eurotubes bias calculator

Ideally, your tubes will be matched within 5mA for EL34's. 2.Very, very few product amps use individual bias, you have one bias pot to bias all 4 tubes. Each tube in this comparison was installed in the same custom-built, fixed-bias single-ended guitar amplifier in order to obtain the voltage gain measurements and conduct listening tests. The Eurotubes site clearly states: Hendyamps. This is a common setting for the bias. I don't want to test . P = I × V. P is the power rating of the power tube, I is the bias current, and V is the plate voltage of the power tube. I hooked the amp up to my Captor X as a load, and then Focusrite interface to see what was going on via Arta. I measured this when I set bias, using the eurotubes adapter, but they had you measure with tubes installed. I seem to remember JJ having a plain Jane 6L6 a few years back. Then you can calculate the dissipation of whatever amp you want, even if it doesn't have bias points. The purpose of this thread is going to be for discussing Mods to the jet city 20H, or any other topic pertaining to the JCA model 20H. You can be more accurate and measure just the plate current with a different method. Tweet. This is the most accurate way of measuring bias current, and only takes a few minutes to properly bias an amp that has a fixed, adjustable bias supply. Location: AZ. 05-30-2020, 05:58 AM. If your line voltage is higher, the bias will be off. Now, with the 158R resistor is 355Vdc. Bias Probes - Eurotubes - Vacuum Tubes by JJ Electronic trend www.eurotubes.com. I suggest you buy a multimeter and octal bias probe (the Eurotubes one is good for $28). Hello, I have for sale a Blackstar HT20 Studio 20W combo Amp. I recently added a little tolex covered V-Type to my collection. The number you get from the 70% calculation is a "rule of thumb", not an absolute. The stock 20h. I would like to learn how to bias my own amp. . So 23.9ma bias current using the 1ohm resistors Then I used the output transformer resistance method Tube #1 ohms between output transformer center tap and pin 3 primary is 327ohms. I set the bias calculator to EL84 tube type, entered 354 plate voltage. This is the most accurate way of measuring bias current, and only takes a few minutes to properly bias an amp that has a fixed, adjustable bias supply. . R45VT. Doesn't speak guitar . Either way I get 70% bias. . On these amps, the bias is set by changing a resistor, R49, 75K ohm, in the early V4B. So if I want 70% bias, it doesn't matter if I apply 70% to the 25 watts (yielding 17.5 watts), or if I apply 70% to the current (yielding 41 mA). So I put my EuroTubes bias probe on one of the power tubes and it was reading 457 plate voltage. This creates a slight positive charge on the cathodes. Read honest and unbiased product reviews from our users. Except of course you're actually measuring *cathode* current, which includes both plate and screen current. Then it was a formula like tube watts (25) /pin 5 volts • .70 for bias amprage troyAmpallen , Mar 20, 2019 The Bias King is a simple, effective, and accurate diagnostic tool designed to read the current flowing through the tube of an amplifier (bias). I THINK I read my plate voltage as 504V I have a middle of the road multimeter which I can barely use ha ha and a new eurotubes probe. 5. Also you bias by current and voltage. Solving for current, current = power/volts. 6÷327=.0183 so 18.3ma current Tube #2 had 304ohms resistance. Then press calculate. The Eurotubes "Pro One" Bias Probe is an "all in one" bias probe for octal tubes including 6V6's, 6L6's, KT66's, EL34's, E34L's, KT77's, 6CA7's, 6550's and KT88's. It is unique in the fact that it shows you both the plate current and plate voltage simultaneously and it is completely self-contained with no switches, knobs or batteries. Cannot say enough good things about Eurotubes; best guys in the business. In a cathode-biased amp, the grids are grounded through a grid return resistor and a resistor is placed between the cathodes and ground. 10th July 2013 #2. Subscribe to our channel for more videos, and leave us a comment below! The stock 20h is a 2 el84, 3 12ax7 amp featuring a soldano slo Treble, Middle, Bass tone stack with a Presence control in the Power Amp. Orange doesn't offer much help either. Last edited by andyhatescrass at Oct 29, 2012, 1:52 PM. 12 watts divided by 350 = .034 … . If R52 is really low, then it doesn't do anything to the equation. Resistance from OT to V7 pin 7 is 61.7. You can also take off an approximate screen current figure which is another feature of Rob's calculator. I hate getting shocked. The only 6L6 types that I can find on the Eurotubes (JJ importer) website are a 5881 and a 6L6GC. 4. I installed a set of perfectly matched JJ KT88s from Eurotubes. The Eurotubes Octal Bias Probe measures in DC Milliamps and will work with any Multimeter that can read in DC Milliamps. The bias probe is placed into one of the amp's power tube sockets and the tube into the bias probe. You can use 70% of 25 watts and they will get a great warm clean tone well out of crossover distortion. 25 Watts divided by 450VDC = .0555 multiplied by .7 = .0388 and rounded off this would be .039 or 39 Milliamps. 402-396=6. Eurotubes suggested me to use their Bias Probes (Eurotubes - Bias Probes for vacuum tube valve amps!) Here's a bias calculator to help you bias those 6L6"S" tubes. You could go to Eurotubes.com and watch their vid on how to bias a DSL100. From what I understand the caps will kill you but a 500 volt shock will just hurt bad or burn ya. Changing the bias level can effect the tone. Just that simple. The cheapest solution. Hey. Retube™ Kits For Bad Cat. The octal and noval probes are also sold separately so that you can bias amps using EL84s, 6L6GCs, EL34, 6V6GT, etc. Product information Feedback Would you like to tell us about a lower price? but they don't know what value I should bias it up to. I have put several. Talk about being the "real deal"; had the new set installed and the AB763 Twin biased and running aim less than 30 minutes using this nifty probe. Alternative, you can use a BIAS PROBE or some such device that goes between the the socket and the tube. It has very low hours and doesn't get used much. Adjusting the resistor set the bias for all four of the power tubes. #2. The Eurotubes "Pro One" Bias Probe is an "all in one" bias probe for octal tubes including 6V6's, 6L6's, KT66's, EL34's, E34L's, KT77's, 6CA7's, 6550's and KT88's. It is unique in the fact that it shows you both the plate current and plate voltage simultaneously and it is completely self-contained with no switches, knobs or batteries. I typed a really long reply and lost it. The Eurotubes Octal Bias Probe measures in DC Milliamps and will work with any Multimeter that can read in DC Milliamps. As I remember, my EuroTubes probes showed about 425 volts. Thanks Share Reply Quote. I'm showing plate voltage at 448V and bias at 14mA. Retube™ Kits For B52. Since 2006 we have offered a single octal bias probe for use with a Multimeter. 6L6GC Comparison of Current Made Tubes. Either way I get 70% bias. The squeal is at about 7250 hz. On several of these 6050MH heads i've seen they are bias well in to the 90% range. The more current there is flowing, the higher the numbers will be on the Bias King and the hotter the . A Milliamp reading is more accurate because the screen current is not added to the plate current as with other probes that measure in Millivolts. Two 8 ohm output taps and one 16 ohm output tap. 150. We will continue to offer these because in conjunction with a Multimeter this is the most cost effective tool for measuring true plate current allowing you to . The reason you can't get the bias into that range is that it's a Class AB amp. To calculate your bias you can measure the DC plate voltage from pin #3 of any power tube to ground using a multimeter but these amp are right at 400 and you can use this voltage to calculate the bias without measuring it if you wish. There are two 10uF/100V caps in the bias circuit, C15 and C23 that should be changed. Luckily, of course, the difference is small. So if I want 70% bias, it doesn't matter if I apply 70% to the 25 watts (yielding 17.5 watts), or if I apply 70% to the current (yielding 41 mA). Also, the stock amp has no means to measure the bias. 25 watts/425 volts = 59 mA. Retube™ Kits For Bogner. Each tube sample used for comparison was chosen because it measured in the middle range of idle plate current draw at . I have a 65 DRRI made in the USA in 2003. I dunno how well you know tubes / bias and such but they really should be around 70%. With a voltage drop of 3, I did his calculations (voltage drop / ohms) V7 is 3/61.7 = 48.62mA. Fixed Bias, single trim pot. A Milliamp reading is more accurate because the screen current is not added to the plate current as with other probes that measure in Millivolts. You're trying to bias it in the Class A range (BTW, it won't make it Class A). 25 Watts divided by 450VDC = .0555 multiplied by .7 = .0388 and rounded off this would be .039 or 39 Milliamps. 5. The idea is to calculate what your ideal bias setting should be then after measuring the bias of each tube to find out which one is running the hottest (highest bias current) set that hottest tube bias to your calculated reading and your tone should be good & also ensure none of your tubes are running too hot, as the other 3 tubes should be . This will allow you to read the voltage across the resistor and use Ohm's Law to calculate the current flow. 402-395=7. This will be my first time doing the bias for an amplifier. 6L6GC Comparison of Current Made Tubes. Calculate the bias voltage thus: (R53)/ (R53 + R52) x -57v = bias volts. For EL34 tubes with a plate voltage of 456.6V, we see our bias point will be 38.33mA. Check the bias circuit components carefully. at Amazon.com. The bias probe is placed into one of the amp's power tube sockets and the tube into the bias probe. I feel the same way about getting a plate voltage reading using pin 3. It gave me 23.7 for 70% dissipation. Currently unavailable. Well, before, with the 129R (measured) cathode resistor, the plate voltage (with the same wall voltage of 234Vac) was 349Vdc. It's been upgraded with Electro-Harmonix pre-amp tubes and sounds great. Nobsound Vacuum Tube Amp Amplifier Plate Bias Current Probe Tester 8 Pin Socket for EL34, KT88, 6L6, 6V6 . This could be what this tube is. The BiasMaster is available in an octal and noval version. okay sorry guys for asking too many questions about tube amplifiers (I'm really getting anxious with the tubes replacement ideas). You need to know where the bias pot is located. Eurotubes 9 Pin Noval Bias Probe Brand: Eurotubes. Some old schoolers don't think much of the bias probe method but we can tell you from experience that it not only works but it works very well. . It's in perfect shape never gigged and only used in a smoke free home. The amp is a push-pull, Class AB1 amp. This calculator uses the power equation. The higher the current the lower the plate voltage and vice / versa. But the individual dissipation was well below 50% of 76 mV. Also from Bob at Eurotubes: "The bias is adjustable on these amps and for all you guys asking "Where's the trim pot?" here are a couple pic's. My recommendation is to use a bias probe to set the bias and anywhere between 36 to 40mA per tube is very nice. My tubes are 6CA7 rated at 25 watts each. The 2204 is a 50 watt amp. Bias Probes - Eurotubes - Vacuum Tubes by JJ Electronic hot www.eurotubes.com. I won't quote the EuroTubes instructions again. You can see the bias probes Eurotubes makes here. 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, using our calculator. Just scroll down to the section: Gives a good visual as well as info written there too. Join date: Dec 2009 . It looks like I'll need to have the 65 DRRI bias when I put in the new JJ tubes. Then, enter the plate voltage in the next empty box. I bought the eurotubes bias meter. With a voltage drop of 3, I did his calculations (voltage drop / ohms) V7 is 3/61.7 = 48.62mA. Eurotubes Bias Probe $60 (Central Square ) pic hide this posting . Oct 29, 2012, 1:51 PM. that said they are amazing amps and with a little tweaking should be . Yes, the plate voltage will vary a little with the bias. The easiest solution is to install 10 Ohm 1 watt resistors in each tube cathode from the cathode to ground. Each tube sample used for comparison was chosen because it measured in the middle range of idle plate current draw at . .70 X 12 watts / divided by plate voltage will get you the current setting you need. 60% is another common choice. How many milliamps should a 65 DRRI be drawing? Solving for current, current = power/volts. If the bias probe breaks the circuit at the plate connection and inserts itself there you will read plate current directly without any screen current. best www.amazon.com. I read about the test points on Eurotubes.com and have jsut confirmed that they are not that accurate, assuming that a bias probe is the accurate way. It will take around 3 times to get it correct. When I go above 14mA I start to get a high pitched oscillating or squeal. It is the first thing I would buy for the amp. I seem to remember JJ having a plain Jane 6L6 a few years back. Then, go to the web page above and select the tube type. Picked the bias probe up to bias a new set of Eurotubes JJ tubes for a '65 Fender Twin RI. Many people bias amps by ear, only using the meter to make sure it's not set too hot. I am familiar with the probe you have from Eurotubes. I already switched the switch to 6l6 inside the amp. Those sound like SED Winged C EL34s which are really good tubes. This may not be the case for all of them but peavey now builds in china so QC should be subject to scrutiny. In the case of your amp, the results will show up in the "Class AB fixed bias" row. You need to turn the bias down in order to raise the idle current (down is up for bias today). My tubes are 6CA7 rated at 25 watts each. Hullo people, I have a complete set of JJ Telsa's coming from Eurotubes.com. Bias Calculator - Granger Amplification trend grangeramp.com. Bias the amp to whatever point sounds good to you. Changing the tubes of a Marshall JCM900 (EL34) Tubes are easy to change but you absolutely need to bias them once installed (power tubes). Retube™ Kits For Blackheart. 1. This could be what this tube is. He said that it's true that Rectos have a cold bias, but you must install a bias trimmer in order to get KT88's to work properly. In this video, we'll show you how to bias your tube amp using the TAD BiasMaster. Here's a bias calculator to help you bias those 6L6"S" tubes. They basically tell anyone that asks for the proper settings to take it to a licensed tech for service. 3.3k is a standard value, nothing cosmic about 3k exactly. It doesn't have an HUGE impact on bias calculation, however I see your point, especially since the plate voltage is already on the high side. Videos We will be using the 70% bias point. Retube™ Kits For Bugera. But, it really doesn't need to be exact. Around 40-70% dissipation is acceptable. I just checked my stock JSX bias at the test points and got a reading of 6mA (!). Just be very careful because you are dealing with high voltage. Yes, that bias point may not be optimal from a crossover distortion perspective, but if that is the tone you like, set it there and enjoy. Tube rated max watts, times 0.7, divided by the plate voltage, equal bias mA, each tube. https://robrobinette.com/Tube_Bias_Calculator.htm First, put the bias probe in one of your 6V6 slots. If you want to set an exact value for the bias, you need to iterate - check V, calc, set bias, check V, calc, set bias etc. The formula for biasing is the plate dissipation of the tube ( 14 watts for a 6V6 ) divided by the plate . 25 watts/425 volts = 59 mA. The bias setting will affect the cathode current. All explained in the sheet that comes with it, however (briefly) you divide the tube's maximum dissipation (in watts) by the plate voltage, multiply by .7, and that is your target for the bias. So for 6L6, 30 watt tube, in an amp with 400 plate volts, would be; (30 x 0.7)/400 = 52 mA per tube. I guess you can consider them a 19 watt . Used a few calculator sites.. This looks like the 6L6GC, but who knows? In a fixed bias amp, a constant negative voltage is injected to the grids of the output tubes while the cathode is grounded to the chassis. The ET "Pro One" Bias Probe is an "all in one" bias probe for octal tubes including 6V6's, 6L6's, KT66's, EL34's, E34L's, KT77's, 6CA7's, 6550's and KT88's. It is unique in the fact that it shows you both the plate current and plate voltage simultaneously and it is completely self-contained with no switches, knobs or batteries. Resistance from OT to V7 pin 7 is 61.7. Also included is a Eurotubes BIAS probe if you ever want to upgrade the power tubes. 7÷304=.0230 so 23ma current And then you swap the probe from tube to tube to check the bias off all four tubes. it'll get closer and closer every time. Not sure why some manufacturers bias so cold, other than to extend tube life. However this does not mean you have to calculate them at 30 watts to get out of crossover distortion. I've read the article from Eurotubes before and asked about using Kt88's in a Dual Rec from a local tube wizard and importer. Resistance from OT to V6 pin 7 is 75.6. 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T=27849 '' > bias help 6L6 models < /a > the bias down in order to properly the.: //www.amazon.ca/Eurotubes-Bias-Probe-Octal-Tubes/dp/B019PAVXPG '' > bias fucking YEAH bias by current and voltage tech for service to. Web page above and select the tube type, entered 354 plate.... While and re-check the bias pot $ 60 ( Central Square ) pic hide posting... When or if this item will be off power equation - Check Math... Current Made tubes get it correct was reading 457 plate voltage in early... Typed a really long reply and lost it in a cathode-biased amp, the is! With one tube, dial in the early V4B it doesn & # x27 ; t anything!
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