B1 with Korg Triode

[rayma]

Yes, the black probe goes to any ground. Not naive, the manual should be revised.
Many building these kits are beginners and should have clear instructions.

 

[Avance Concrete Fan]

GREAT - THANK YOU!!!

 

[rayma]

Watch out for the "probe slip and short the circuit out" problem.
It will ruin your day.

 

[TomR.]

Just took my first test measurements of my build. Had a nearly perfect measurement for the 24 volt test but am only getting 9 volts at the diode where I should have 9.5 volts. Is this close enough or indicative of an issue?

 

[Brijac]

You may proceed with ease 😊 It's within norm.

 

[rayma]

That's fine, the voltage varies with the device matching and the power supply DC voltage.

 

[TomR.]

Thanks to you both!

 

[Ben Mah]

It's a 9.1V zener diode with a manufacturing tolerance of 5%, so it could be between 8.645V and 9.555V.

 

[TomR.]

Finished the build earlier today and have been listening for the past few hours. First, I want to thank the designers of this kit and the build guide for making this easy. Secondly, I am blown away by the soundstage. Simply incredible. What a fantastic sounding little preamp.

 

[slk23]

Like others, one of my triodes has burned out after approx. 750 hours of use. Is there something that can be done to increase longevity, or should I just accept that I'll need to spend $50 on a replacement Korg NuTube every year or so?

 

[Brijac]

I do feel like generally there needs to be warranty from manufacturer for it. 30000h spec and there has been instances like yours often.
Unfortunatelly no, it is designed by pops with longevity in mind as by datasheet spec. It seems to be QC of the manufacturer which is lacking.

 

[Toys4Boys]

Pretty interesting, wondering how this compares w/ ACP+? Currently I am waiting for an SP14, have a set of Shuguang CV181T to play with. The appeal of the ACP+ is combined with 1 of my ACA Minis it would make a really cool form factor, I know build them all, LOL, and maybe someday I will.

 

[Ben Mah]

Some differences:

ACP+

• Preamp and headphone amplifier
• 9dB gain
• low distortion

B1 Korg

• Preamp only
• 16dB gain
• high distortion

 

[andrewhogge]

Damn one channel on my B1 just stopped output. Not sure where to start w/ trouble shooting but curious, do you turn yours off? I've had it on for about 2 years, but that shouldn't fry a Nutube right?

 

[Ben Mah]

From https://www.korg.com/caen/news/2015/012212/ :

• High reliability and long life.:
  The unique design and state of the art Japanese production facility ensures the Nutubes are built to the highest standard and offer up to 30,000 hours of continuous operating life. The high reliability means that it can be attached directly to the circuit board with confidence knowing that it will not need to be replaced regularly like a 12AX7.

But stuff happens.

Does the Nutube glow on the side that is not producing sound?

Measure the voltages at the test points outlined in the B1 Korg manual. Are they still good?

Some pictures of your build may be helpful.

 

[andrewhogge]

@Ben Mah Thank you for that link! Yes will try to get into the build in the next day or so and and test voltage outputs. Def something weird because its totally zero output on only one side, its not just diminished. And it was a sudden thing.

 

[ghitus]

As Ben Mah answered you, does the Nutube glow on the side which is not outputting music? If yes, it could be a good signal, may be the culprit is somewhere else on the board and not the Nutube itself...

Gaetano.

 

[gwam]

So I have been playing around with different things on the Korg preamp for about a week I have a stock DIYaudio store B1 Korg and a modified version one with:

-GAZ's single ended Artemis power supply
-3300uf audio caps in the 4 power supply positions
-1000uf audio caps for the rest of the non signal caps.
-Different signal path caps.

In the DC blocking signal caps I tried a couple of different things. I first tried high end 10uf Stealth caps using wire leads to run to the caps. There was a hum which I suspect was due to all of the wires. It sounded fuller and richer than the stock unit but the hum was too much and washed out any potential gains from using boutique caps. So I decided it's probably better to save these for different project.

I am not an engineer but I do know that Mr. Pass doesn't seem to like caps in the signal path. So my thought is that using as small a cap that is of the film variety is probably the closest to no cap. So I switched to .22 WIMA on the input, 1uf in the middle position leading to the grids, and 4.7uf caps on the output. These caps were just something that I had in my parts drawer. I may try some small value PPP boutique caps.

The modified version sounds really nice. Switching between the stock preamp, and the modified version, the stock sounds thinner, a little harsher on the edges (Of coarse still very excellent due to the wonderful circuit design. Thank you Mr. Pass!). The modified version has a bigger sound, the spacial details float a little more. The whole sound is still very detailed. The bass is a bit more reinforced. Horns sound a little richer which makes listening to artists like Von Freeman and Arturo Sandoval very fun. I don't click the skip button as readily when busier songs from artists like Radiohead come on like. Arturo Sandoval is a very good trumpetist and worth checking out if you haven't. He is both very technically fascinating but his slower jazz pieces are very soulful. I just rediscovered him recently. Listening to a song like London Grammer's Rooting for You has a bit more decay to the sound. The bass at the end rumbles a bit more.

I think if I had only the stock unit and wanted to try two easy inexpensive mods, I would try increasing the size of the power supply caps to maybe 2,200uf like claud did in the stock chassis, and changing the caps out for films. Maybe the MKP vs the MKS like I did. Note that the 3300 uf caps will not fit in the standard chassis from the store unless you get a little creative. So all in all, about $30 on your next parts order could be your ticket for a fun little experiment. I suspect that the power supply is not a bottleneck as the tube takes longer to light due to the larger power supply caps on the modified unit.

Attached are a couple of pics. The wood chassis isn't complete yet. I'll post a pic of that when it's done.

https://www.audiosy.net/2021/03/17/first-look-artemis-single-rail-power-supply-rev-b/

https://www.mouser.com/ProductDetail/647-UKT1E332MHD

https://www.mouser.com/ProductDetail/647-UKA1E102MPD

https://www.mouser.com/ProductDetail/WIMA/MKS2D032201C00JA00?qs=2G4irm/qADzO1u6WizA70A==

https://www.mouser.com/ProductDetail/WIMA/MKS2B041001C00JSSD?qs=sJjjjplDs9sEiGXANiKLag==

I'm a complete novice here, but interested in film cap modifications for the Korg B1. I noticed in Mike's mod (above ) he has small Wima film caps that look much easier to install as compared to the much larger Cornell Dubilier 940 caps. Seems much easier to do it Mike's way. Am I missing something?

 

[rayma]

The smaller caps probably have a lower voltage rating.
The CDE caps have a rather high voltage rating.

 

[Mikerodrig27]

I'm a complete novice here, but interested in film cap modifications for the Korg B1. I noticed in Mike's mod (above ) he has small Wima film caps that look much easier to install as compared to the much larger Cornell Dubilier 940 caps. Seems much easier to do it Mike's way. Am I missing something?

I did play a bit more with that preamp. The best that it has sounded is with REL capacitors. But the wima caps were certainly nicer sounding to me than the stock Silmic caps.

Regarding mounting, you can follow the traces on the 10uf caps and J hook a larger sized cap onto the lead of the next component. Say a resistor. Simply raise the resistor up a bit when building the preamp.