Korg B1 completion kit pioneer batch feedback

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The RK27 has been around a long time (and arguably stood the test of time).
I have a preamp that's almost 30 years old with one (or at least it looks the same)
and the volume control is still smooth and quiet.

It looks to be used in at least one current production high-end headphone amp. :)
 

6L6

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So when the switch is on the OFF position, the top connectors will actually be powered? I don't think you want this, I'd rather make the bottom connectors go to the socket power and the middle pair go the board, so that in the off position the top pair is actually off.


Thats not a bad suggestion - and if it were an AC switch I'd never have it wired with the top terminals hot. But it is low voltage DC, and there's a LOT of photos that would have to be re-shot because the resistor would have to change position... as well as the drawings. It's not an insignificant amount of work to change it
 
Thats not a bad suggestion - and if it were an AC switch I'd never have it wired with the top terminals hot. But it is low voltage DC, and there's a LOT of photos that would have to be re-shot because the resistor would have to change position... as well as the drawings. It's not an insignificant amount of work to change it

Well, it actually works with the LED and resistor soldered as on your existent photos -- that's the way I did it. In the off position, the anode end of the LED is floating and the cathode is connected to the "ground" via the resistor. One may argue it still leaves a path from the power socket to the circuit in the OFF state, but so is the case with power wired to the middle pair.
 
I feel it's probably worth spelling out what happens with the switch in OFF position in both cases (the ON position should be equivalent from what I understand). I'm using this photo https://www.diyaudio.com/forums/pass-labs/313612-b1-korg-triode-306.html#post5906536 as a reference of what 6L6 suggests, please correct me if I'm wrong.

In 6L6's wiring:
PS "+" comes to the the middle post and is connected to the top contact of the switch, and therefore to both LED anode and cathode and (via the resistor) to the PCB "GND" (PCB "+" is not connected).
PS "-" comes to the middle post and is connected to the top contact that is not connected.

In my wiring:
PS "+" comes to the bottom post and is not connected.
PS "-" comes to the the bottom post and is connected via the resistor to the cathode of the LED (and then via LED to the "+" of the PCB; PCB "GND" is not connected).

Now that I think of it, the ideal way to connect the ground end of the resistor would perhaps be the middle post, as it would leave the circuit entirely disconnected with the switch in the OFF position. Considering PCB ground may actually be grounded somewhere (e.g. through in/out grounds) this leaves the possibility of small (2.4mA) current going through the resistor in the off state.
 
Good morning all !

My package has arrived in France and I look forward to receiving it to go to the assembly of the kit ! In the meantime, I heat my soldering iron ...

I think I read somewhere post about the size of the case used in the kit, but I can not find it anymore ! What are the external ratings ???

PS: sorry for the rough English, but the years of high school are only a distant memory ...
 
Good morning all !

My package has arrived in France and I look forward to receiving it to go to the assembly of the kit ! In the meantime, I heat my soldering iron ...

I think I read somewhere post about the size of the case used in the kit, but I can not find it anymore ! What are the external ratings ???

PS: sorry for the rough English, but the years of high school are only a distant memory ...

This is the chassis we have used for the Korg B1 project :)

Galaxy GX247 230 x 170 x 40 mm 10mm BLACK front panel
 
I can not wait to start working on this kit which will complete my current audio installation (Player Jriver + NAS Netgear + PC Win 10 dedicated - audio CD DiY - DAC Matrix Mini Pro i - Aleph mini clone power amp - SUPRAVOX Sheridane high sensitivity speaker).

I have been building and modifying since many years various Hifi equiments: audio CD player, tube and transistor amplifiers, radio receivers, etc ...

I intend to publish here a report on the construction of this preamplifier based Korg Nutube kit, as well as many photos of the various stages of the assembly of it.

Thanks to Mr. Nelson Pass and to all the other members of this forum (6L6 ...) to make available to the community of DiY these highly musical electronic shematics, as well as the associated know-how !
 
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I finished the build last night.

I have nothing but great things to say about it. The chassis is excellent. The parts quality high. Once I admitted to myself that a magnifying lamp was an acceptable purchase, assembly was a snap.

I just swapped the preamp into in my office stereo, and I don't think I'll be leaving today. This thing plays music. Really, really well.

Thanks for the great kit, and the opportunity to do an early build.
 
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Another Korg B1 finished

I finished the preamp kit two days ago and have been listening to it with an ACA and an F5.

It is a very nice piece of kit. The construction was very straight forward once I had worked out the JFET locations.



My only suggestion involves setting the voltage using the test points. Before this build, I had built two of Pete Millett's NuHybrid Headphone amp. In Pete's BOM's there are test point connectors that make it easy to clip a lead to the test point and make the needed adjustments. Unless you drop them on the floor during the build, they really free up your hands while making the voltage adjustments.



On the Korg B1, it was tricky to hold the meter lead on the test point and ground while adjusting the pot. More so since the adjustment on my unit was very sensitive. Building the ACA's, F5, Whammy and Starving student units did not present as much difficulty with the voltage adjustments as this unit presented. Of course I may have been missing the place to clip a test lead on a component leg due to my inexperience.



With the F5 last night it was very delicate in sound character but lacked something. Then I remembered from Nelson's article that it was inverting the signal and the simple fix was to invert the speaker connectors. After this change it was truly wonderful and the sound stage had me smiling broadly.



I had some Isolate it hemispheres left over and used them in place of the stock feet. There did not seem to be any ringing, My NuTube was mounted with the sticky foam pads included.




Thank you to the DIY store and Nelson for the opportunity to built such a great sounding preamp.
 
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A new Korg B1 Nutube preamplifier is alive (and makes music ...) !

I received my package the day before yesterday only 7 days after the order. Almost faster than Amazon ! And I did not have any customs fees to pay ...

Two days later, I started assembling the kit and I must say that it is very simple when you already have some experience.

So, for beginners, I recommend using a soldering iron with the finest tip and a fine solder wire, with lead, because the lead-free solder does not give such nice welds and requires a temperature of the iron soldering of at least 400° C which is a lot for some components.

I also strongly advise to use an antistatic wrist strap when handling JFET transistors that are indeed very sensitive to static electricity !

The components are really very good, like the Dale resistors, the electrochemical capacitors and the Alps potentiometer.

By cons, I find that the connection pads on the printed circuit are too small, while it is not necessary for most, except for transistors and Nutube !

It is also a pity that there are no more convenient test points (with pins ?).

Another complaint : the wiring of the LED of the ON / OFF switch is not easy and the hole provided for the LED is too small, so the LED is almost invisible when turned on, it's a shame, so I replaced the original LED by a blue LED with a serial resistance of 2.2 kOhms and I inserted it in the hole provided for this purpose after having bored to 3mm. The connection of the LED is now with a plug-in connector. This is the only modification made to 6L6's work with the use of flexible wires and a larger gauge for 24 Volt wiring.

Otherwise, I must say that I am extremely satisfied with the result and especially the excellence of the sound ! (And I have absolutely no microphonic effect, but I do not listen to music at a high level ...)

Thank you once again to Mr. Nelson Pass for making public this achievement and 6L6 among others for his valuable advice throughout the many pages devoted to the realization of this project !

Here are some pictures of the different stages of construction and the final result.

The opening of the package:
An externally hosted image should be here but it was not working when we last tested it.


The completion kit bag :
An externally hosted image should be here but it was not working when we last tested it.


Use of an antistatic wrist strap :
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It must be connected to the earth, of course !
An externally hosted image should be here but it was not working when we last tested it.


The printed circuit board is finished !
An externally hosted image should be here but it was not working when we last tested it.


Mechanical assembly :
An externally hosted image should be here but it was not working when we last tested it.


The Korg Nutube double triode :
An externally hosted image should be here but it was not working when we last tested it.


Mounting of power resistors with little steatite posts :
An externally hosted image should be here but it was not working when we last tested it.


Final wiring :
An externally hosted image should be here but it was not working when we last tested it.


Wiring modified ON / OFF switch and LED :
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In good company !
An externally hosted image should be here but it was not working when we last tested it.


It's all for today !
 
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I finished the preamp kit two days ago and have been listening to it with an ACA and an F5.

With the F5 last night it was very delicate in sound character but lacked something. Then I remembered from Nelson's article that it was inverting the signal and the simple fix was to invert the speaker connectors. After this change it was truly wonderful and the sound stage had me smiling broadly.

I spent the day, whilst working, trying some stuff:
- F5
- F5 with BK1
- 2x ACAs in bridged mono
- 2x ACAs in bridged mono with BK1

Only source was non-DAC'd (well, internal Mac stuff) iTunes. Smallish room, 88db speakers.

Was really fascinating. It REALLY depended on what I was playing. Overall I preferred the F5 with BK1. Depending on what I was listening too I couldn't tell if I was hearing microphony or bad recording or both—as soon as I'd felt that I'd figured it out—I'd switch musical genres and things would sound 100% epic—classical, Jazz, vocals, rock. "Quality" really seemed to depend on recordings or type of music and live vs studio (it all sounded great, I'm trying to be picky). I suspect that once I plug this into my main setup with sensitive speakers in a much bigger room I'd better be prepared to sit down for awhile. It's a whole new world. I too found that inverting the speaker signals made a massive difference with B1K in the chain. I's say the dual ACAs are totally amazing for what they are—but they are not nearly as nuanced as the F5 and seemed range bound. BK1 is adding something to both of them however. And it's good for me. I do want to try/build a preamp that's not described as having "color"... so I can understand that. I am getting a slightly bigger volume range out of 2x ACAs + B1K than F5 + B1K, or put it this way, if I don't touch the volume on the B1K and switch between the 2x ACA and F5 the F5 is quieter... Just something I observed that surprised whatever it is I thought I knew.
 

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When ordering this kit does it come with pre-released diy guide (with pics)/manual so we can compare our install experience against? I know diyaudio is asking for feedback but it would be good to give feedback on the install guide, even though it looks pretty simple.

Just noticed when checking out that Paypal is not accepted any longer - It's been awhile since I bought kit at the store. What a pity.
 
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6L6

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There will be a guide, I've got the photography done and need to write the text and put it all together in the guide platform. It will be done soon, where "soon" means whenever I get around to it in what time I have. This is an all-volunteer job fore me, so real life has to come first.


The basic idea of the "pioneer" batch was to have a beta release and see if there were any glaring or subtle issues with the parts kit itself, but we've got enough feedback here and elsewhere to see that it's good for normal release. :)
 
Just starting my build. Supporting the store and all that have contributed to this project. I built the Pete Millett head amp awhile back and know how the vibrations affect the Korg tube.
Kudos to the person or persons bagging the parts for the kit. Just finished my board and everything was there. Nice!!
Rather than buy a commercial isolator, with the spirit of DIY here is my take on some homemade isolators. Please note the attempt at Pass blue. These are silicon dampers used in keyboards. A few cents apiece. The grids they are mounted on is some plastic screen I had on hand. Some 3mm screws and a stack of four dampers with the circuit board in place along with the tallest component will fit. Hopefully this will help some on vibrations. The two adhesives I found that would work with the dampers I bought are shown in one of the photos.
More to follow.
 

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Ok finished mine this evening. Voltages check at first then, all decline.
I checked all solder connections, then passive components and then active.
Ah Ha moment. I didn't check the bag of Q1 and Q2 to make sure that I had same four transistors in each.
Q1 bag = 4- J113 KH33
Q2 bag = 3- J113 KH43 and 1-KH33
I suspect this is why I have nothing.

Please help me Nelson!!

Regards
David
 
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