Should have done several double blind tests so that YOU the player didn't know which was which and THEN see if what you "heard" matched what was installed. Would have been easy to have had someone else switch out or not switch out the rectifiers and then try maybe 5 or 10 trials and keep score. Expectation bias could have been a factor here or not. I do know that people say the low end of a tube rectifier amp has sag. Was that evident?
There is no mystery about why is the cathode current higher than Plate current. As soo nas you have beaming quattrode or pentode you ill have this "phenomenon". In triodes they will have the same value. You got it already? Yes it is the screen current. Screen takes its own few mili Amperes current. So plus come from the plate from the output transformer and screen gets it's plus voltage from screen resistor or in the case of ultra linear tube amplifiers from output transformers screen tap. In both cases screens have usually smaller voltage than plate. On the tube you have only one connection to negative side and that is the cathode so that is the only place to go for both currents. So Cathode current is Plate current plus screen current. Usually screen currents are a few mili Amperes (3-5 for common output tubes). Also as soon as you do change bias current to new value you need to measure plate voltage that will correspond with new situation. You can't just measure palte voltage and think it is going to stay the same no matter what plate current we draw. It might be sort of logical to think like that because plate currents are mili ampers and that should not make much difference right? Wrong. 5 mA more will drop plate voltage considerably. It will lover it down. When you are lowering the plate current your palte voltage will go up. So you always have to measure both values. To be honest 60 percent is all you need nowadays with the fixed bias amplifiers. Your working currents will reach the maximum value with maximum signal even with 60 percent value. 60 percent is not sounding worse either. Especially not in cleaner amplifiers. Fixed bias amplifiers are more efficient and therefore it is easier and more clever to make a big amplifier with fixed bias power stage. Plus with NFB those big amplifiers will stay usable and not turn into the unplayable monsters. One thing is true we are talking about percentage of the dissipation power and not about the mili Amperes. Though we have to obey the tube datasheet and not overstep the maximum plate current. For example in some nice amplifiers designers use lover voltage overall. They do not care about how to use full power of the tube they are after the sound it self. So for example they do not go with 450V for 6L6GC but they opt to go with 320V. If that would be a cathode bias amplifier to reach 90 percent of maximum plate dissipation you might have to go more than maximum plate current. Then they do leave it at lower biassing current and do not achieve 90 percent. But if that sounds good who cares?? Who cares is it 20 or 30 or 40 watt amplifier? They are after the tone and not the power in such amplifiers. Plus if that turns out to be no NFB cathode bias amplifier with big output tubes and not that much power still it is going to sound bigger and louder than actual Watt numbers would make you think. Think VoxAC30. Not many people were complaining it is not loud enough for what it is. There is no shame in bringing your amplifier for tube change and inspection and biasing to proper tube amp tech. Amplifiers contain lethal dose of DC Voltage. Voltage that stays present in the filter caps even when the amplifier is off. Most of the amplifiers have discharging resistors but those take time to drop the voltage to safe levels. Plus there is a benefit to it. Proper tech will check everything and find if something is lose or broken and your amplifier will be back as new again. Ask me how I know? Well people brought me amplifiers with one issue and most of the times there are more issues. Like one amplifier came to me for tube change and biassing and checkup and I found out that presence cap have had broken hookup wire. Presence can't work without that cap. And that was in really good built boutique amplifier. Once owner got it back he called me after his first gig and asked WTH have I doen to it and how come it sounds so much better now :) Well new tubes, fixed presence and overall cleaning and check up and reflow of few spots does that. Just make sure that if you own really valuable amplifier you do not go to random guy. Often you see bad parts and parts that lower the value of the amplifier. Also if he will not call you after the initial checkup and before he fixes what he thinks needs to be done without consulting you about costs and what needs to be done I would avoid those people. Some people just assume you got money and you want everything done so they just go and do their stuff and charge you after it. You need good communication and pictures and even videos.
I love KT66, however in the dirty channel. the EL34 has more grit. I can always clearly hear and feel the 3rd-order harmonics in my EL34 powered amp, but I prefer the added noise.. A chacun son gout!
Don't forget about the infamous Fender hybrid fixed/cathode bias circuits, introduced around 1968 and quickly abandoned. I happen to own 2 of those beauties, a 1968 Bassman (AC568) and a 1969 Bandmaster Reverb (AA768). Both had the bias balance (output tube matching) pots, so I added a bias trim pot and use the output transformer resistance method to bias them.
These comments kill me. No matter how ac is rectified, as long as it’s smoothed, there is no tonal difference at all. Because the DC is the same. Difference? Amp manufactures manipulate the circuits to sell you shit. End of story.
Only an armature would trust an amps factory bias test points. Real pro's use a bias meter taking the results directly from the tube. I have proven time and time again the bias testing circuits build in amps are GROSSLY incorrect.
EL34 There is a notable difference in the midrange of an EL34. Online info says the EL34 has a more scooped midrange than the 6L6. I disagree. My ears has always found the midrange in the EL34 to be more pronounced, interesting, and pleasing to my ear. I own several high gain/ high power guitar amps that uses a 6L6 power section. Recently picked up a Magnatone Super 59 M80 that uses EL34's in the power section. The midrange response, especially when driven hard, is prominent and consistent with other EL34 power sections I've used and heard. Whether or not that sound is something you like or not is a matter of personal taste. Keep in mind that speaker selection and other factors can negate this difference or increase it. I'm not getting rid of any of my 6L6 driven amps. But I'm definitely not going to let go of my new Magnatone either. Each amp and sound has its place. They're all good.
No I couldn't hear The Difference at all Really and it's you should be able to because I have played a lot of old Transistor amps and I got Really Into tube amplifiers and I've played all sorts of news of bunch of different types of power tubes and it creates a lot of different sound even though they say it's just a pre amp tubes that shape the sound and it's b******* because even EL84 like a box doesn't sound anywhere near like EL34 which is Marshall. I played a lot of bands but they're really really old harmony brand 30382 rectify amp just 1 part 2 born premium 2 and 1 direct to fire 2 but it's just a few small components cause 1962 they didn't have circuit boards and all that garbage and when you open up it was really genius looking on the inside I've never seen anything quite like it but those things get consistent tons and sound quality where is I'm looking at spenders and other brand amplifiers are getting 8 and 9's at their best in song quality even my offenders super 60 which is one of the most liked amps out there because it's got 6L6 tubes which is rare for a fender . Most splendor tube stuff I've been seeing over the years this EL84 which I really don't care for and then there is the 6V6 and I really don't care for those either I guess there's a Castillo ray Vaughan type of blues type amp I'm got KT88 which are awesome but maybe a little too much for some people cause that's what the most didoordered like Marshall's and stuff that I've seen you don't see a lot of those around but it's like the guy from slayer or another really heavy bands used KT88I. I used 6L6 amplifiers The most, a lot of brands use it 11:26 boogie being one of the best really great. American sound. . It's very much like the EL34 is in Marshall those are the best sounds I think but little boutique amps sometimes they could make a yo 84 type power tube so good if you've got the right components and like the 2 rectifier ant pie head nobody is using what I consider roll 2 band fires you guys are doing solid State versus tube but yet you guys aren't getting the stuff out of it I get out of it I have taken a couple different types of analog distortions and I've cranked the sand up the song exactly like Norman green bomb spirit and Sky with session in the same amount of sag it's like a truly crazy psychedelic sound I've never knew anybody doing that I've seen a bunch of people playing Santana and I'm all sorts of cool stuff in these boutique amps I'm not seeing any of that kind of smoothness and then these videos and I was able to pull off in indigoted Devita by Iron Butterfly and a whole lot of other sounds that you can't get out of a guitar amplifier anymore. All these so-called newer tube amplifiers are not tubed to me they just sound like too transistor like ever since Steve I had and then I got stolen my 1962 harmony 303 a which harmony is a cheaper brand of back then generic stuff was still good because they didn't have the circuit boards and achieve components from China get equipment like the look almost all the batteries that take 9 V are garbage except for the first ones from the 1960s like the Russian bigmouth get here that on tons of recordings tons and tons of recordings through the 60s and then up again up through the 80s and 90s nineties had a huge reassurance surgeons though it's a band's like Bush and smash and pumpkins and also to them using Russian bigmouth instead of the distortion that comes on the amplifier which is f****** amazing on its own. Sadly they're still promoting and selling Marshall's transistor c*** letting people think that they could buy a martial stack for cheaper and it's really good on like a martial stack no sorry but transistors s*** is f****** garbage and you sit there and play it in a room by yourself without distractions you hear WHY people are willing to spend thousands of dollars for a Tube amplifier instead of transistor garbage that a lot of a started off with. This is like the third video I've seen today and it's still is it's not showing enough of the difference and this is the person who's owned these and I know what I'm a trip but I was getting that alarm and green bomb tone I just used an old analog boss turbo overdrive that weighs like 20 pounds and I crank that going into the amp I turned up all the knobs my volume knob turned up all the knobs on the pedal all the knobs on the app with the exception of volume just to use that the control of the volume and it was insane troopy sagginess nerves also all sorts of crazy other tones coming through there too that sounded familiar to me like psychedelic stuff futuristic stuff a little bit like Rock and roll fantasy by bad company is It's a Synthesizer guitar From the 70s used on that song and it's got a lot that analog crazy distortion sound . So I was able to whip the sag around just like that just unbelievable trippy and then I was able to twist the pedal around to do some other stuff and I was able to get the sound from in the gotta Devito by Iron Butterfly which is like a f****** buzz saw one of the solos he does in that song is amazing it sounds demotic sometimes you can't tell guitar what it is but yet psychiatrist doing some amazing ship that demox owned is solo people used to take acid and listen to that song it's supposed to be people to kill themselves and stuff the long 18 Minute version of Iron Butterfly and their song indegattadavida. is very demonic and very Powerful. . That's the first psychedelic and also the first metal sound there wasn't much dark metal type music ever before that the kink's being like going to talk back to using power chords at that time.
In this video, the example given is only standard full-wave rectification, not bridge, so only 2 diodes are required for that. Bridge rectification, as well as half-wave is mentioned around 2:14 but for the purpose of the video, we stick with normal full-wave. But yes, full-wave bridge would require 4 diodes (common in 100W amp power supplies), and half-wave would require only one (common in fixed-biased amps' bias supplies.)
Thanks for the informative video. What does it usually mean if the bias is drifting a lot? The bias on my two rock studio pro 35 amp test point varied from 0.054v to 0.074v during a gig after I set it at the recommended 0.064 initially! Also the test point feels soft with the multimeter probe almost like I’m stabbing it into play dough!! I’m so confused!! The tubes are new and quality matched tested ones so unlikely to be the cause.
So without know much about that amp, it looks like it’s a single test point shared across both tubes? So, when that’s the case, the accuracy isn’t going to be as good, because you have divide by 2 to get the average bias value for each tube. So, for example, if you’re see 0.074V on that single test point, it means that, on average, the cathode current is about 0.037V (or 0.037A) per tube. Bias drifting up or down before, during and after use isn’t uncommon by a small margin. But because it’s a single test point shared across the tubes, that could explain why it seems greater, because it’s the sum of a possible drift across both tubes. All that said, a couple additional things that could present higher-than-normal bias drift: 1. The tubes are new - which you said they are. Depending on the brand, they may need to be “broken in” for a few hours before they “settle down” into a more stable bias setting that requires less adjustment. 2. The amount of AC voltage at the wall can significantly change the amount of B+ DC voltage available to the amp. When that happens, the bias can drift as well and may any require an adjustment.
@@sonictoneamps thanks for taking the time to reply. It is a single test point for 2 tubes yes. On reflection I was thinking more along the lines of the bias pot / bias circuitry having a problem as I’ve never known the bias to drift anywhere near as severely as this in all the years I’ve owned and gigged the amp. Just worried I’ll burn out the tubes or cause a serious problem soon with it going above 0.070 which is the absolute maximum recommended current in the amp manual.
So if the tubes behave normally in other amps, then as you suggested- the bias circuit in the Two Rock amp may have some components that are failing and preventing a consistent negative DC bias voltage from getting to the grids. Probably best to have that checked out.
The only important difference is that with tube rectif you will never get AC into circuit( if tube goes off any current stops) if diode is damaged it is not so good
For me I think that a great amp as a pedal platform is a JTM45 clone amp with KT66, when using heavy distorted pedals I think that the KT66 sounds better in a JTM45 compared to the EL34. It seem like the KT66 have more dynamics than the EL34, some people would disagree with me on that but in my opinon the KT66 is super great tubes. I don't know any better amp for a pedal platform than JTM45 or some sort..
Actually I do agree with you that if you're using a JTM45-style amp as pedal platform, the KT66s would prob be the way to go. The JTM45 is a seriously underrated amp/circuit. FYI, the SonicTone '67 Special 50W attempts to capture both the JTM45 as well as the 1987 circuits all in one (and of course you can get with KT66s or EL34s)
@@sonictoneamps I agree, even if we are not talking about pedal-platform, the JTM style amps are great, its possible to crank it and get some really nice vintage tones out of it. And, and it's possible to get really clean tones from it also, which of course will make it a really good pedal-platform. I should build a JTM45 clone with the EL34 tubes and make a full side by side comparison ... some day.
@@HearGear Fun fact - years ago, the JTM45 amp circuit was my first build. I was drawn to it for some reason. Came out great. Had a pre-PI MV. I gigged with it a good bit, before stripping it down and using the parts to make the first '67 Special prototype.
Great video man. I have both ss and tube amps. I'll take my tube amp over my ss anytime. Tube amps have a more natural sustain clean or dirty, the ss when holding a sustained chord breaks and cracks before the notes die out at the end.
The differences are so subtle that you will never notice them on a stage playing with a band. In that case, I would always go with the SS rectifier, as they are more reliable. However, it should be pointed out that if you change your rectifier tube out for a SS version you will almost certainly increase the voltages supplied to the plate etc. of your tubes. Be careful. Don't cook your tubes. On my Vox AC30 CC2, the GZ34 puts out 352VDC with the amp running idle. With the SS rectifier, 374VDC. Way too hot IMO. Amps where the ability to switch in/out an SS rectifier is designed into the amp itself will be just fine, but be careful when swapping your tube rectifier out of your Vox, Fender, Marshall amp etc.
The El-34's were better with the gain, just had that great growl and compression in the midrange. The Kt-66 had a nice clean tone, but seemed a bit stiff and hard 😅 distorted.
I don’t think your calculations for cathode bias are correct. Plate voltage is with respect to cathode, not to ground, so plate dissipation Pd = (Va-Vk) * Ia.
There's one more important thing I forgot to mention about the Tube/SS rectifier switch. An additional benefit to having this switch is that if the tube rectifier goes out for some reason, you can switch to the SS rectifier and be good to go. This actually happened to me at a show one time with the RC30. At the time, I could only get my hands on a cheaper GZ34 rectifier tube and that's what was in the amp. I went through soundcheck without an issue, but when it was time to start the show, I flipped the standby switch and there was no sound. I knew right away in my head that the cheap rectifier tube had blown. I quickly switched to the SS rectifier and the amp came back to life and I proceeded to play an almost 4 hour show without any issue. Afterwards, I replaced that bad rectifier tube with a more robust one and haven't had an issue since.
The EL34 sounds good on this amp. The KT88 had a honk to it that would probably be a good choice for a live 2 guitar setup that would cut thru maybe a little better. Superb tones for sure.
SONICTONE< you didn't show how you measured or calculated the plates voltage drop? once your got the plates voltage drop * bias current = tubes power dissipation, how do you compute to get the tubes power dissipation?
Apologies - in the interest of time, calculating the voltage drop was glossed over when going over the XLS file and calculator. Around 13:40 I talk about how I probed the amp and got the B+ voltage of 431.2 and the plate voltage of 428.8. From there a simple subtraction formula is plugged into the XLS file to subtract the plate voltage from the B+ voltage to get the voltage drop (431.2V - 428.8V = 2.40V) After that, Ohm's law is also plugged into the XLS file (as well the example done in the SonicTone calculator) to get the current by dividing the voltage drop by the resistance of the primary winding: V = IR, flipped to V / R = I, so 2.40V / 46R = 52.17 mA [or 0.05217A] From there, those values are applied to the power formula (P = IV), so 0.05217A * 428.8V = 22.37W (which is about 74.57% plate dissipation of a 30W 6L6GC tube.) Let me know if that helps clarify things. Thanks.
@@sonictoneamps yes thanks. I think VHT Fryette Amplifications will measure the plates voltage drop using a DVM volt meter while the amplifiers is LIVE and also measuring the phase inverters balance using the oscilloscope. Its a very different way of biasing amplifiers which I'm not sure what this biasing technique is called because its mostly based on the plates voltage drop to balance them both out with the phase inverter. The 50s and early 60s used germanium transistors which have a lot of leakage current. The old biasing technique were called "leakage biasing" which you have to subtract and apply the leakage current into the biasing formula. Maybe you can make lessons about these other biasing techniques.
I fully expected to prefer the EL-34’s but I found the KT-66’s more pleasing to the ears than the EL-34’s. I’m a big fan of the Soldano sound so I’ve always liked the KT-88’s .. But for what I do (mostly small bedroom) they’re pretty unpractical..
I’m still learning so I have a question, isn’t the B+ voltage inclusive of the -voltage on the bias? As an example, the figures of the voltage be B+ and - bias voltage =512 volts in your example. I’m not saying I’m correct, genuinely interested to know. Thanks for the video and am learning a lot from them.
Thanks - appreciate the question. No, the bias voltage is its own separate, independent voltage supply. Typically, it's half-wave rectified in the negative direction to give you the negative voltage. Also, the value of the bias supply voltage is much lower, typically between -50 and -60 volts (it's not a high voltage like the B+ at 400 or 450 volts.) Around the 12:28 I probe the separate bias supply and show that the available bias voltage is about -62.8 VDC. The actually bias voltage at the grid is -41.6 VDC, which is what's needed to put the current flow through the tubes where we want it. Hope that helps.
Ahh ok that makes sense now. Appreciate the time you spent replying. I have a Mesa that needs work on it (all the time), local techs won’t work on the brand…. So I’m learning myself, have worked through two JTM style kit builds to get some experience…. And read several of Gerald Weber’s books, More for fun really. I find your type of content very helpful!
@@braddenyar3641Im actually taking his tube amp course right now (Gerald Weber). Really great stuff with a ton of info plus you can ask him questions as you go through it. Highly recommend
The power supply and rectifier portion of the schematic weren't included for space reasons. It was simplified to the basics for the purposes of this video. The rectification would be "off-screen" sending the B+ DC voltage into the primary center tap of the output transformer (on the left side of the transformer diagram.) The output transformer secondary is on the right side of the transformer diagram, sending the speaker load to the speaker jacks (with an impedance selector switch.)
That's covered in the video at about the 5:00 mark ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-xHKWrFLVRBc.html The B+ voltage difference is small enough that the amp doesn't need to be re-biased. In most cases, the difference in bias is about 3-5% plate dissipation at idle. So for example, on the tube rect, the PD at idle might be about 70% and on the SS rect, the PD at idle might be about 73%, which is within good nominal range.
U should try digging in rather than just strumming shit. More NFB gives more traction but limits immediacy, less is more explosive. Without control of the left hand u can't really notice anything. Good try though
Hey - so the master volume is post-phase. But the volume 2 control is pre-phase, so you get the best of both worlds. You can play around with the two and drive one more than the other. Or, you can turn the master volume all the up and have volume 2 act like the master volume on a 2203. This amp, like all SonicTone amps, is handwired on custom-designed, handmade turret boards. All transformers are Heyboer. Let me know if you have any other questions. Thanks!
@@sonictoneamps thanks for the reply.. you use all good quality stuff. I'm looking for the AFD tone without the post phase master... I don't like what it does to the high end and feel... slash's amps never used the ppimv. Do you think you will offer a straight modded 2203 circuit with an extra gain stage and the slash voicing (.1uf/10k) in the future?
@@marvelharris9540 well just as an FYI, the post-phase MV used is the type with the dual-gang pot (commonly called the "Lar/Mar" type) - and I find that to be the most transparent of the post-phase MVs out there. That said, while we don't do much customization to what's set in the current product line-up, if a customer wanted to switch the Snakecharmer's MV to pre-phase, we could definitely accommodate that. At that point, the Snakecharmer would be what you're asking for - more of a 2203 pre-phase MV circuit with the extra gain stage and Slash voicing
What I really want is a twin cabinet with this 64 Viber champ as the clean Channel and a deluxe as the dirty Channel with vibrato and Reverb and an effects Loop that would be the ultimate amp
Check out the SonicTone Clarksdale - that might be pretty close to what you're describing there. Really beautiful clean on channel 1, a nice dirty tone for channel 2 and a tube-driven FX loop. (no vibrato or reverb, but you can run pedals or external units through the warm tube FX loop to get you there.) All in a 2x12 combo cab. www.sonictoneamps.com/amplifiers/vintage-series/clarksdale
