Korg Nutube B1
** The B1K B1K Pre-Order has now completed and we have a limited number of left over units available for sale. **
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:
What's in the completion kit?
Everything else you need to complete the project other than 1, 2 and 3 above. 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.
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
What are the chassis specifications?
- Galaxy 230x170 full aluminum chassis, anodized black with white printing
- Internal dimensions 40x210x170mm
- LED hole ø2mm
- Left switch
- Hole ø6.5mm
- 15mm x 15mm square rear recess, 7mm deep
- Right switch
- Hole ø6.5mm
- 15mm x 24mm rectangular rear recess (allows for switch and LED), 7mm deep
- Potentiometer hole ø10mm, with ø32mm round recess in the front ø8mm deep
- Rear RCA holes ø10mm
- Rear power switch hole ø11mm
The kit is quite easy to set up, and the tuning too if you go smoothly. I encountered a microphonic issue that I solved by placing a small ball of Patafix under the Nutube. I think it could be useful to isolate the PCB from the chassis because I have a very slight ringing noise when I turn the potentiometer (audible through the headphones). Finally, I placed the switches behind the front panel for aesthetic reasons. I had some worries because the input wires are not shielded, but in reality there is no residual noise. Now I will probably connect it to an F5 (to be built) for two reasons: the simplicity of the schematic and the class A operation. Many thanks for the useful guide.
The Korg NuTube kit was a joy to assemble. An easy build, I spread it out over two days (through ps test on day 1). Everything powered up with all test points in spec and no problem setting a stable bias on the triode. The sound is a great complement to a DAC with a low noise and high dynamic range output. It seems to soften the edges but also gives it a fuller, more detailed but still bright sound. This preamp seems to make the rolled-off nature of vinyl at the high and low end as well as the midrange coloration more obvious. I am using this with Klipsch bookshelf speakers (RP-150M) and an ACA; I may compare this preamp to a passive preamp for playback of vinyl in future.
Nice kit. Enjoyed the build. Very decent sound. Only issue was to find manual for final adjustments.
Will build more of these 🤓
Thank Nelson Pass and diyaudiostore team for having me a lifetime preamp.
This is hobby, so I deviated couple of parts from originals:
4 X 2200uf cap on power supply, 6 X 6.8 uf Wima cap for coupling, greyhill rotary switch for 4 input, and mono stepped volume controls, also added isodamp on nu tube and opposite side of pcb. I do know about level of distortion, but this amp just sound good and excellent.
The Nutube B1 was my second build. I started out with the ACA and wanted a preamp to go along with it. All I can say is WOW!!!! If your looking for a great way to enter into this hobby and end up with an impressive beyond beginner system this is it. I used the B1 and ACA to power my Zu Omen DW and was immediately greeted with beautiful sound. Having the ability to use the B1 to tailor the sound to your liking is a huge plus!!!! Overall VERY satisfied with the cost, fit and finish, ease of build, customer service, and most importantly the sound!!!!!!
I completed the build today, I was trying to fit it into a Hammond 1590J guitar pedal box, so it will go with my small system. The tube was lifted and facing the front, the six small holes let the light shines through, so I don't need a bright LED. Turned it on and it worked! This is my first diy project and it was easy enough to build and it sounds quite good compare to my other tube preamps. This can be my summer preamp when it's too hot to use real tubes. Very happy with the outcome!
Thinking about trying better components like potentiometer, capacitors and power supply later.
I just received this yesterday and finished it today. I have about 4 1/2 hours of work put into it. It sounds terrific. Extremely clear sounding. The tube is microphonic but it doesn't seem to be an issue unless you tap on it or mess with the preamp. I haven't done anything yet to treat it. In the build guide it is suggested to tape a pencil eraser to it. If needed I'll try that.
The completeness of all of the parts is terrific. Everything you need is there. Just bring your tools. The feet aren't the best but that doesn't really matter, especially at this price point. They serve the purpost.
The quality of sound that this preamplifier produces is top tier and hangs in there with the best that I have ever heard. It is by far the best I have had in my home. The clarity is ridiculous. It goes beyond hearing all the separate instruments and little details like people breathing etc. The little nuances have a lot of resolution and depth to them. It is hard to believe things can be recorded in such detail. I am using it with a Threshold S/500 amplifier soon to be PassDIY F6.
You cannot adjust the tone. I will say that the tone of the amp is very flat as far as I can tell. I don't notice the tube being overly warm. In fact, my Adcom GFP-565 had a much warmer tone than this preamp. I don't think I'll miss the tone controls as I really am enjoying the way this amp sounds. On my Adcom, I had the bass and Treble turned up just a tad. I don't feel the need to bother with this amp even though It has less bass than the Adcom (how I had it set).
I recommend a soldering gun with a small tip. A lot of the soldering pads are really tiny. Also good solder is a great help. I use Cardas Eutectic solder but I believe DIYaudioStore has a highly regarded solder as well. I also recommend you read the whole build guide before opening any of the zip lock bags. Some items are organized in their individual bags.
I didn't have any real issues putting the unit together. The guide is very complete. 6L6 did a terrific job which is to be expected. There are two trimmers and two test locations for the bias adjustment. T7 and T8. Locate these before you power the unit up after completing the project. You will need to set your multimeter to DC volts, touch black to ground and the red to T7 and then T8. You should receive 9.5v. The trimmers adjust this reading.
Hope you purchase the kit! It is by far the best improvement I have made outside of my speakers.
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