputs driving the cold cruel world outside the box. Also, the coupling cap from the cathode of the cathode follower to the halfway point of the input tube's split plate resistance will need a quite large value of C for good bass extension. DeathRex. JojoD . perfectly balanced outputs. 5k ohm Output impedance = 133 ohm Cathode followers work best when they are used to produce a low source resistance, rather than to drive a low load resistance. A Cathode follower is often connected directly to the output of a high impedance Anode load pre-amp. Optimized White cathode follower with Ra=Rp/mu another good suggestion maybe? Does it sound really good vs single ended ccsed cathode NEW Matt presents bias and operation data for the 6V6 tube in SE operation - 6V6 Single-Ended (SE) Ultra Linear (UL) Bias Optimization. If you are using this in the preamp stage, the gain will be about ā21v/v or 26. C. I am curious what consensus here is regarding the sonic merit of cathode followers. In other words, each channel Maybe use the 12AU7 (or the 6189) as a cathode follower: less gain and low output impedance? Reactions: myfirstamplifier. Reasons for its staggering popularity are not hard to find. In V4, it reduced the amp's volume level about 2 dial position markers. These are all 12AX7ās too by the looks of it as the 2x 12AU7ās are cathode followers. Many, How can I modify the cathode follower (currently with ecc82) To me this 12au7 seems polarized with little current, from the readings I have done on this forum. Making a bipolar, high-voltage power supply is not difficult, We use the 12AX7 triode as the input tube and Yes, Merlinb, I realized after posting that I forgot to include the 12BH7 stage in the cathode follower output stage in the schematic. 12au7 Cathode Follower Schematic. 12AX7. > 12au7 white cathode follower What are you driving? If only 10K and up, 12AU7 is not the ultimate choice but very good. Thread starter woodturner-fran; Start date 2021-12-20 8:45 pm; Jump to Latest W. 5K. In the schematic 12AU7 (ECC82) Cathode Follower Tube Preamplifier Schematic This schematic below is a simple two stage line-level preamplifier using a single 12AU7 (ECC82) tube per channel. Here is schematics: An externally hosted image should be here but it was not working when we last tested it. Senior Member. It would allow you two channels with just two tubes. H. Joined 2005. 12AU7 Tube Preamplifier Schematic by Tim William High gm valves are well suited to cathode follower part of the circuit (such as an ECC82 / 12AU7). There should be an additional RC filter between the second stage and the cathode follower. Joined 2011. Youāll note that I have the B+ listed at 300v. a. Is this okay? Attached schematics used for simulation and frequency plot Thank you for helping. Good clarity, but too much volume loss. In this schematic all resistors are 1/2w except the 10kĻ cathode follower load resistor which should be 1w. 2021-12-20 8:45 Va=233V (50V or so lower than the Any tube will do in that position, a cathode follower is a topology that doesnt provide "colour" to the sound, you could even put a wimpy 12ax7 (requires changing cathode resistor like any other different tube) because the driver requeriments of a 6y6 in that configuration are not very high, if you have 6n1p, 6n6p, 12au7, 6sn7, ecc88 variants they will all be equally The cathode resistor is also an essential part of the 12AU7 preamp schematic. However, you do need to After all I had a cathode-follower in my mind originally. I figured I could do without the power tubes and make a simple stereo vacuum tube design using 2 (or so) pre-amp tubes minimizing much of The schematic says the output impedance should be 220k Ohms. Cathode followers themselves function from local degenerative feedback. I did this because both the 4S and the cathode follower work better up there. Cathode follower, opamp chip, etc would be a fix. Better go with a ECC82 / 12AU7 / 5814A. Attached schematics used for simulation and frequency plot Thank you for helping. Please login or register. 8K. Seeking advice. I just made myself a couple of load lines for the cathode follower part of the schematic. What do you guys think of using LED to bias a 12AU7 cathode follower? How does LED bias compare to using the B+ with a potential divider on the grid? How does LED bias compare to cathode resistor bias Back to needing your schematic. Don't know the reasons why this tubet sounds good in mu follower and awful in a simple grounded cathode configuration (so don't ask me). In a SRPP the cathode on the upper triode has a voltage potential of roughly 1/2 the applied B+. My phono preamp uses some in the cathode follower output stage and either type will do fine there. But even when not explicitly needed, The ECC81 / 12AT7, ECC82 / 12AU7, and 12AY7, also have the same pinout. com. 12au7 ecc82 cathode follower tube preamp schematic. I visited The Valve Wizard a lot, and the schematics of cathode follower that I use in original post is from that website. Level 5; Does anyone have a schematic for adding a balanced line output? I just want to double check what I have done on a bass amp I built for a friend. The 12au7 ecc82 is a twin triode vacuum tube it is very popular in the audio world because it is rather rugged and can be operated at lower voltages. HP8903B. Schematic. two stage12au7 tube preamp schematic 12ax7 / 12au7 tube preamplifier schematicLm3886 gainclone supply cathode follower power application 56w note diy 90v 12au7 calculating using bridge schematics size recommend study also. Iāll post a power supply schematic shortly. Thats why I was thinking some goofy NFB correction thing going on. 2K to keep the overall output impedance less than 2K. DC coupled cathode follower - Design Q's 02-05-2011 and the tubes are 12au7's. The overall If you need less gain, take a look at the RCA 12AU7 / ECC82 Cathode Follower Tube Preamp Schematic which has a gain of about 8. I think that That would be nice to use the 12AX7 for the amplfier and the 12AU7 for the cathode follower part. A higher negative bias voltage would be advisable, even for a cathode follower. Mar 22, 2024 - 12AU7 (ECC82) Cathode Follower Tube Preamplifier Schematic. The 12AX7 is a hi gain hi Z tube which is happy as a clam at 1mA. For such individuals, the 12AX7 & 12AU7 combination will realize a gain of 200 (+46dB), but the 12AX7 cannot compete in a low-noise race with the previously listed tubes. You will need the Vp (plate voltage) of V1 to be 1/2 of B+ voltage. two stageTube 12au7 preamplifier preamp schematic diy amp valve amplifier circuit headphone guitar circuits schematics diagram electronics tubed electronic tubes tim Cathode follower 12ax7 rocket speak12ax7 schematic tube preamp amp preamplifier bass circuit diy kit vacuum amplifier Not really liking mu-follower though. 5 dB with a unbypassed cathode and ā33v/v or 30. Joined 2003. If we are to use tubes with Vhk max of 100V, we are really close to the limit. Capable of driving a very low impedance. The cathode resistor for V2 will be the same value. 12au7 / ecc82 cathode follower tube preamplifier schematic Cathode follower output load tubecad 2005 june. The input volume control doesn't have to be The FX Buffer Cathode Follower is used to prevent FX pedals from loading down the high impedance guitar signal an inverted signal at its plate but also acts like a cathode follower by outputting a non-inverted signal at its cathode. So I put a 12AU7 cathode follower at the end of the chain, and -1. Member. This is not a particularly accurate answer, since the method of determining g m was crude, but this does not matter, since it is usual to operate an audio cathode follower Yeah, I could live with 2K output impedance if the split cathode resistance scenario offered significantly less gain, like 0. You don't see 12AU7's in guitar amp FX loops very often because they tend to use more current than the entire rest of the preamp by the time you get a decent signal swing out of them. However, I'm having trouble understanding what to do about the heater-to-cathode voltage. 12BH7 I have 2 types. 1; 2; 3; With 12au7 20*2400 (single cathode value) grid leak" is incorporated the way it is because the "fixed biased" by virtue of the d. I have not tried 12AU7 in V3. The overall gain is about 8 times. I donāt think it is power supply related, as the original 4S was pretty much dead silent except for a bit of tube rush at full volume. I would like to use 12AU7's as I have several of them. The schematic shows 300 Volts B+. This schematic below is a simple two stage line-level preamplifier using a single 12AU7 (ECC82) tube per channel. 4S Universal Preamplifier for 12A*7 Tubes - (Project) NEW ; 12AU7 / ECC82 / ECC802S Tube SRPP Preamp Schematic - (Project) 12AX7 Tube Hi-Fi Preamplifier Schematic - (Project) 12AU7 / ECC82 Cathode Follower Tube Preamplifier Schematic; 5687 (LED bias) Tube Hi-Fi Preamplifier Schematic - (Project) I am looking for a Grommes 260A schematic for the circuit that has 3 X 12AU7. The grid bias on the cathode follower is only -0. Depends on how your heaters are set up, if the setup in schematic design is poor quality then DC heaters will reduce noise. However in my travels online for a solution, I noticed that on this site the 12AX7's and other similar valves were used in linestage designs postedand that the 12AU7 (ECC82) Cathode Follower Tube Preamplifier Schematic - as listed in this site - appears to show promise in being able to be used/modified into the cathode follower stage of the The cathode follower doesn't have any gain, but the first stage common-cathode 12AX7 certainly has gain. The plate of the 12AU7 used for a cathode follower is at 266 Volts as well. With 300V HT+, this difference is about 200V. Choose the plate resistor value for V1. 3V at 2. coupling from the prior stage cathode follower. However in my travels online for a solution, I noticed that on this site the 12AX7's and other similar valves were used in linestage designs postedand that the 12AU7 (ECC82) Cathode Follower Tube Preamplifier Schematic - as listed in this site - appears to show promise in being able to be used/modified into the cathode follower stage of the Cathode follower schematic circuit features click diagram description below specialCalculating cathode follower using 12au7 for 90v supply More cathode follower stuffBrains & brawn cathode follower. Common-cathode (a. Unfortunately for all of you, it is in German but I think the schematic speeks for itself. ā From reading whatever I could find, it seems a 12au7 cathode follower usually has a very low impedance, like below 600ohms. Explore different circuit designs, component choices, and wiring diagrams for optimal sound quality. Nevertheless I could not find yet a complete schematic for a IRF820 buffer. Actually, in keeping with the first law of engineering (āNothing of value comes without a costā), this extra resistorās added benefits must be paid for with a higher output impedance and slightly less voltage and current swing. The preamp is basically a voltage amplifier (VA) DC coupled to a cathode follower (CF) stage. 6 to 1. 4S Universal Preamplifier for 12A*7 Tubes - (Project) NEW ; 12AU7 / ECC82 / ECC802S Tube SRPP Preamp Schematic - (Project) 12AX7 Tube Hi-Fi Preamplifier Schematic - (Project) 12AU7 / ECC82 Cathode Follower Tube Preamplifier Schematic; 5687 (LED bias) Tube Hi-Fi Preamplifier Schematic - (Project) The 4S preamp has a gain which is dependent on the tube used and dependent on whether the cathode is bypassed or not. woodturner-fran. No question about this. But, I checked one of my suppliers, and I can source In a SRPP the cathode on the upper triode has a voltage potential of roughly 1/2 the applied B+. ILoveHiFi Post subject: Re: Post subject: Re: 4S Tube Preamp with 12AU7 Cathode-Follower Output Stage. It sounds quite good. Designing an AC Cathode Follower The ECC82/12AU7 is well suited to this job because it is cheap and plentiful, its low internal anode resistance allows it to deliver relatively large signal swings into heavy loads, and its moderate transconductance will guarentee fairly low output impedance which ensures wide bandwidth. One pair EH, one pair GE NOS. In the schematic below, we see both a cathode follower and a White cathode follower with extra cathode resistors. Post Cancel. Prev. I looked at the mu-follower too. Posted: 02 Jan 2020 3:25 pm . sbwrtx datf hlajt dzrx kjvr jem sveyy ploa vgsli ifphccv