diyAudio Passworks Korg NuTube Preamp Kit Build Tips & Hints

[Music] please pause the video and take a moment to read this important safety message hi mark here at blue glow electronics hopefully a fun little video today you know i've been following the development of the korg new tube uh for a couple years now and i've just been intrigued by it and wanted to play with it what it is is a modern day vacuum tube that has been developed that's designed to operate at lower voltages and when i say low voltage that's somewhat of a relative term it uh they operate around the 70 volt range which is you know much lower than the typical three four five six hundred volts that you see on most vacuum tube amplifiers and it gets it down into a safe to work with range so any rate i saw this kit pop up one day and it was a pre-order type deal from a company called diy audio store and this is their korg b1 full kit and i thought what the heck it was like 300 bucks and i thought i just want to play around with this thing so we ordered it so i thought i'd do two videos on this topic the first video is going to be building this unit and the second video will then be bench testing this unit so let's dive on into video number one when you place your order they'll give you a link to instructions on how to install this and it's written by 6l6 and it's just basically a you know a pictorial walkthrough shows you everything from unpacking and assembling the panels and whatnot and it kind of walks you through step by step really detailed close look a picture so you don't need my video to build this you can certainly use this step-by-step guide but and my video is not designed to be a step-by-step guide because if you read here it says time required somewhere between four and six hours and it's a moderate build and you guys probably don't want to watch a four to six hour video but i thought i'd hit a few highlights along the way and talk about any challenges or things i might would have done differently than what they're recommending here and that's what we would make this video about today so with the kit you really get four packages one is the actual chassis itself you get the actual tube itself you get the pc board and a couple components here and then the remainder of the components are in this bag i'm assuming so let's get these opened up but you can kind of see you get the uh you get the plates here and we're gonna get all this unpacked okay included inside the manila envelope is a piece of paper one side has a nice schematic on it the other side has the bomb for the parts here and when building a kit like this i always like to go through and as you can see here i've already started checking off items on the list just because what you don't want to do is get done building it and then realize oh gosh they didn't seem any rca jacks and i'm stuck now i usually like to start a project and finish it all at once and i will tell you they used good quality stuff this is an alps volume pot here these are not cheap rca jacks you can tell they've got some weight to them so they did not skimp here on the parts i will say all right we've got all our parts checked off now and are in good shape one thing to notice on the chassis one side of these have uh have a bezel beveled uh sunken screw holes and the other sides are flat just pay attention to that as these are countersunk screws right here that'll drop right into those little countersunk spaces and up next um i use a little metal you guys have seen these in my videos before probably but little magnetic trays is great for holding all these screws as you get them built and one of the first things you've got to do here is insert these nuts and they kind of slide down into this channel pretty neat little system here another thing that differs a little from the pitchers and from the instructions they have online these no longer have venting holes in the chassis in the top or the bottom here and it's interesting there's a thread out on line where you can kind of follow along and read about this amplifier and i'll try to link it as well and that was one of the things that to try to get rid of some of the microphonics associated with the new tube people had recommended tape taping over the actual um vent holes so it looks like maybe they'd this was an iteration of the design without those one thing that is a little bit of a pain here is getting these uh nuts aligned up where they need to be for the screws to drop in there so all i did here was kind of tilt the chassis up here on the edge of this and then i'm able to slide the nuts along and get them where they need to be here before then moving it over on top of it and putting the screws in all right as you can see here i've laid them out um kind of um you can always remember um for left and right channel r is always red or for red so we're going to go ahead and get these mounted before we mount that this back panel into the chassis i think it make will make it easier and that's kind of how the instructions tell us to do it here's a trick i learned a long time ago if you want this ground lug to linda end up over here on the center you start over here with it cocked off a little bit so as you go to tighten this down at the end um and you get it where it's really getting tight then you can keep turning it and spin it around just where you want it otherwise you're trying to hold that and it it's tough i'll tell you all right i took a slightly different approach than the instruction shows i went ahead and mounted my power switch here into the chassis i thought it made it easier to kind of just hold and work with and holding the little bitty switch and then i was able to get these wires stripped and soldered on by the way when you strip these wires on the end i like to use a pair of flat nose pliers like this to kind of flatten the wires out and you just kind of work your way around them so that you've got straight wires you're soldering and not these curled up ends like this um anything and i use these flat nose pliers to do all the bends on the wiring down here so just take your time it's a little bit tedious make sure you get the led the flat side of it in the right location and make sure you get all the wires wired up according to the instructions okay we got these three soldered on here and i did notice when i finished that i got the blue wires on the bottom and the orange and white on the top and according to their instructions it's the other way around but i'm not going to unsolder this because all they do is go connect to the back of the amplifier and the colors mean nothing as long as you get it wired up properly so keep in mind if you make mistakes like that kind of analyze the the outcome from it and if the outcome is just you're you know connecting to another point and you can swap those points around uh it's not that big a deal save you a lot of rework along the way okay and i went ahead and mounted the peat millet diy audio board onto the um alps pot here it was just simple as sitting it down on here and soldering it on and i actually mounted the pot first which made it easy to just hold this on here and solder it then and then i've started routing uh some of the wires as they suggest like the brown wire here on the middle come over and go to this bn a n and then i've got the the a out and a b an a common here but that's not been soldered yet it's still a loose hanging wire at this point i'm going to go ahead and put these uh these screws that hold the front cover in and it comes with a little wrench i've i've got a similar sized little allen wrench here that i'm going to use but um i might go ahead and get the front plate mounted on this unit so that uh so the front's kind of tidied up and held steel and i went ahead and threw a couple uh just nylon zip ties nothing fancy none of the these didn't come with the unit but uh just plain old simple little nylon zip ties you could use black or the clear ones i'm using but i'm just starting to route these wires around and while i'm routing them i like to kind of bundle and get them where i want them and i'll i'll time up a little ways i won't go the whole way because you're going to need these free to be able to work and solder back here on this side okay the instructions shows soldering all this up with the panel off the back and i agree it would be easier i did go ahead and run some some wires between here and this is just some green wire i had all you're doing is tying the uh common grounds on these two together but um i'm gonna go ahead and bolt mine up because i'm comfortable soldering down in here with it fixed and it'll allow me to get these wires to the exact length because if you got it out here and then you get done you're going to have you know maybe an inch of excess or so to to deal with so it's a uh easy versus neat kind of thing as you can see i've kind of routed it down laced it up and now i've got this top one here kind of fit in together and make sure when you're soldering you get both the wires and the lug you're soldering to good and hot let it flow a little bit and then you can uh take your soldering iron off by the way i'm just using a hako um fx888d soldering iron love them you can see this little crinkly wire i've got here literally just sitting here with the flat nose pliers kind of working you have to kind of work it from two planes both up and down and then side to side from the other side but you will get this entire wire just as straight as you want it to be and all you're doing is crimping between these flat pliers all right you can see i've got the blue wire solid blue wire routed inside of this right here side of the rca lug these take a little while let them heat up hold your iron on there let the you know a little bit of solder will help the flow and creates more surface area for the soldering iron here once you finally get it make sure you can actually touch the jack itself and that the solder will melt by touching the jack instead of your your iron all right good and soldered and as you can see nice and neat all soldered up all right we've got all these wired up at this point and you can tell my blue white is on this side and orange white or brown white orange white is over here and in the instructions that were backwards but it really doesn't matter because we've got it the same on both ends okay up next we're going to come off the middle wires here remember there's three lugs to the switch the middle being common here we're going to come off of it and come back here and tie it to this little barrel lug and input and the brown solid brown is going to go into the center here as you can see here soldered up the brown in the middle the white brown to the tab and i'm just trimming up any little excess wires here with a pair of wire snippers and you kind of see the neatness here i was able to achieve versus if i left the back down um you end up with this loop of wire here you end up with all this excess here that you're having to deal with that just kind of cramps up and that's okay because if you ever wanted to service it you could drop it back down you'd have all that to play with i just felt comfortable being able to solder and work with it on the back so i went ahead and did that okay this time we're going to go ahead and set this aside because this other connection here will end up going to the board and then there's connections from this that will go to the board and some more connections from here that'll go down to the board but um we can set this aside now and it's time to get out of resistors and the instructions do tell you to to empty out your bag of resistors and check all the resistor values before you before you get going here i'm just going to use a little fluke 179. we'll flip it over on resistance and we're gonna go through and check all these and make sure the values marked on them are correct and uh some of these are small so a lot of times i'm an old guy here um you know i pull out my handy dandy magnifying glass and and look at these things okay we've got everything for the board laid out all my resistors checked out well um you've got q2s which it shows on here as j113 and q1 is j113 i think we're just gonna have to go with the q1 and q2's here and you can see right here where your q2s go there's where some q1s go some q2s and some q1s and we'll we'll look at what those are here on the bomb in a minute but i've got my uh there's a couple other resistors in the pack with these laid out here i haven't tested those i will you got two potentiometers here you've got a diode and these and we're ready to go i will use the fault finer solder here this is .032 and there again it's a 6337 solder really like this stuff let me zoom in a little bit and show you a few things one it tells you in the instructions to not mix these up and that these resistors here are specifically um value-wise picked to match these fets and if you'll notice here on the schematic you have q2 q2 q2 q2 q2 q2 q2 q2 so you're going one two three four five six seven eight q2s yet i've only got four q2s in the bag well if you'll notice on this picture here of the uh of the layout that only the top spots are used here so like q2 goes right here this one sets empty q2 is used right here this one sits empty q2 is used here this sits empty and these little values here called r1 neither are they marked on the board anywhere it just says r1 that is where you will match up with these four resistors that are specifically designed to match with q2 so i am personally going to put in these transistors first and get that out of the way now it will tell you that these are jfets are static sensitive devices my bench top i use here is an anti-static bench top and um and i'll use a ground strap when putting those in as you can see here once i get them inserted through i'm just touching each little just it doesn't take a lot here just a teeny little drip make sure you get the uh both the circuit trace and the and the lead heated up and then it's just a matter of snipping these off with a pair of wire snippers here on the back and you're good to go the good news is all these small resistors um are going to have a spacing of .05 so that'll be right here on a little bending lead if you happen to have one of these tools if not they're super handy and you can get a little three pack like this for less than i think they're about eight dollars online uh just be careful some of them come out of china and they take a while to get here so if you need them quick you might have to pay a little more from a u.s source these these are prp resistors are made here in america right above if you start scrolling from the bottom towards you you'll come across t 100 which is the size and style of resistor then you'll see the percentage these are all one percent resistors and then next above it you'll see a number and this will say 100k i've been just sorting through some they do a good job marking them uh this one here is uh let's see 7.5 k so you you can see them and then you just use the lead benders um you just hold the resistor in the very middle and you just bend each side straight down and like i said this .05 i mean excuse me 0.5 and 0.75 and then you just find the resistor that matches that value slot and on here and fill it in don't forget the four that came with the uh the jfets they're going to go right above it in the space mart r1 and i'm going to go ahead and bend those and put those in as well okay the good news is once you get these bent with the lead bender then it's just a matter of dropping it into the hole that it needs to go in here and they drop right down i like to use i like to keep to keep my resistors off the pc board just slightly and this is just a piece of like manila folder and i'll um i'll flip it over and it's consistent i'll use it like this on every one of them and then what i'll do is flip it over like this once i've got that held in there and i'll be in one lead one way and i'll be in the other lead the other way so i've still got this piece in here keeping it equal distance off of the board and then once i have that bent over then you just flip it over like this and then it's just a matter of uh i almost call it a tack welding here but it's just a really simple little solder and make sure you get the the eyelet hot as well not just the um not just the little lead and then once you've got that you can cut off the lead on each side here super simple you pull that out and now if you notice i've got that equally spaced off the board right here i've just seen too many boards burnt over the years and darkened um and i just like to give that a little bit of air space in there for cooling air to come up underneath the resistor by the way as i cut these little leads off i save these i have a little just a little box full of them later down the road you may be repairing a piece of equipment or whatnot you may have a burn up circuit trace and you could just use this piece to lay across and replace that trace and solder on one side and solder on the other little pieces of these come in handy all the time around here okay as you can see i've got the four resistors on here matched up with there for um they're four fets and we'll keep rolling through it i would not drag you through the soldering of each of these it'll be pretty boring for you and as you can see these little prp resistors are mounting down the exact same way same little air space under them i'm gonna keep rolling you can see here if you've got multiple resistors in a row you can feed them like that bend them over on the back side and solder them all at once they did do a good job of marking these boards i also like the prp resistors that are clearly marked really easy to read so i'm happy with the components they used in this and i'm really happy with the boards and the layout and markings they did on this the only thing i really warn you about on these there are a lot of common values here so there's a hundred r there's a hundred k there's a 3.32 k and there's a 332 k so a lot of very similar values here that um you know can trip you up so just pay the double attention it's probably really hard to tell here but i also bent the leads when i bent them with the resistor values facing up so now that they're dropped down into the boards you can actually read the resistor values on top makes troubleshooting down the road much easier now on these power resistors even more critical to keep them spaced a little bit off the board as you can see here i doubled my piece of manila folder over a little bit and then uh i'll bend this over solder it up and it'll have good spacing okay i found them i found my first hole here that wasn't large enough for the diode it was tight on one end and wouldn't fit in and i ended up using just a little bitty uh like dental pick to go in there and kind of wobble around and open the hole up just a hair enough and sure enough then it fits right on in there it's just a little bit thicker lead and yet they use the same hole sizes as they did for all the resistors you do have to pay attention to the stripe the cathode end of this zener diode it looks like it's a 9.1 volt zener i think it's used in the schematic let's see here the 9.1 volt is sitting right here to establish a voltage on this rail h which feeds over here and it's establishing the uh the cathode bias it looks like here on the triode these little potentiometers i would not advise putting spacing underneath those you want those as tight down to the board as you can get them that way um as you adjust it there's no wiggle from the legs of the of the unit all right i love these tronics wire snippers this is a 772 and they're perfect for cutting off all three soldered leads of a transistor they've got the right angle and they've got the length i have no association with these guys other than i absolutely love their love their tools all right maybe you can see in the middle of my bench mounted up under it there i've got this haiko fr 400 they call it a smoke absorber but it's basically the filtered exhaust fan here that i use while soldering i didn't show that while doing the soldering because it makes a lot of noise but i do use this while i'm soldering on the bench and up next we have our bag of capacitors just pay attention here these are polarized one side here will have the uh little stripes on it for minus and and the other side won't and so as you go to put these in a lot of times they'll be like right here it's it's marked plus on this this is a thousand microfarad looks like the one i've got here in my hand is a thousand microfarad and it has a plus on this side so i know the stripe on the other little side there will go away from that and you'll mount these down all the way in you don't have to hold these off the board and similarly i'll kind of spread them apart like that and solder it up you've heard the old uh carpenter adage measure twice cut once same holds true with soldering and electrocalytic compounder capacitors check the polarity twice solder once okay we've got all the capacitors soldered in i even after i've soldered my i'll go through a third time and check everything just to make sure i've got the polarity right and it's easy to do from top down because you can see the stripe from the top and you can see the plus real easy it's just worth that extra check but we're in good shape here i think we're ready to open up the tube kit interesting inside the box we have the tube itself here and maybe it looks like no actual socket looks like maybe we'll solder it straight on looks like some two-sided tape maybe that'll go beneath it i don't know we'll read the instructions and see what's next okay i found out they did provide this it's a piece of two-sided tape and really the purpose you're going to use it for here is to um much like we have been doing with the manila folder here we've been they're recommending using it to hold one side of the new tube up off the board you do not want it to end up touching the board at the end of all this okay it took a little bit of playing to get the tube down in here and then once we get it we're gonna have to hold it from the bottom side while we tack two of these really gently with some solder the best way to do that is to just get a little bit of solder on the tip of your your soldering iron here um so you got a little bit of a blob there and then you can just kind of hold it on to one end here and really all we're trying to do we can come back along and solder it here in a minute better but you just want to tack it so that you're kind of holding the two ends on and the tube doesn't fall out anymore i use a stiff brustled uh toothbrush on the back side here nothing but nothing more than a regular toothbrush to try to get rid of some of the excess rosin that gets comes from the inside of the solder as you can see here the tube is floating off the board here kind of suspended one thing i forgot to do earlier we're back to the chassis and i just now noticed this i need to slide in four of these little nuts here into this chassis rail so i'm just going to drop this down just enough to be able to slide in two of these on each side okay i got those four slit in here in the back back on it now what we got to do is mount these standoffs and the way they will work is the their little brass on one end got got threads on it those will come up like this and then we'll go underneath of this unit and we will mount screws in that hold these standoffs in place i found it easiest just to to lay the unit on its side kind of feed the screw through here start it on here from the top side and then just use your screwdriver here and tighten them down then it's just a simple matter of dropping the board down on this and putting your four screws usually these would come with some type of lock washer but these didn't so all right you get the idea you'll just tighten these four little screws down oh yeah by the way maybe some people have asked me about this on my bench before but um this little wire set here um has just about every it comes with a stand has just about every tool known here from uh phillips to flathead to hex to um you name it it's in there but one of the things it comes with is a nut driver whole set of nut drivers here for small stuff like this and that one fits on there perfectly and they got the little spinning head on the top a little sets of i want to say about 140 to maybe a little more dollars but but well well worth it all right we've got it mounted in here now it's just time to complete the wiring there's a couple more wires that'll come from here down we've got to finish wiring up the input jacks here and we've got to wire the power supply to the board okay soldering these wires in and to stay consistent with what i did on the other side i'm swapping the orange white blue white um on this so that the right side is blue just like i had here on the back and if you notice the white striped one here goes down in with the a common and that that little lug already had a wire coming into it from the bottom much like the uh the b common wheel right here so you'll have to kind of feed it down from the top and share it in the same hole with the the one from the bottom but you get the idea we'll solder up the uh the other side here as well okay we've got these matched up the a common down here to ground the a out down here to rn the b common down here to ground and the b out down here to left in and i did swap the colors to match with where i had accidentally swapped the colors earlier one thing when you're feeding these wires down through here make sure you don't strip too much because you could you could feed so much down in there you end up touching the board underneath and i'll likely lift my board off here and just kind of peek under it make sure that the wires aren't too long or are touching down all the way underneath and you'll see what i'm talking about i just want to make sure that these are not too long and any excess here kind of gets trimmed off on the back side so that i don't have to worry about it touching the chassis and shorting anything out and i'm going to go ahead and leave these nuts off for now while i solder the rest of this just so i can peek underneath the other sides and do the same then we'll put those back on i admit i'm not much of a rule follower and so i skipped kind of went off track from the uh the instructions that they provided that 6l6 did they recommended before putting in the fets and before putting in the tube that you hook up the power supply to this board and solder and check the 24 volts coming out of the little wall wart into this unit make sure the board's running right and give you give you a test point for 24 volts i'm pretty confident in what i've been doing along the way here so i didn't follow that step but um for someone less experienced or less confident along the way i did a little bit of what you call a shotgun approach did it all at once here while i'm just talking a little bit while solar but um you could certainly follow the instructions they provided and take take the safer route and much like before or here's red for right i'm going to feed it down here to r out r out i'll go to the center and then the log will go to ground and i'm going to use much like um i've made everything backwards color wise i'm going to use the blue here and the orange on the left just to keep it consistent throughout the amp okay we've got it all wired up and all soldered at this point in time nothing special here did a nice neat job i thought okay here we are the moment of truth we've got our rca jacks here feeding out into a i have a bin champ i keep um on the bench it's a single ended kt 88 amp i've got the rca's coming in here into input one i'm just feeding for my little ipad i keep on my bench and then i've got the wall wart fitting in here and we're gonna power it on not sure if you can hear that i hear a little bit of ringing but it's starting to dissipate at this point and now if you read page 8 of nelson pass's instruction sheet on this it will talk about down here first off it says with a volt meter reference to ground and it's kind of hard to hold a connection onto a uh a mounting hole so i also noted that the anode of the zener right here this side the side without the stripe is um is ground as well in this schematic so it's a simple place to hook onto here with one end of your meter and then what it talks about is t7 and t8 should be set for 10 volts while the unit warms up so we're going to use just a let's see t7 right here and we're at 11 volts and this little potentiometer will adjust that we're going to take it down to like it said um 10 volts here a little touchy as you get right around it we're close enough there and then t8 here we're 10.71 and we're going to take it down to 10 volts roughly okay what it says is it says leave it on for a little while and let this unit warm up at this point and then it goes on into some more detail here talking about at various voltages is when you start to play with uh says it 12 volts you have a second harmonic null point where you get about point three point point three percent distortion in third order harmonics as we go lower we start getting pop positive positive phase two harmonics and it will hit about one point five percent at one volt so on and so forth um and then it says with with about nine volts here on t7 net t8 but ultimately keep reading if some of that doesn't make a lot of sense to you it says the reference setting for this project is 9.5 volts on t7 and t8 once this unit's warmed up which gives a positive phase at about 1.5 percent at one volt output you're free to set it elsewhere it does also go on to talk about on the next page that this is a phase inverting preamp so you can either address that a few ways um one way would be to run your speaker outputs backwards going into your speaker the positive and the negative negative and the positive the other would be to just leave it phase inverted him and it goes on to talk about how some people actually like the fact that it sounds better phase inverted i'm going to pause the video for a minute let this thing warm up then i'm going to come back and set them both at 9.5 volts okay i got them about as close as i can get them to 9.5 volts on both of them that one's 9.52 and that one's 9.53 so we're we're close enough at this point let's uh see how this unit sounds all right let's see what we get out of it here [Music] so [Music] sounds really good um maybe slightly heavy on the basin because i use this bench amp all the time so i'm very very familiar with how it how it should sound um but yeah i know it's sounding sounding really good here [Music] super impressed with how it sounds here i'll definitely do some more listening um you know i was going to make a video too with um do a bunch of uh spectrum analysis and frequency response and all that but i noticed in the nelson pass uh this is a long document he does he covers all that and he's using an audio precision device to do it with so i don't know whether it's worth me doing that or not um i'll i'll see here but i'll tell you this thing's sounding really good [Music] [Applause] can't count the bodies [Music] i've been listening to it for a few hours now and the mids are just amazing on this a little bit maybe slightly heavy on the on the bottom end uh highs are just perfect the mids though are just right there spot on i'm i'm happy for some 300 this was a heck of a fun kit and um made for a great thanksgiving here at the house uh you know it said four to six hours i i built this probably and even with making this video in about two and a half um you know it may take you a little longer if you know if it's not something you do all the time but anyway a lot of fun hope you guys enjoyed it and uh definitely would recommend this little kit for a preamp if you need one and it's uh you know modern age low voltage tube set up here it's designed by nelson pass it doesn't get much better than that so i'll call it a win-win thanks for watching everybody hope you enjoyed

Channel: Blueglow Electronics

Views: 18,929

Rating: 4.9272728 out of 5

Keywords: dynaco, heathkit, AR, audio research, cary, klipsch, marantz, luxman, knight, mcintosh, altec, sencore, tektronix, fluke, fisher, hh scott, western electric, akai, pioneer, sansui, harmon kardon, gibson, fender, mesa, 300b, single ended, tube amplifier, tube amp, solid state amplifier, krell, analog discovery, bottlehead, output transformers, transformers, hammond, alinco, atlas, collins, drake, dentron, elecraft, flexradio, hallicrafters, galaxy, gonset, icom, yeasu, hy-gain, kenwood, national, swan, ten-tec, passlabs

Id: YYm5LM3qOzk

Length: 37min 58sec (2278 seconds)

Published: Sat Nov 28 2020