B1 with Korg Triode (B1K) Full Kit
At the Burning Amp Festival in 2017 Nelson presented a pre-amp using the Korg Nutube dual triode. The latest revision of the circuit available is now available complete with Fairchild JFETs and all directly supplied by Nelson Pass.
Please check the following links for more information:
There are 4 elements to building a complete preamplifier. Purchase the elements separately, or all together as a "full kit" bundle for $299. To build a complete preamplifier you will need:
- Korg Nutube ($49.99)
- B1K PCB + JFETs ($25)
- B1K Chassis ($129)
- B1K Completion Kit ($99)
What's in the completion kit?
Everything else you need to complete the project other than the Nutube, PCB + JFETs and Chassis. It's an assortment of bits and pieces that joins the Nutube, PCB and Chassis together, turning the whole things into a "full kit", hence the name "completion kit".
The included "wall wart" style power adapter supports an input voltage of 90-264V and has a US style plug. If you don't live in the US you will need to obtain a suitable plug adapter.
Each kit contains high-quality audio-grade parts that have been carefully chosen for their suitability for this project.
At the time of writing (November 2021), we're still in middle of a pandemic-related global-supply-chain traffic jam. These are predicted to extend until 2023. While we'd like to have everything match the build guide visually, quantities of some of the parts you see in the guide might not be available right now. In those cases we have included well considered substitutions. You'll have to use a little imagination when following the guide.
Discussion threads / Links:
- Technical discussion: B1K main thread
- Build Guide: B1K Build Guide
- Pre-order Q&A (old news) in the B1K pre-order Q&A thread
- Prototype feedback (old news): B1K pioneer batch feedback
- Pre-order status (old news): B1K pre-order status page
I did build the B1 preamp within 4 hours. The kit is of high quality, likewise the case, and the documentation.
I built an external power supply, which is an VRDN designed by Mark Johnson from the DIYAudio forum.
After the build, I checked the voltages as indicated in Nelson Pass' documentation for the NuTube preamp: T5 showed 0.59V, T6 showed 0.615V; I adjusted T7 to 9.505V and T8 to 9.51V.
Everything looked good.
I connected the preamp where my Quad 66 preamp was connected: between a hifiberry DAC and a QUAD 306 poweramp.
Result: the NuTube preamp has way too much gain (compared to the 66 preamp): totally saturated sound, and way too loud.
Ok, the Quads are known for being sensitive; however, when I restored my 306, I reduced its sensitivity from 500 mV to 1V (for full output power). I guess either the NuTube's input sensitivity id too high, or I must reduce the poweramp's input sensitivity to fit the NuTube's output.
However: it was a fun build.
Built two ACAs, (running them in bridge mode mono), then built the B1K as the pre-amp into the ACAs. Takes 30 to 45 minutes of play to warm up and then sounds super. B1K adds some warmth to the music. Both are great kits to build, it is surprising how good the combination sounds. Adjust voltages carefully on both for best sound - per designer recommendations.
This kit is a fun build. I suppose if you're in a hurry, you can complete it in one day, but I took my time and enjoyed the process. Built it just as provided with all the kit parts. Didn't feel any need to substitute designer parts in, as the standard parts all were of excellent quality. Opted to include an SMPS DC Filter P089ZB Kit and Pete Millett's NuTube anti-vibration mount as part of the build. Note only the blue foam on the anti-vibration mount fit. The B1 is paired with a set of ancient Welbourne Laurel tube mono amps with a Raspberry Pi running Moode Audio Player and a JDS Labs ODAC providing the inputs. I'm loving the sound. There's always a surprise in re-listening to music that I've heard many times before, as this combo is revealing details that I'd missed before. Great clarity and channel separation.
This is a high-quality kit throughout. It really amazes me that I was able to possess a Nelson Pass preamp design for such a great price. I enjoyed putting it together and appreciated the step-by-step directions. Thank goodness for BK1 thread, which identified my goof when I swapped a couple of resistors. It is a very revealing preamp and will make you reassess every other component in your system. I did notice that the Nutube got more microphonic over time. I ended up using the eraser trick in the instructions, which smoothed out the sound a lot. If I had to do it over again, I would build it with the Pete Millett vibration mount for the Nutube.
This was my second kit and from start to finish I had a great time building the preamp. The instructions were very easy to follow and the sound is superb in my system where I have paired it with an Amp Camp Amp. Thanks to Mr. Pass, DYI Audio store and the DYI audio community for helping novices getting started with their hifi audio journeys and dreams.
Thanks Mr pass for sharing this great kit with the world.
I build it in about a day and it was a lot of fun. The standard kit sounds great. Well balanced.
I startend replacing resistors with vishay dale, caps with nichicon fg and the coupling and output capacitors with elna silmic II. Each upgrade made the sound bigger and more clear. I did try out various caps prior to comming to this "endstate" basicly im in sonic heaven. Its that good. Well hete you have it, my Franken build, Well recommended
I have never build an amp before, it work out flawlessly from first attempt, sounds great with taste of tube with modern details and dynamic sound, even better after upgrade to a 25W linear PS.
Bought the Nutube and PCB/JFETs from the DIYA store, and sourced remaining components from Digikey (the Completion Kit was far and way backordered at the time) - Results were spot on at first power-up, even got lucky with zero Nutube noise - Sounds just wonderful as a front end for my DIY Pass A2.
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