6l6gc bias adjustment on amplifiers
M-OV of Britain in and marketed for application as a power amplifier for audio frequencies and driver for radio frequencies. Because the beam tetrode design eliminated the tetrode kink in the lower parts of the tetrode's voltage-current characteristic curves, M-OV marketed this tube family as the "KT" series, standing for kinkless tetrode. The KT66 was one of the "International series" introduced in This series utilized the "American Octal" base and had characteristics equivalent to tubes by U. The KT66 was very popular in European radios and audio amplifiers.
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Antique Radio Forums
A handful of output tube types have been associated with the sounds of classic amps throughout the decades, and have therefore become part of the aural iconography, if you will, with which we define guitar tone in general. Some amp makers will tell you that a good circuit designer can coax just about any tone out of any type of output tube. Leo Fender might have used 6V6s and 6L6s for his tweed Deluxe and Twin Reverb respectively—to name but two examples—because they were available and affordable, but now that those sounds have been canonized we know exactly which tubes to use to get them.
Undoubtedly a talented maker can achieve a wide range of sounds from any tube set, and most can be manipulated to sound fantastic clean or overdriven and anywhere in between. In most cases output tubes are the biggest—or at least tallest—tubes in the back of your amp although a tube rectifier, if your amp has one, can also be mistaken for one of these. Many different types of output tubes were used in the glory days of these thermionic devices, when they appeared not only in guitar amplifiers, but in radios, stereos, TVs, broadcasting equipment, radar, and many other applications.
Today, only about half a dozen varieties of output tubes are used regularly by contemporary amp manufacturers, and just four of these are seen in any great numbers.
Among the more common types, EL84s and lesser-seen 6BM8s and s are the same diameter as most preamp tubes, although taller, and use the same 9-pin socket. The rest all use large 8-pin octal sockets. While they might appear interchangeable in terms of socket size, however, most have different circuit, voltage, and bias requirements, and they cannot simply be substituted one for the other in most amps. For the most part, though, a maker will design an amp with a very specific tube type in mind, and will work toward the performance and sonic characteristics of that tube.
This is the big-amp output tube traditionally seen in American-made amplifiers of more than 25 watts, and it has a bold, solid voice with firm lows and prominent highs.
The sound can almost be strident in loud, clean amps that were designed for maximum headroom, or silkier and more rounded in softer designs like many of the tweed-style amps. A pair of these will generate around 40 to 50 watts in an efficient class AB amp, and a quartet can put out up to watts.
Big Dumbles like the Overdrive Special also favored 6L6s and the similar This is the classic Marshall tube and the big boy of British amplification from the late s onward. It can be driven at higher voltages to produce a little more output than the 6L6GC, and it sounds somewhat different, too, characterized by a fat and juicy but softer low end, sizzling highs, and a thick midrange that exhibits a classic crispy-crunchy tone when pushed into distortion.
Configure it a little differently—say in a Hiwatt DR—and the EL34 can also deliver the relatively tighter and bone-crunchingly punchy sounds that have rocked arena stages for decades.
It also appears in the classic Hiwatt models and was featured in the big amps of Orange, Vox, and Sound City, as well as several from Selmer, Traynor, and others. Naturally, when a contemporary maker looks to recreate that Brit-stack kerrang! Plenty of modern makers also use this big tube in more original designs. They produce about half the output of their big brother, the 6L6, and are therefore more easily driven into clipping.
A pair of 6V6GTs will generate a maximum of about 22 watts in a fixed-bias circuit, and around 15 to 18 watts in a cathode-biased circuit think Deluxe Reverb and 5E3 tweed Deluxe, respectively. From the late s to late s reliable contemporary 6V6s were hard to come by, so few manufacturers designed new amps around this tube.
This is what led Fender to seemingly uncharacteristically produce amps that used EL84s, such as the Blues Junior. This was rectified by the release of a rugged and reliable 6V6 from Electro-Harmonix, first, then contemporary makers like JJ and others, leading to a renewed popularity for this tube. Today, it proliferates again in the watt-and-under range… alongside the next of our most popular subwatt tubes.
This tall, narrow, 9-pin output tube is best known for its use in classic Vox amps such as the AC15 and AC30, and is most often used today in nominally Class-A circuits that follow those templates. Classic sonic characteristics of the EL84 include sweet, bright, sparkly cleans and juicy, rich, harmonically saturated overdrive. Think jangle and chime with the volume reined in; shimmer, bloom, and sting when pushed a little harder.
Much like the 6V6GT, a pair of EL84s will generate 15 to 18 watts, while four can deliver upward of 30 to 36 watts. The EL84 can still exhibit a pretty firm, chunky low end in the right amp, but is best known for its detailed highs and a midrange that is crunchy and aggressive when pushed.
Although we think of it as a classically British-voiced tube, many ELloaded amps make great partners with a Telecaster when pushed just to the edge of breakup for a harmonically resplendent flavor of biting twang. The declining availability of great examples meant that it was rarely used in new amps in the couple of decades following that, but it has made a comeback with appreciative boutique amp designers in particular in the 21 st century.
It also has greater maximum volume capabilities. KT88 This massive output tube was used in mega-powered classics like the watt Marshall Major, where four big bottles generated about twice the wattage as the same number of EL34s in a watt Super Lead.
Appearing like a larger KT66 in a fat, Coke bottle-shaped glass envelope, the KT88 is capable of operating on extremely high voltages and producing a lot of wattage as a result, with a big, bold, firm sound to go with all that power. That being said, several modern amp designers have discovered they can also coax a lot of sweetness out of this tube by pushing it a little more gently and putting the right preamp in front of it.
I had a Sound City head and cab over 40 years ago. I loved it, way better than a Marshall. You must be logged in to post a comment. We will only send you relevant information. We will never sell your information to any third parties. You can, of course, unsubscribe at any time. View our full privacy policy. Electro-Harmonix EL Tung-Sol EL Genalex Gold Lion KT Tung-Sol Electro-Harmonix KT Thank you Dave Hunter for putting this together….
JJ Electronics Amplifier Tube (T-6L6GC-JJ)
One of the most popular and revered guitar amplifiers in the world, the Blackface Super Reverb can be heard on countless recordings from the 60s. Like any tube amplifier, the Super Reverb requires periodic adjustment. Biasing a tube amplifier is an important aspect of maintenance and is essential to ensuring its proper operation. Like performing a tune-up on a vehicle, biasing an amp will make it sound better and help the power tubes last longer, providing years of musical enjoyment. Setting the bias on a Blackface Super Reverb allows you to adjust the sound based on your musical and playing style.
Elekit TU-8200R @ Amp Camp
Dual tester worked great, biasing a new set of 6L6GC tubes. You will still need to manually obtain cathode-plate voltage and calculate conversion formula included ; Unit AB switch allows single multimeter use providing mV conversion of current draw, so you can determine your optimal bias point. Overall, it's a quality product. Delivery was quick as well. Reliable vendor. This tool is indispensable in getting your bias settings right, fast and easy. Make sure to measure plate voltage and then look up the recomemnded bias for the voltage against the Jim Jones Bias Bible. This tool is easy to use and is very accurate.
can anyone give me instructions on how to reset the bias on a 94 fender twinn amp..
Hello, i'm a french without google translate! Of course, i've replace all the cap. Thanks for your help. Skip to main content. Log in or register to post comments.
Why Should I Match My Tubes?
There is a lot of discussion on the black magic of setting the bias on the output valves in your amp. This is also related to the matching of the valves. I am attempting to write this so as the musicians can understand and so the idea is that I make it hopefully simple to understand. This is a challenge as my wife tells me that I can make a cheese sandwich sound complicated! Output valves need to have a certain amount of current flowing through them even when sitting doing nothing.
Announcement
Bassman 50 red plate and bias. I can adjust it so both tubes are just slightly red at the seam of the fin best seen with the lights out. I'm considering increasing the value of the 15K resistor from the wiper of the balance pot to ground. This will increase the bias and reduce the cathode current. So my basic question is "Is this how guitar amps run which contributes to short tube life? Or is the amp running too hot.? Gimp, Are you sure the schematic is for that amp? If it is then the bias is adjustable at that pot.
No biasing needed for 6V6 tubes because they can only be used in cathode bias position. Any man worth his salt can fix almost any problem with this stuff alone. Howdy, Stranger! It looks like you're new here.
Our first amplifier, and our flagship model. EL34s, KT77s, 6L6s, s, KT66s or s - your power tube choice ultimately decides where you wish the sound to take you. Complex harmonics, bold and clean focused clarity, with plenty of aggression when pushed. Play Komet 60 demo video Part 1.
By animal69 , August 22, in Amps. I've done biasing before. The Weber site assumes the power is 30W for the tube. This gives me 33mA. Lower the valuue to about 28ma, then from there raise it a little, maybe 2ma play it for a while and see how you like it. Raise it another 2ma to 32ma and play it again for a bit.
Moderators: pompeiisneaks , Colossal. Post by noddyhead » Sun Nov 17, pm. Post by pompeiisneaks » Sun Nov 17, pm. Post by Kagliostro » Sun Nov 17, pm.
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