Here is an interesting circuit that I found in my notebooks... Single-Ended Power Buffers Note that there are no cathode resistors on the 12AX7 and that the input transformer is floating, with no ground connection! We all know what a single-ended amplifier is. The simplest push-pull V-to-I amplifier would be one that used only two active devices. A quick recap: my preferred phono stage arrangement is to nest a passive RIAA EQ between two gain stages. Otherwise, why bother? Why? This isn’t easy to do, as very little has been written on the topic. The next non-phase-inverting tube circuit that comes to mind is the cathode-coupled amplifier. We near the Tube CAD Journal’s ten-year anniversary and during that near decade I have written much on just about every tube-related topic: a veritable omnium-gatherum of tube technology. Taking the heater’s transformer’s winding and rectifying it, however, is not the same. In the last post, we saw a patent from NASA for Manuel Kramer's "Electronic Amplifier with Power Supply Switching," which was a class-H amplifier push-pull power amplifier. a brilliant move; "?" Ideally, our buffers should only be run under class-A operation. How do we proceed? Thanks patrons. Grounded-Cathode-Amplifier Disambiguation But the problem with a cathode follower is that due to the large amount of degenerative negative feedback is intrinsically employs in its operation, it doesn't add much harmonic distortion. Soon after creating the Broskie OTL, my first thought was, How good a headphone amplifier would it be? So far, my overview has been fairly abstract, as I wanted to get the circuit’s functioning across. Work, gobs of work. E Aikido noval stereo PCB, which holds two polypropylene-based RC filters, one for each channel, that I decided to create the PS-20 power supply. I can't help myself. 21 Nov 2015. SE MOSFET Buffers/Amplifiers Now that we have mentally stretched, we can move on to an interesting Circlotron design I created. Well, that is not what I did. And I have finally built one, as shown above. PDF Version One potential downside to the crossover is its incompatibility with bi-wiring—unless you are willing to think outside the loudspeaker enclosure... Three-Way Series Crossovers 28 Dec 2004, Murray Amplifier The big downside to the grounded-grid amplifier is its low input impedance. Odd Experience 18 Apr 2015. It holds two sets of output coupling capacitors and two B+ RC filters, one per channel... Aikido Cascade In previous posts on the super-triode concept, I have mostly shown potential single-ended amplifier designs. I made a few changes to the Aikido noval stereo PCB, so it is now in revision F. The most important change is the return to the option of building an Aikido push-pull headphone amplifier... New: Dual/Bipolar LV-Reg PDF Updated 04 May 2005 15 Jan 2008, More Classic Articles? Transformer-Coupled Power Buffers Balanced Outputs Higher-Ratio Impedance-Multiplier Circuits So, how do we go about turning the tube Gomes amplifier into a solid-state equivalent? The e-mail I have received lately both encourages and discourages. The idea behind this headphone amplifier was to use a single-ended FET input buffer to lend some 2nd harmonic enrichment and use robust output transistors that would not seem out-of-place in a 60W power amplifier, so a heavy class-A idle current (250mA per channel) could safely be run... Music Recommendations: Okay, I admit it: have soft spot for American country music—not all of it, of course. First of all, I must say that asking for a design procedure is in itself something of an accomplishment, as most solder slingers go about in a strikingly different way. About two years later, when out of money, I opened the book and, like a gift from heaven, the bill tumbled onto my face. The following circuits may look like one of Nelson Pass’s Zen amplifiers, but they all differ in one major fundamental way: they push and pull, whereas the Zen amplifier only pulls: What is the sound of one MOSFET output device? I have covered this mode of operation many times before; check out posts Number 20 and 22 and 284 and 285. While still on the topic of OpAmps, I cannot resist telling a story. I was hoping that this first post of 2018 would sport a new wider format that would automatically scale to the viewing device. The following circuit is one that I came up with over a decade ago. 05 Feb 2020. Santa Baby is a good example. John Broskie 's Rant 10 Nov 2004, Solid-State E-Mail By the way, we can use this PNP-cathode-bias technique to cathode-bias a grounded-cathode amplifier. RMAF 2016 Reality Check The idea here is that a differential current-output DAC can work into two 60-ohm resistors, which will develop enough just voltage gain to allow a 12AX7-based differential amplifier to bring up to a useable voltage swing.... No, what had so troubled him was the dawning comprehension that we would soon run out of all the possible acronyms... First, I believe that I rather jumped the gun last time by revealing the I-to-V Moskido amplifier, as that design was a push-pull type and I should have begun with only single-ended MOSFET-based designs, so let me backtrack a bit. Sneak Peek of New PCB A reader sent me the following schematic of an all-tube phono stage designed by Fred Nachbaur. 18 Aug 2012. I listened to an RMAF attendee being scolded for fancying that wire—interconnects, loudspeaker cables, and power cords—are the MOST important part of a sound system. Since the Tilt Control is passive, it does not require a power supply. I can see his point, but probably for different reasons. For our purposes, namely, using a solid-state power buffer after a vacuum tube voltage amplifier, low distortion is primary; with low-output impedance and freedom from feedback coming second and third. Audio must live on the crumbs that fall off the technology table.”... Recap Time In my last two posts, I described how I had made a sonic test of the new Unbalancer Two with regular single-ended, unbalanced input signals, such as those produced by FM tuners, CD players, and DACs—basically any signal source that holds RCA jacks. Nor have I indulged in Colorado's new marijuana frenzy. Well, now you can add class-AB + C Circlotrons to the list.... Class A + AB + C Circlotron Amplifier I was impressed with balanced XLR cables at the time and I found much to prefer over unbalanced RCA-terminated interconnects. Well, every time I think that I cannot say anymore on a particular circuit, I discover something new to write about; so it is with the cathode-coupled amplifier.... I must admit that I quickly wrote that blog entry, so it was a bit too brief, too formless to avoid some misunderstandings. If I could keep only few books about tube electronics, this would certainly be one of my choices. Triodes require a high cathode-to-plate voltage to summon forth a flood of current. 03 Apr 2016. Why? I had an experiment to perform with two of them, which I had mentioned in post 384. Back in blog post number 228, I covered the SRCFPP topology. The reason behind this is that you are free to whichever power supply you wish: tube rectification form some, regulated solid-state high-voltage for others... Push-Pull Tube Operation Having just gone through all the work of building the 12SX7-based headphone amplifier and having just written all I've written, I must confess, that the Octal All-in-One LSA/HPA would work much, much better as a line-stage amplifier. It was a three-way design, with electrostatic woofer and midrange and a mylar dome tweeter, which I believe was made by Philips. Last time, we saw several possible 6C33C-based OTL power amplifiers, both hybrid and pure OTL, both single-ended and push-pull. DGNNAHA, Once Again The following design is much like the previous design, as it, too, includes two stages and no phase inversion at the output. For example, reasonably priced audio equipment. Truly uplifting... The first problem can be eliminated by doing away with one of the feedback loops... Hybrid Triangle Circuit 15 Aug 2018. I know that I have already lost many readers, as they do not feel comfortable with solid-state devices; period. The RIAA equalization is actively implemented.... Music Recommendation: 31 Dec 2013. The schematic has been corrected. What I heard was precisely what I wished existed, but never had encountered, a sincere modern composition that both sounded centuries old and yet younger than tomorrow. Letters from Acme Tube Design These amplifiers held more glass than my wallet could bear to contemplate. I then reply that it cannot, but it is used nonetheless... E Aikido noval stereo PCB, which holds two polypropylene-based RC filters, one for each channel, that I decided to create the PS-20 power supply. This will be welcome news to many audiophiles, particularly for those who need to convert their DAC's balanced output to an unbalanced output signal, as the Unbalancer can readily receive its balanced signal. Aikido Noval Rev. Second, bipolar power supplies often allow us to place the output at (or near) ground potential, which is why 99.9% of solid-state power amplifiers use a bipolar power supply. By nature, I am an essayist, not a diarist Post-It-note scribbler... Why not? A few posts back, I described transistor-based phase splitters for use in OTL amplifiers. I imagine that somewhere atop a seldom-traveled mountain or deep inside some unruly jungle there people who do not know that the World’s economic fortunes have turned bleak. More About the 24V Aikido So, I set upon seeing how to implement these electronic functions with tube circuitry and my first efforts were producing far too complex topologies that required far too many tubes... Current-Output Amplifiers Desktop switching power supplies usually stop at 52Vdc, with 48Vdc being the more commonly encountered voltage limit. Here is the quick summery from Analog Devices.... Auto-Bias Hybrid Single-Ended Amplifier In the schematic below, we see a BUZ906 attaching at the triode’s plate resistor. So, next time we will see circuits like the following.... 18 Mar 2006, European Triode Festival & Thanks to Eric Barbour and John Atwood for the following: This setup can be made to work, but requires huge effort, as the feedback resistors and capacitors define a crazy load in themsel... Second Gain Stages Since reading about the 6H30 being available in an octal envelope, I have been eager to get hold of a few to try out. And it does provide gain, making the voltage amplifier answer partially right. Like so much that is Italian, the design and layout are gorgeous, displaying a refined elegance and an extravagant and opulent use of white space; just a decade later, this near classical clarity of design layout will succumb to the drug-induced altered consciousness of the late 1960s.... More Split-Load Phase Splitters Normally, the capacitors would arrive in a few days. An output of 8Vpk into an 8-ohm load results in 4 watts of power, as does 11.3Vpk into 16 ohms, as does 5.66Vpk into 4 ohms. Well, another possible use would be to create an electrostatic headphone amplifier... Music Recommendation: It's the All in One PCB, which holds two Aikido line-stage amplifiers and it includes the heater and high voltage B+ power supplies—all the same PCB. No, what I am halfway to is to writing my post number 1,000, and it has taken me 21 years to get to post 500.... Found Time My first draft is my final draft. The totem-pole input stage offers some signal gain and allows stereo blend and balance control. The following design is a fairly old one. ... PS-3: High-Voltage If I had to pigeonhole their musical genre, it would be in jazz, but we can easily hear classical, folk, and rock songs in the mix.... What the Heck is Aikido Anyway? One thing that I love about OpAmp circuits is being able to hook up two 9-volt batteries and run, with just a single bypass capacitor across the positive and negative power supply pins—no lethal voltages and no heater power supply to worry about. He didn't expect big watts, just sweet sound... 6C33-Based Push-Pull OTL Super high-wattage tube power amplifiers can be built. Having just written the above section, I must quickly announce that the following design idea is not limited to power buffers; it just that power buffers were what I was examining when the idea came to me. We could fairly easily build a small box that would hold a passive filter, made with air-core (or common-mode) inductors and film or ceramic capacitors; such a box would be placed in series with the Duet and its switcher wallwart. If you don’t know what the attenuator is all about, you didn’t follow the link to the GlassWare Yahoo! The 12SX7 is a wonderful tube, but like any decades-old NOS tube, you can encounter functional problems; nor are they cheap, and this tube is much happier with loads greater than 300 ohms. One trick we can use is to configure the output stage for push-pull operation which will effectively quadruple the maximum output power, bringing us to a staggering 4W.... 16W 6C33-Based OTL with External IMC Simple amplifiers usually make extra demands of the rest of the system and their performance is usually compromised in a few key specifications, such as output impedance, input impedance, frequency response, and distortion. I have played with the 6H30 before and I was never overwhelmed, in spite of its stellar specifications. In fact, although I am sure that six-way loudspeakers are made, I don't remember seeing any. How dare I even consider displaying anything so irreverent as a single-triode Circlotron? Perhaps when the economy seems to be improving, audiophiles gravitate towards extravagant single-ended amplifiers; but when the economy seems to be heading south, they become interested in more efficient class-AB, push-pull designs.... Single-Ended Super-Triode Amplifiers The BCF receives a balanced input signal and converts it to an unbalanced output. Bob Prangnell, long-time TCJ reader (a “tcjer,” what do you think of the term?) Cathode-Coupled Circuits I have mentioned my experiments with remote feedback here several times before, see Blog 183 and 184. Amazing. A floating power supply is one that is not grounded. No, not always; sometimes more is, indeed, more. It is an auto-bias/driver circuit for solid state output stages, mostly MOSFET-based output stages.... Back to the Aikido Mono Solo PCB Second, the 6N1P should be run much hotter than a 12AX7, 5mA per triode, not the 1mA that a 12AX7 can get away with. A quick scan of DIY postings on the web reveals that the National Semiconductor Overture™ series of OpAmp power amplifier all hold the same Achilles’ tendon: heat dissipation. 10 Feb 2009, New and Slightly Improved Or, the small rooms at the RMAF better suit the small speaker, which do not require the expansively large rooms to breathe that the big loudspeaker require. We started with the White cathode follower, then the Taylor amplifier, then the Taylor source follower, then the Macaulay amplifier, and then the Broskie-Macaulay amplifier, each defining a signpost on the same road. You know this type of enthusiast, as he owns scores of tweeters, dozens of midranges, and many woofers. One possibility is that most classic albums are quite good. Note the B+ voltage, which is substantially lower than in the pure-tube version.... More on the Broskie Buffer A few months ago, I was pondering how add another sonic control to an ultimate tube-based headphone amplifier. This small oddity can be exploited by using the pass tube’s cathode voltage to drive the pentode’s grid number 2, thereby adding a DC feedback loop, which will help keep the DC operating points in line, as the tubes age or are replaced.... Solid-state, high-feedback power amplifiers come close. The obvious choice is a FET (or depletion-mode MOSFET), but a transistor or MOSFET could also be used.... Creole Mass... Unlike triodes and pentodes, transistors exhibit a sharp turn-on voltage, as shown in the graph below.... I-to-V Triadtron Both will be missed greatly. As I stated at the beginning, most Ultrapath power amplifiers are single-ended affairs. 18 Feb 2020. Driving 8-ohm loudspeakers, or even Grado 32-ohm headphones, will take much more muscle. 27 Aug 2011. In my previous post, I promised the unveiling of the new GlassWare Tilt Control. What if you do not own a hard-drive-based music system? Mar 22 2014. they asked. Throughout my long life, I have run into weirdoes—or at least to me seemingly weird people. What is that in the image above? Since that last circuit departed from the theme of strict cathode-coupled amplifiers, I might as well go over the cascoded differential amplifier, which at least holds two coupled cathodes. If 100Vdc appears at one end, 100Vdc will appear at the other end all the taps. In other words, we can always backtrack to a safe, conventional 8-ohm load if we wish. And Blacks living elsewhere have created an equally impressive long list... In my last post, while on the topic of grounded-grid amplifiers, I showed a battery being used to bias a triode's grid to a voltage below ground. Kick-Butt Cathode-Coupled Line Stage
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