John Broskie's Guide to Tube Circuit Analysis & Design

10 October 2015


2015 RMAF
“Great Expectations,” the title Charles Dickens gave his novel, was not what I felt, as I drove down to the 2015 RMAF held in Denver. Realistic expectations are my goal. I expected huge crowds, long waits at the elevator, thumping but soggy bass notes and blaring highs, clueless sales reps, and music tracks found only in audiophile music collections: the usual stereo show, in other words. Surprisingly, I was surprised. Smaller crowds, the overall sound much improved over previous shows, fewer sales reps and more owners and designers, and a greater variety of music—truly a pleasant surprise.

If you attend a car show, your expectations will be met if you see fabulous cars and fine-looking women. The last thing that you could expect to encounter would be roaring engines, plumes of hot exhaust, and peeling tires, just as you would never expect to hear gunshots or smell gun-smoke at a gun show. Stereo shows are different, as we do expect to see sumptuous stereo equipment and hear seductive sounds. My own expectations are lower, as seductively splendid sounds is a bit much to ask from mausoleum-sized hotel rooms, cheaply-made rooms stuffed with more people than a subway car at rush hour. My take has always been that if I do hear good sounds, then the equipment must be good; but if I hear bad sounds, then the equipment might still be good, but hindered by the show environment. Well, at the 2015 RMAF, I found the general quality to have improved over my past four visits. The interesting question is: Why?

First answer: fewer attendees and fewer exhibitors. The waits at the elevators were brief, in sharp contrast to the first RMAF I attended, where I had to wait through two cycles of unloading and loading the elevator before I could enter it. Not this time. Saturday, the second day of the show seemed particularly sparsely populated compared to past shows. This sliver-lined cloud had it dark shadow unfortunately, as I had enjoyed past RMAF Saturdays’ healthier mix of younger men, women, and children. Surely good sound can be enjoyed by everyone. What can be drearier than an all-male event? Women civilize; they bring out the best in a man and suppress his worst inclinations. In previous shows, exhibiting rooms were separated by but a single quiet room. This time, the gap seemed bigger, with two or more rooms in between. This was a welcome feature, as less bass seeped from room to room, making for a clearer sound.

Second answer: better music sources. This time, no one seemed troubled by recalcitrant and unmanageable computer music servers, unlike previous years. Indeed, computer-based music servers have arrived. In the Vanatoo room I beheld a small miracle, a $100 computer music server that sounded great.

Vanatoo had partnered a $100 WinBook tablet with their small active speakers, Transparent One model, which contain their own DACs and power amplifiers. The touch-screen tablet then streamed the digital music data through a USB cable to the loudspeakers. That was it. The sound was more than good; indeed, it would make a fine bedroom, studio, kitchen, or dorm room system. Add a BlueTooth keyboard and you have the ultimate remote control. No, you are not likely to give your Quad or Magico loudspeakers to Goodwill, but the Vanatoo $500 pair of loudspeakers with the $100 tablet made a big authoritative sound that belied both its cost and size. Armed with active equalization and passive radiator on the rear of the speakers, the Vanatoo Transparent One powered small speakers do not sound small.

In spite of the recent taming of digital music sources, analog—in the form of LPs—poured forth in many rooms. I should have kept count, but my guesstimate is that almost half of the rooms sported turntables. LPs engage the ear—perhaps for the wrong reasons, but even modest turntables and inexpensive cartridges prove engaging. Wrong reasons? Our prehistoric ancestors had to instantly discern which sounds could be safely ignored, such as crickets chirping, whereas a twig snapping could proceed death. Perhaps, LPs, with their unexpected ticks and pops, tickle that part of the brain that deals with important sounds, forcing us to pay more attention. In addition, LP playback is live event, as the needle traces the micro wiggles; in contrast, our brains know that digital music is canned and dead as the tuna in its can. Another possibility is that the phono cartridge's poor high-frequency separation might prove beneficial, rather than deleterious to stereo reproduction, as less separation is needed with high frequencies to create a believable image. (See "Image Movement in Stereophonic Sound Systems," by F.O. Edeko, Electronics World, Oct. 1998) Whatever the cause, LPs sound great and I was happy to hear them at the RMAF.

Third answer: the harsh economy has culled the silly and prevented the only tangentially-related audio companies from showing. No doubt, some very fine audio companies have also died, and their presence was missed. In contrast, during booming times, many companies would show, in spite of having little to offer the serious audiophile. For example, in years past, car stereo and ceiling speaker makers displayed their products to a largely indifferent audience.

Conclusion: Two conclusions actually. You should attend next year's RMAF. Bigger is not necessarily better. A smaller RMAF might be the optimal size for such an event. Second, I am glad that I went. Yes, there was a chance that I wouldn't.

Pleasant Surprises
Early on, I was surprised to hear so much quaffable sound, i.e. readily pleasing sound that invites continued and long listening. For example, Alta Audio's Rhea speakers produced an eminently quaffable sound.

The Rhea is relatively small but big sounding. The ribbon tweeter did just what we expect a ribbon tweeter to do: sound super fast and detailed. The single 7 inch woofer sounded far larger and more powerful than its modest size would seem to imply, no doubt due to the transmission-line loading. Combined, these two drivers created an effortless sound that contradict their low price of $4495 for the pair, sounding far more expensive.

Another truly impressive speaker was the LRE Audio Laura speaker. I had only negative expectations as I entered LRE Audio's room, as I beheld a $100 class-D power amplifier and tall rectangular speakers pressed against the rear wall. Definitely a pleasant surprise. The speaker is a two-way system with a crossover of 180Hz. Two 12 inch woofers are used with a single 4-inch mid-tweeter. I would have bet money that it wouldn't sound good and I would have lost my bet, as they can sing. Think about it: since the single driver handles the overwhelming range of frequencies, no discontinuities can occur in the all important midrange, giving the speaker a seamless characteristic that is only matched by fullrange speakers and headphones. At $1900 the pair, they should be on your short list of candidates.

Once again, I had super low expectations as I walked into the Odyssey Audio's room, as a disco light show sparkled across the dark room. The Kismet Liquid 2.5 loudspeakers, however, stunned me with their amazing imaging. Jaw-droppingly good. As my eyes adjusted to the dim light, I could see the fairly tall speakers, with non-parallel side walls, beautifully made with gorgeous wood veneers. To my ears, they sound far, far more expensive than their modest $6,000 the pair price tag would seem to imply. Considering that the Kismet speakers were mated to relatively inexpensive equipment, they are even bigger bargains. Odyssey Audio's room at the RMAF proved two things: you can create magical sonic soundscapes in even a small hotel room and you do not have to be in the top 1% to enjoy the top 1% of sound.


The Year of Electrostatic Speaker
Speaking of the top 1%, Muraudio's omni-directional electrostatic speakers cost a fortune and are worth it. At $58,000 the pair, their Domain Omni speakers should thrill and they do.

They fill the room with a spacious, yet specified stereo image. Standing in between the speakers, my back facing the rear wall, I still heard an accurate stereo image—behind me, as if I stood on a stage and the band played behind me. Eerie, inexplicable, but satisfying. If only I had the money.

Speaking of money, Dave Shagle has built bi-ammped, direct-drive, tube amplifiers into a rebuilt pair of Quad 57 speakers. The resulting sound was at once familiar and cutting edge. It was as if the British Quad speaker had a taller, more handsome, more muscular American cousin, yet a strong family resemblance remained. Oh yes, money. If you have gobs of it, contact Dave for more details. He is willing to build another much improved 57 to match your decor.

Moving down to reality, at least my reality, I was once again mightily impressed by the Sanders Sound Systems hybrid electrostatic speakers. But first let me go off on one of my signature tangents.

Audio needs something like John Rawl's "Veil of Ignorance," which is a thought experiment wherein you judge any given social construct's morality by the thought that you could be be born in to it randomly, perhaps at the top, perhaps at the bottom. No privilege and preference confirmed by famous and rich parents. No blame or burden imparted by poor parents or the wrong skin color or sex or religion. Well, audio sorely needs a veil of blindness. For example, rather than grant the use of the large ballrooms at the RMAF to large companies with deep pockets, the RMAF should hold continuous listening sessions in one ballroom, with the gear in use behind a sonically transparent curtain. A large lazy-susan of sorts could be implemented, so one of four systems would face the audience. The same tracks would play all day and all that the audience would know is that system 1, 2, 3, or 4 was playing. Nothing else. My prediction is that there would be many upsets, as the sonic race would not always belong to the most expensive system. In addition, such a blind auditioning would undo visual prejudices.

Okay, returning to the Sanders hybrid electrostatic speakers, they look like hybrids, so I expect them to sound like hybrids. They don't. I have tried to hear a sonic discontinuity between the electrostatic driver and the woofer, but I cannot. They sound like a full-range electrostatic, in spite of what my eyes tell me.

If you have read Roger Sanders many articles in Audio Amateur and Speaker Builder magazines or read his book, Electrostatic Loudspeaker Design Cookbook, you know that he knows what he is doing. I had a long talk with Roger this time at the RMAF and he was kind enough to share some of  his knowledge with me, which I much appreciated. Returning to the veil of blindness, his speakers would do quite well in such a setup, as they sound great. In fact, they are relatively inexpensive. At $15,000 the pair, are you serious, John? I am. Here is why; the speakers include the digital crossovers and high-quality, 900 watt, class-AB power Magtech amplifiers. Let's be honest: it is relatively easy for most audiophiles to make a great-sounding speaker sound bad by pairing it to a mismatched power amplifier or electronic crossover, something that is impossible with Sanders' hybrid electrostatic speakers, which come with their preset crossover and power amplifiers.


Tubes at RMAF
Like LPs, tubes were ever present. If the Oxford English Dictionary ever gets around to defining high-end audio, the definition will have to include tubes in its framing. I had a great time talking to Roger Gibboni of Rogers High Fidelity. He knows his stuff and he isn't shy about sharing it. By the way, if you want to buy a collectable audio classic that is modern, look into his product line. For example, his A-1A phono preamplifier drips with retro cool and high-tech build.

All the Rogers power amplifiers sport meters and some come in a fire-engine red chassis.

All of their equipment is hand-built and point-to-point wired in New York state. Impressive.


2015 Can Jam
At the other extreme, the Can Jam headphone show within a show held at the RMAF allows you to hear at the show what you would hear at home. The Can Jam grows larger each year and it over spilled its large room, pouring out into the hall in front. Here is where you will see the highest concentration of young people. The young love headphones—with good cause, as headphones do not cost more than a car and they do not require 100lbs power amplifiers or understanding roommates or neighbors.

I heard $5,000 headphones, but I was not that impressed, alas. The best sound I heard was at Cavalli Audio's booth.

I wanted to dislike the Abyss AB-1266 Deluxe headphones due to their size, cost, and appearance, which looked to my eye like some medieval torture device. I couldn't, as they sound fabulous connected to Cavalli Audio's balanced amplifier.

By the way, although Alex Cavilli and I have e-mailed, this was the first time I had met him in person. I am glad I did, as I had a great time talking to him audio and things not audio. He was kind enough to introduce me to George Cardas, with whom another great conversation ensued.

Many of my friends make the mistake of bypassing the Can Jam portion of the RMAF. A big mistake. For example, one of the most impressive pieces of equipment was located there. Soekris Engineering showed their DAC 1101, which holds a discrete R-2R sign-magnitude DAC in a cute little headphone amplifier.

This is not your everyday, high-end audio $5 DAC, as it uses 200 discrete resistors. Be sure to check out Soekris' sister webpage.


Why I Hate the Best Sound Awards
Meeting with friends after the show always ends up with the same question: What was the best sound at the show? Best for what? is what I immediately wonder. Best for jazz or rock or string quartets or punk or rap... Best for my mood or my budget or listening room... In addition, silver is often preferred over gold; and second best proves better than best. A better question might be: Which sound system would you most like to take home with you?

This question came to me after I had listened to over 15 minutes of Vinni Rossi's setup. The reason the question came to mind was that I already knew the answer, as I was listening to it. His battery and switched-mega-capacitor equipment sounded so quaffable, so pain-free, so pleasing that I didn't want it to end. This is rare, all too rare. Hi-Fi sound often dazzles and fatigues at the same time. The sound in Rossi's room was different. It was involving, inviting, and compelling. Vinni is certainly on to something important in his severed connection to the wall socket.


Next Time
Many new developments.


User Guides for GlassWare Software
Just click on any of the above images to download a PDF of the user guides. By the way, all the links for the PCB user guides shown at the right now work.

Since I am still getting e-mail asking how to buy these GlassWare software programs:

For those of you who still have old computers running Windows XP (32-bit) or any other Windows 32-bit OS, I have setup the download availability of my old old standards: Tube CAD, SE Amp CAD, and Audio Gadgets. The downloads are at the GlassWare-Yahoo store and the price is only $9.95 for each program.

So many have asked that I had to do it.


One day, I do plan on remaking all of these programs into 64-bit versions, but it will be a huge ordeal, as programming requires vast chunks of noise-free time, something very rare with children running about. Ideally, I would love to come out with versions that run on iPads and Android-OS tablets.





Kit User Guide PDFs
Click image to download

BCF User Guide

Download PS-3 User Guide

Janus regulator user guide

E-mail from GlassWare Customers

Hi John,

I received the Aikido PCB today - thank you for the first rate shipping

Wanted to let you know that this is simply the best PCB I have had in my hands, bar none. The quality is fabulous, and your documentation is superb. I know you do this because you love audio, but I think your price of $39 is a bit of a giveaway! I'm sure you could charge double and still have happy customers.

Looking forward to building the Aikido, will send some comments when I'm done!

Thank you, regards,


Mr Broskie,

I bought an Aikido stereo linestage kit from you some days ago, and I received it just this Monday. I have a few things to say about it. Firstly, I'm extremely impressed at the quality of what I've been sent. In fact, this is the highest quality kit I've seen anywhere, of anything. I have no idea how you managed to fit all this stuff in under what I paid for it. Second, your shipping was lightning-quick. Just more satisfaction in the bag, there. I wish everyone did business like you.

Sean H.

High-quality, double-sided, extra thick, 2-oz traces, plated-through holes, dual sets of resistor pads and pads for two coupling capacitors. Stereo and mono, octal and 9-pin printed circuit boards available.

   Designed by John Broskie & Made in USA

Aikido PCBs for as little as $24


Only $9.95
to start designing
tube-based crossovers
and much more...

TCJ Filter Design

The Tube CAD Journal's first companion program, TCJ Filter Design lets you design a filter or crossover (passive, OpAmp or tube) without having to check out thick textbooks from the library and without having to breakout the scientific calculator. This program's goal is to provide a quick and easy display not only of the frequency response, but also of the resistor and capacitor values for a passive and active filters and crossovers.

TCJ Filter Design is easy to use, but not lightweight, holding over 60 different filter topologies and up to four filter alignments:


While the program's main concern is active filters, solid-state and tube, it also does passive filters. In fact, it can be used to calculate passive crossovers for use with speakers by entering 8 ohms as the terminating resistance. Click on the image below to see the full screen capture.

Tube crossovers are a major part of this program; both buffered and un-buffered tube based filters along with mono-polar and bipolar power supply topologies are covered. Available on a CD-ROM and a downloadable version (4 Megabytes).

Download or CD ROM
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