Bias setting for el34. Feb 29, 2012 · Ex: Average plate voltage-475VDC (.

Bias setting for el34 If it don't sound rough at low level, the bias is fine. 16 Ohms goes to 8, 8 goes to 4) to double the primary impedance. Adaptive AutoBias will adjust itself to the new tube type, making experimenting with different power tubes very easy. Thanks. Speaker are Vandersteen 2CE Signatures on the 8 ohm tap. Most of my listening in part 2 of the TU-8340VK review was done with these tubes. Click to expand Jun 2, 2012 · For the cathode bias test all instructional posts say to break the ground connection between cathode and ground and replace with 1ohm resistor for every tube. Jul 25, 2009 · The amps owners manual states the amp can use EL34, 6550, KT66, KT77, KT88, or KT90 output tubes, but mentions only one bias setting of 200mA. I warm the amp up for 15 minutes, then set the bias for 40mA, if I check again 10 minutes later it can be anywhere between 36 and 50mA. If you are using EL34's, you should set the current for 70% of max power or 25 watts/ (plate voltage)*0. You don't need to go finding resisters and fuses and doing complicated math. Consult your local PrimaLuna Partner or contact PrimaLuna USA directly before attempting the procedure outlined below. What is the danger of having EL34 tubes in while the bias is set to 6l6? Dec 13, 2021 · I'm currently looking at a pair of mid 80s EL34 PP monoblocks on the bench (these beasts have 8 EL34 per block arranged in 4-4 parallel push pull). operated or Mar 18, 2022 · Adjust the bias pots accordingly to obtain a 50mA reading on each of the milliamp meters My question is, since the 6L6GC is a 30 watt tube, as opposed to the EL34 25watt tube, should it be biased higher? Dec 9, 2024 · Adjust the bias to between 20 to 25mA which is a conservative setting for most all amps while you note the DC plate voltage and use the formula above to calculate the bias you want. Each tube will have a different effect on the sound. This is for a 6L6GC tube type with some common amp voltages and safe dissipation settings. A bias meter is a device that can measure current in a tube amplifier. Aug 14, 2015 · How to Bias a Marshall JCM800 Biasing any Marshall has many pitfalls, and it will be a daunting task to try and demonstrate the ‘proper’ way to set up your Marshall (or any other amplifier equipped with EL34’s). The fixed bias setting is a totally different sounding amp, the EL 34’s are set to 70% bias. Best Regards. 60-. Look online for Jims bias. Anyway after a bit of testing cold vs hot bias I found they had the best crunch and clarity when set at 60% dissipation. 5 to get your bias setting. That could explain why your new EL34's won't bias up correctly. The bias circuit itself should be checked, the parts may not be Mar 2, 2016 · You could also set up the bias on the follower circuit so that it only partially provides all the negative bias that is needed and then use a resistor in the cathode circuit (which the cathode capacitor bypasses) to track any changing DC parameter of tubes going out of balance. However, the most important parameter is missing: the value at which th idle current should be set. I currently have svetlana el 34's in there, and I also have two matched pairs on hand with about 1 year of moderate use. I prefer the 60% setting. This can either simply be calculated, or e working in a stable state. I just dropped in a set of 6CA7's to mix with the 34's and am really liking the results after day 1. Here's my findings, in bullet point style: TECHNICAL FINDINGS: • A resistor change IS necessary to go from KT88's to EL34s. Feb 6, 2006 · what is the tone differnce if one were to bias (el34) the tubes at say 35 mA VS. Mar 20, 2013 · Wow this is cool. Settings for class AB push-pull s actually setting the bias. kt66, 6f6, 6v6, 5881 I used the cathode bias setting, works perfectly that way. That calculates what the bias current needs to be. 400 volts, . . In fact, I bias 6L6s using 22w as a design center value. Feb 29, 2012 · Ex: Average plate voltage-475VDC (. Here is how to bias a kt77. May 11, 2023 · Our much-loved former columnist Jeff Bober returns to explain how to check and reset the bias of your amp’s output tubes—and delivers some potentially shocking warnings about a few common but dangerous techniques. ) tube type (el34. 7V, was at -34V). The octal socket says set the bias voltage between ground and the bias setting pin to 1. This means that with the flip of a switch you can choose for the optimum bias setting for EL34 type of tubes or KT 8 type of tubes. Tubes are more expensive today and people like to optimize the performance of the amp to get the most out of the set of tubes. Enter the plate voltage and type of power tubes to get the bias current at various levels of plate dissipation. Jul 7, 2018 · According to my Groove Tubes bias kit manual, that means 20-50 mV is the range, with a nominal set point of 37. Dec 8, 2024 · All of the above mentioned amps are adjustable bias and routinely come from the factory with the bias set pretty cold. I was instructed by GTA Yahoo group members to bias on installation, again at 10 hours of use, and then again at 50 hours of use. Too much current will shorten its lifespan while too little will cause unwanted distortion. I don't think that Ampmaker advise the power tube cathode resistor be reduced below 270 ohms (stock value is 470). Bias setting is necessary because of the design of the tubes and the fact that each is slightly different. Dec 18, 2013 · Then divide that number into 17. Dec 3, 2009 · The Story: Current setting for the new Tung-Sol tubes is 460mv; I expect them to settle down to 450mv by themselves in the next few months as this has been the pattern during the early tube break-in period. 7 Typical settings are anywhere between 60 or 70% of max power of 25 watts. May 20, 2020 · Author Topic: Fixed Bias setting for 6GW8 (Read 3196 times) 0 Members and 1 Guest are viewing this topic. Repeat the steps several times as you get the bias dialed in. 42 mA? and what the heck is biasing a tube 'cold" or hot" mean? the higher the bias number , the hotter the tube? Jun 18, 2008 · The guy i bought it from said he put EL34's in it, but i looked at the bias switch and it was pointed to 6l6. An amplifier tube controls the flow of electrons running through it. I honestly do not know how the EVH 5153 is set up. In a nutshell, here are a few things to watch out for. 7K primay impedance, there is no bias setting that will keep the output tubes from redplating at some point in the power curve, even if you bias the amp at 0mA! Jan 20, 2021 · Circles » Audio/Video Gear and Systems » Tube-o-phile Circle (Moderator: JakeJ) » Topic: Fat Bottle 6CA7 vs EL34/6CA7 May 10, 2005 · It was a single ended cathode biased amp, a heavily modded Fender silverface Champ, and after I installed a fixed bias pot, fixed/cathode bias switch, and bias test jack from Area 51 audio I set the fixed bias pot for el34, then when I wanted to run 6l6. 6L6GC Bias Point By Voltage If you have a class AB amplifier that uses fixed bias and requires the setting to be changed with every tube change, this chart can help you. These amps like warmer tubes. Feb 26, 2024 · If that head is factory biased, I can guarantee it's biased remarkably cold, so if nothing else, maybe consider biasing up to 50-70% if that suits you, but it's important to remember that a bias control on an amp is not a tone control or voice shaping mechanism Oct 16, 2015 · I'm surprised by the bias setting of the EL34 output tubes. Because of the 220V to 230V switch during the last 10 years or so, the tube has more than 500V on the plate while the optimal idle current has around 60mA on the meter. May 4, 2008 · The amp is a push-pull EL34 with bias set by adjusting a pot near each tube. As the current increases, plate voltage will lower and a new calculation is needed. I've been running my 6550's lower at . Biasing strictly by the ‘crossover method’ will often leave your EL34’s dangerously close to exceeding maximum idle tube amp information, tubes, guitar tube amps, vintage tube amp parts, vintage tube amp parts, new and vintage tube amps, tubes, tube amps, 1 The instructions that came with my amp (not one of Roger's) recommend setting the bias at . Jan 8, 2018 · Assuming DC voltage setting for bias is . is used on the EL34 setting; one could take a bias-reading and if the bias didn't exceed safe limits; it could be run in the EL34 setting. Just switch tu Jul 16, 2012 · Amp is a Randall RM100 so I can bias each individual tube. GENERAL This valve is a high slope output pentode designed for operation in A. Is there a voltage I can read of the board to check it is set correctly? A have the standard valve set installed. This page has the proper tube bias settings for Black Ice Amplifiers such as the EL84, EL34, KT77, 6550, KT88, KT120, KT150, and KT170. I'm confused about the correlation between voltage and current. Then we turned the bias down to a cold 20mA and the voltage at the test points read 48 volts. jeff vinylkid58, Dec 20, 2022 #2 The bias supply can be sending different negative voltage levels to each tube. Jul 21, 2018 · Also they don't bias like a EL34 so depending of the amp, it's not a swap: sometimes you need to adjust the bias range in order to get them right. At the time, the 6CA7 tubes that Traynor bought had a tight tolerance and were pretty much plug and play. Hoffman Amplifiers Tube Amp Forum, Bias setting??What's wrong with 15mA? The "70% rule" says (Jazbo beat me) 23mA, which is near-enuff for all practical purpose. In my Nov 4, 2011 · I went ahead, out of curiosity, and mixed mesa 6l6 outer, winged 34 inner (one of which was the red plating el34) and heres what I got 36,20,28,35 (6l6 setting). I bought this Marshall 2203 jcm 800, changed 4 x 50uf caps and all the valves and it works, before it kept blowing a fuse. May 28, 2009 · i'm sort of conducting a random unscientific sampling of what folks are setting thier bias at on different models of Marshall amps. Oct 20, 2007 · Keeping safety first and foremost, biasing power tubes is relatively easy in most amplifiers. Try playing the amp to see which bias setting sounds best. 65 multiplier if you like. tables. If you want to run a little hotter bias, try running EL34 mode with Spongy/Tube Rectifier. 65VDC. I would like to know how to calculate the bias voltage. The issue I'm having is the schematic clearly says that the bias at point "Y" pin 8 on the EL34 output tubes is set at 1/2 VDC. Jan 16, 2010 · "The KT77's are calculated the same as EL34's, so using your bias probe you can run these in your JSX between 36 and 42ma per tube, based on you preference for headroom" when you turn the Dias adjustment counter clockwiese on the JSX it gets hotter (number goes up0 so it runs a little hotter . If your calculated bias point happens to be 40mA then adjust the bias current up. 7K primay impedance, there is no bias setting that will keep the output tubes from redplating at some point in the power curve, even if you bias the amp at 0mA! Again, the "sweet spot" in between is where most techs set the bias. Apr 3, 2023 · Due to tube aging, the tube bias settings need to checked periodically. I now have all of them at just over 31mV. 450 volts for KT66's and KT77's, and . C. The bias for the two (should be) set differently; but if a 6L6 or 6V6 etc. Here are A FEW of the changes from the original: 1)The is no connection between the two 270K resistors at point 21 on the board. Stock, that amp has the dual-pot bias adjustment: one pot adjusts the actual bias voltage, the other one adjusts the balance. Mar 4, 2014 · You could try to adjust the bias until the EL34 plate dissipates its rated 25W but the power supply will likely overheat and fail well before that point. They will not be unnecessarily loaded, which contribut Jun 9, 2010 · Re: Cathode bias and being able to use 6l6, el34, 6v6 in a 5f2a by Cliff Schecht » Wed Jun 09, 2010 2:10 pm A common trick is to design the amp to take either a 6L6 and a EL34. If you need more information on biasing your Granger amplifier, please contact us. 5 Start the 0. Most amps with two or more 6L6 or EL34 power tubes fall into this category. Tubes arrived today: matched JJ EL34 quads, Sovtek 5AR4, 1 NOS GE 6GH8A, 1 NOS Zenith 6GH8A, both in adaptors. My question is this: Is there any reason to over bias (bias cold) a tube in a guitar amp simply because the plate voltages run higher than normal? Biasing Tube Amplifier Calculator Use this calculator to determine the bias current for an amplifier’s power tubes. Thanks! Jul 17, 2006 · In 6L6 mode, the hottest bias is obtained by going with Bold/SS rectifier. I saw one post where Roger recommended . So last night, I finally bit the bullet and performed some minor amp-surgery, and swapped the KT88s with EL34s in my Bogner Shiva 20th Anniversary. Feb 27, 2012 · Below are some tubes that can be mixed in Herbert and their suggested mA setting. Need a bias probe? Order our bias probe from the Custom Shop. Under bias will reduce the power level while over bias might over heat your tube. Jul 10, 2025 · Are you learning the inner workings of biasing a tube amp to get the best sound out of your guitar rig? Get to know all about how to bias a tube amp. I really dig the tone as it is but I would like to experiment a little with different bias settings. The tube can stop the flow completely (called cutoff) or let it flow at maximum (called Jan 8, 2023 · I have replaced the 4 EH EL34's with a matched quad of JJ KT77's. 500 volts for KT88's or 6550's. Looking at the bottom of the socket, pin 3 is the Dec 13, 2009 · There are four individual pots for setting bias on each tube I presume. so I re-bias it, listen for a while and check it again, and it's usually changed on one particular tube position. Author Topic: Proper bias voltage range for EL34s (Read 7562 times) 0 Members and 1 Guest are viewing this topic. Nov 1, 2020 · Oldchen Chi-Fi EL34-B amp, auto bias, running in ultralinear mode. Jul 22, 2008 · Make sure they didn't modify the bias supply. Normally I have to decrease the voltage when putting other EL34 valves into this amp. from the bias supply. Without the right biasing, your tube might be under or over biased. 2deaf's circuit mostly uses pots as traditional voltage dividers which wouldn The tubes will be running at a slightly cooler bias, but many customers have been using these higher dissipation tubes with great success. But then it's not necessary good for a "normal" el34 so How to make and use a Bias Current Checker More recent bias checker versions can be found on the This bias checker was the first one and the most primitive Simple Bias Current Checker: Basically the way this thing works is that pins 1,2,3,4,5 and 7 pass uninterrupted through the device from tube base to tube socket. It is a resistor that will be able to read the negative bias voltage on one end and is connected to ground on the other Sep 12, 2013 · Surprisingly compared to the TAD EL34B-STR valves I had to increase the bias voltage (currently at -36. Heres the thing my amp from Triode has two ef86 (winged c) and an 12au7 (JJ) in the preamp section and curently JJ el34's for power and my instruction manual says to set the bias at 1. just curious. Is this correct for the EL34? I ask because I just purchased the ST-120 kit and I have both 6550's and Gold Lion KT-88's for it. They don’t cost big bucks as power tubes go. Nevertheless, you can never go wrong setting it by ear (provided you know the relative range on the trimpots where they should be). 7 X 25W)/475V then the bias would be set @ 37 mA for a 70% idle setting Also you could use a . Mar 13, 2025 · I have an original, unmodified ST-70 with EL34 outputs. Not all tube amps have adjustable bias, but most larger tube amps do (output power of 40 watts or greater, typically). 35 for EL-34, what should the setting be for the KT-77 and KT-88 ? My thoughts (uneducated), is the KT-77 should be similar to the EL-34, but the KT-88 a bit higher ? For example, in a 100W EL34 amp with 480V on the plates and a 1. 4 to 0. Doable, or am I asking for trouble? Aug 4, 2006 · I have 6L6s in my Triple Recto and I use the EL34/Tube/Bold modes. 356VDC measured at "Y" May 3, 2010 · Running KT77's in the EL34 mode with a probe installed and the bias set to 36mA the test points measured 45 volts. The amp in question is a Traynor YBA-1A (2x EL34) which has been previously modded with a trimmer pot on the bias supply and 1 ohm resistor on only one of the tubes. Then there is an easy math formula to compute which will tell you what your bias setting Circles » Audio/Video Gear and Systems » Tube-o-phile Circle (Moderator: JakeJ) » Topic: How to bias a Cayin manual biased amp Apr 29, 2014 · The OP’s amp can accommodate either an El34 or Kt88 tubes and these aforementioned bias setting are also quoted in the OP. May 26, 2019 · I plan to replace the electro-harmonix EL34 tubes in my Manley amplifier with new production Mullard EL-34's. The maths bit was to see if I can set the bias without having to buy any adapters or sockets or anything. that's all. Jun 22, 2012 · The amp is fixed bias. When I have adjusted the bias those few times so far, I attempt to set the milliamp per tube values- 26ma for 5881 or 42 ma for EL34. ) The 6L6 weren't for me and I've now been trying to bias the set of EL34's it came with Dec 4, 2011 · If it is a Latino built with the VTA board there is a bias adjustment for each tube and with EL34's or 6L6's the bias should be . Not hard. Put the positive probe of a voltmeter with a 1 VDC range to the pin 8 of the tube V4 (EL34), the negative probe to ground. The bias range for a 6L6 tube is typically between 20mA and 60mA. I tried searching this forum for clarity on where the ideal bias setting is but am having some trouble. To change the bias a resistor in the bias circuit has to be changed. This page is a step by step guide on how to adjust Black Ice Fusion tube amplifier bias. EL34 Sound Signatures: Styles and Variations Many musicians mistakenly think that all tubes sound the same, when in fact these components can radically alter the texture and color of the sound. Hi, I wonder if someone could help me with the best way to check my bias setting on my Fender Blues Jr turret board coversion. What is Bias? Bias voltage is the voltage difference between a tube's cathode and control grid. Always refer to the manufacturer’s tube datasheet for absolute values. I measured the plate voltage (new tubes in) and its was 465, by turning VR1 I adjusted the bias from 70, 56, 52, & 58, (4 el34's) down to around 37mA on all tubes, thats 25 watts divided by Plate Power tubes like EL34's and KT88's are good for about 2500 hours or more but may go longer in an amplifier with a conservative design. That means you’ll need to take measurements of your plate voltage with either a multi-meter or buy a bias probe. jmp. That's especially true with more robust circuits where a pot is used to shunt voltage to ground, so the failure condition (pot loses contact) is more negative voltage, instead of lost contact/bias. e. According to Buddy was playing around with my dual recto the other night, started messing with some settings on the back panel when I was in another room and ended up flipping the bias setting to EL34 mode. I would like to know if tubes of the same type (EL34) have the same bias setting when they are different brands? Thank you in advance. Measure B+ voltage, calculate dissipation, measure plate current, adjust bias voltage. Also, if you make a mistake and turn the AutoBias setting too high, you may cause severe damage to your tubes or even the amplifier, and such an event would void your warranty. 55VDC for KT88, 6550 and even KT120's. I had previously bought a set of JJ 6L6, which I had no problem biasing ( with the exception of the 6L6 setting running out of correction at 32 MA, which I've heard is not uncommon. Each of these resistors runs to a 150K pot. There can be some WIDE bias variations from tube to tube, regardless of brand name. 30 to . You begin to learn the finesse of the adjustment and dial it in. The EL34 is the perfect illustration: depending on the amp and circuit in which it resides, it can assume very different sonic personalities. I got a factory built ST70, bought with no tubes. Top BinkyTheCat Post subject: Re: Different recommended bias settings Posted: Tue Apr 29, 2014 2:51 pm Joined: Thu Jul 24, 2008 1:04 am Mar 25, 2012 · You still bias the tubes for the desired dissipation. Enter the Plate-to-Cathode Voltage which is measured between the plate and cathode tube socket pins, not between the plate and ground Jan 11, 2021 · Plate voltage warmed up at idle on EL34 is 380, screens about 15 volts lower. Amp class: Plate voltage: VDC Bias current for one tube: mA Note: This calculator is intended for quick reference only. With amp operating at 120vac, I have a . Oct 20, 2020 · I posted this topic in the Dynaco photos area of the forum, but wanted to repost here to get a few more eyes and comments. With a 6550 of KT88 I would use a 30W multiplier. Marshall 100 watt amps EL34's -36 to -45 Recommended -42 Marshall 50 watt amps EL34's -34 to -40 Recommended -36 Jan 31, 2025 · Hello Everyone! I am working on a MusicMan HD130 amp and have a question about the proper biasing. For those who have done this, which setting produced the most desirab Jun 2, 2010 · Re: Amp biasing question -- Bogner EL34 Shiva It's been a while since I checked the bias on mine, but I don't seem to remember them biased that far apart. I also am installing the digital meters in the octal socket holes. 56 volts. There's also high-power and low-power settings that affect the bias voltage, so make sure that Switch 11 (S11) is working right. 5 mA for El34's. If it do sound rough, I'd try fresh GOOD brand EL34. the only info i'm looking for is the model. I ran mine at 39ma and it sounded great. Very conservative. Jul 26, 2001 · No, you don't use the absolute maximum values for biasing. You need a I've read Bob at Eurotubes does something like this because suppoedly the fixed 6L6 bias setting is set too cold so he switches it to EL34 to get the bias warmer and get a warmer tone. Sep 17, 2022 · Need to replace a worn-out tube in your amplifier or simply want to upgrade? In this guide, we'll help you find the best El34 tubes. Pin 8 from the tube Apr 6, 2016 · People complained and then the bias mod came out for that amp to increase the range of the variable resistor so people could make it 'hotter'. 39V on the setting we have it on). All readings are mA. Let’s explore three major “flavors” of tone achievable Low bias switch. Retubing my Lynchbox with some Mullard's EL34'swhere should I bias them? Feb 21, 2007 · I'm going to attemp to bias my amp myself due to the extremely long waits for techs, not to mention costs. 40VDC with no problems. I see different voltages listed on bias adjustments- -37 volts or even 57 volts. 0 vdc. Find the right balance for you! Jul 20, 2019 · This is also known as setting the bias, which refers to setting the amount of current that runs through their base plates when the amplifier is idling. The amp sounds much better on the cathode setting, lots of compression and some nice wanted sag, l really like the tone. 6 X 25W)/475V then the bias would be set @ 32 mA for a 60% idle setting (. EVH® Product ManualsSupport Product Manuals EVH® Owner's ManualDownload EVH®5150III® 2x12 50W 6L6 Combo Owner's ManualDownload EVH®5150III® 1x12 50W 6L6 Combo Owner's ManualDownload EVH®5150III® 5150III® 50S 6L6 Head Owner's ManualDownload EVH®5150III® 50W 6L6 Head Owner's ManualDownload EVH®5150III® 50W EL34 Head Owner's ManualDownload EVH®5150III® 15W LBX-S Head Owner's Mar 30, 2022 · Here's are safe bias ranges to work within safely: From Dan Torres book Inside Tube amps. Dec 20, 2022 · Without looking at the schematic for your amp, I'll take a WAG and say it's possible the old carbon comp resistors in the bias network have drifted well beyond their original values. Sep 16, 2010 · Hey guys. I was just wanting to change out my tubes on my dynaclone to 6ca7's or kt77's and I did not know what to set the bias to. For example, in a 100W EL34 amp with 480V on the plates and a 1. Small signal tubes with numbers like 12AX7, 12AU7, and 6922 and rectifier tubes like 5AR4 may go 10,000 hours. kt 66. Now to biasing, inside on the pcb there are 2 voltage regulators, VR1, VR2. l have no PPIMV, just pre-amp master, 220k grid leaks. 30VDC for EL34 Oct 5, 2001 · The problem/question is will it hurt to run the amp with 6L6 tubes while in the EL34 bias position? It's essentially just a different bias setting correct? It would also appear that the amp would benefit from a re-bias of the 6L6 trim pot with the Ruby Tubes 6L6's in it. This value is 25w for an EL34, and actually about 19w for a 6L6, so as you can see, even using 25w for a 6L6 is ambitious. etc) and how many ma or mv your bias is set at. That being said, with a hi-fi amp, I believe the bias percentage can change drastically, depending on the class of amp you have. Forget the 30w figure. Jul 18, 2004 · Carefully insert a long-handled slotted screwdriver into the bias adjustment pot corresponding to the EL34 tube socket you're on (see the purple arrow in the picture below). These are the bias voltage measured in DCV negative voltage method measured on Pin 5 of you power tube socket. Select the Tube Type from the scrolling list. I would hazard a guess that a KT120 tubes bias is 500mv, but I cannot confirm this. EL34/6CA7: Aggressive, slender low end, higher total harmonic distortion… Recommended bias setting: 30-35mA 5881/6L6: Great tube for clean sounds, good bluesy tones, also has strong bass and excellent clarity… Recommended bias setting: 25-35mA. (jcm 800. The plate voltage should be measured from pin 3. That means using the tubes on the edge and implying a short tube life (1000-1500 hours I guess). Is the voltage relevant to the tube function or is Connecting the Bias Meter Now that we have gained access to the internal circuitry of the amplifier, the bias meter should be connected. Most bias circuits present a changing resistance with adjustment, which messes up many shared negative voltage supplies. Following the instructions for initial setting in the Aug 26, 2005 · With the bias probes you need to read the plate voltage first, then set the current for 70% power dissipation. If you do not have a bias pot, you will have to figure out where the fixed resistor is in the bias circuit that controls the negative bias voltage. If you listen as you switch between all the modes, you can hear it go from fuzzy and grainy on the 6L6 modes to warm and growling on the EL34 modes. My question is- how Sep 25, 2023 · You can still bias the same way, just have to figure out how it relates to your particular set up. When you want to use a 6V6, you just move the speaker jack down one impedance setting (i. Kt77’s natural bias is set at 0. I'm going to put together a bias circuit for EL34 or 5881 (6L6). Apr 11, 2014 · I have a JSX head I'm attempting to bias with a set of Ruby EL34's. Now, leaving the bias set for el34s made my amp sound a lot better, more dynamic and punchy. Apr 19, 2017 · For nearly twice the cost of the E-H EL34, they ought to offer more; the mids of the EL34 – especially with a high bias setting in the Eiclone – were “nicer”. No hassle with screwdrivers, no messing around with meters etc. Pin 6 is not used and so there is no need to wire it up. Bias current is the amount of electrons flowing from the cathode to the plate with no audio signal on the control grid (idle current). You use the design center values. It uses a set of probes that are plugged into the tube sockets and the tubes are then plugged into the probes. However, you cannot give an accurate chart of all the bias points for the modes, as each grade of tubes biases up a little differently. Some run their KT120's between . Carvin’s recommendation for bias is also cold, setting a quad of EL34’s or 6L6GC’s at a 100mA draw across the standby switch is only pulling about 20 to 25mA per tube. And at 743V (!!) I would not want to get too close to the edge. These had a few badly swollen capacitors, which were obviously in need of replacement and I've done that job. There are exceptions. That should be the coldest EL34 bias, but it will still be hotter than 6L6/Bold/SS. Again, the "sweet spot" in between is where most techs set the bias. 4 Jan 31, 2005 · I was trying my amp out with EL34's the other day, so I had the amps bias switch set over to "el-34," and of course when I put my 6L6's back in I forgot to change the bias back to 6L6. Is this the same bias setting for all these power tube types, or does the bias setting vary for each different tube type? Many thanks in advance for any replies. I wanted to do a check on bias etc to May 30, 2020 · Changing the tubes of a Marshall JCM900 (EL34) Tubes are easy to change but you absolutely need to bias them once installed (power tubes). Looking at the spec sheets, they both have max dissipation of 25 watts I am assuming that this means the KT77's bias at the same levels (the recommended setting for the EL34's, is anywhere from 360 - 440 mv for the Jolida 3502 Tube Bias Calculator Instructions & Help Enter values in blue and click any Calculate button. Mar 31, 2020 · How to bias kt77 Once you have decided to change your el34 for the kt77, the next step is to bias the latter. You'll see the chart for EL34 tubes, under the measured plate voltage, select the desired dissipation, and adjust the bias control for the listed current. 6l6's are 25 to 60, with a set point of 45 mA. Slowly rotate the screwdriver to adjust the bias voltage until it reads '390' on the multimeter (which means 0. I had all Winged C 34's in the RM100 biased up each one between 30mV and 31mV. etc. If your tube isn't listed then pick one with the same Max Dissipation Rate which is shown to the right in the tube list. zfgxv wqyj glxnn rpjus lahhnf autwn eqisnfb vdfcsfs rdpn qske uoaol ifuo jleuf mtungg kucuik