diyAudio Passworks Korg NuTube Preamp Kit Build Tips & Hints 

It is refreshing to see someone else teaching others how to install components leaving an air gap between the board and component. My grandfather, Dad and Uncle all had electronics backgrounds and instilled in me how important it is to have air flow around components, I have been doing this ever since.

Thanks for showing off this kit build, lots of good little tips sprinkled throughout.

Loved all your little tips as you went along.

Just finished the build and calibration - as you say a pretty straight forward project but fun. Have now attached to my Quad 405-2 and some no name speakers and am pretty happy with is output. Has good clarity , great midrange - Bass is pretty good for me ( too much 70" s rock) not overemphasized. Great construction notes and good testing advice - almost ideal notes . Thanks Mark for alerting me of this . No microphonics !

Thanks for the video, I'm planning to have one. Waiting for the next update

Thanks, ive got the kit, just ablut to start building it and your video has given me confidence, ive built a couple of the amp camp amos so looking forward to hearing how it sounds witb them. Thanks again

Great build Mark! One tweak you might try is bypassing the electrolytic coupling caps with some 1uF Panasonic polypropylene caps mounted under the board. One thing I like about the NuTube is the 30,000 hour lifespan. I can fall asleep with the unit playing, and I don't feel guilty about wasting the precious life of a valuable NOS tube.

Great build! Very thorough and informative. Thank you.

Mark you are the best! I did build your KT88 amp and working perfect I using it for Sherwood turntable thanks a lot for great tutorials I build my custom output transformers for it and sounds great

Very interesting video, looking forward to the test video. Thank you.

Good assembly tips and tricks. NuTube makes the jucy tone of triodes available at beginner safe voltages.

Thanks for this vid, Mark. Because this preamp was designed by the legendary Nelson Pass, it makes me especially curious about it. I keep meaning to order one. It also just looks like a fun project. I’m sure you’ve heard this before, but you’re kinda the Bob Ross of audio videos, and I love em! As it should be, repairing anything electronic takes patience, and one should take their time as well. You’re teaching such extremely valuable information and it is truly appreciated.

EXCELLENT VIDEO!!! THANK YOU!!

Hi Mark! One of these days can you do a video on the criteria needed to replace obsolete transistors? TIA

Very good video, you made it look very easy to do. You should make a video of the building of it's companion piece - the "Amp Camp Amp" which had gotten rave reviews.

Interesting device, good build. I guess I'm old school. I like tubes that look like tubes.

Hi Mark good tips for beginner kit builders. I have been watching your videos for some time now but I would like to get some of that blues music that you occasionally play. Where or how would that be possible?

Hi. Question. Will this preamp work in conjunction with any amplifier? Or does it have to be mated with a specific DIY amp that I'm not aware of? I'm thinking about building one of these and hooking it up to a pair of solid state Marantz monoblock amps. Will that work? Thanks

Excellent video Mark, the volume / potentiometer from preamp affects T7 and T8 voltage. Set at 9.5v when volume increases T7 and 8 voltage increases. What setting should the potentiometer be at when we set the 9.5 v? Min max middle?

So have you ever thought of doing the Hagerman Bugle 2, I had fun building mine.

Great practical tips... Manila envelope wedge takes the cake! About the preamp, I heard this is a phase shift one where the speaker wire polarity needs to be reversed. Any observations?

I think multi turn trim pots would be the way to go with this project. It should give you better control of dialing in the voltage.

Great video, Mark. I've been skeptical of these because of the very low gain. I think I read somewhere you need about 10x of them to get the same gain as a 12AX7 stage. Just seems almost pointless. I hope it works out though.

Would it be better to use multi turn trim pots to dial in the voltages more easily?

Intersting but I would miss seeing tubes on the top glowing lol

Love this guide. Some really great tips. Question: what about resistor DIRECTION? I know that a lot of these components are directional, how do you determine the correct way to install?

Isn't that kind of strange wiring of the input connectors where Left and Right signal wires are made in twisted pairs instead of twisting together Signal and Ground wires for each input?

Would be nice to get a whole lot of the KORG 6P1 Nu-tubes and build build something like a Williamson type amplifier that works on a B+ of 50-90V and a Heater Voltage of 1.5V

What a fun project. So what's the final verdict... are NuTubes a gimmick or are they serious contenders ?

You might find in those situations where you've got to line up a bolt where they nut is to put the bolts through first sticking through the plate and you can just chase the nuts and just nip it up with your fingers and then do the second one it allows you to see what's going on makes it dead easy

hi do you know the output impedance of nu tube. thanks

Thanks for the video and demonstration. I bought the kit too and about to get started on it. Now that I saw your video, i want to ask if you ever gets any feedback ringing when you touch the tube or alot of microphonics from the Nutube itself ? Alot of people report that they have terrible microphonics ringing from the Nutube. Thanks!

I am considering buying this kit. But i would need twin outputs so that i can bi amp with a pair of stereo power amps. I presume that electrically they would be wired in parallel with the original output rca sockets.

Hi Mark, could you provide a link for that socket screw driver with the stand

The 12AX7 along with many, many triodes are still easily obtainable. Most have much better specs. They would require more power. The Nutube might be good to get a different sound for an effect.

Is your 270R getting really hot? I can't hold my finger on it for longer than 5s.

Great video!!! I wish they incorporated some tone control in the design.

Was going to buy Tronix wire cutters. Dang, they are pricey! About $65- $90 on Amazon.

So it's almost 2021 and I can still buy a 12AX7, new, used, or NOS. Now what are the chances that special tube featured here will still be available in five years??? P.S. is that wire just CAT5 scraps? OMG, the audiophiles will have a fit over that. Let's see, CAT5 wire will make it sound very "digital" :)

A preamp that doesn't correct the phase before it leaves the unit? Is that common?

Nice little preamp. Sorry to be slightly off the point but what was the first track you played, sounded very cool but Shazam doesn't recognise it.

When it’s a Nelson Pass design is famous for making transistor sound like tubes that nice soft analog sound. I purchased and built the Pete Millet version of this NuTube. I have built other Nelson Pass design amplifiers and preamps. One thing for sure you can never go wrong building a Nelson Pass design. The help you get from Do It Yourself Audio (DYIAUDIO.com) from other members for newbies building their first project is incredible. Sometimes the price point is a little too high for some people the majority the cost comes from purchasing the fancy aluminum chassis. If you’re on a budget you could get a eBay or electronics project case for a couple dollars to keep your costs down.

Neat.

Pete's got some interesting designs. I've seen his NuTube designs on his site. Probably some form of this circuit. I built a 2 channel version of his tube mic preamp last year. Sounds amazing.

I take it this is a line stage preamp and not a phono preamp...?

Great vid. Somehow I thought that pad under the KORG piece was to dampen micro-phonics. EDIT (it is).

AND WHAT NOT!!!!

I’ve been eyeballing this for a bit. Not sure that I want to pull the trigger without hearing one.

There is One thing I don't get, why is everyone that build this little preamp always twisting the 2 live wire ??? Maybe it is me, but if you twist 2 live wire you make the opportunity for introduced bad channel separation and hum since it isn't the ground you use for each set of live wire.

You were kidding I hope when you said some people like it inverted, it sounds better to them.. smiles, right. Think about that, with out another of the same media non-inverted in the same volume of space, can you detect if a AC audio signal is an inverted signal ? If you can you are one special human indeed.

Is that Cat5 or Cat6 wires?

Unrelated, but I think you mentioned this a while back, Mark; any idea about repairing the feet on a Micro Seiki BL-91?

I thought the KORG NU TUBE kit ran off a wall wart running 24 VDC. I don't remember any 70 vdc power supplies.

This little pre-amp is high end audio for peanuts money - it's the same circuit as the Neslon Pass First watt sets sold in limited numbers and tested my 6 moons and declared to have sound quality close to that of some $10,000 pre-amps. The whole point is you can adjust just how warm you want it. Huge sound stage. TKD volume pot is a good upgrade along with better spec wiring and power supply. 6moons.com/audioreviews2/firstwatt4/1.html

Nice kit and nice build. Only think I do not like is using that kind of solid core twisted pair for unbalanced high impedance audio. It won't give same kind of shielding as proper coaxial cable would, and even worse input has two channels twisted together, not ground and signal which will defeat whole point of twisted cable. This seems to be common problem with many "high fidelity" diy builds, I don't know if this comes from just ignorance and using wires stripped from old ethernet cables, or if builders have seen twisted signal lines used in proper professional balanced setups and have just tried to copy that look.

The nutube is just a VFD in disguise

Theres no point in using audio resitors when your using standard caps, huge bottleneck, first caps then resitors. The demo photo of a built one uses Fine gold caps because its audio use.

How can anything sound really good with a phone driving it? The 500 mv output is much to low and the DACs are pathetic in a phones. If you think it sounds good now, buy a $100 DAC (M.S.M.L) and feed the DAC a digital signal via USB from your phone. The DAC will have a 2V output and MUCH cleaner and sweeter sound. A phone can't possibly do your preamp justice. Sound quality can only be as good as the weakest link. Especially when it's a weak source going through several amplification stages in the preamp and amplifier.

Deez nutz

To pricey!

First!

Sounds not really good isn’t it

They are microphonic. The worst microphonic i have heard.This have to be decoupled from any vibrations.In that way they are real bad.

Poor design. Don't wast your time. Try Tube Cad.com. D.C.

I have seen people doing preamps using old tube displays