Elekit TU-8600, Part 2: Building the Kit, and the Lundahl upgrade
In Part 1 of this series, I covered (mainly) the Elekit TU-8600’s performance. That amp came to me fully assembled, as a “Rev.2 prototype”. And in my mind, I’d thought (hoped?) that I’d be able to buy and keep that amp. That didn’t happen. Elekit/VK needed it back, and Victor sent me a brand new kit. So I ended up starting where everyone else would start. Time to fire up the old soldering iron!
What I’ll cover in this part will be the build process, and the upgrade to the Lundahl output transformers.
Building the Kit
How did it go? Overall, I had a pretty smooth experience. There are aspects of this amp kit that are more complex than the TU-8500 preamp, which I built last year – but the preamp had more PCB’s, and tighter spacing overall. So I think going into this amp build, I was feeling “confident” I’d have an eas(ier) time with the 8600, and it turned out to be a little more challenging than I expected. But wherever I encountered a problem, the problem was me. I may not be the world’s worst DIY’er, but I might be the most impatient!
First off, the kit arrived with everything nicely bundled and the parts sorted and arranged into their own bags. Very tidy and professional – no surprise, this is Elekit. The 32-page manual deserves special mention. This is likely the best audio documentation I’ve ever seen. Novice builders especially should take note: look at the little icons on the PCB, look at the drawings in the manual – look for clues. If something seems complex, you’re not looking. They’ve done everything you could think of (and more) to make each step as simple and clear as it can be. There should be any confusion. Just take your time, enjoy each step and try not to race ahead.
You can count all the parts if you like, but the people who package these kits are fanatically attentive to detail, and the chances of encountering a miss are very low. I just started stuffing. My technique was to stuff the board with a full set of parts (resistors, diodes, etc) and then solder that set before starting on the next set. Actually with the resistors you might want to solder some as you go, because there are so many. You just follow along in the order the instructions are written. They don’t always tell you exactly when to solder, but you soon pick up on what’s happening. You don’t want to stuff the entire board, flip it over to start soldering, and have a dozen parts fall out. So keep soldering as you work through it.
The PCB is very well laid out and clear, and in general, there’s enough room to make soldering easy (there are a few tight spaces, but thankfully not too many). “Take your time” is the best advice I can give here. Another general comment: the bigger the part, the more careful you need to be. A part with three pins is a lot more difficult to desolder than a resistor or cap with two legs. The bigger parts become anchored in, and removing them can be a bit of a nightmare.
I made a couple such blunders. I soldered a seven pin connector into the eight pin position. Bad. Desoldering a part like this involves some brute force, and the part isn’t likely to survive. Of course, the part itself is easy enough to replace. You want to be more careful (while desoldering) not to damage the board itself..a ruined board spells a horrendous amount of rework! Please take your time: as you get deeper into the build you will naturally want to go faster. That’s the time to go slower.
After my replacement connector arrived in the mail (thanks Victor), I finished up the kit – and only then did I notice that the headphone jack wasn’t soldered well. The part wasn’t seated down on the board like it needs to be. ARGH. This means that when you assemble the chassis, the h/p jack isn’t in the right spot where its hole is. Bad. I got it desoldered ok (again with brute force, the part was toast), and finished the build. In hindsight, I should have tried harder to seat the thing. Because unfortunately, the headphone circuit is integral to the amp’s operation: its ‘disengaged position’ allows the electrons to flow to the speaker taps. So, with no connector in place, my amp turned on, the tubes lit up, I could take measurements, but I had no sound – it was as though a pair of headphones were plugged in. Frustrating! Victor said he had an extra Jack and would have it for me at the TAVES show when I saw him there. (thanks Victor)
Wait, and wait some more.
So while waiting…well, I got impatient and decided I’d try to paint the amp, for a more funky look. I suppose memories of the red TU-8300R may have been responsible. I thought a red and white scheme would look nice – it would match the bases of the Genelex Gold Lion tubes, and the colours of the Canadian and Japanese flags. (Wall of Sound, Elekit, Japanada. You know what I mean)
Don’t do this. Just. Please. Don’t.
Not unless you know what you’re doing. A metal chassis like this needs the correct preparation before it can be painted. It needs to be cleaned well, with an appropriate solvent, sanded down where appropriate, and primed with the right primer. Even then, there may be issues if you aren’t a pro at applying finishes. I will make a long story short, my ‘test area’ under the bottom chassis seemed to hold up well (sprayed primer and then white sprayed Krylon). But once I sprayed more of the chassis, well, I ran into numerous issues getting the right coverage. In the end, the paint looked ok for a day or two, but started flaking off almost immediately; by the time I had the final part (h/p jack) to complete the amp, I had spent several hours removing the paint. So, my amp is a plain Ellie again, and the colours are a memory preserved in photos. Humbling. I may take the chassis parts to a powder coating place someday and get a nice paint job done. When funds permit. Maybe.
Back to measurements. Initially my readings were a bit of a mess. What you want to do first off, is some careful review (a magnifying glass helps a lot) and touchup of any questionable solder joints. After doing this, I had 37 out of the 38 test points measuring well. However, TP28 was still extremely low, I only had around 0.65V where it should have been 20V. This is the Right channel Ripple Filter circuit – so the result was a hum in the right channel. Victor diagnosed (correctly) that the J13007 transistor was the issue (Q201 position on the board). Removing and resoldering this transistor proved too much, and the part was fried – it then measured 0V. Time for another email to Victor. And more waiting. Victor sent me a new J13007, along with a nearby FET, as well as the new PTC’s that Elekit recommends, since the originals were discovered to be inferior. (thanks Victor)
One correction from what I wrote in Part 1. The headphone gain adjustments are accessible – remove the 300B tubes and the top plate, and you can access the jumpers. I don’t think people will be changing these very often, but if you need to, it’s a fairly quick procedure.
Another thing every builder should do is sand down the chassis to bare metal around the point where the volume pot parts make contact with the chassis. This eliminates any noise related to grounding this part of the circuit.
Et voila! The amp is built, and it sounds fantastic. The build process overall was enjoyable, and of course, it sounds better since I built it myself (grin). Victor gives excellent support – both by email/phone as well as on his forums on Diyaudio and AA. In fact, he had 3 or 4 trade shows almost back to back during this period, and never missed a beat. The man is tireless. There are a few ‘legends’ in the audio DIY business, like Nelson Pass, who continually give and give to the community. I count Victor Kung in that small number who truly deserve our gratitude.
And now….the Lundahl Upgrade
Earlier this year, Victor commissioned Lundahl to make the LL2770 output transformers for the TU8600, as an extra cost upgrade option. My prototype kit arrived with the stock transformers, as well as the Lundahls. I listened to the stock amp for about 4 weeks before switching over. It was hard to wait! But I knew that the chance of wanting to “switch back” was low, and I wanted to give the stock opt’s a fair shake. And to be fair, they are not bad at all. But high end iron is where the bulk of tube amp costs reside, and you can really see that with the Lundahls. You can even feel it when you pick one up, they are close to 6 lbs each according to my bathroom scale. Victor supplies the Lundahls with the parts needed for a seemless installation: bolts, washers, standoffs, as well as custom PCB’s to tidy up the leads and allow the Lundahls to hook up to the Elekit board with the supplied quick connectors.
The photos don’t really do the Lundahls justice. These are big, weighty and robust, they’re beautifully built. They’re designed to extract the last ounce of performance from your 300B SET amp. And I think they do just that.
For me, there wasn’t a night-and-day difference upon installing the Lundahls. What I heard was a subtle, across the board improvement. The bass was a little tighter; the mids a touch more vivid. The top end sparkle was slightly more refined. Imaging ability was a little sharper. Most of all, the music seemed to have a better flow – where at times it was ponderous, it now seemed faster, and more assured. This was especially noticeable to me with modal and ‘west coast’ jazz listening. With better electron flow, the notes and beats are less confused, the music makes more sense.
Again, this wasn’t a super dramatic, jaw on the floor difference. But it was clear and audible. And I think that also reflects my system – I don’t currently have a super high resolution setup. It’s plenty resolving enough for me, but in a more high res context, I think the improvements would be even more apparent. For me it felt like ~15-20% improvement. It was substantial.
Did I switch back? No. And I don’t think anyone else would, either. However, let’s remember that single-ended output transformers are often directly coupled to full range speaker drivers, or to a minimal crossover network – so it is hard to talk about the performance of an opt without considering the speaker coupling. Better iron is better, but I do want to reiterate my feeling that the stock transformers were also very competent. I don’t want that point to be missed. If the cost of the stock amp is stretching your budget, stick with the Elekit-supplied opt’s and don’t sweat it. You will probably have 85-90% of the enjoyment (how can anyone really quantify it?). I’m saying this because, for some of us, another $550 is a big deal. For others, it’s not a big deal, and in that case I can highly recommend the Lundahls. They take this amp to another level, and the cost is well worth it.
So there you have it, it’s a worthwhile upgrade, but not a must do if you’re on a tight budget. I’d rather see someone get into the TU-8600, even with the stock trafos and a cheap set of tubes, than sit it out waiting for enough funds to accumulate. You won’t regret it, either way.
Lundahl LL2770 upgrade: highly recommended!
In the next (and final) segment, I’ll take the TU-8600 out on a road tour, to hear it in better rooms than mine – with better speakers than what I currently have. It may be close to Christmas before I can finish that, I have to catch up on other stuff. As always, we welcome your comments and experiences.
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I strongly suggest that anyone building this kit should spend a little time on YouTube learning good soldering and desoldering technique. Soldering isn’t really difficult but things can get messy in a hurry! And solder wick is great stuff! It’s a sort of braided copper that sucks up excess solder when you are removing components. Also a desoldering pump is a good investment.
I miss RadioShack sometimes since electronic shops are few and far these days. B&E Electronics in Calgary is pretty good for soldering equipment ( no affiliation…just a happy customer) and they have an online store. They have very good prices for soldering irons too. I recommend the hakko soldering station. Also for me I stick with the 60/40 lead tin solder. I find silver has too high of a melting point and is a bit harder to work with, but your experience may vary.
I have four elekit amps now and enjoy them all…yes I may have a problem!
Thanks for the review.
Cart it here the next time you are in Montreal.
You mentioned tubelab. I presently have a breadboarded version of the tubelab se with 300b’s and was curious if you built this amp and how you would compare it to the elekit tu-8600.I may consider the elekit instead for now as I’m at the chassis stage and really don’t enjoy that part of diy.
That wasn’t me. Steve talked about Tubelab a while back. I’m not familiar with them.
Ok, thanks Noam.
Considering Hashimoto’s trafo’s a good alternative for TU-8600, I bought a pair of H-30-3.5S O.P.T.’s and installed it. It came with potting and a square tall case, which luckily could be fitten laid down on its side on the trafo bridge. There was just enough speace under the hood with the top cover installed. But because it only has two windings, short of the thid feedback winding of the Elekit’s original OPT’s, I have to use its 16ohm output taps for NFB feeding.
Result: stunning. FR was up a notch in the highs, distortion lower, and it actually runs better with my JBL 4320 (2-way mon 96dB/W/m SPL) giving deeper bass response and better control there.
That cost me nearly $900 though.
Nice! I guess you aren’t able to use the headphone taps though.
Can you share the modifications needed to install the Hasimoto OPT’s .
I hope so…
What you have done is increased the NFB levels that the third winding in this version of the elekit was introduced to reduce. Some of the magic may be lost. If more bass and more feedback is what you wanted perhaps it wasn’t a tube amp you needed?
I have a pair of JBL L100, sensitivity is 90dB/w/m. Can this amp drive JBL L100’s without issues?
Shouldn’t be an issue, but if you are expecting concert hall levels i.e. limitless clean power, then I’d recommend a more powerful amp.
Does the Lundahl LL2770 upgrade still fit under the cover?
Yes, they fit on the rack behind the tubes, which has a taller cover. Once the cover is on there’s no difference from the smaller Elekit trafos.
Hey.. great review. I am going to build one of these myself. Which 300B’s have you tried with it? Wondering if the JJ or the EH would be sufficient as opposed to the Gold Lion
Thanks, in the Elekit I’ve only tried the Gold Lion, and briefly, the Shuguang treasure tubes. I did a comparison of 300B tubes a few years back that may be useful as you shop for tubes.
Hi, I’m enjoying mine immensely with DeVore speakers. Did you ever get to take it on the road as mentioned in your review, and if so will you be reporting on it? Thanks,
The answer is yes and no, long story. I sent you an email to explain.
Did you build your kit stock or use upgraded resistors (the Takman carbon) or Mundorf caps?
Regardless, do you have any thoughts on those upgrade options?
Yes, mine had Mundorf caps and Amtrans resistors. I haven’t compared, but it seems all of VK’s upgrades are worthwhile, and reasonably priced. For a great bang for buck, see if you can get a TKD volume pot to fit in it.
Just finished my TU-8600 and loving it so far. I fitted a TKD pot and it is definitely a nice improvement over the Alps Blue Velvet!
BTW, my voltages are close but I have some variations. I am curious specifically about TP27 and TP28.. were those 20V after you replaced the transistor? Both of mine read 16V
Built the TU-8600 in March and have been enjoying so far. I opted for the Takman resistors, Lundahl LL2770 OPTs and TKD volume pot initially. I did swap the supplied output transformers for comparison but quickly went back to the Lundahls.
Experimented with swapping the B+ and C- supply rectifiers. Replaced the supplied HER208 Schottky rectifiers with third generation silicon carbide rectifiers. I used ON FFSP05120A in a TO-220-2L package. Takes a bit of careful lead bending but the 9 rectifiers will fit with no vertical clearance problems.
Listening impression was very detailed upper mids and bass. Very worthwhile modification.
Currently studying the supplied low ESR capacitors to determine the ratings. Newer organic polymer capacitors are available with resistance in the 7 Mohm range.
Squeezing every little bit of detail…
Very cool – thanks for sharing.
You’re most welcome.
Another tidbit I might add, for the renewal parts shelf, some of the semiconductors used in the TU-8600 are considered “end of life” or obsolete and getting harder to find.
One example is the Sanken Electric RBA-406B Schottky Full Wave Bridge rectifier (D105, 205 and 306), used in the filament supply, is no longer listed in Sanken’s product matrix, not even their obsolete list. I’ve only found one distributor in the Philadelphia area that has them.
Another example is the NDDL1N60Z FET (Q102, 202). ON Semiconductor has it listed as “end of life”. I found a good supply at Mouser.
It was not difficult to assemble a spare supply of semiconductors just in case. Also, not a lot of money either. If one intends to keep the amplifier for a while, this would be something to consider.
Again, great info. Thanks Daniel.
I would expect that Elekit has a stockpile of parts for all their models, but I’m not sure. Victor Kung told me the parts failure rate is very low – but of course, the risk of damage while assembling/soldering is real. He usually responds to comments here. As well as on his VK Music forums.
Just recently built the Elekit 8600s with upgraded Lundahl 2785B transformers and the new Western Electric 300B tubes. It was my first kit and the instructions are well written and easy to follow. The amp is amazing. Exceeds all my expectations. I also have a 300w solid state amp from LampizatOr and have used Melody M845 mono amps in the past. The Elekit is maybe not their equal but hard to tell the difference in pure enjoyment. Highly recommended if you want a 300B tube amp.
Congrats Jason, and thanks for commenting. So are the new WE’s worth the price?