Best 6l6 bias adjustment chart amp. Most neutral new production are JJ's.
Best 6l6 bias adjustment chart amp Takes a tough tube to put up with that. The red or positive test lead is the one you want to touch off to the test Music Man Amplifiers SERVICE BULLETIN #1 _____ Section I DRIVER TRANSISTOR BIAS CALIBRATION PROCEDURE A. 2. The 7027A's are 35 watt mx dissipation tubes, 6L6GC's are only 30 watt tubes and are generally less robust than the 7027's. 1, 9, and on older tubes Fender Groove tube 17. My 6505+ combo is this way. This mod allows wide range of adjustment to bias 6V6, 6L6, EL34, KT66, KT77 and KT88 power tubes. A missing 5AR4 rectifier. The complex midrange and sweet highs are outstanding. In the case of power amplifier tubes, the quiescent current setting is much more important than with preamplifiers. Unrated Tubes, a bias adjust, and you have a bias probe. Didn’t realize NFB had a different Unlike an EL34 this tube can be used in place of a 6L6 in Fender amps with minimal modifications. There is a bias adjustment pot on the circuit board. I have a bad tube in my amp, so I need to replace them. For amps with cathode bias resistors you can simply measure their voltage drop and use the Tube Dissipation Using Cathode Resistor Voltage Drop calculator. These tubes, vital components in tube amplifiers, significantly shape the sound of your guitar amp. jeff The hum adjust procedure is in there. It has been a staple in American-made amplifiers and is especially favored for genres like blues and rock, where a Changing power tubes (no bias adjustments needed!) allows you to c u s t o m i z e your amp, dramatically changing the p o w e r,tone and response. As long as the best tone is within 10-20 of max plate dissipation you're safe. If the Pentode amp load and G2 voltage were optimized for Power Output: switching G2 to 40% taps is gonna cause a loss of power due to low G2 voltage at the pull-down peak of the cycle. THE BOTTOM LINE With its new independent gain and volume controls for channels 1 and 2 and comprehensive variety of pro-quality tones, the EVH 5150III 50-watt 6L6 Head is the perfect gigging and studio amp for discriminating players, while its A bias setting between 30 to 45 is best for the JJ 6V6's. I would recommend installing the tubes with an initial bias setting close to your target and check them again after ten minutes in play The power amp has a pair of 6L6 beam power tetrodes in a push-pull configuration, from which we can expect a lot of power. So the bias point (on the bias wheel) from one amp to the next will vary quite a bit to arrive at the same reading, say 60mv. I've been on 110 lately, but the lower the voltage, the less the tubes seem to red plate - that could be Some amps have individual bias adjustment for each power tube-- if your amp doesn't but uses fixed (not cathode) bias, it might be a reasonably simple mod to add individual bias. Should bias be adjusted for power output that I am using or what is the proper way to adjust bias. B. Victory Kraken Guitar Amps External bias test Do I need to bias my amp? Maybe, maybe not. Adjust bias until crossover notch just disappears. They were built better, with the best materials, but also speced to run lower voltages. I did not change any resistor value in the ^ This BIAS has to be adjusted. com Also for parts check https: 7027A are a 6l6 family tube that’s true, and functionally they’re the same plus two internal pins, but a true 7027A has a plate max of 600V compared to 500V for a 6L6GC. I don't often make any bias adjustment even though I've checked many times. There are 2 main types of amps, as far as bias is concerned. I don't know what your B+ Plate voltages are, so I can only speculate, but any of the calculators out there will tell you if a bias point is good enough or not. The only way to adjust bias is to modify the bias supply. Those rare amps simply require a bias adjustment, however the majority will likely require some physical modifications. Conclusion: The Best KT66 Tube Is Choosing a new tube for your amp is a very personal choice. They tend to vary a lot on the Devilles that is on one amplifier I have gone around the 70mV mark, on others I have gone a lot closer to 78mV or so. In the event you have to reship your unit, always use the original carton and packing material. I have had a Bias Adjustment kit fitted to my Fender Blues Deluxe and I am now running JJ 6V6 power tubes. Drive it with a 1 to 2 kHz signal to just below the point of clipping. S. The 6L6, 7581A, 6V6, 6550, EL34, 5881, KT66, KT88, KT90, KT100, etc. Thank you for the suggestions and for the excellent article! I've run the amp at wall voltage (about 120-122 typically), 117 and 110. This is standard/normal. X-100B Musical Instrument Amplifier manuals and instructions online. While many early rockers gravitated to Fender amps, the 6L6 sound was perhaps most celebrated by Dick Dale and his incredibly loud Fender Showman as If you replace the tubes with 6L6 type tubes be sure to make sure the bias is correct for those tubes. Adjust the bias: If necessary, make If I were servicing your amp and you had chosen tubes that would enable it to produce the maximum power and clean headroom, I would more than likely bias your amplifier in the 20–35mA range, based on the performance of the tube. Fender Frontman 10G Electric Guitar Amplifier - Midnight Blue Austin Bazaar-7%. LOAD IMPEDANCE: Selects amp output Other brands of 6L6's like the chinese tad tubes and sovtek, grade and sometimes these will top out at 75 to 80mv but if its headroom you're after then that is a good place to bias the amp. These features should only be used by an authorized service technician to adjust the bias of the amplifier tubes. Joined Jan 6, 2007 That's the starting point, best to use your ears after that for fine tuning. Cathode biased amps run at max signal at idle, so with cathode biased amps usually 90% is acceptable for real class A, and 80% to 85% for class AB1. It also has a bias adjustment pot as well. Tube Amp Doctor 6L6GC (discontinued) 5. You could remove that resistor and replace it with a pot and smaller resistor, so adjustment is done more easily in the future, this is what I did to my VT 22. Bias adjustment: Note: Bias adjustment should be made without any load connected to the amplifier’s output, and no signal connected to the amplifier’s input. $16 per 12ax/at7 and $42 for matched set of 6L6's. mark v you have to run all el34 or all 6l6 power tubes. Not all valves idle the same way, and you could end up burning up your new set if the amp is running too hot. Some like to use 60% thinking it may extend the tube life. EL34 tubes don’t draw quite as much power as 6L6 tubes. 6L6 tubes are frequently used in fixed bias configurations, demanding a precise bias voltage for optimal operation. slayer44 Well-known member. option. have told this story several times, mine was glued wide open from the factory! Literally had to chip away the glue to adjust the bias pot. This is a 30watt mono 6L6GC PP amp with 2 5814-A (12AU7) driver/tone control tubes. I converted the bias pot to the AB763 arrangement. Turn trimpot R16 counterclockwise until it reaches 0. This means adjusting a preset control INSIDE the amp in the amplifier bias circuit. are to ensure that your power transformer can supply an extra 500ma of heater current per tube and that the range of bias Papa & Diezel Crew will load their amps with the most consistent sounding, best quality-per-price ratio, widely/generally available "en masse" tubes. Tube Amp Doctor 6L6WGC-STR (discontinued) 5. 1 OHM, 1%, 1/2 WATT PRECISION METAL-FILM RESISTOR FOR Peavey XXX amps have a "fixed bias" and a bias adjustment knob. of 6L6GC's. Or, you could ask the vendor for something with a higher or lower It's a good idea to at least check the bias on any fixed bias amp when changing power tubes, you may or may not need to change/adjust the bias. It is fixed bias but doesn't appear to have adjustable bias. $89. This allows you to get more power-tube distortion at lower overall acoustic volumes, as well as give your amp some of that famous British EL84 flavor. "You measure the The 5150 III 50 watt is biased at 30mA or so. If you are going to be biasing a lot, spend the money and get a bias probe tool from Amp-Wares. This is something that must be done no matter which tubes you are changing. com showing the different rectifier voltage drops: The 5Y3's current rating of only 125 milliamps This is the grid bias we’ve been zoning in on, and the vast majority of tube guitar amps boast this type of bias. Here is s video to simplify the process. lettmusic New member. How you adjust the fixed-bias voltage supplied to the control grid often varies from amp to amp and from brand to Hark! Hark! Find special audio and hifi tubes from leading brands like Psvane or KR Audio! Top design and best quality to listen and enjoy! Three-dimensionality, depth and scale, diversification. PRR wrote: Plotting loadlines Looking for 6L6 Guitar Combo Amps? Sweetwater has Easy Payments, FREE Shipping, and FREE Sweetwater Support for Guitar Combo Amps! Call in for the best savings! (800) 222-4700. was a good experience for me and knowledge is power Great end results. It was like 48mV from the store, pretty cold i think. And that's all the 70% number is - "safe". 25 Watt Tubes. Series effects loop. #5 Killer Looks 50W EL34 amp: The amp is a pushpull of 6l6's ; the manual recommends to bias each tube at 35ma; I want to use 6L6 GC tubes instead; should I keep the same biasing or what is the optimized operating point per tube for a plate supply of approx 335V? 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. Listen for the "sweet spot". The Fender bias circuit is simpler than your Marshall circuit and it will provide enough bias voltage for 6L6 tubes. This applies to all models containing the following circuit boards: DB-2, DB-3, DB-4, GP-1, GP-2, GP-3, GP-3A,GD-1,GD-2 AND GD-2A. Along with Mullard 6L6GC, these new generation 6L6GC tubes are packaged in a compact form. reading time 13 minutes. For Hotrod Deville's the bias for 6V6's should be between 30 to 35mv at the test points because of the higher plate voltage. I have not found a detailed factory procedure description on the factory bias test points on the back of the amp. Is rated 40-50 watts. I've seen mention on the forum of biasing the 6V6s at 39mV - I presume that's for both tubes? I have set the amp up that way, but I still can't get any real breakup on the clean channel, The 6L6 tubes in the power amp section provide the same thick, dynamic tones of the original version. Are these ok to use, since Home. Your meter should be set to The test jacks on the back of the amp are used read the Bias Voltage, which can be tweaked using the Bias Adjust control located next to the power tubes. the tungsol 6v6gt is a much warmer tube than the jj and can handle over 450 volts; definitely my favourite of the two. More Information. Does anyone know what the recommended replacement tubes (pre and output) and bias currents are for the Archon 100 with 6L6? Does anyone have a tube chart with function vs. No more weird fizz on the note trails just solid clear tone. 6l6gc's are 30 watts max plate dissipation per tube. 1uf cap from the vibrato circuitry with no improvement. I use a In the course of learning various biasing methods for his amps, some of which are cathode-biased, others adjustable fixed-bias, he has used a couple of online resources which have been useful, but I think can be confusing for new builders. Typically you set the bias voltage to the maximum and check the current. https://www. . Some smaller amps with 6V6 power tubes I had a discussion with my amptech about biassing 6L6 tubes. and the plate voltage is close to the same. Use a wooden or plastic tool such as those commonly used to adjust inductor coils. i think if The TAD 6L6 that usually sounds good in my Randall MTS doesn't really quite work in the EVH, but I did find a Mesa Boogie 12AX7 works a bit better in the phase inverter than the JJ. 1x12 extension cabinets start at £619, 2x12 cabs sell from £899, full-fat 4x12 is £1,299; CONTACT: Victory Amplification I bought another JSX to put EL34's in versus the 6L6 tubes. Tung-Sol This is the grid bias we’ve been zoning in on, and the vast majority of tube guitar amps boast this type of bias. in the TRRI bias circuit, the 10k pot gives enough sweep to bias both 6l6 or 6v6 tubes, but i had to change the bias resistor to get me into the As can be seen from the data, it looks like the 6W6 is the best best for power and low distortion, the 6L6 is a good trade between the two, and the 6F6 is low power but also lower distortion than the 6V6 at moderate drive conditions. Bias test points and overall bias adjustment on rear panel; OPTIONS: None; RANGE OPTIONS: Kraken V4 amp pedal (£849), VX Kraken MKII compact head in wooden sleeve (£1,529), VX Kraken 100 head (£2,199). They offer subtly different tonal characteristics in terms of power stage overdrive and also overall frequency response. The 6L6 tube is famed for its ability to deliver substantial power (around 25 watts, although the newest versions are able to cope with upwards of 30 watts), and also its robust construction, which is a big factor in its popularity with touring guitarists. 4. so basically, you are using the same branded 6L6 tubes. But I'll try hereI'll take your last questions and work back to the beginning. Has a clean, warm sound, that overdrives nicely. Now without adjusting the bias control any further at this point, testing the various NEW out of the box matched set of JJ tubes I got 23. One of the best know is the old Sylvania 6L6 tall bottles with the designation STR387. the amp sounds best to me. does, the overdrive is gorgeously smooth, supple, organic and balanced. jonarobb Well-known member. 6v6 (power): works on variac setting (low b+) only & all wattage modes with bias select on "6l6". It is recommended that this adjustment be done by a technician, but if you are handy with a Volt Meter you can check the voltage yourself. Pre amp: 12AX7A; Power: 2 x 6L6; Bias: Fixed with adjustment pot Rectifier: Solid the Vibro-Kings were one of the amps that flew under the radar, and s/n dating for these amps are a guess at best. It doesn't work. In some amps, there is no 'pot' so I set the bias adjustment low to see what readings I'd get. I checked the online Weber bias chart for these 6L6s and proceeded to gradually increase the bias current as I played the amp. A 6L6/EL34 bias switch allows the use of EL34's with no bias adjustment. Can In this guide we'll highlight five of the best Victory amps and review the pros and cons of each to help you find which suits your style most. 29mV and 475V respectively. I have run original Tung Sol 5881s in my Revisions to the original metal 6L6 such as increased power handling and glass envelopes yielded new designations such as 6L6G, 6L6GA, 6L6GB and finally 6L6GC (introduced by GE in the late 1950s). On a 6L6 this won;t matter, but the EL34 needs pin 1 to be grounded, or at least This amp will handle all the higher dissipation members of the 6L6 family including the 6L6GC and the 5881. My plate voltage is 455 V. I'm using 6L6s so the whole range of the knob is supposedly safe to use. Jim made his amps late 70's - early 80's and he's back at it now, working in conjunction with John Suhr, and both are TAG members. the plate leads on their way to pin 3 are also connected to pin 1. For your amp, I'd probably If your amp comes with one of the common octal power-tube types (6L6, EL34, 6V6, 6550, 7027, or 7591), these converters allow you to plug cathode-biased EL84s in their place without bias adjustment. Should the knob be turned all the way to the right (clockwise) or to the left (counter-clockwise)? Having it set too hot may sound nice at low volumes, but Measure the bias voltage: Connect a multimeter set to DC voltage mode to the bias adjustment points. Unless ordered otherwise, your S30 amp will come equipped with our very best 6L6, a matched Duet of the GT6L6GE tubes, our USAmade Power Tetrode. 60% is a nice plate dissipation number for the JJs. The 7868 is only rated at 19 watts. There is a bias chart and calculator on Webers site (click on Bias Rite) that will help you figure out the numbers in the future. For high-gain amps, the tone is often dominated by the preamp, lower gain amps rely much more on the power amp section. location? The Archon is a great amp, but the manual is not useful. Without any tools to read voltage, I just want to bias it as hotly as possible. Eddie himself made this modification on his original 100-watt Stealth head to control the voltage produced by the tubes while touring across the globe. Hope that helps! Stephen . Tung-Sol 6L6-G: 3. Bias should always be adjusted to each particular set of tubes anyway IMO. When comparing the 6L6 vs KT66 vacuum tubes, you’re diving into the heart of guitar amplifier tone. 070mV at the "test point" (see linked video), but you could go to . work on both power settings & all wattage modes with bias select on "el34". fixed bias Adjust the Bias control in front of the tube to be biased with the supplied screw driver to . Click to view our 6L6 / 5881 Tube Comparison Chart. Good thing #2 is, I've found the 6L6 version of the Mesa 50 cal to be the better one. I have a hand drawn schematic with voltages I measured while clipping in three different value resistors . There is a lot of material available on the topic of bias measuring methods both here and elsewhere online Just note that the 6L6 family of Tubes biases in a good amount different then those others you will run so to get the best out of which ever you run you might want to use 2 separate cathode resistors and of course separate bypass caps that are selectable by means of a switch. I get the second amp, put JJ EL34's (not matched, i need to get a matched quad)and JJ12ax7's matched quad 803s series. elvis Click to expand PRS amps can sometimes take either tube type with a bias adjustment. EL34 tubes, however, To the best of my knowledge, these changes should have no effect on the power tube bias. If the Pentode amp was optimized for G2 voltage nearly equal to plate voltage: bias stays essentially the same. In fixed bias amps you have more options. 5. Does this sound right to you amp gurus? I have mine at about 66-67mV. I like the JJ tubes as well I recently picked up a Harmon Kardon CA-35 PA amp. Metlupass2 Well-known member. It will likely be fairly low. 6L6 GE bias setting in old fender amp? Thread starter JPP100; Start date Dec 8, 2009; Dec 8, 2009 #1 J. If you replace the 10K with a 5K in series with the element of a 10K bias pot, and take the bias voltage from the wiper of the pot, you will have a variable divider with a range of about 79% to 93% of the rectified DC voltage. A colder bias will make the amp play cleaner with more headroom, but OTOH it may make the amp sound a bit sterile. 5, a Sovtek 6L6WXT rated 8. Connect a multimeter to one of the emitter resistor leads and set the multimeter to mV scale. These amps were 40 watts, fixed bias with a bias adjustment pot, and the tubes were 4 x 7025, 2 x 12AX7, 2 x 5881 with a solidstate rectifier. So re-biasing is necessary. you can easily find the manufacture year by looking at the tag inside the amp. Can anyone shed some light on what the solution to this There are many web sites that explain setting bias. This webpage offers two ways to calculate tube bias and plate dissipation. ampegv4. and someone else might confirm this, the Ampeg V2 from 1975 does not have a Bias adjustment does it? All I see is a hum balance. Ensure the multimeter’s probes are correctly connected to the amplifier’s bias points. Requires separate digital volt-ohmmeter capable of reading current. The cathode of any octal based amp (EL-34's, 6L6's, 6550's, 6V6's, KT-88's, 7027's) is on PIN 8. Many earlier Fender tube amps used rectifier tubes. There is only one source of bias voltage, so the voltage at every tube's grid will be the same (it better be!). 6v6 & 6l6 (power): BEST CHOICE! (IMHO, YMMV, etc. So let me know what you think of the 6L6 “Spalted Alder The front of amp has a high power 100watt and low power 25watt switch. 3, 13, 11. My recommended bias measurement method is the "Output Transformer Resistance Method. Someone on here or the gear page posted a pic of the amp with a meter on it. These amps were 40 watts, fixed bias nonadjustable, and the tubes were 5 x 7025, 2 x 6L6GC with a solidstate rectifier. 0182 or 18 milliamps If you’re verifying the bias on a Class A or Cathode biased amp you’ll find that most manufacturers run the tubes at 100% of the tubes maximum dissipation. Fender 6L6 Amp HELP!!! . The previous owner replaced the 6L6 power tubes with EL34s, I understand there is a switch and adjustment for either type of tube. I added a 5U4 and brought it up slowly on a varaic. 3 How to Measure Bias. I need a lesson Tweed early Princeton. A few years ago Mesa amps came with all Chinese tubes from the factory, my Maverick had them. The '66 Bandmasters used the AB763 circuit. This design alteration makes accessing the bias port convenient and without having to remove the chassis. When I adjust bias for low power then check bias at high power I get different readings that are much higher. NOTE: Always turn your amp off, and let the tubes cool I have a new build that I am trying to figure out the value of the cathode resistor of the 6l6 tube . You have to date by the small silver The BIAS pot, as labeled on the schematic goes from 0 to 12. These were Sovtek 6l6wxt+, and I have a spare set of Ruby 6L6gcms. Turn the amplifier to "ON" with the HI / LO Standby switch in the HI Fitment issues may be possible because KT66 is wider than 6L6. RESONANCE: Adjusts power amp low-frequency response. Best 6L6 Tube Reivew Looking for 6L6 Tubes? Check out our 6L6 Tube Catalog Page for 6L6 tubes we stock. For 8-pin power tubes such as 6L6, 6V6, 5881, 6550, EL34, KT88, KT66, KT100, etc. Hook a scope across the output. 0257 or 26 milliamps X . Set the bias to the suggested figure on the Schematic or in the owner's manual. Note that data In most Fender style amps with 6L6s I prefer 65% or lower so the low-end stays a bit tighter. The JJ Electronics’ T-6L6GC-JJ-MP amplifier tubes find widespread application in guitar amps serve as the yardstick for all 6L6 tubes. Most amps sound best biased a bit on the hotter side - warmer tone, earlier breakup. Tube values can vary greatly from one amp to the next. 5. 5k, but even turned all the way down, there is still some slight red plating. The plate voltage of these amps is designed for the 6L6 tubes and this is the reason why the previous owner has used a pair of JJ's You can choose to run either EL34 or 6L6 power valves. The purpose of this comparison is simply to provide guitar players with a frame of reference to help in finding the best current production 6L6GC for their needs. Back in 1946 when the amp was produced, however, no more than about 20 watts was considered Different plate dissapation simply require a different bias adjestment if the 6L6GC has 30 watt PD and the 5881 has 25 watt PD. Hmm. I later converted that to 6L6. They are NOT 6L6GC equivalent, so you need to dial back the idle dissipation if you're going to use them in a fixed bias amp. It taps pin 3 for plate voltage and pin 8 (inserts a 1 ohm resister) for bias current (actually a bias And remember if you are biasing 6L6 tubes in the 6l6 mode on the amp and the bias will not go above 35mA even with the trim pot turned all the way up, flip to the EL34 mode and bias it up from them. I mentioned that I use the Weber Bias Rite and that I ran my 6L6s around 42mA (according to I Bias them at . In a power amplifier, the power amplifier tubes react much more sensitively to Ended up taking the amp to a tech and after a scope check and bias down to the 73Mv range. Most of the time, checking bias requires experience working in an amplifier. Hello all! Recently bought this amp, it has yellow led inside I suspect it's old model. If you have an amp which uses power tubes which are not listed above, you will need to consult a spec With that amp I had to take the chassis out of the headshell and turn it upside down. I rewired the gawd-awful bias balance circuit into a true bias adjust circuit. If you have a 6SL7 amp, use only types 6SL7, 5691, 6113, or 6188 in this socket. It might not be the best sounding bias point for the guitar amp but the tubes will last a long time; longer than the Then an adjustment will be required. do not mix w/ 6l6 type tubes! biasing system on mark v is different from iv. I like the warmer lead tone out of the 34's and the deeper bottom end out of the 6L6. Turn the trim pot to adjust the plate current to the desired setting. The small form factor reduces vibration and The bias voltage requirements for these tubes differ, affecting the overall amp design and tone. This is a variable potentiometer. 0 / 5 by 33 customers! while the new 6L6's I installed spec around 60 so bringing the bias up to 56 was a breeze with the help of the external bias adjustment. How you adjust the fixed-bias voltage supplied to the control grid often varies from amp to amp and from brand to brand. As I start my next design I won't have to just use pentode bias points and hope for the best. At least on paper. 5u4gb (rect): default tubes. They have powerful deep bass and a clear, airy top end. :mrgreen: say for example you buy a 6L6 amp. so, i dont see why the bias pot mod wouldnt work just fine. Each manufacturer’s tube will achieve its best performance for this desired result at different bias current Please see the chart below for some quick comparisons, and read on for more information on power-tube tone and development. The schematic shows 6L6GC power tubes. Without a true bias adjustment pot I can't lower the bias of the tubes. They are good tubes thou, but maybe not as plentiful as they once were. ) Reactions: dogrocketp, bodia and 88prs. And really, the 1 ohm method works for both fixed bias and cathode bias circuits. My question is- how The amp comes standard with 6L6's. The stock power tubes on a Blues Deluxe and Hot Rod Deluxe amps are the 6L6's. The 5150III 50S 6L6 50-Watt Head is the perfect amp for players who want EVH signature touring tone, arena volume and performance in a compact package. So for Archon, the difference would be more subtle than for a 2-ch I want to verify the bias on my 120w Triple XXX. True 5881 tube are about 23-24 watt max. And I love the amp. If you’re in the market for a compact amp then the EL34 or 6L6 could be just what you’re looking for. Hit me with the comments of being a "noob" but, I am. Joined Jan 2, 2002 Messages 1,678. Best 6L6 Tubes. My current 6L6 project amp has the UL taps but I have it switchable btw UL and Triode-Strapped. Now, leaving the bias set for el34s made my amp sound a lot better, more dynamic and punchy. But he used a 470Ω between the transformer and the diode. I use the amp with the front switch in the low power position. This Twin Amp reissue is the 5E8-A schematic. like a mark iii or mark iv. L. If you want to bias the amp properly, you will need either a bias probe, Hook a scope across the output. turn on and adjust bias if necessary. Though not all amps with Pretty sure I've seen pics of those amps with 6P3S-E's, which are basically 5881 equivalent. These power tubes will be operated far below their limits but will provide good performance and long life. In all but a few cases, 6L6 and EL34 tubes are not interchangeable without modification. 1 OHM, 1%, 1/2 WATT PRECISION METAL-FILM RESISTOR FOR In fixed biased amps 70% is usually considered the max bias at idle. Note if the pot wiper ever does disconnect from the track, the bias voltage just swings down to its lowest (most negative) value allowed, as if the pot was turned all the way in that direction--the result being that the output tubes never totally lose bias and thus protect the tubes in the case of a bias pot failure. Nov 30, 2020 #8 Yep drop them in a bias up! Sounded brutal! I had mine at 28mv Here is the bias circuit in my amp as an attachment (Vibroverb clone bias circuitry). I dig mine because it has a kill mode but also does a lot of nice clean tones and takes pedals well. Our top selling go-to 6L6GC tube is TungSol 6L6GC-STR. Weber Speakers will be closed to spend time with our families -- Dec 24, 25, 26 and Dec 31, Jan 1 Have a wonderful holiday season and Safe and Happy New Year Celebration. The 5881 and 6L6 come from the same family of tubes. Biasing is such a grey area for me, and I'd like to correct that here. The best setting Fender was fond of using a 50VAC bias tap for his bias circuit. 0. It seemed appropriate to use this as a reference tube and it did not disappoint. Again, there is a gut shot out there showing it Run it into a load bank. First, you must use what the manufacturer has suggested. This is the best resource for these amps. The problem is that my tubes now balance out at 58mA which is way to high for safe operation. Dec 13, 2009 #12 Kap'n New member. Replace them with a matched set of tubes rated Sovtek Medium or an equivalent. 7 = . It depends on your own amplifier and I would suggest you trust your ears. 075mV and shouldn't have any tube problems. Some amps will be damaged if you use something else. The earlier amps were being sent out biased HI all, just curious what the proper voltage should be at the bias check point in a fender blues deluxe amp? I read on another website that the 6L6's int eh hot rod deluxe should be around 68mV. The bias range for the Hot Rod Deville can go between 70mV-80mV. Fender 6L6 Amp HELP!!! Thread starter mjarve Bias adjust for each 6L6GC tube and even gain on 12AT7 I just finished modifying my Fender Twin 135RMS and it sounds better than the day I bought it in 1976. 99. I just want to verify that it was done correctly. A bias setting between 30 to 45 is best for the JJ 6V6's. Mine sounded best with the Sovtek 5881's, wafer bottoms like in an SLO. My point is simple, the technology to make tubes every bit as good as but, you cant run el34 tubes on each end and 6l6 tubes in the middle. Music Man Amplifiers SERVICE BULLETIN #1 _____ Section I DRIVER TRANSISTOR BIAS CALIBRATION PROCEDURE A. If you have a 6SC7 amp, do NOT attempt to substitute other types, as the 6SC7 has an unusual pinout. This will always be a little bit on the cold side, but perfectly adequate for a guitar amp. The few that he made before he had to stop were some of the best 6L6's ever made and are highly sought after. greg October 18, 2015 at 4:45 am. That alone could be the source of the problem. Most neutral new production are JJ's. smallest, with the mighty V130 Super Countess being the largest and loudest. This morning, as recommended, I disconnected the cap from the 250k intensity pot and moving the wiper away from the 55v bias end resulted in the voltage on the wiper going progressively positive into As for the best 6L6, I prefer the winged C in my Mark 4. Ive owned Soldano's, Mesa's, Marshall's, etc etc but one thing I found all higher gain amps have in common is that Many tubes are run over specs in guitar amps but it sounds like a real 6L6 has more stamina than a real 5881 regarding higher voltages. As to why the 6L6 tube family is not an optimum tube for use with UL operation; it has nothing to do with voltage or dissipation ratings, but can be traced back to the design of the tube itself -- specifically, as it relates to its perveance. I just use the same bias probe and technique I used with my Soldano, nothing different. If you find that your bias adjustment does not run hot or cold enough bias circuit of the amp must be modified to change the range of bias voltage it can produce. The bias setting for any amp depends on the actual voltage the amp runs at. This should be very safe for matched JAN No, calibrating tubes isn’t always necessary. The schematic shows a voltage of -48 at the junction of the two 270K resistors. Rated 5. How to Bias a Fender Bassman (AB165) The 6L6 amplifier I chose is a 1969 Fender Bassman head (AB165). Joined Dec 12, 2005 Messages 107 You have to mod the amp to add a bias adjustment to use non-Mesa tubes? Stephen . For fixed bias amps without a bias adjust pot, the resistor can be changed to a different value, or a pot can be added in order to Est. These were almost always at For 6L6 valves then yes you would be around the 70mV range. (bias voltage) in a fixed bias amp. If your Mesa amp has this option and you are considering venturing into experimental mode, there are a few important things you should know. I think they still have a stash of them. The existing 10K and 56K resistors form a divider that puts ~85% of the rectified DC voltage at the junction of the 220K bias feed resistors. Some people question why such high-end amps come with such common tubes - the point is, no sense upcharging buyers for top-drawer glass when For bias adjustment I used a 25W 1 k-ohm rheostat bypassed with a 200 uF capacitor which allowed me to set the bias at each operating point. The Switchable Bias feature in Mesa amps allows the user to choose between 6L6 or EL-34 power tubes with just the flip of a switch (and once the corresponding tubes are installed). Amps with bias-wobble-trem need to be biased a bit colder (let's say 55%) to On the other hand, cathode bias shows a more smooth amp - biased on the hot side ~ 100mA's per tube @ 430V on plates - with none of the agressive character of fixed Amps without adjustable bias include Mesa-Boogie amps, some Peavey amps, and even some Fender amps (early versions of the Hot Rod Deluxe/Deville and Blues Deluxe/Deville, for example). Choice is limited to available NOS for 6SC7/SC7GT and to recent Russian-made 6SL7s. Right knob not responding at But it's best practice to at least check the bias in a fixed bias amp. i've got a pair of jj's and a pair of tungsols in my twin that i can switch between, depending on the tone i want. These are the original 6L6's and you Jeff West is the best at all the minutae regarding tube nomenclature. 95! Internal Variable Bias Control, Effects Loop, and Fender Spring Reverb - Black $1,299. It also has 2 12AX7 mic drivers. I bought another JSX to put EL34's in versus the 6L6 tubes. The Sovtek 5881 that became the standard 6L6 during the 90's is pretty much a regular 6L6. More important than a bias adjustment is knowing the condition of the tubes you are using. Download CARVIN X-100B PDF manual. However, when trying to check and adjust bias according to manual (2 bias adjustment knobs) something looks really strange. As long as I use a 6L6GC or equivalent (5881, for example), there is no need (or possible way) to change the bias. I don't know if 470Ω will work with your circuit but I would try before switching to the 345VAC source. A click should be heard. are common guitar amplifier power tubes, and are all easily biased with this method. I get a little confused when it comes to ALL the dffs in tube prefixes. Vintage Fender amps usually use pins 1 and 6 as tie-off points for input grids and screen grids, mounting resistors on the socket. May 26, 2014 #4 the other 20ma. Of course a good tube compliment and speaker change helped too. Tonewise; RCA are the best for Fender black face era amps and earlier. The newest version has an adjustable bias for just about any octal tube. which can be tweaked using the Bias Adjust control located next to the power tubes. CARVIN and the shipping company are not liable for any damage caused by The Best 6L6 / 6L6GC / 5881 Power Tubes - Reviews and Guide. It will also handle the KT88 and 6550 tubes without modification. This design allows the use of many of the octal base output tubes including the 6V6, 6L6, 5881, 6550, KT66,KT77 & Here is a good read and explanation of how to measure and set bias in a Tube amp. Jim's amp runs a quad of 6V6 at nearly 500V on the plates. Be sure you have the space for its large bottle. EDIT: The location and bias information is posted in one of the replies This website uses cookies to ensure that you get the best experience. you always purchase the EXACT same pack of tubes from the EXACT same store. You can go to their #4 Bias Ports 50S 6L6 amp: The bias port is unique to the 50S 6L6 amp. The amp as designed gets its tone from the preamp, the power amp is loud and strong, but the tubes run very cool. The 6L6GC tubes we carry work great in any 6L6 tube amps. 55 VDC Specific favorites in my Fire Bottle amp: Output: Best overall sound: Groove Tube Gold Series GT6L6GE Performance Rating 5 (#2: Russian military 6P3S-E, Try a pair of NOS 6L6G/GA tubes with a 5Y3 rectifier in your amp. Over the years, several brands have come stock - Ruby, JJ, etc. B+ 440v. Yesterday I replaced the . 1. This will provide the best possible protection during shipment. Joined Oct 15 In this Killer Rig article, we’ll take a look at some of the best 6l6 tubes on the market today and see how they compare. single ended != class a, you could have a class b single ended amp, but it would sound like <insert epithet here> single ended != cathode bias My first build was a G5, a French project that used an EL34 single-ended. As mentioned, looks like the 5F6/6-A Bassman ran them around 425v or so. I think they are cheaper than buying from Mesa online. This amp, I leave it all together. e. Adjustment is as follows: 1. Adjust bias until crossover notch just Based on B+ of 380V and a screen supply voltage of roughly 300V, I predict you'll need about 22V to 24V bias, and that a 250Ω resistor will get close to this. Forums. Set the bias according to the directions on the Schematic or in the owner's manual. So if you see a big resistor between pin 8 and ground, it's most likely the cathode resistor, meaning the amp is cathode biased. The primary modification necessary is to properly bias the amp. but from what i have heard so far JJ's are the best for this amp . 25 watts for 6L6’s, EL34’s, EL34II’s, would be as follows 9 watts divided by 350 = . The Peavey 5150 has no adjustment for bias. If you just stick in tubes and don't know their quality, you're only guessing and a bias adjustment isn't getting you much. Accept Cookies What exactly is Bias? The best analogy of bias adjustment that we can think of goes back to older cars that had carburetors. I used to run JJ Peavey XXX amps have a "fixed bias" and a bias adjustment knob. If he left the bias balance pot intact and added a bias adjust pot, you may have turned the wrong dial as they say shifting the bias to only one tube and There are many web sites that explain setting bias. What exactly is Bias? The best analogy of bias adjustment that we can think of goes back to older cars that had carburetors. I would take it to a tech or get a bias probe to be sure, an adjustment of the bias may enhance the quality of your tone over the factory cool settings. NOS Tung-Sol 5881 (used for reference) - This is one of those tubes long considered to be the "Holy Grail" of tone. It has been Adjust the bias to obtain the best tone, while keeping the tubes within specifications. J. If this isn't you, I recommend taking the thing for a quick service with an amp tech. Moreover, bias adjustment is also mandatory because the plate dissipation at 30Watts of the 6L6GC exceeds 25W of the KT66. It is a fixed bias amp and the bias setting can be changed by changing the bias resistor. I would recommend this to any rectifier user, it makes a great amplifier even better. When selecting new power tubes for your amplifier, there are many things to consider. If you have for example a 250 ohm cathode resistor for cathode bias, adding a 1 ohm resistor in series with that won;t change the bias to the tube On more amps than you'd think it is simply impossible to adjust the bias anyway, and not just in cathode bias amps like Vox. But this doesn’t mean that they don’t need a bias-setting I have the problem with my KT88 PP stereo integrated amp to set bias voltages of KT88 of which scheme as below; If I set Vk to the same value by adjusting the pots for both tubes, I have audible hum so I cannot set them to the same value but different values, I. It looks like yours is a Fixed Bias amp so I would use 70% of max plate dissipation per tube. You can still get it by Christmas for only $29. Buy a matched pair. Some circuits have internal trim pots, while others may have adjustment controls on the rear panel. I used the Sovtek 5881's and biased it properly and the amp just crushed. I say test your tubes first, so you know if their good. 2, and one sovtek rated 9. Here is EL34 mode. Here's a chart from 300guitars. Very easy to do. Biasing was easy and well within the range of the Answer – set the amplifier bias adjustment for that set of tubes in that particular amplifier. I have a couple of questions relating to biasing the amp and getting the best out of it. This is based on a champ circuit , no negative feedback , with the pre-amp section from Doug Hoffmans stout circuit . 435v, etc. Preamp tube is a 6SC7 or 6SC7GT (in earliest versions) or 6SL7 (later version). 410v and 0. Any work inside a tube amp is not "safe," so exercising due caution, this method would not be a threat to you. The 6L6 tube is renowned for its robust headroom and clarity. 12ax7 (pre): default tubes. The power delivered by 6L6 tubes is extremely punchy, and highly responsive to changes in . For 6L6 mode, resistor R1 is switched out to create a shunt resistance of Read Sweetwater customer reviews for EVH 5150III 50S 6L6 50-watt Tube Head - Black Stealth. Adjust to maximum negative bias. Because of one 6L6 power tube that was red plateing I installed an old set of tubes to see if the problem was only the tube. for 400VDC on 6L6GCs in Class AB, RobRob's site says 45mA is 60% dissipation For 360VDC, Class AB, 50mA. The AB763 Schematic specifies a voltage of -52V at the junction of the two 220K resistors that feed all the grids of the power tubes. Boogies have set bias-you can't change the bias. Having it set too hot may sound nice at low volumes, but your sound turns to mush when you turn the amp up. As to how to improve the sound, those guitar amplifier fans that read both the Tubes / Valves threads, and Instruments and Amps threads would be the best ones to answer. Reply. Turn the amplifier to "ON" with the HI / LO Standby switch in the HI The bias on the amplifier is set at the factory with whatever tubes are in it on the date it was born. JPP100 New member. JJ Electronics is celebrated for creating performance-driven heavy-duty preamp vacuum tubes, and the T EL34s operate best with the taps at 33% using fixed bias, while the EL84 family works best with fixed bias and the taps placed at 25%. Permalink. I'll be able to consult the data I collected and intelligently chose an operating point that meets my design goals and works well 6L6 Tube Overview. does that still need biasing? IMO, always at least test the bias when changing output tubes in a fixed-bias amp (that includes ones with and without bias adjustment pots, so don't get the term If you want to try 6V6s in a 6L6 amp, plate voltage and bias must be adjusted and a suitable output transformer should also be installed. Looks like the only modern updates are a fuse in the 5v recto heater circuit, filter caps upped to 22uF, 12AX7s instead of 12AY7s in the preamp, and bias adjust pot. First, I'm not sure about RCA Dates. Notice we said subtle! There’s a bias range switch to get The Mesa/Boogie Dual Rectifier has a grid bias supply that is switchable to support EL34 power pentodes or 6L6 beam power tetrodes. At about 40mV, things started smoothing out, and at 45 the amp sounded very The term "fixed bias" is simply the way that the circuit "fixes" or "sets" the bias level, and many fixed bias amps will have an adjustment pot, and some only have a non adjustable resistor to set the bias level. The best way is to observe the live current.