Classic Line Kits

19 reviews for Classic Line Kits

horaciojervis (Reviewing Stepped Attenuator) – September 24, 2025

Click To Expand “Adding the attenuator was like cleaning my eyeglasses when I thought they were clean.”

This kit took me approximately 6 hours to complete, working on and off across three days, not including the time it took to finish the wooden chassis. I’ve spent the last 10 days listening to it for several hours per day. For reference purposes, the following is the equipment I’m using: Soundsmith cartridge, VPI turntable, Bob’s Devices SUT, Manley Chinook phono preamplifier, PrimaLuna EVO 300 preamplifier, 45 tube SET monoblock amplifiers,100dB open baffle speakers with full range drivers, and of course, the Mellow Tone Stepped Attenuator Kit with the Set B resistors.

Initially, I had the stepped attenuator positioned between my phono preamp (91 ohms output) and control preamp. Later, I found it really sounded best positioned between the control preamp(256 ohms output) and my amplifiers.

I played around with my phono preamp’s gain options, and took the SUT in and out of the chain. In the end, I simply preferred the sound with the SUT and the 65dB of gain with the 0.4mV cartridge.

Consequently, because of this higher gain, and my speaker’s sensitivity, I’ve done as you suggested, and lowered the control preamp’s volume pot until it’s “trimmed” to my liking. I am typically setting the attenuator to its 9th step/240ohm or 10th step/300ohm, and adjusting the preamp’s volume pot accordingly. I will play around with this more. I like the idea of being able to max out the preamp’s volume control(“removing” it from the circuit) and simply use the attenuator to adjust the volume. I am assuming that being able to do this, would result in getting the maximum benefits the attenuator has to offer.

My rig is pretty transparent and open sounding, with a deep soundstage, including good height, width, and precise imagining, along with a palpable holographic presence. The stepped attenuator kit has simply refined this presentation. Improving, and making all the important bits better. This has not been a subtle change, but the kind of improvement that is “in step” with a significant preamp or cartridge upgrade. I honestly am astonished at the difference this has made (perfectly matched resistors in a simple circuit design!). Keep in mind that my preamp sports the well regarded 100Kohm Alps Blue Velvet motorized potentiometer, arguably no slouch. For me, with my gear, the stepped attenuator is better.

My first reaction was that adding the attenuator was like cleaning my eyeglasses when I thought they were clean, and then being surprised by their subsequent clarity. Except the attenuator is better, because it offers more than just clarity, delivering greater detail, tighter focus, increased sound staging, improved presence and body.

The other aspect that has delighted me, is that adding the attenuator either before or after the control preamp did not add any noise. I realize that it is a passive device, yet I’m impressed and happy that it is dead silent, especially when running my phono preamp into it; zero grounding issues.

I have enjoyed absolutely everything about this kit. Building it was a blast (soldering the resistors to the attenuator was my favorite part), the instructional videos are very well done, and the kit itself feels like a quality product, the cherry wood frame and metalwork are substantial, elegant and attractive in their simplicity.

Thank you for the time, effort, and detail both you and Charles put into these kits and videos. Also, thank you Jim for taking all this time to work with me, provide consultation, offer feedback, read my long emails, and for being patient and kind with me. Much appreciated.

This has been a really worthy investment, money well spent, and a great education and learning experience. I’m glad I found you guys.
Stefan Auer (Reviewing GU-50 8W Monoblock) – September 24, 2025

Click To Expand “The stereo separation, the soundstage and first and foremost the detailing and layering capability is phenomenal! Very, very, very natural!”

Finally, I could accompany my recent but first ever own built MTK 6or12SN7 Universal Preamp with an appropriate power stage!
This time, I even dared to apply as a test builder what I do not regret! More than that, I feel honored very much that I got the chance!
Like for the preamp, the build videos and schematics guided me well through the build and I enjoyed it very much and I also improved my skills in this regard.
In a way, I found it almost easier than the preamp kit but I’d suggest to emphasize handling the top plate with the heavy transformers on with extra caution and best to lay it upside down into the plinth when working on the wiring.

My background in Hifi electronics and loudspeakers goes way back to my teenage years but I must admit, I’m fairly new to building tube amp kits. In fact, I started my journey on this with the MTK preamp mentioned above only 6 months ago. (And got addicted right away).

My current gear in use:
Preamp: MTK 6or12SN7 Universal Preamp (my favourite tubes at the moment: Sylvania 7N7 – with loctal adapter)
Loudspeaker: Tannoy Cheviot 1978 (original from first hand owner)
CD: Exposure 2010
DAC: Chord Mojo (1) & Cambridge DacMagic 200M
Turntable: Micro Seiki DDX1000, Cartridge: Grado Statement Reference 2 & Denon DL-103R
Phono preamp: Audiolab

Now regarding the sound:
I could use a lot of words to describe the sound but still it would not be enough – If I had to choose some: dynamic, clear, tight, crisp, detail – detail – detail but still all warmth, utmost lively!
And in addition, that’s what I call synergy – A perfect match to the 6or12SN7 Universal Pre!!

Well, I must say that I have absolutely liked the Willsenton R8 and I still do, but the GU50 monoblocks clearly play in another league!
I always thought that you only can get precise and detailed sound by sacrificing warmth… Obviously, that is not necessarily true as these amplifiers prove. That must be due to the SE Class A design, I had only heard about before until now…

The first record I played was the new album by Brad Mehldau “Your mother should know” (the Beatles covers) – “I am the walrus” among other tracks is simply outstanding! It is indeed a really good live recording though but hearing it through these amps makes you feel it is right happening in the room!
The same applies to Nick Caves solo (alone) piano concert “Idiot Prayers”, Keith Jarretts “Sun Bear Concerts”, etc.
The dynamics on “Oslo” by Michael Wollny is in fact astonishing! So is Cathal Coughlans “Black River Falls” and Kham Meslens album “Fantômes… Futures”! Jan Harbecks saxophone on album “Balanced” sounds absolutely incredible!
Only to mention a view – I could go on for ever…

Another funny thing is, as that I hear the music differently than before, I started liking albums which I didn’t particularly before.
Bass is tight and precise – Moreover, it really sounds so natural and the bass drum for instance actually has a ‘tone’ and is not only heard as a “Bump”! I do like that! In fact, that clarity undeniably applies to the whole frequency range – And all that while still carrying the warmth! And not only that, it really carries emotions!

Also the stereo separation, the soundstage and first and foremost the detailing and layering capability is phenomenal! Very, very, very natural!
What is really pleasing me is the details to be heard apart from the music itself: the slightest “pffft” sounds and even the operation of the flaps from a saxophone or pedal noises from a piano, not to mention the attack and the timbre of string instruments!
All in all, I’d like to use an expression Jim uses to say on Mullard EL34 xf2’s: IT SOUNDS LIKE LIQUID GOLD! I would say that nails it perfectly also here!

When listening in the evening when it’s already darkened outside, by looking at the amps, it is like looking into the open fire of a chimney on a winter evening…

While I’m currently simply enjoying listening on my current gear, I look forward to building another Mellow Tone Kit – I can’t wait for the Headphone Amplifier Kit…!

As always, thank you very much, Jim & Charles, for keeping us up on quality vintage tubes, the weekly very informative Tube Lab videos and the development of the fantastic Mellow Tone kits!

Sincere regards from Switzerland!
Stanton Bailey (Reviewing GU-50 8W Monoblock) – September 24, 2025

Click To Expand “Bottom line – fantastic sound, fun easy build.”

The GU-50 monoblock amplifiers are a fantastic way to improve your audiophile experience while also learning a ton about tubes and the actual electronics you’re using.

First the sound. I substituted these amplifiers for my outstanding Primalunda Evo 300 power amplifier and used the Evo as my comparison. I ran the GU-50s using a SOTA Comet turntable with an Ortofon 2M bronze and streamed from an Ultrarendu into a Schiit Gungnir/Freya+ combo. I used three sets of speakers with dual Rel subs to listen with the following efficiencies. Zu Audio Omen Def Supremes – 101 dB, Sonus Faber Sonetto IIIs – 89 dB, Von Schweikert VR-1s – 89 dB. All of the pairings were loud enough for my comfort and listening style with plenty to spare. The Omen Defs could shake the room but I felt like the Von Schweikrts paired the best with the speakers disappearing into the music in an amazing way. The first thing I did was just sit and smile amazed at how much better the music seemed to be. I noticed a much stronger, tighter bass. I had to dial down my subs. The result was a nicer timbre from string instruments. Not just the upright bass but violins, trumpets, and electric guitars sounded more quick and alive. Acoustic guitars had a richer tone. Kick drums and cajons were more palpable and punchy. Midrange was full and engaging as if the singer and sax were there in my living room. The treble didn’t seem to change significantly for better or worse. The next huge difference was in the black deep silence between notes and pauses. Turned all the way up without input there was just silence from my 101 dB speakers. No amp I have used was this quiet. The Primaluna has a notable hum with an ear next to the speaker despite all my efforts to eliminate it. I was just plain gobsmacked. Probably the next very notable change was in instrument separation and the spacing around singers and instruments. Singers in duets and groups seemed to move apart and I noted a greater depth to the sound stage with a bit more holographic imaging. Remember with taxes we’re talking $5,000 for the Primaluna vs. $2,000 for the GU-50’s. Also putting new “Budget” tubes in the Primaluna would be around $400 vs. $200 for “Premium” tubes in the GU-50s. I racked my brain to come up with a criticism regarding the performance and I couldn’t think of one.

The build was just plain fun and so straightforward forward I think anyone can do this. I come from a ham radio background and have built numerous kits in the past. This would be a project I would recommend for anyone as a starter kit. The soldering is dead simple but the build can get complex so one has to be attentive and exacting at times. Jim and Charles literally hold your hand through the whole build and explain everything in such detail I think a high school student would easily be able to complete this without a problem. I recently built a Bottlehead Crack and found it more difficult than this kit. However the hand-holding would be my only criticism regarding the build. I would like to see a written guide so you don’t have to go through all the videos again for the second amp. I literally watched the videos and wrote my own instructions so I could just build without having to start and stop the video on my iPad while I worked.

Bottom line – fantastic sound, fun easy build. For me it’s a joy to listen to and having built it brings me a great sense of pride and ownership. It will be something I hand down to my kids when Jim and Charles come up with the next best thing.
Thanks guys
Stan
crakers7 (Reviewing E80CC Dual Mono Preamp) – September 24, 2025

Click To Expand “Jim was a pleasure to do business with and a big help in the build process. Cheers!”

I have just finished the E80cc build and after a couple of dramas which were totally my fault I have now started listening to it in my system and all I can say is WOW ,I honestly did not expect the much of a difference, it truly sounds incredible!! Im using it plugged into my Willsenton R8 with 96db efficienct speakers , I was previously using a Denafrips Athena preamp which is their top of the line pre and costs 4 or 5 times more than the E80cc and sounds wonderful but this E80cc blows it out of the water, the increase in soundstage, detail, dynamics is incredible . I Can highly recommend this kit preamp and the tubes it uses are so well priced . Jim was a pleasure to do business with and a big help in the build process. Cheers!
marchunter (Reviewing E80CC Dual Mono Preamp) – September 24, 2025

Click To Expand “It has become my daily driver. Great job guys, this thing rocks.”

I built both the Universal and E80cc Kit Preamps. Both preamps are wonderful and a joy to build. I just finished doing a plug and play shootout between the two preamps. Of course we know the layouts are similar so the difference may be the tubes used and the corresponding circuit for each. Having said that I am surprised that I actually prefer the E80CC pre. Why? It has the same detail as the universal pre but the warmth (I know) is so much nicer to my ears. I could listen to this preamp all day on my Klipsch Fortes and be fine. Just for your information I’m running either a digital receiver or a turntable through the pre, then I’m running out of the pre into an ST70 (EL34) clone then into the Forte’s. I’m running the Tungsram E80cc’s in the pre. In the universal pre I’m running Sylvania JAN 12SN7’s out of Jim’s good bin. The difference is apparent from the first few notes. I understand why the universal pre sells better than the E80cc pre (6SN7’s are great) but truly there is no reason for that when you listen to them both. This pre is wonderful. You will not be sorry you bought this pre ever. It has become my daily driver. Great job guys, this thing rocks.
Marc
Jesse Curran (Reviewing E80CC Dual Mono Preamp) – September 24, 2025

Click To Expand “This E80cc Pre-amp kit build was an absolute joy to put together.”

This E80cc Pre-amp kit build was an absolute joy to put together. I am a complete novice, no prior experience at all… Just an enthusiastic audiophile! The videos and the customer service is great! I felt like I had a friend walking me through each step of the way….. now that I’ve finished and started listening…… I was just stunned and needed to take time to articulate how amazing the changes are. I’m an owner of the Willsenton R8 integrated amp, The synergy between these two components is unbelievable. Sound stage is deeper, taller, wider and more holographic. Instruments have more weight and density to them and are floating effortlessly. The music is so much more dynamic and exciting… Explosive! So much less compression between the soft and the loud… Clarity, the music is just bigger and fatter and has more weight to it. I’ve never heard such detail in the bass and clarity with acoustic music. It’s live, evolving and emotionally engaging ….. spooky good! Top-tier for sure…… It gets my highest recommendation!
fdranger610 (Reviewing E80CC Dual Mono Preamp) – September 24, 2025

Click To Expand “I am now discovering/experiencing much more dynamics and harmonic resolution in my favorite music collection.”

The E80CC Dual Mono Class A Preamp design simply helps to create an exciting and balanced life like sound at all volume levels in my listening room. I am now discovering/experiencing much more dynamics and harmonic resolution in my favorite music collection. In the Fall season of 2021 I was riding my electric bike from a distance toward a local high school marching band playing on a practice field. As I got much closer I could feel all the lifelike dynamics of their music. My system now has the same exciting musical dynamics using the E80CC Preamp. Thank you Jim and Charles for this wonderful preamp design and your careful and thoughtful kit building episodes with excellent customer support! I bought the soldering station, solder type, and flux that you recommended in the build list. When you gave soldering iron temperatures in the build episodes to solder the various parts…. they went together well because of your directions. The kit was fun to build! Thanks again!
Gary West (Reviewing 6or12SN7 Universal Preamp) – September 24, 2025

Click To Expand “It was so much fun to build.”

I am so glad I got the 6or12SN7 kit. It was so much fun to build. I learned so much about how it works by watching the build videos. It is super satisfying to listen to music on a piece of equipment that you built yourself. It makes me wonder how satisfying it must be for Jim and Charles having designed and built all their own equipment.

After I was done testing it making sure all the voltage values were correct and checking the noise floor it was time to listen. I closed my eyes, melted into my chair for hours and just enjoyed all the little details. I kept thinking I hope I can replicate the experience over and over. Only time will tell.

Thank you so much for making this kit
-Gary
Matt W (Reviewing 6or12SN7 Universal Preamp) – September 24, 2025

Click To Expand “This was my first build that included such great directions and video’s to help the builder.”

Very nice kit with quality sound. This wasn’t my first preamp kit or tube audio build..but this was my first build that included such great directions and video’s to help the builder. I can’t stress enough how vital it is having good build notes & help when doing a project. If you are a first timer my feelings are that this is a GREAT project to start with. Jim is an Email away if something in the schematic or videos are not clear enough for you. Jim responds quickly & is very patient. He is a good dude.

The build was pretty easy for me. I suggest doing as Jim says and watch the video first before building that segment. The videos are very thorough. The build is broken down into sections so you can take your time with it if you want. He even gives you the right temperature for each job or section..a small thing that will make a huge difference for those without a lot of experience.
A tip I will share is when wiring to the RCA jacks. If you are slow with this process you can melt the internal plastic insulation. I did this on my first build a couple years ago. What I do now is preload each RCA jack with a little solder before even attaching (screwing in) the RCA jack to the top of the chassis..which is a quick process. When it’s eventually time to wire to the RCA’s you just warm up the preloaded solder with one hand, push the wire in with the other hand, back off the soldering iron, and done.

When completed this preamp is a beautiful piece. Something you can be proud of and put on display. The preamp is quiet. Very balanced in sound. Lots of detail & good dynamics. Not oldskool CJ tubey or overly rounded soft edges but hint more weight & richness compared to most mid-fi solid state. Takes the glare & smidge of sibilance off my digital listening. Now a lot of what you hear will come down to the tubes used…but the circuit is fundamentally good.

I’m in my 50’s and have had more preamps than I can remember. This Universal unit is a proper preamplifier. Absolutely nothing wrong with it. I jumped the first input caps & eventually upgraded the other caps to more high dollar boutique types. I even upgraded some resistors. What I will say is that the parts that are supplied are of great quality..and there really is no need to try and upgrade. But the way the layout & build is done if ever you want to change or repair anything it is super easy to take the boards out. I love how none of the wiring is soldered to the boards or heaters. MTK has really thought all of this through. I also only use the preamp for streaming so I don’t use the input switch..im wired straight from one set of inputs to the volume pot.

I’ve tried a few tubes and have had great success with all of them. I prefer the 12sn7 family but I’m currently using some RCA 5962’s. I get a wide & deep soundstage with great clarity & detail. Certain tubes have qualities about them that may be better than others but I didn’t encounter any tubes that made the preamp sound bad. I even tried some 12au7’s with adapters and found the preamp to still sound & perform well.

So yeah, I feel just like the other people that left reviews on this preamp. It’s good. It will last forever. It is something I can pass down to my son one day.
Ilyes (Reviewing 6or12SN7 Universal Preamp) – September 24, 2025

Click To Expand “You are paid off when the preamp comes to life and plays the first track: Wow!”

That was my first DIY gear and my first soldering experience. I enjoyed a lot building the whole thing thanks to Jim’s instructions in the build videos. The most difficult soldering work was the RCA jacks, otherwise the soldering job was not so hard.
For a beginner like me it was a real challenge, I made 2 mistakes and learned a lot: mainly keep an eye on schematics, they prevail on building videos.
You are paid off when the preamp comes to life and plays the first track: Wow!
Overall, the preamp coupled with Willsenton R8 (tubed with EL34 Mullard xf2 ) improved the vocals, soundstage, detail, tones and bass compared to the same Willsenton R8 tubed with Sylvania 6SN7GTB and 6SL7 in preamp stage:
– Performers voices are clear well defined and forward as if they are standing in front of me
– The soundstage is more holographic with better instrument separation and placement
– Tone, clarity and Instruments sounds much better

Depending on tubes used in the preamp the perceived music is slightly different
– Sylvania 7N7/6SN7GTW bought from Valvesnmore
– Vocals are crystal clear, very well defined and more forward (Anette Askvik, Eva Cassidy, Norah Jones never sounded so good)
– The soundstage is impressive in some tracks (Birds on a wire – Jennifer Warnes) especially in prog rock
– Tone seems to be better controlled making instrument sounding very realistic (Eric Clapton unplugged, Anouar Brahem instrument …)
– Bass bass bass: the bass is so well defined that I turned off my subwoofer in almost all tracks (including electro, dance …), except maybe couple of electro songs that require very low (deep) bass

– Fotons 6SN7GTB
– Details are just amazing, allowing me to discover some sounds better than the Sylvania
– Instrument separation are accentuated more than Sylvania
However more distortion is present (can be appreciated by some people)

This preamp is really amazing and improved so much the overall sounding that I am enjoying relistening to all my favorite tracks.
I would like to thank Jim and Charles for their patience and advises in the building process and for components quality and tubes.

My setup: DAC Mojo 2 – Universal 6or12SN7 Dual Mono PreAmp – Willsenton R8 – Jean Marie Reynaud Euterpe speakers 90db.

Ilyes
Ted Sid (Reviewing 6or12sn7 Universal Preamp V3.0 Upgrade) – September 24, 2025

Click To Expand “The change in the circuit, while simple, has taken my PreAmp to another level of enjoyment.”

The V3.0 upgrade kit for the Universal 6or12SN7 Dual Mono PreAmp is a wonderful update to a great kit.

The change in the circuit, while simple, has taken my PreAmp to another level of enjoyment.

The first change to notice is easy to hear, the bass has more detail and drive. it is not over the top but easily heard from the first listen.

For myself, I realized the other improvements while listening to tracks I was very familiar with. What I heard was an overall improvement in pace, drive and especially leading edge sounds of instruments.

The result, for myself, was an enjoyable improvement of an already much loved preamp, but also that of a more relaxing listening experience as I realized it took less mental energy for my mind to see the instruments being played.

That change was not as obvious to me right away, but became VERY apparent and easy to hear the difference when playing much loved tracks.

Overall this upgrade kit is an easy recommendation. The kit will not change anything you love about your existing preamp, but expand and improve on the things you already appreciate.

A very good kit and improvement! I hope everyone can experience and enjoy this kit if they get the chance to.
Juergen (Reviewing 6or12sn7 Universal Preamp) – September 24, 2025

Click To Expand “What a great sound. A lot of clarity and a really well balanced sound.”

I just received my Preamp Kit last week and finished the build over the weekend. What a great sound. A lot of clarity and a really well balanced sound. Great work Jim and Charles!!!
The build was easy and the video instructions are great.
I am running the Preamp with a solid state power amp which I also have build myself. This is a great combination.
I am already thinking about building the mono blocks. I will see, because my speakers have only 89db efficiency.
I can highly recommend this kit to anybody who likes to listen to high quality sound. I am using Psvane CV181-T-MII/2 / 6SN7GT tubes.
Thanks again Jim and Charles!
Kind regards
Juergen from Germany
Auers (Reviewing 6or12sn7 Universal Preamp) – September 24, 2025

Click To Expand “The clarity and stereo separation is in another dimension, the soundstage seems twice as wide!”

I can entirely confirm everything other reviewers mentioned but still want to express also my experience.

*Back story*
I got to know valvesNmore more or less by chance through their Tube Lab videos on YouTube, just after I had received my first tube amplifier – the much quoted Willsenton R8. That was at the end of 2021. After all, I had watched all the episodes of Tube Lab videos on YouTube that had been released until then and finally ordered Svetlana 6550C’s and Sylvania 6SN7/6SL7’s from valvesNmore for the R8 to replace the stock tubes.

*Why I chose this kit?*
Finally, after a long hesitation, I still wanted to dare to build the 6or12SN7 Universal Dual Mono Preamp Kit. I must say, I am not a beginner in hifi electronics, but I had “only” built crossovers for loudspeakers up to now, and have never built an amplifier.
There are probably 1001+ kits in the world and I have also looked at one or the other, but Jim and Charles gave me the greatest confidence from the beginning with the Tube Lab videos! And that finally proved true with my own experiences!!!

*How did I experience the build?*
However, my initial self-doubt had quickly vanished into thin air! The reason: The building instruction videos are so detailed and well explained that building was just as satisfying as finally enjoying listening to music!
Well, I must admit, I had problems with the wiring of the primary side of the main transformer, because there was a discrepancy in the schematic for 240VAC voltage. But Jim was immediately on the spot in each case and always promptly responded to e-mails.

*How do I experience listening to music with it?*
Even I find the Willsenton R8 to be sounding very musical, warm and still clear (which of course also depends on the tubes), I now have to admit that the 6or12SN7 Universal Dual Mono Preamp is in a completely different league! I can confirm so far everything that Jim has emphasized several times: The clarity and stereo separation is in another dimension, the soundstage seems twice as wide!

Meanwhile, I have rolled various 6SN7’s – For a long time my clear favourite was the MELZ 6N8S – The clear sound of this tube does not sacrifice warm mids at all and is indeed a dream for me harmonically! I would have thought this can hardly been beaten but unexpectedly this Loctal still stepped it up a notch – in particular regarding clarity: Sylvania 7N7 (with the Loctal to Octal adapter)! The details these reveal goes literally on and on…! Highly recommended to try these out!

*My Configuration/Setup*
Currently I’m running the preamp on the R8’s preamp input, but hopefully soon on the Mellow Tone Kits GU50 monoblocks…! (are close to completion :-))
Loudspeaker: Tannoy Cheviot 1978 (original from first hand owner)
CD: Exposure 2010
DAC: Chord Mojo & Cambridge DacMagic 200M
Turntable: Micro Seiki DDX1000, Cartridge: Grado Statement Reference 2 & Denon DL-103R
Phono preamp: Audiolab

*My recommendation*
I can recommend this kit to any friend of good sound, especially to those who enjoy DIY.
Among the required skills I would count soldering and basic knowledge in reading electrical schematics. But that’s all! Amateur level is quite sufficient.
Plus, Jim and Charles always give very helpful tips in the how-to videos, so anyone with half a practical talent is sure to make it!

Jim & Charles, thank you again for running the online store, the informative Tube Lab videos and the development of the fantastic Mellow Tone kits!

Best regards from Switzerland!
Justin Frakes (Reviewing 6or12sn7 Universal Preamp) – September 24, 2025

Click To Expand “The customer service provided was second to none”

First, the build of this kit was on the easier side for a Kit Amp. I did make one error by getting a tube socket off by one pin but that wasn’t due to bad instructions. Jim was very clear in the video on how to keep from making this error and I simply reversed my socket while marking it. The error was caught during final inspection so no harm no foul. The customer service provided was second to none, when fellow test-builders found shortages in white wire length and nuts, replacements were sent immediately without question. I did not have the shortages but had spare inventory from my Yuri builds.

This preamp is a tube rollers dream as one can adapt the sound to taste depending on the tubes used. I critically listened with the following tubes:
#145 Sylvania JAN 12SN7GT
#247U Sylvania 12SN7GT “Bad Boys”
#250 Tung Sol JAN 12SN7GT “Mouse Ears”
#154 RCA 12SN7GT
#246 CBS Hytron 12SN7GT
#1b Sylvania 6SN7GTB
#138 Canadian GE 6SN7GTB
With all of the tubes the sound stage width was very similar in my room varying less than about an inch or two. The imaging was good to excellent in all cases. The differences I could pick out distinctly, were mainly the low to mid bass presentation (toms and snare in a drum kit and male vocals) and in the details (think cymbals shimmering and things like finger snaps or claps.) In some cases the separation between the singers and instruments had more “air” to my ear but it’s hard to explain. The Universal Preamp was also Dead Silent. With it turned all the way up to “11” there was nothing coming from my highly efficient Klipsch Forte III’s.

For non-critical Rock-N-Roll listening I’d go with the #246 CBS Hytron 12SN7GT. You trade detail for more mid bass muscle kind of like a loudness button from the old days (a great match to my Klipsch speakers.) while listening to Tools “Chocolate Chip Trip” the drum solo section leapt from my speakers and literally had me pumping my fists. For critical listening when you want the most detail, go with the #250 Tung-Sol JAN 12SN7GT. In this case the bass is more neutral and less visceral; however, the clarity of the details more than makes up for the reduction on bass. In Michael Jacksons “Billie Jean” his finger snaps sounded like Mike was in my listen room! The best mix of detail with bass presence were any of the Sylvanias with the #1b 6SN7GTB very slightly edging out the other two (these are my most broken in pair so that could be a factor.) The bass was much better controlled but still present, more like what live drums sound like. The Sylvania family had a very nice “calming” effect on instruments that can be very harsh with other tubes; for example, the harmonica in Chris Jones/Steve Baker’s “Soul Storm Comin’.” I love this song and the record, but if poorly reproduced the harmonica can induce fatigue very quickly. My final litmus test for comparisons is Jackson Browne’s “Running On Empty.” My fathers favorite singer/song, so I’ve heard it about a million times during my life. This live recording comes alive in my system with the Sylvania’s, I just wish my dad was still here to enjoy it with me.

I wanted to compare the Universal Preamp to my old Schiit Freya + using the same tubes so I swapped and compared the 6SN7’s I have on hand. The sound stage was narrower on the Freya, still wider than my speakers but noticeably less enveloping. Imaging was close but details took a back seat to the Mellow Tone kit. Not quite a “blanket” over the sound but both sets of tubes sounded better in the Universal Preamp. I think the dual-mono design of the universal preamp is contributing to this phenomena (but what do I know.) The Freya + also had a strange tone present in all of the listening I did. Almost like the low-mid treble was pumped up, i had never noticed this in my previous listening to the Freya + but in a back-to-back listening session it was very apparent. Thinking it might have been because I was using XLR connectors from my DAC to the Freya and RCA for the Universal, I swapped cables and the tone was still there. The Schiit is a fine preamp (more so with a tube upgrade) with a lot of connectivity options and could serve anyone well. That said, if the options of the Universal 6/12SN7 Preamp cover your needs AND you have a DIY spirit and want to learn how your audiophile equipment works I’d strongly suggest giving one a try. Its also a relative bargain compared to the Freya at $300-350 dollars less.

For my review I used the following equipment:
Raspberry Pi running RoPiee (controlled with Roon)
Tidal Streaming
Schitt Modius DAC
Yuri Mono-Block Amplifiers
Klipsch Forte III speakers
All cables DIY using Mogami cable and Neutrex connectors
Ted Sid (Reviewing 6or12sn7 Universal Preamp) – September 24, 2025

Click To Expand “The system now sounds the best I have had in all my years of playing”

This was a great kit for a first timer. Because I was late to the test build I benefited from all the updated tips.

I had one issue when I was testing the power. I had no output from the transformer, or very little. I had all my power in but none out. I started from the very start of the power chain and discovered I had somehow broken the neutral jumper wire that goes from the power input to the switch.

With the little extra white wire left over and the extra spade terminals in the kit I was able to make a new wire and all is well!

I listened for hours last night. I had to sit there and let track after track play from a playlist I have, play through. Every song was more enjoyable and I even ended up turning the music up a little louder than I usually do due to the quality of the sound.

Right now the preamplifier is driving a little 5watt class A amplifier that Nelson Pass gave to me right from his workbench!

I used to have an Ocellia preamplifier(passive for digital, tube active for phono) and 300B monoblocks.

The system now sounds the best I have had in all my years of playing.
And I have had everything from Atmosphere, McIntosh, Rogue, Bryston, Quad, NAD, Mastersound, Vfet Sonys and others.

Like you say, the tubes ARE the amplifier! And I still have some Tung-Sol “Mouse Ears” to try out!

There is something special about having built something yourself that makes everything all the more sweeter, but without your great kit and videos, I would probably not have tried to build my own preamplifier.

Thank you again for the gift of sound and reward of building something myself!

Ted
Mike Baron (Reviewing 6or12sn7 Universal Preamp) – September 24, 2025

Click To Expand “The kit is a joy to build with great instructions”

I appreciate the time Mellow Tone Kits took with this design, creating an affordable great sounding preamp that we all can take advantage of. Anyone considering this preamp should be confident that the kit is a joy to build with great instruction, and the sound truly improved my system. In my case that is pairing with the Willsenton R8 using the preamp input.
Clarity and imaging with sound stage improvements were my first impressions and I could not stay away from higher volumes – yes I heard new instruments come out on some of my favorite tracks that I have listened to for years.
I plan to pair this pre up with a solid state amp for my next nirvana endeavor.
Thanks Again!!
Mike
marchunter (Reviewing 6or12sn7 Universal Preamp) – September 24, 2025

Click To Expand “A wonderful experience”

I couldn’t stop listening as soon as I fired it up.
I had a wonderful time building the Universal Preamp and learned a lot. It was so fun I couldn’t stop and finished ahead of Jim’s instruction build. I had a couple hiccups but they were of my own making and easy to fix because of the thoughtful layout. My hiccups were also very instructional. A wonderful experience.
The sound is where you really get paid off for your labors. All terms you’ve heard apply here. Soundstage, separation, warm yet focused. It’s all here and you built it yourself!
I can’t recommend this kit highly enough.
Thanks guys
Justin Frakes (Reviewing Yuri Monoblock Amplifier) – September 24, 2025

Click To Expand “I can fully recommend this amp to any aspiring audiophile or DIY’r”

These kits are very well designed with quality components. Along with the video build guides the build process is easy if you can solder.

The sound of these amps is incredible and they are dead silent at idle. My system previously was a Freya + with Valesnmore upgrade tubes into mono-block Schiit Vidar class AB amplifiers. This fed Klipsch Fotre 3’s. The Yuri’s were put in place of the Vidars for my listening.

My listening impressions are a substantial increase in the mid-to-high bass presence as well as the low mids. Very nice and full sounding. The soundstage was a touch wider but the depth was increased very noticeably. On Jennifer Warnes “Ballad of the runaway horse ” the bass moved back into the mix and Jennifers voice was front and center. The imaging was also improved. It is easier to pick up where singers and instruments are placed in a live performance. For example, The Eagles Hell Freezes Over performance of “Hotel California” each member is distinctly placed in front of you.

With my speakers I was able to easily drive them to 90dB (a very loud listening level for me) and the sonic improvements were still evident at a more modest 75-80dB (my usual listening level.) I’ve listened to other SET tube mono-blocks in systems similar to mine and the Yuri’s are very competitive with commercial offerings costing much more.

I can fully recommend this amp to any aspiring audiophile or DIY’r. This product is first rate and the service Jim provides is unparalleled.
pmoxhay (Reviewing Yuri Monoblock Amplifier) – September 24, 2025

Click To Expand “I highly recommend the Yuri”

I have just completed the Yuri monoblock with three high school students as an electronics project. This is a great product, and the support was superb. The videos gave very precise guidance. Students with minimal soldering and fabrication skills were able to follow the videos easily. The music sounds great even with a single channel without a preamp, and we look forward to incorporating this component into a full-fledged system in a future project. I highly recommend the Yuri and the high quality of support provided during the assembly process!