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Old 6th August 2019, 05:27 AM   #1
vkung is offline vkung  Canada
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Join Date: May 2005
Location: Vancouver BC Canada
Default Review of TU-8600R from William Calkins

Review of the EleKit TU-8600R a power amp using 300B tubes
- Bill Calkins

This bit of visual verbiage is written especially for those folks who really want to hear music beautifully reproduced in their home or workspace and would like to build the equipment they use to listen to it. If you have lots of spare cash, it’s easy - sign the check, open the boxes, connect the wires - enjoy! If you don’t have lots of spare cash, read the reviews, plan carefully, buy with on a money back satisfaction guaranteed basis. Now, if you don’t have much cash, or refuse to spend it, you can build great audio gear for one tenth or so of the price of the heavily advertised fancy gear. For instance, a company whose name features the letter “S” twice advertises their model M3 at $1699.99 a pair, ready to go from the factory. This is a three way design with a soft dome midrange driver and a flat panel tweeter. Both drivers have neodymium magnets. The woofer is a 6 inch woven kevlar unit with a phase plug. The drivers alone (from Hi-Vi) will run you $263.

If you buy the kit version, the bill is $289.99! The kit saves you the $1410 the company had to charge for the labor of the folks who cut the wood, built and finished the cabinet, put the parts in the cabinets, package the final product, put them into boxes, and let UPS know they are ready to be picked up for delivery.* And the company has to make a decent profit. Would you like to earn $1410 for a few evenings work in the garage or, if you live alone, on the dining room table? If you can assemble IKEA furniture, you can build this kit. Less than $300, if you don’t put a lot of money into the finish on the cabinets. Not Bad! This tells you a lot about the equipment business.

*(Hint: replace all the capacitors in the crossover with Mundorf units with similar ratings. You can thank me later.)

For potential DIYers, speakers are the place to save BIG $$ in equipment. Check out the Linkwitz Labs web site. Be thou informed.

When you started reading, you expected a review of a tube amp kit. It’s coming.

Solid state vs tube amps - is there really a difference? Among well designed units, yes. Now, let’s get real - tube amps cost more. They are much less efficient. They get hot, the heat is not good for them. The tube cages keep the heat in. They are heavy. But they might keep you food warm while you answer the phone or search for that parts catalog.

You can buy a fully populated circuit board with two 65 watt amp chips on it for $30 or so. The chips themselves are $11 retail. Add a power transformer, input and output connectors, a cabinet, and a power cord. Music happens! If you know where to buy your parts, you’re out for less than a dollar a watt! How does it sound - great! For pennies more you can have 85 watts per channel. Solid state amps are cheap, and easy to build. A well know Canadian outfit uses the same chips in their well reviewed amps.

You can get a well reviewed (made in USA) kit 50 wpc power amp kit for under $400 that sounds wonderful. Nicely packaged, good instructions. Same amp chips, regulated power supply. We’ll compare it’s sound with the EleKit TU-8600R soon. You probably know the EleKit’s price is between $1200ish to $2700ish depending on what options you choose. There is no point in buying the least expensive version. You will have all the tube amp’s weaknesses (although with EleKit they are few) and none of its glories.

I agonized over buying the EleKit TU-8600R for over a year. (My income is from a Social Security check.) Look at the photos in the April 2019 issue of Stereophile. Where have you seen transformers like that? Of course, that photo is of the top of the line version. But the parts in this kit are the finest available. Look at the transformers on the Rogue Cronus Magnum III power amp. Although the Rogue unit is a high value, well regarded product, which sounds very good, those output transformers are tiny compared to the fancy ones included in the EleKit TU-8600R (don’t you wish it had a shorter, cuter name?). And the power transformer - straight out of a science fiction time machine!

Now let’s get to how that clumsily named amp sounds. We will compare it to the Camp Amp Nelson Pass has his students build (you may be able to get one from DIY Audio - $300+, 8 wpc class A); Emotiva’s (now discontinued) Mini X a-100, 45wpc); Akitika’s GT-102 (50 wpc, uses the same amp chips as the Chinese amp boards mentioned later, regulated power supply); Rega Brio R (integrated amp 50 wpc, now discontinued); home constructed chip amps using the Yuan-Jing 2 x 68 watt LM3886 and NE5532 integrated circuits stereo amp board ($30 ish) AND Yuan-Jing TDA7293 85 watt mono amp board ($28 ish pair) (there is so little difference between these amp boards that I will discuss them together); and finally, at least four Interga AV Receivers ($100 - $200 bought used, great value).

What kind of music shall we test with? Humans singing and playing real instruments, of course. The most difficult passage I can find is in a song called “I Eat Dinner” by Kate and Anna McGarriggle on their album “Heartbeats Accelerating,” track two. The thing to listen for is the background vocals, guitar accompaniment, and the small hand drums (there are two) that come in on the second passage (about 1:34 minutes into the song). Listen for the initial tap on the drum head, the skin sound, and the resonance of the tap within the wooden body of the drum. There is lots of artificial reverb, how real does it seem? Is it just on the vocals or on everything? Use the best speakers and cables you can find. You can make those too, for very little $$. Note: tube amps are much fussier about cables than solid state amps.

Results of listening tests:

EleKit TU-8600R Smooth, easy, non-fatiguing; skin sound from hand drums, wood body of small drums is three dimensionally present. Highly articulate guitar sounds.
Very good depth of sound stage. Very “clean.”

Camp Amp More “air” than the EleKit, excellent depth, tighter bass, NO skin sound, NO body on the small drums, just the tap.

Emotiva MiniX a-100 More air than the EleKit, less than the Camp Amp; good depth; good cymbals; very good guitar articulation (as good as EleKit, better than Camp Amp); but where are the small drums? Not there!

Akitika GT-102 Very slight mechanical hum, outstanding clarity, very natural, less tone in small drum body than the EleKit, good skin sound, best details in guitar notes.

Rega Brio R An Integrated Amp. Unpleasantly crowded speaker terminals, more air than the EleKit, less than the Camp Amp; very good clarity, best guitar sound (tied with Atikita), good depth, bass less prominent, but hand drums almost not there at all. How can that be? - just the initial tap. Highest gain amp, fast acting remote. Slight, but perceptible “edge;” seems to go with the “air.” What is “air” anyway? Is it really in the ecording? Could it be an artifact of all the high frequencies getting tangled up in the feedback loop(s)? What is the solid state “edge” really?

Chinese Chip Amp boards Very good clarity, good drum sounds, very good depth, excellent value, perceptible “edge.”

Integra AV Receivers Obtained used for little money, good overall but when using surround sound features, tone controls, etc sound becomes slightly veiled due to all the extra circuitry used; perceptible “edge;” some skin sound on drums but no body resonance; a very easy way to get into surround sound which is great fun. Build your own speakers and upgrade the electronics later.


There is absolutely no reason to fool around with tube amps unless you want the best sound, the best clarity and intonation, the heart of the music (at least most music), the emotion of the performers. The EleKit TU-8600 cannot be beat for the money, provided you use efficient speakers. 9 (yes, nine) watts is louder than you think, but you’re not going to shake any walls. If want pipe organs (or bagpipes) to chase the vermin out of the walls and basement - go solid state. If you listen to rock music, with its deliberately distorted guitars, buy a used AV receiver and set up a surround system. Its also very nice for movie soundtracks and video games.

A Word About Watts
Sound is a funny thing. You can go to Niagara Falls, where the sound of the falling water shakes the guard rails and your clothing, where you must shout at the top of your voice so the person next to you can hear you - and not die. You can be trying to sleep in that hotel room in the tropical resort and hear the mosquito buzzing around in the far corner of the room and hear it clearly. A mother can hear her baby turn over in its crib through two closed doors while making love. Our ears are amazing.

We hear on a logarithmic scale. Ten times the power to a loudspeaker sounds about three times louder. So, to make the music sound ten times louder, you need - let’s see - ten times more watts gives you three times in loudness, ten times again gives you nine times louder, plus another bit of boosting (about 125 times more electrical power) to get your ten times louder music in the room. Most people listen at 1/4 to 2 watts depending on the speaker’s efficiency. The fellow who upgrades from a 68 watt amp to an 85 watt amp is unlikely to hear any difference. You’ve got to go ten times the power of your old amp to hear a meaningful improvement. So, the EleKit TU-8600’s nine watts isn’t enough? Don’t waste your time on 25 or 60 watt amps, go to 100 watts. It’s a nice number and still an affordable price point. But, do you listen to girl singers accompanying themselves on a guitar or piano? Ukulele maybe? Chamber music? Sonatas for bassoon and boat whistle? Nine watts from tubes (designed before you were born?) is plenty and you’ll never get tired of listening. Almost any solid state amp will wear you out after nine or ten hours of listening. You’ll be looking for a ball game on TV. The EleKit’s 300B tubes won’t do that to you. They will glow warm and soft and sing in your ear like your favorite cat purring in contentment.

Building the EleKit is a formidable undertaking. You will be working with very high quality parts and it would a shame to mess them up. Build something else first. A preamp maybe; some passive speaker crossover boards. If you are meticulous and careful; if you read the directions in your new car’s manual before driving it home - give it a try after you learn to solder. Or, if you’re a grab and go kind of person, hire a high school electronics hobbyist to build it for you. There are plenty of $10,000 and up tube amps out there that are not as good as the TU-8600R. The 300B tube was invented for the sound movie business. It was made to make music. The circuitry in this unit is as modern as it gets. This not a rehash of a “classic” design. This is a new design that gets the full potential of a durable workhorse of a tube that exceeds what its designers thought it could do. It is 98% of perfection at a reasonable price. As they say in the magazines - highly recommended!

Last edited by vkung; 6th August 2019 at 05:29 AM.
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Old 3rd September 2019, 02:18 AM   #2
vkung is offline vkung  Canada
diyAudio Member
Join Date: May 2005
Location: Vancouver BC Canada
More feedback from Bill
A Peek At The Schematic - Old Age or Space Age?

Let’s see, the parts list says: three bridge rectifiers; seven transistors; four photo couplers (optoisolators - opto who?); here’s something that looks like an integrated circuit - wait there’s three of them!; heat sinks?; thermal pads? Yikes! They’ve sent me the wrong kit! I wanted a tube amp! This can’t be right. This is solid state stuff! Not a turret board or seven lug terminal strip in sight. A big printed circuit board? No point to point wiring? No rows of capacitors lined up neatly with big resistors in between? (Won’t I need my needle nosed pliers for exotic wire bending?) Pin headers? What gives? There’s ninteen axial diodes in there? Five tubes (at last), four photo couplers, three ICs, two phono jacks, and - is there a Pear Tree? A partridge maybe? Ninety-one resistors? I thought tube amp circuits were simple!

Welcome to the Age of Synthesis. This is not some throwback amp with its roots in the birth of “talkies” (talking movies) way back when cars had cranks to start their motors. No big glass bottles to turn AC into DC when a bit of silicon can do a better job.

This is a very modern circuit. Yes, it has tubes in the input, driver, and output stages. Yes, it has output transformers. That printed circuit board has space for five tube sockets. Most of the resistors are not in the signal path. Calm yourself. Tube circuits are simple, it’s the circuits that support the tubes that are complicated and clever!

Everybody knows tube amps are supposed to sound better somehow. Maybe electrons flowing through space have an easier trip than electrons fighting their way through the gaps in the lattice structure of some kind of crystal. How many twists and turns to they have to make on that journey? “It’s three lefts and four rights, repeat 87,000 times through that bit of silicon and then you zig zag through the forest of whiz bang atoms before you get to jump into the end of the copper wire” says one electron to its pal. “If only we had tubes! Sailing peacefully through space from filament or cathode to plate - such bliss!”

Clever folks have figured out how to assure that the tubes can do their jobs under optimum conditions. Something like helping old ladies to cross the street, or making ballet slippers that are easier on the dancer’s feet. Greasing the skids so everything works smoother, got it? Like capacitors across the heaters of the 300B tubes, and regulating the heater power so that fluctuations in the power line (like when the dishwasher or ‘fridge come on) don’t affect the behavior of the tubes. Optical couplers in the feedback loops? This is one sophisticated package of parts! And you can even opt for a super-duper 12AX7 tube (yes, they all sound different) for a sound that flows as effortlessly as a stream through a meadow.

Let’s take a few minutes about what’s what with watts. Let’s suppose you decide to get all the available options & upgrades for the Elekit TU-8600R; so you spent $337 or so per watt for an eight watt per channel amp. That might sound a bit expensive. An 80 wpc amp might seem a better choice. Do you realize that 80 watts is only 10 db louder than 8 watts? Have you watched a Vu Meter while playing music? Ten db louder sounds about three times louder than wherever you started from. The average listener is running about 0.1 to 2 watts, depending on the efficiency of the loudspeakers in use. So why does anybody need a big amp? Because sometimes you want to play it LOUD! Maybe you need to break a lease, get rid of an annoying guest (or relative), drive out vermin, whatever. Maybe Hayden’s Surprise Symphony just snuck up on you and the crescendo sounded bad: crunchy, squashed. Your car gets good mileage at 55 mph on a flat road with a tailwind (West Texas); but not such good mileage pulling a 40 foot trailer through the Rocky Mountains (Rifle Colorado), right? Honda Civics get better mileage than Land Rovers, right? So a small amp pushing an inefficient speaker is not smart.

For every 3db of loudness increase, you need to double the power to a loudspeaker. So if your amp is putting out 1/2 watt and the music calls for a 12 db increase in volume, you need four doublings of power: 1 watt, 2 watts, 4 watts, 8 watts. What (watt?) does that mean in the real world? Most serious home speakers have sensitivities in the 80s. Consider a highly rated small speaker. It’s senstivity is rated at 83 db per watt (dbw) and costs $21,5000 a pair. A very highly regarded speaker costing $235,000 per pair has a sensitivity of 89 dbw. The 6 db difference means the big one needs only one quarter the power to play as loudly as the smaller speaker. So the big one plays as loudly with one watt as the small one plays with four watts. Another company with less expensive, more efficient speakers makes a model (less than $5000 - way less) with a sensitivity of 95 dbw. It needs only 1/4 watt to play as loudly as the expensive small speaker with four watts. That’s the kind of speaker you want for a low power amp. You can find speakers rated at 101 dbw and they only need 1/8 watt to play as loudly as that small expensive speaker with four watts! You can easily build fine sounding speakers in the 95 - 105 dbw sensitivity range.

So lets put all this together: an eight watt amp with 95 dbw sensitivity loudspeakers plays as loudly as an 80 watt amp with 85 dbw sensitivity speakers! Ponder that.

There are many excellent amps rated at 30 wpc. They are all more expensive than the TU-8600R. How much louder can they play? Eight watts doubles to 16, that doubles to 32 - WAIT A MINUTE, the 30 watt amp plays only 5db louder than the 8 watter? Very True. Five db is hardly noticeable. There is very little listening difference in an eight watt amp and a 30 watt amp. One of the best 30 watters sells for $12,000 and is “easily the best amplifier I’ve ever heard” (p 114 of the May/June 2019 issue of “The Absolute Sound”). The 8600R will play LOUDER with a 95 dbw speaker than the 30 watter will play with 85 dbw speakers. Are you getting the message? It is not difficult to build or buy efficient, great sounding speakers. It is difficult to find glorious sounding amps. Read the last two sentences five more times. Now you know why the tube fans won’t give up. They won’t give up being able to hear the difference when the soprano got her braces off on the new record. They won’t give up saying, “Listen to the sound of the artist’s new sax. He had it custom made!” They love to point out how much better singer X sounds since he switched to the new studio. You can hear the sound of the tongue moving in the mouth of your favorite, well recorded, vocalist. Is it “Eeeeeeuuw!” or “Wow!” Either way, you can hear it. Build the EleKit!
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