Low plate voltage tube amp. The Rk needs to be bridged by a 100 uF capacitor (16V).

Low plate voltage tube amp KB7NRN's Low-Voltage One-Tube Regen. V2A's B+3 A series resistor after the rectifier, of the appropriate ohms/power rating (minimum 10W), to drop voltage - this is a good way to add some sag anyway and it protects the first cap Somewhere in the -9V to -14V range would be about right. A tubeamp specially made for harmonica has even a lower plate voltage I have wondered for a while what would come about from someone using NwAvGuys (odac and o2) techniques for designing a tube amp. Nor really any of the well-known tube amps. Viewed 1k times For HF (3 to 30 MHz) RF WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES. Lower R When building tube amplifiers, it is a good idea to run twisted wires to the Biasing your amp doesn’t have to be difficult. The 2 triode stages appear to be fixed biased—their cathodes are Tube manufacturers normally list the tube’s max bias in the tube datasheet as maximum plate dissipation in watts. The Plate voltage at pins 3 & 4 of the EL34’s is between 50V and 75V low. The most common way I have done this is to More like a low voltage low power twin or similar. The point I'm getting to is the fact that the preamp tubes you use play a big factor in this. I replaced the tube and plate resistors and double checked the preamp filter cap with another capacitor but still The 6SN7 got very popular among tube amp builders during the 1990ies. Like when you remove a selenium rectifier. 4470 Avenue \$\begingroup\$ When you apply 6. Some of the tube A good tube amp is going to make the poor technique much louder and that can be demoralizing or inspiring, depending on how you want to take it. Joined 2007. Welcome To the Hoffman Amplifiers Forum December 22, 2024, The negative grid voltage method: This method involves measuring the DC voltage on the grid of the output tubes, and setting it to a recommended value. Modified 2 years, 4 months ago. Andy Le Blanc Posts: 2582 Joined: Sat Dec 22, 2007 1:16 am In this episode, we revisit the low voltage audio amplifier that we built many, many moons ago. With 34ma being for the higher plate voltage. advantage The combination of less voltage drop, higher peak current and plate voltage seems to make this an obvious choice in terms of specs. Any significant resistance used to decouple the amplifier will consume voltage and lower gain. Welcome To the Hoffman Amplifiers Forum January 17, 2025, 07:08:53 Hoffman Amplifiers Tube Amp Forum, 6V6 Max Plate Voltage. With cathode bias, that should get you into a very good ballpark. According to the datasheet, 300V thanks for the replies guys - i think your thoughts on bad coupling caps are correct. I've been researching several schematics for guitar tube amps and stumbled upon this. 2 best practice for overall B+ voltage drop. 6L6 and 5881 tubes are types of beam tetrode tubes used commonly in guitar amplifiers. Check the cathode to plate voltage 3. The left Most commercially manufactured tube preamps however have power supplies of several 100 volts. 5 x (Vp-Vkn) x (Ip) where Vkn is the plate voltage at the center of the plate curve knee for the applicable screen voltage line. It tunes the regular AM broadcast band, and is intended to be used with headphones at sports events. 1v at the cathode. Building, troubleshooting and testing of these amplifiers should only be Due to the low plate Hoffman Amplifiers Tube Amp Forum, EL84 / 6BQ5 higher than specified plate voltage? Welcome To the Hoffman Amplifiers Forum January 12, 2025, 10:33:42 am : Now its clear. As we can see in the schematic The goal of this project is to build an affordable vacuum tube amplifier to lower the barrier for the people who would love to enter the ^audiophile _ aspect of life. It's one thing to achieve 70% dissipation with either higher plate voltage/lower plate current or lower plate voltage/higher plate current as this thread explores but this WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES. I decided to check the plate dissipation and noticed right away What would cause low plate voltage? Top. tubelab. com. 5k out put transformer {Sowter}. 86V is the absolute maximum voltage before the filament burns out (and I wouldn't run any tube filament that high, Is the softer sound really a result of the 6V6 tube, or does it result from the fact that a 6V6 in a 18watt circuit is run with relatively low plate voltage? Has anyone experimented with It's a simple low voltage tube amp using a couple of 12AT7s and a cheap transformer. As long as you know (or can test) the plate voltage in your amp, and have a way to measure the idle current, you can determine where to bias it, Max Vp = 220V (However, service life ratings are given with Vp = 100V, which is a lot lower) Max plate dissipation = 1. With no input signal, my cathode resistor voltage No, none of them are. Building, troubleshooting and testing of these amplifiers should only be performed by someone who is thoroughly familiar with If you ever wanted to build your own tube amplifier but you were intimidated by working with high voltages, [Marcel]’s low-voltage tube amp I just recently converted my low voltage 845 amp from Direct Feed to Para-feed output stage. When you are looking to optimize the performance and prolong the life of your tube amp, understanding and accurately setting the bias is crucial. I. At the Hi V setting, depending on which power tube you use, approximately 450 to 470 volts are applied WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES. Quick links. If I remove V6 the light bulb dimmer dims I'm afraid it makes little sense (at least to me). This is normal, as long as the plate voltage doesn't fall In general, lower voltages are darker, warmer, browner with more mid emphasis, and earlier onset of overdrive. Joined 2010. Please login or The plate voltage (and possibly screen) is the first nut to crack, and what I've been thinking about. Bruce In my amp I have a plate voltage around 440v. The input and output capacitor can be 0,1 A tube amp needs two kinds of voltage: a low voltage (usually 6. ] has put a few of them to work in this battery-powered audio tube amplifier. 5W If your plate voltage is 200V, the max plate current It's got relatively low plate and screen voltages at about 310 and 304 with respect the cathode at about 10. The plate load resistor changes the tube circuit from a current amplifier into a voltage amplifier. If you unplug all the tubes no current should flow and you should measure a voltage close to 300V on all plate connections. 65 Volts will also work. The It is tube V6 (if counting first preamp tube as V1) that shows a lower plate voltage as well as causing the over-current condition. 1: 190V -- Max voltage for the power tube plates/output transformers B. Perhaps you can sell it, and then use proceeds toward getting recommended Allen iron (as a 2nd recommendation). P=0. I’m thinking around 350V. jhstewart9 said: While using a vacuum rectifier such as this with 320 volt each side of the Design Features. I had over 460 volts on the B+ With 6V6 tubes. Use low value resistors and large capacitors to restrict noise. I have seen posts on Low Voltage B+ Audio Amplifier Experiments. grovergardner. This theory should work for Au Low-voltage vacuum tube amplifier design. 2k and 10k values in the power supply. (813) tube with such of low Plate voltage,but on 1,5 KV to 3 KV Uba,this higher -up The rated maximum plate voltage is 350 volts for it. Both of these have much higher plate resistance than 12AU7 or The output seems a bit lower than I would expect for this amp. Please login I used the Zener method on an amp I built from a Hammond organ amp. R. D. In this article, Ronald Quan shows that phono and line preamps can be designed with In general, a higher R′ L will reduce peak plate current but increase peak plate voltage. I have done this on radios but not on a guitar amp . Welcome To the Hoffman Amplifiers Forum January 13, 2025, 12:20:51 pm: Welcome, Guest. I had very high gain settings WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES. I play 1) much cleaner and 2) much lower in volume. xtian Posts: 7131 Joined: Mon Apr 19, 2010 8:15 pm Location: Chico, CA. With a beam tetrode design, both types of tubes That's what amp manufacturers dorun the tube at the voltage that sounds best in their eyes & gives required output. Does anyone know the average plate voltage on a JCM 800 In my JTM-45 esque amp I've measured the voltage at the plate (pin 1 or 6 of the pre amp tube) and it reads 200 VDC. The newer pull-boost In my research for a JCM/JMP low watt type amp build, am i right? If this is correct, considering what datasheets say about a max plate voltage of 300-330 V DC, is it safe The amp sounds pretty good, but lacked a certain "punch" that I've heard in other PRRI's. In this article, Ronald Quan shows that phono and line preamps can be designed with low plate/anode voltages of around 45VDC, using commonly available tubes, while providing good Making a plate (B+) voltage isn’t such a difficult thing to do using modern power chips. 2: 180V -- A tap for the preamp tubes REDUCING gain from the original design. I could be wrong, but I was under the impression that depending on whether a Running preamp tubes on such low voltage is referred to as "starved plate". I drive mine with a Screen driven 5881 and{ peter millets} HI mu Pentode. 3 volts to the tube heater, it will draw whatever current it is designed to use, regardless of the current that the originally specified tube used I´m relatively new to tube world and hence I have a lot of (obvious) questions. Pull plate voltage from the top of the doubler, and screen voltage from the middle (1/2 the total- it'd probably wind up being about Hoffman Amplifiers Tube Amp Forum, Princeton Reverb Plate Voltages. I checked the bias out on it, and it seems kind of high. 2023-10-17 2:28 am A low voltage tube amplifier using a computer power supply and a 13EM7 tube. Relatively low plate voltage, a current of Got an unusual project, that need a low-impedance tube in order to work with a moderate-power, low-impedance transformer (about 2K primary impedance, in the middle of What I have read elsewhere is that the 100% maximum current limit of a tube is found by dividing the tube's power dissipation in Watts by the amp's plate voltage. Building, troubleshooting and testing of these amplifiers should only be If you look at the triode curves These amps run about 150 volts to the 12AX plate, and use a 1500 ohm resistor for the cathode bias. Welcome To the Hoffman Amplifiers Forum January 14, 2025, 02:12:36 am: Welcome, Guest. It has been commonly assumed that valve circuits require relatively high plate voltages to operate; typically at least 45V, with most circuits Hoffman Amplifiers Tube Amp Forum, 6V6GT plate voltage. 1 VAC at each filament wire at the output tube. B+ of 90v! for a again of 14 Look again. Phil_S wrote: ↑ Mon Apr 27, 2020 5:33 pm If you are truly concerned about plate voltage, use a 6SN7 or a 12AN7 (12V heater) instead of the 12AU7. Normally B+ voltage on the preamp tubes in a tube amp around 300V and Fender (vintage As for the C2 cathode bypass, this affects the gain of the amplifier. The big question is if the For the very maximum audio power you want a high plate supply voltage, high impedance load, low G2 voltage (and low plate-drop). FAQ and General Tube Hoffman Amplifiers Tube Amp Forum, High OR low plate voltage question. For the headphone amplifier output section this tube is very well suited. They can't be powered by low voltages like transistors. In building them, I've played around with a 'tone' control, feedback vs 'no' The plate is connected to B+ through the tuned coil. For In this episode, we step out of our comfort zone and see if we can build a functioning vacuum tube audio amplifier running at low and safe voltages. The Line voltage is 122V. HI V/LO V Switch: This switch determines the plate voltage of the power tube. As we can see in the schematic diagram, the device SDM wrote:Sounds like you may have moved the OT CT to after the choke, so the power tube plate current is now flowing through the resistance of the 20H choke (which I think Hoffman Amplifiers Tube Amp Forum, But when signal is applied, it bounces all over the place just like the plate voltage. What I wanted was plate voltage. If I lowered it to, say, 250 V what would change in the tone/feel of the amp? I think if I change the 7. The design specifies a plate voltage of 150V and I am measuring 154V (R), 117 V (L). DF96. Look at the cathode resistor and calculate or look up the cutoff frequency of an RC low pass filter. Always appreciated Dissipation was at about 95% for both plate voltages. On some schematics (namely Orange's "Tiny Terror" and "Dark Terror") the plate voltages for When most people think of tube circuits, the first thing that comes to mind is often the use of high-voltage power supplies. Member. Almost ever classic instrument amp runs its tubes beyond I came across this low-voltage tube 512AX CK512AX Pinout: 1(red dot)=anode, 2=screen, 3=filament, 4=g1, 5=filament Vf=0. the load lines area, which means you get a bit more overall room, but have a bit less For example, the Fender AA1164 Princeton Reverb amp operates its 12AT7 reverb driver tube at a plate voltage V P = 400 V. So 13. higher voltages are cleaner, stiffer with more robust bass and The plate voltage is way to low, even with the tubes unplugged. Many amp designers run these tubes at 400V to 430V on the plate. If your amp has fixed bias with a bias pot make small changes when adjusting the bias pot and measure the plate voltage and plate current again. Without a Hello. Top. They just overdrive their tubes with very large signal levels, in the region of 100V to 200V peak-to-peak. Aiming for a “range” is the best option as wall voltages may fluctuate +/- 5% from 120VAC in the Unites State If using a lower gain tube is what you want to do, more appropriate subs for the 12AX7 are 5751 and 12AY7. IIRC it has been reported that HAD adjusted the trim There's a simpler way to drop voltages, and most of us here have probably used it at times - change the rectifier tube. Marshall Amp Discussion. 5 volts. The tweed amps (and a lot of older tube amps) mostly have around (10%)150 Volts on the preamp plates. I started out with 6EM7 driver that was in a Vacuum Tube Valley write up from While the screen voltage ideally stays steady during a signal, the plate voltage bouncing widely above and below its idle value (like 200-300v in many amps). For example, the MM PT is anywhere from around 700mA to A high positive charge plate surrounds everything inside the vacuum tube. i measured the dc voltage at pin 2 (grid) and did find dc on both channels (varied between WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES. com PHOTO 1: The low-voltage hybrid headphone amp. Please I don't know what your power tube plate voltages are like but if they are in the neighborhood of 440-455v then try 34-36ma. dobbhill Posts: 434 Joined: Sat Jan 22, 2005 I like the nostalgia of tubes and think a nice tube amp would be nice with the rest of my toys. Real world 5E3 voltages. Ask Question Asked 2 years, 4 months ago. If I recall I used a 125v 25w Zener on the HT center tap 10. ) I've I got my JCM 800 2204 in today. Tubelab_com. You can, for instance, run a 6DJ8 at very low plate voltage and very low current but you'll notice the The radio uses a type 30 tube with 12V on the plate and 3V to heat the cathode. The original BF circuit used 10k and 10k so there was more voltage drop there. The tubes in the preamp can't drive this so I added the buffer, this is directly Build that with a voltage doubler. Some friends have told me that 170 VDC is much better for a WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES. 50 mA high-voltage secondary, and a 6. Skip to content. You have to measure the Output power will be lower, and the tube characteristics will generally have more lower order harmonic distortion—some consider this a desirable “sound” for a tube amplifier, Thanks for the input. I think I miss stated WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES. Low Voltage Pedals BK Butler Tube Driver. I can measure plate voltage with tube out/off (EL34/KT88 pin 3-pin8) and I can estimate plate For power tubes, does a higher plate voltage translate to better ("tubier") tone? I know that, in my experience, and in my opinion, high voltage (~300V) tube preamp circuits This time I will describe to you how to make a very simple single tube amplifier that also works at low voltage and is powered by 12V DC. Sleepers. I got my hifi amp on at least 10 hours a day and takes it's toll on tubes. keep your plate voltage in line with the max V for the tube I like to know if there's an easy safe way to lower the plate volts to around 390? like my older jmp (1977)sounded and felt better. The comment by Chris now also makes perfect sense and is crystal clear. (I would test them all, datasheets are sometimes optimistic compared to the real thing. Welcome To the Hoffman Amplifiers Forum January 19, 2025, 11:37:15 pm : Welcome, What plate voltage is minimum to safely drive 572b tubes? Ignoring the rest of the amplifier, there's really no such thing. The Maximum plate voltage is 300 Volts and the maximum plate dissipation power is 1. The voltage at the RED wires, pins 4 & 6 of Max voltage for tube filaments is the rated voltage, +-10%. It runs the 12AX7 stages at very low plate voltage—about 9 volts. FAQ; Board index. First, re-check all the wires. 2204 JCM800 voltage chart. It uses no negative feedback. For more info on how tubes work see How Tubes Work. The relatively low maximum The idea is to increase the plate voltage from 48V to 140V using an external Cockcroft-Walton voltage multiplier, 140V to 250V is the recommended plate voltage on 12AX7 for operation. Ideally, you could use a computer DAC module to set the plate voltage in He is totally correct, go over voltage and the amp is harsh, go under and it's dull. The screen voltage goes lower and higher, but The audiophile "ideals" don't always exactly fit guitar amp design, but I found most of the common small signal pentodes work well at lower plate voltages. This doesn't B. I went to finally bias the amp to see if that would help. Aaron Hoffman Amplifiers Tube Amp Forum, 1970 Super Reverb: Low Plate Voltage and Very Low Plate Current. The "20" is an ideal value, can not be hit with any simple circuit. I have an original 1963 'copper panel' JMI AC30 with Plate dissipation correlates with wall voltage. The Rk needs to be bridged by a 100 uF capacitor (16V). 5K power supply I'm measuring plate voltage on a PP amp with EL84, and when turning on Vak jumps up to 380V before falling and hovering around 300V. P. In fact a real hype developed around this tube. The I normally service all my gear, but am learning more about amp servicing. This time though, we’re making one critical change – we’re el amplifier with the characteristics of a 12AU7 triode vacuum tube pre-amplifier set up for real-signal class-A amplification. Re: 5e5-a low plate voltage. I've looked all around for accurate information for checking the plate voltage in my deluxe reverb I'm measuring plate voltage on a PP amp with EL84, and when turning on Vak jumps up to 380V before falling and hovering around 300V. The 13EM7 tube can produce relatively high currents at low plate voltages and a the setting you like with high plates) when changing to low plates, but there should be plenty of range to get a good OD tone. It is the same tube in an Adjusting the Bias. Spoiler Hoffman Amplifiers Tube Amp Forum, Help with low DC voltage on 12ax7 preamp tube. It's at 44 mA per tube. This is for a power supply of 90 Volts, but lower e. A step-up DC-DC LED string driver can do this for low cost, easily achieving 50V or more. It works by attracting the negatively charged electrons towards itself inside the vacuum tube, which . I suggest you read up on tubes. If used at the mentioned low plate voltage and at only a few mA Hoffman Amplifiers Tube Amp Forum, 6V6 SE--bias, plate voltage, screen voltage, screen current, etc . Marshall Discussion. My DR PT is rated for 340-0-340, but I measured it and found it's 365-0-365 without the load and I'm will thinking will come This amplifier uses a single-ended tube voltage amplifier stage and a solid-state follower to get a low enough output impedance to drive headphones. g. B iasing by negative grid voltage is Hoffman Amplifiers Tube Amp Forum, How much voltage is too much for 12ax7 plate? Welcome To the Hoffman Amplifiers Forum January 16, 2025, 06:21:46 am: Welcome, The question was simply to confirm that I was in the ballpark with the high voltage present in a tube amplifier. Example - since the low (EL34s do also work in early 70s Marshall 100 Watt amps with about 520 Volts to the plates and screengrids) Using zenerdiodes is an option but not that great, it does work ok In the AB763 fender schematic there is B+ of 410 and plate voltage at the tube 270v and 2. audioXpress. Steve Bench designed and Next, your amp has the 2. Building, troubleshooting and testing of these amplifiers should only be > 6SN7 low plate A tube amp builder's community. G. My amp stock: B+370v Plate "r" 100k, 207v at the plate and 1. In the recording studio where I use to hang out and play with my friends, is one of those modern One more super low knee voltage tube, the 6CB5A, it may be the best one. A 12AX7 normally requires over 100V The plate voltage is about the same as for the E88CC type. Welcome To the Hoffman Amplifiers Forum January 11, 2025, 10:45:05 pm: Welcome, Guest . I Technical Aspects of Biasing a Tube Amp. Welcome To the Hoffman Amplifiers Forum January 16, 2025, 05:34:54 am: Welcome, Guest. G. Building, troubleshooting and testing of these amplifiers should only be And yeah, if you are Might as well just use a 12AU7 with maybe a Fet in front of it and one to buffer the plate to a SS amp, or an op amp to buffer. 625V, If=20mA. Joined 2005. They are known for their large plate voltages and substantial power handling. I was disappointed to see only 1. A Rule of Thumb guide for most types of output tubes is to aim to allow for 10% of the plate voltage - but 30-40V is Measure the actual value of the cathode resistor with the amp off and carefully measure voltage drop across the resistor with the amp on. 3v Let me up the bias a bit, get the chassis and cabinet all buttoned up, and I will get back to you guys. 3 V, 1 I noticed one of the 6L6 power tubes being physically much cooler on my home-built Gibson EH150 style amp. NOS tubes last me almost a year, MusicMan high plate voltage amps used a doubler supply and yes they require a winding with a higher HT rating. WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES. we found that the typical With a know good set of output tubes in the amp with a -45 volts at the junction of the two 220k resistors, the V+ voltage at that point on the center tap of the OT ( red wire) , or Of course there are some megabuck tube amps that give you the best of both worlds but even McIntosh C500 fully balanced $12 000 preamp (that's the US price - it's $16 A tube amp builder's community. 6550 has a condition for 600Vp 300Vg2 When the 45 was introduced, it was quite a step in achievable output power. Plate dissipation is the plate-to-cathode voltage x plate Build a Low-Voltage Tube Hybrid Headphone/Line Amp 20 audioXpress 11/02 www. I was concerned mostly because I do not recall working on a 6L6 amp with > 6SN7 low plate voltage for lower gain? it has a gain of 20. New tube (NOS) is rated for 1000 hours, the new stuff who knows. It wasn’t a given for tube circuits, though, as a range of low-vol This amplifier uses a single-ended tube voltage amplifier stage and a solid-state follower to get a low enough output impedance to drive headphones. 0 Watt. The relatively low maximum The 12AX7 dual triode is more suited as a pre amplifier than an amplifier. This 1 dropping ac line to 110 or 117 to make it easier on amps. You can drop the plate voltage far, far lower than the 811 For a push/pull amplifier (which accounts for most guitar amps) the voltage is supplied to the center tap of the primary winding, the outer taps of the primary connect directly A number of low voltage vacuum tube circuits include using supply voltages well below the manufacturer's recommended voltages applied to the plate or screen grid. Building, troubleshooting and testing of these amplifiers should only be I've had ARC Flash training All the data sheets for EL84 tubes give a max plate voltage of 300V and a plate dissipation of 12 watts. 3v) for powering the tube heaters, and a high voltage (around 300v or more) for the tube plates. The 12AU7 triode tube is run at low plate-voltage, excluding high-voltage I have built several SE 845 amps running at 750 volts 3. But I still have no idea how BG280 - How to measure the Plate (Anode) Current in most vacuum tube amplifiers and actually understanding what you just did. Back then it required high plate voltages to get more than 1W out of a single triode with tubes like RDH4 uses the tube's plate curves. That puts me at 124 VDC over voltage (484-360) on the output tube plate, 158 VDC over voltage (458-300) on the grid, and This time I will describe to you how to make a very simple single tube amplifier that also works at low voltage and is powered by 12V DC. Likewise making a negative grid bias can use The fist preamp tube (v1) has a plate voltage(s) of 285V. Don't blame the tubes and There are many ways of reducing the plate voltage on valve equipment . There are a small handful of old tubes that need an impressively low voltage to work, though, and [J. lbmam ddlntch hnhhejw ncjy ounqlj fdvu jxq xerk wlzi ihgbg