Elekit TU8800 (Single-Ended Pentode) Tube Amp- Build & Impressions

1. Intro:
Elekit has been on my radar since I got the DIY bug not too long ago. I've also heard only great things about Elekit amps and the building experience, but there wasn't much impressions out there for their relatively new-ish amp TU8800, their singled-ended pentode amp with a f**k ton of tube rolling options (both blessing and a curse I guess) due to various power mode and two connection modes (Triode and Ultralinear mode). I didn't think too much of the UL mode until I heard @ChaChaRealSmooth 's one off Eddie Current's Ultralinear amp. My god, that amp made my JAR650 into a slam cannon with ZERO Sennheiser veil. It's definitely one of my favorite synergistic amps I've heard with the HD6x0 series. Unless I could somehow trick Chacha into selling me his amp, my chances of obtaining that amp was close to zero. This is where Elekit comes in.

If you've read my previous impressions, I've been running the DNA Starlett as my main amp for a while. It's a great amp and awesome for long term ownership due to cheap-af tube types with not much tube rolling options. My main reason for the Starlett was that it was easy to live with, but I didn't feel like I got the best synergy possible with the JAR650 and prefer something more along the lines of Eddie Current stuff. For neutral/bright headphones like HD800 and Utopia, I could live with Starlett and call it a day, but HD650 is my main headphone that gets majority of my listening time so I wanted to find something that has better synergy while retaining a similar technicalities to Starlett.

Let me briefly talk about its main features:
- There's a toggle switch for 3 different power modes (Low, Mid, and High) so you can roll various tube types shown below + many others I'm sure
- Another set of toggle switch for 2 different connection modes (Triode and Ultralinear). Sound differences are actually quite stark and not a gimmick. I'll explain further in my impressions.
- 6 different selectable output levels for both low/high impedance headphones by changing the jumper positions inside the board. Kind of annoying and see it as a design flaw since you have to unscrew and open the casing to switch the jumpers. A cool dude named @SonnyMarrow has discovered a solution to this issue.
- Also has a speaker output and can run high efficiency speakers apparently (Unfortunately, I don't own any speakers to try :/ maybe in the future or someone else can fill in this part of the review) I think I remember others saying Elekit is a speaker amp first? Maybe someone can chime in on this aspect to further clarify.



Shit, this is actually getting a bit lengthy so I'll actually break it up into parts: 1. Intro 2. Building 3. Impressions & Comparison. Stay tuned for now I guess heh

 

2. Building
So to preface this, I've never built Elekit stuff before nor have much soldering experience other than previously building a Bottlehead Crack + SB looooong time ago.

I'll try to be as transparent as possible and be upfront about the total costs from building. It's slightly more expensive than purchasing a brand new DNA Starlett, but to my unrefined, NON-golden ears I think the sound is comparable and no 6 months wait. Plus, if you like DIY, I think you should definitely explore this option as well. You can always just start from the stock configuration which I think is ~$1100? then if you feel like upgrading, you can always buy the other stuff later. This is the invoice I got from Victor basically listing all the upgrades I bought. I opted for the Lundahl Transformers, some nice caps?, some TAKman resistors (funny because Tak is my last name), and a TKD pot. Victor gave me the TAKman resistors and Silver Solder for free as a part of a bundle deal. I highly suggest you email him directly instead of buying it from the website. You are more likely to get a better deal by doing this.


My customer experience with Victor was very pleasant, seemed like a nice guy based on my email exchanges with him.

The items arrived in 2 shipment (1 for Elekit amplifier kit and 1 for a set of Lundahl tranformers) after just couple days of ordering.




- My advice from someone who has just built the amp is that take your time, enjoy the process, and....make sure you have a good soldering iron! I thought I could get by with my $15 soldering iron from amazon, but I ended up having to resolder ~90% of my joints the next day. Once I switched to Hakko, man what a game changer! made my life so much easier.
- In the package, you'll receive all the parts neatly organized in plastic bags. I'd recommend labeling the baggies with a sharpie in which component each bag contains while going through the checklist. Trust me, it will make your life easier once you start building. Like I said before, TAKE YOUR TIME & enjoy the process!
- I also read over the instruction manual 2-3 times, highlighting stuff I thought was important and took some notes on which parts the upgrade caps go. There's couple parts that look very similar until you bring them up close and read the tiny-ass writing (Ex. P01118MA vs. LMV431)
- If you get the TAKman resistors, you're going to have to bend a f**k ton of resistors a certain way because the PCB slot doesn't allow for it to be flushed all the way from a regular bend. Some hates this part, but I had a lot of fun. Once you do a couple, just go on autopilot mode while listening to some music.

- some progress pics. Finally found some usage for these Funko dolls that I got as a B-day gift long time ago.


- overall, the instruction manual is very easy to follow for even a dummy like me, but one part that confused the crap out of me was the TKD pot. Instruction manual only shows you how to do it for the stock pot and the instructions that come with the TKD pot shows pics for the TU8600, not the 8800 so they look a bit different. I wasn't sure, until I asked Sonny for some pics. This clarified a lot for me, so I'll include it here:

(this one is my pic from the side, don't look at my crappy soldering joints! I ended up resoldering it the next day with Hakko)

- After a day of trouble shooting and resoldering, it works!
**Amp sounds like absolute garbage the first 30min - 1hr. Don't worry, it's normal apparently lol When I first started listening to the amp, it had zero bass, and the highs were tinny and shrill. I'd say after 24 hours, I didn't notice any change.


Would I recommend this kit? Yes, if you enjoy DIY! I know there are some people who just prefer buying stuff that's already polished and pre-built, nothing wrong with that either! For me, it was a ton of fun building, picked up a couple new skills and feel very proud that this is something I built on my own (with a help from more experienced friends haha)

 

3. Impressions & Comparison

Like I mentioned previously, this amp comes with 2 Connection modes: Ultralinear and Triode. Each mode has a certain sound so I'll try to divide it up into parts:
Listening Rig:
Pi2AES > Sonic Frontiers SFD2 Mk2 > DNA Starlett | Elekit TU8800 > JAR650 | ESX900 | HD800sdr+sbaf+cork | @pure5152 's Utopia

Ultralinear mode:
- Tonally, it's an aggressive sounding amp, very different sound from the slightly laid back, polite sound of DNA Starlett, which has a more traditional SET sound. They're both engaging amps, just different flavors I guess. I thought its aggressive sound was a much better match for the 650's laidback nature. Also HD650's smooth mids to treble transition just seems to be a perfect match with this amp. Dream synergy...
- OK, right off the bat, it has the reminiscent, "grab the transducer by the cajones" feel that I get from something like ECP 3F or EC's Ultralinear. Macrodynamics is stellar, one of my favorite aspects of this amp. Obviously with the JAR650, the bass is still wimpy with some lowest low end roll offs, but man this amp really makes the 650s work.
- microdynamics is great as well, engaging and lively sound that can readily portray the nuance and subtleties of music. Love how visceral string instruments sounds on this amp. It's a sound you just want to keep listening and I would often lose track of time till I realize it's way past my schedule and I should sleep.
- Another aspect that impressed me was how clear it sounded especially with my JAR650. Sennheiser veil? I dunno anything about that. In ultralinear mode, the amp cuts through the veil like butter without adding any treble glare or nasties.
- Believe it or not, resolve and plankton seems to be on the level of starlett and other similarly priced amps. Don't let the DIY aspect fool you. I don't get the unsettling feeling that I'm missing some information in my music when I switch back and forth between the two amps.
- staging wise, it's good, but I think the triode mode is the better setting if you're craving for that immersive headstaging experience. You'll lose a bit of depth and expansiveness of the triode mode for the grippy bass and control of the ultralinear mode, really depends on what your sonic preferences are, I'm sure you'll be happy with one or both of these modes.
- headphone synergy wise, I really like listening to this mode with JAR650 and ESX900 (modded TH900). I do have to switch the amp's output impedance level when using the ESX900 to two levels lower than then one I use with my 300 ohm Sennheisers, but no big deal (just flipping switches)
*** I absolutely LOVE the synergy with my JAR650 and I just want to crank these up to recreate that "live concert feel." Even if the amp only had Ultralinear mode, I'd still get it for this synergy since 650s are my daily drivers. Not sure how it fares with the EC ultralinear, but hopefully that comparison could happen one day.

Triode mode:
- Some would think that a single amp having two different connection mode must mean one of them is just an afterthought and sucks major ass, but that's not the case here. I enjoyed listening to triode mode just as much for a different synergy with headphones like HD800 and Utopia.
- On the very surface level, it has the similar traits to "traditional SET sound" of DNA Starlett, maybe with a slightly more forgiving nature but it still sounds like an Elekit.
- The insane macrodynamics/slam from the Ultralinear mode is dialed down, but it's just as dynamic on the micro level along with similar resolve.
- staging is much more expansive and mids to treble transition seems to be smoother than in Ultralinear mode.
- the hyper clarity that I experienced from Ultralinear mode is also toned down, but still retains a good overall presence and lively nature.
- Headphone synergy wise, I enjoyed listening to the modded HD800, Utopia, and a vintage Beyer DT990 600ohm. JAR650 sounds fine here too, it's just I rather listen to ultralinear mode on this headphone. For ESX900, it's a toss up between the two modes depending on my mood.

Overall, it really does feel like this amp is carrying two different, but both awesome sound that can be decided based on specific synergy of your transducer. I enjoyed neutral/slightly bright cans with Triode mode and warm-ish neutral can with Ultralinear mode. If you are not allergic to DIY, I think this amp could be an excellent alternative option to consider around this price range.

I'll try to add the comparison soon, sorry for the wait!

 

Good job!
Just stock tubes so far?

 

Thx! yes, stock tubes so far, though I do have some tubes coming in. I originally wanted to do a write up for tube rolling, but I think I'll let others fill in that portion instead. Just got the PCB for the mods too from Sonny, so I'm about to open up the amp again.

 

***Disclaimer: This mod is not necessary, but done for convenience sake. I'm not responsible for any damages done while performing this mod. Does not impact the sound at all.***

So one of the annoying aspects of this amp is that whenever you want to change the output impedance of the amp, you have to unscrew and open the chassis and move the jumper pins to desired level. @SonnyMarrow basically made a small rectangular cut and added these two components + PCB to be able to switch the impedance without all the hassle.
You will need 2 of each of these:
https://www.mouser.com/ProductDetail/Samtec/ESQ-106-33-L-D?qs=PB6/jmICvI2TNwdDwUwSWw==
https://www.mouser.com/ProductDetai...ha2pyFadug6QT0tTQeTJf5BL6QhatD7JYMb%2BhqNmIU=

I was able to obtain the PCB from Sonny and it looks like this:

all the components connected & soldered:

This is how mine looked after cutting out a small rectangular from the metal body. I had to use a dremel to cut, took me about 30mins? First time for everything haha. Did cut a bit much on the corners, but really not noticeable unless you inspect it closely. I do plan on getting the body repainted to maybe all black so maybe it'll be even less noticeable after.

This is how the amp looks now with the cage on


The mod worked fine, now I don't have to unscrew every time! Weeeeee

 

That looks fantastic! The takman resistor bending becomes a ton of fun after you figure it out.

Holy crap you have a ton of output impedances. I only have 4. Have you figured out what each one is? I asked victor for the 8600 and his answer was, use your ears.... wondering if there is some way to measure it so I dont need to just hope around and guess.

 

Thanks! yeah bending the resistors was strangely calming and somewhat therapeutic.

Not sure which is which tbh, I know Sonny gave me some measurements for his 7581a on triode mode, but not sure how applicable it is for others. I just tried a couple and stayed with what sounded good. I'm currently on the 3rd highest setting (HZ1?) I'll attach it anyway just in case it might be useful for you

 

Looks great! It's a really nice amp that I think a lot of people would enjoy.

As Tommy said, those output impedance measurements were with 7581a tubes on triode mode. I don't have comprehensive measurements of other tubes and settings yet, but it does make a difference. For example, with KT77 on UL mode, I get 3.3 ohm at LZ1.

 

Really interested in hearing what you think of the TU8800. Looking to build an amp and thinking either TU8600 or TU8800.

FYI, i noticed this morning that Victor just posted in the TU8800 on the diy site that the headphone jumper extension is not recommended by Elekit. Sounds like it might be more of a safety issue than anything else but thought I'd mention just in case.

 

If you are looking to save money I would say the 8800 is less of a bottomless money pit than the 8600. Having said that, I love my 8600.

 

Very true. 300B tubes are very pricey. Although with the power tube options on the 8800 I'm sure it's possible to go crazy there too.

 

I didn't find the power tube that much of a pain, I just went with the Elrog and called it a day. The problem is that the input tubes for the 8600 are both more popular (read more expensive) than the 12AT7 in the 8800. Additionally, it's a bit harder to tune the amp to taste since you have to get the 12AX7 and the 12AU7 to synergize with each other and the rest of the setup.

 

100%... please tell that to the money pit of about 60 12au7/12ax7 that are sitting on my shelf...

but on that note, i have also used 12at7 variants with varying levels of success as well in the amp.

 

I saw that response and could not understand what is dangerous about the mod, nor could actual electrical engineers I discussed this with. The only potential issues are that you could (1) leave every switch open and run the amp unloaded or (2) have multiple output impedances selected at once. Probably just a CYA from Elekit.

 

It's good to see Elekit getting some love here. I built mine a couple of months ago and can definitely agree that it's a tube rollers dream. This is coming from someone who owns a liquid glass (prototype version).

It's not just the sheer amount of tubes that can be rolled but also how responsive the amp is to tube rolling (especially the input tubes). In most of the amps I've owned, tube rolling either doesn't do much (CTH, Val2), or just changes the voicing for the most part (EC Super 7). This amp is more chameleon like in that switching to a different combination of tubes can alter the character of the amp quite a bit in terms of both technicalities and tone. Rolling caps also makes a noticeable difference.

This can be a bit of a double edged sword in that getting the sound you want out of it can be a chore. FWIW, I thought it sounded pretty ok with the stock reissue tubes (EH 12at7 & GGL KT-88) but sounded sublime with a pair of NOS M8162 Mullards and Silvania 6l6Gs in my setup.

Here's my setup:

6L6G the poor man's 300b


Tried the stock caps first and then switched to V-Cap CuTF


Reading from his parts list, I think @tommytakis may have gotten a different set of Lundahl OPTs?

Yep, it sure is...


That's some of them but frankly, I'm too lazy to pull out the rest atm. I won't even bother posting all the input tubes I've rolled in this thing.

But yea, for people that like options, shit can get pretty real.

 

are the ones with the adaptor + cap on 807 tubes???? Because that's the tube type I'm rolling next.

Regardless, I'd love to hear your general thoughts on the tube types you've rolled!

I'll try to check the numbers again next time I open the main body. Would be interesting if they're actually different transformers

 

Yup, those are 807's. They seem to work fine in UL mode but not in triode. I'm not sure whether it's the adapters I'm using or the amp circuit. But if memory serves me right, the TU8200DX was able to run 807s in triode mode so it would be interesting to know what changed.


Sure! When work dies down I'd be happy to make a more comprehensive tier list of some sort if you or anyone else wants. But for now here are some very rough impressions, just my personal experience\preference YMMV:


Most European input tubes(ECC81) > Most USA input tubes (12at7)

USA input tubes:
NOS RCA black plate >> Groove Tube Russian re-issue ~= most branded NOS tubes >>> GE 12at7WA

Most USA NOS tubes I've tried were decent but it's hard to consider them an upgrade from the two Russian re-issue tubes I've tried. With the exception of a few GE tubes in the lot, they were generally warmer and (maybe) a bit punchier sounding?

However, the reissues were more detailed, and less rolled off on both ends. Trade offs considered, they're technically close but I preferred the tone of the re-issues.

Two exceptions were a GE 12at7WA which I didn't like (sounded detailed but sterile) and an RCA blackplate, which to me combined the best of both worlds. It also imaged better than both groups IMO.




European input tubes:
Siemens ECC801S ~= Mullard M8168 (1968) > Mullard M8168 (1958) > > most generic Brimar & Mullard > Brimar Yellow T (too soft sounding for most non-vocal genres)

Overall, I preferred the sound of most European tubes I've tried. The better British ones had a nice liquid sounding midrange, smooth extended treble, but without much of the roll off in some of the domestic tubes. Mullards tended to be more balanced than the Brimars at the expense of some treble smoothness and slam in the bass. Both types had a bit more body in the sound that I felt the re-issues lacked.

The best of that bunch were two Mullards stamped with M8168. They were made a decade apart and have very different guts (might post pics later). Anyhow, they were a dynamite pairing with almost any 6L6G tube I tried.

Take the best of the Mullards, add a touch more clarity and detail, then ramp up the microdynamics about two notches. Probably the most realistic sounding pairs but with different colorations (if that somehow makes any sense).



The ECC801S is the only german tube I've tried so far. It's also the most detailed, has the biggest soundstage, and best imaging of all the tubes thus far. This comes at the expensive of some sweetness and "soul" that the M8168 have. The best way to describe it is....if the HD800 ever became a tube, this would be it.




Output tubes: More difficult to rank by region or type but a few that stood out from the pack were:

1. Sylvania & Ken Rad 6L6G
2. EL-37 (before it died)
3. RCA-6L6GC black plate
4. Brimar 6V6G (with Siemens ECC801S)

Also, some combinations have more synergy than others and work better for certain genres of music over others. That being said, some input tubes like the RCA black plates or most of the Mullards sound at least decent with just about any pairing.

 

LOL I was just about to post about the 807 tubes and then I saw your post. My pair just came in couple hours ago and really digging the sound so far. First thing I noticed was how good the treble extension on these were: super airy, yet no grain or sharp peaks even when cranked up. Still slaps like a good solid state amp! These are less warm than the stock KT88, but treble seems to be smoother to my ears.

Yeah I had the same experience when I tried to run them in triode mode. As soon as I flipped the switch, the amp went BRRRrrrrrr so I flipped it back to UL. I think it's explained better here:
https://www.diyaudio.com/forums/tubes-valves/127590-807-tube-triode-connected.html

Even if I can only run them on UL mode, I still really like the sound of these tubes, also super cheap too!

I do want to try the Sylvania 6L6Gs that you have on, but they're a big jump in price so I'm trying to wait for the right deal on them

Thanks for the write up! I'm sure it'll be very valuable to not only me, but future owners of the amp as well.

 

That....clears things up. Thx!

Yea, the 807 was one of the very few tubes I liked in UL. At first I was a bit bummed out when triode wasn't working. Then the music just kept playing and I started caring less and less lol.

If you don't mind buying single tubes and aren't obsessive about tight matching I've seen a few well priced ones floating around. They'll never be 807 cheap though...