I have a new question regarding my nutube. I now want to connect my Nutube to active speakers with XLR in. I have common RCA to XLR adaptor. But how can I invert the phase? Is it possible to invert the phase inside the Nutube? As far as I know to interchange one side of my normal cinch cable and then going into the adaptor does not do the job? Or do I need an active device to create an Symmetric signal and use inverted XLR cables?
This should be pretty trivial: Any RCA to XLR adapter is just going to feed the RCA signal to one pin of the XLR (2 or 3) and ground the other. You can easily build cables that connect the RCA signal to XLR+ or XLR-, as you choose. (I've have suggested it before but will again suggest Gotham Audio GAC-4/1 or GAC-4/1 Ultra Pro for this kind of purpose. They are great cables.)
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I bought a box of it on Amazon. I have tons left...I can get you some. I’m on vacation this week though.
Long time reader, rare poster checking in with a completed Korg B1. This replaces a regular B1 that I've enjoyed since finding out about here 5-6 years go. The B1 caused a turnover in my stack, and the wonderful sounding Korg evolution has driven another full turnover - thanks, Nelson 
!
I wasn't sure I should post a pic in the Pass board: the preamp is built into half of a Landfall chassis, and there's some digital thingie on the other side that we won't talk about. Meanwell 24V SMPS is elsewhere behind a panel on the rack.
The preamp itself was a nice and easy build, the packaging probably took 3-4 longer to work out and complete - but it was a fun puzzle and not hard given all of the advice and experience in this thread. Microphonics, for instance - lots of experience so the combo of a tank-like Landfall chassis, with rubber isolators and some mass-loaded damper stuck on with blue-tack eventually did the job. There's a piece of damper on the back of the Frontpanel Express panel, which seems to do a good job with the snaps from the big ol' source switch (which is way too heavy for small signals, but fit the aesthetic).
Some lessons learned:
1) RG174 coax is super high quality, shielded, with small strands of silver plated wire, looks cool but is a total PITA to work with and probably isn't doing anything that twisted pair doesn't. 7/10 do not recommend.
2) Sharpie makes a great layout marker for aluminum. I had guidelines all over the inside of the case pieces, and a wipe with rubbing alcohol took them all away.
3) Listen to the little voice that says it's time to do something over. The remote volume control was bought from Glasshouse for the B1 and works great, but not with my new TV's remote. After figuring out how it worked it *seemed* like a good idea to replace just the microcontroller with a little Arduino, using all of the power supply and driver stuff on the Glasshouse board. So, so fiddly - building the driver circuits on a new Arduino board would have saved a lot of hassle. I will probably replace the coax, too.
Very much worth the effort, though - the sound is lovely and it motivated me to package everything the way I've wanted for a long time, which has the added benefit of not hearing from Mrs PaddyGarcia about the mess of wires under the TV. Now it's time to build a table for the turntable to go under the TV and wait for all the parts to come in for an AD1852 DAC build. Wallet lighter, but I'm much happier in these weird times - thanks!
! I wasn't sure I should post a pic in the Pass board: the preamp is built into half of a Landfall chassis, and there's some digital thingie on the other side that we won't talk about. Meanwell 24V SMPS is elsewhere behind a panel on the rack.
The preamp itself was a nice and easy build, the packaging probably took 3-4 longer to work out and complete - but it was a fun puzzle and not hard given all of the advice and experience in this thread. Microphonics, for instance - lots of experience so the combo of a tank-like Landfall chassis, with rubber isolators and some mass-loaded damper stuck on with blue-tack eventually did the job. There's a piece of damper on the back of the Frontpanel Express panel, which seems to do a good job with the snaps from the big ol' source switch (which is way too heavy for small signals, but fit the aesthetic).
Some lessons learned:
1) RG174 coax is super high quality, shielded, with small strands of silver plated wire, looks cool but is a total PITA to work with and probably isn't doing anything that twisted pair doesn't. 7/10 do not recommend.
2) Sharpie makes a great layout marker for aluminum. I had guidelines all over the inside of the case pieces, and a wipe with rubbing alcohol took them all away.
3) Listen to the little voice that says it's time to do something over. The remote volume control was bought from Glasshouse for the B1 and works great, but not with my new TV's remote. After figuring out how it worked it *seemed* like a good idea to replace just the microcontroller with a little Arduino, using all of the power supply and driver stuff on the Glasshouse board. So, so fiddly - building the driver circuits on a new Arduino board would have saved a lot of hassle. I will probably replace the coax, too.
Very much worth the effort, though - the sound is lovely and it motivated me to package everything the way I've wanted for a long time, which has the added benefit of not hearing from Mrs PaddyGarcia about the mess of wires under the TV. Now it's time to build a table for the turntable to go under the TV and wait for all the parts to come in for an AD1852 DAC build. Wallet lighter, but I'm much happier in these weird times - thanks!
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Running mine with a pair of ACA as I only need a couple of watts. Given that the ACA shows even less distortion using XLR connections can anyone show how the Korg (or pair of Korg boards) would be wired up to to produce XLR outputs? Or would that be a wasted effort given mostly RCA only sources?
I finally got my Nutube B1 that im using with a pair of Ice power 500asp and 500a amplifier modules. I've notice an increasing high pitched noise on the left speaker after a few seconds after connecting the speaker, which it doesnt happend on the right side. Can this be related to Nutube microphonics? is there a way I can get rid of this?
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For build instructions, 6L6 has well documented the kit build in his typically stellar way. But the standard and kit Korg B1 build is for RCA and not differential XLR. You would need two boards for a diffrential build. one for each channel. I believe there have been several efforts of that, but I am not aware of any build guides.
If your active loudspeaker XLR inputs are truly balanced, you can connect the B1K RCA center pin positive to the XLR negative input pin (usually pin 3) and leave pin 2 unconnected. RCA shield goes to XLR pin 1.
A number of caveats:
*You will lose 6dB of gain running a balanced input unbalanced
*You may have more noise from the unconnected XLR pin 2
*The loudspeaker input circuit may or may not tolerate grounding pin 2 to eliminate or reduce noise
*Some manufacturers still do not conform to the "pin 2 positive" industry standard. You will need to verify this.
That is easy to do with a 1.5V battery while observing woofer cone movement. Alternatively, there are free smart phone apps that do polarity checking (i.e. Audio Control Mobile Tools, available in USA, not sure about other countries)
Ok I managed to debug the issue, it was given because I was just using 1 of the 4 ground points on the Nutube, weird since they are all 4 points connected right? I still found weird I can hear an almost inaudible high pitch on the same same (left), but not on the right side and Im not sure where to check any more. What if I connect all 4 points into a common star ground?
PD: BTW, the trick of the rubber on top of the Nutube? it's super effective
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Ringing is typically a filament ring. If you look at how the Nutube is constructed, the filament wire is stretched across the tube and tacked internally to pins 8/9 (the filament intermediate ground point) and pins 1/2 on the left and 16/17 on the right provided for the filament V+ connections.
During manufacturing, if the filament to one side or the other (left or right channel) is at the wrong tension, it will have a propensity to ring. It's my theory that high enough tension puts any ringing above the audio spectrum and insufficient tension allows it to drop down into the audible range.
Too bad Korg does not QC for this at the factory. In my experience so far, the B1K circuit's lack of negative feedback seems to exacerbate this problem, even though that's part of what we love about this design.
During manufacturing, if the filament to one side or the other (left or right channel) is at the wrong tension, it will have a propensity to ring. It's my theory that high enough tension puts any ringing above the audio spectrum and insufficient tension allows it to drop down into the audible range.
Too bad Korg does not QC for this at the factory. In my experience so far, the B1K circuit's lack of negative feedback seems to exacerbate this problem, even though that's part of what we love about this design.
Tested on two different builds of B1 Nutube (both madly ringing - I don't know why - on "nude" pcb):
- two big rubber erasers on Nutube
- rubber spacers to fix the pcb to the chassis
- sealed chassis
and you get rid of whatever ringing!
Il gae.
Hi everybody.
My B1 Korg is in daily use at home and bringing much joy - dialed in at around 9.5V on T7 and T8 with phase inversion corrected at the speaker terminals.
I'm using the recommended Meanwell SMPS but it's started humming so I'm looking to replace with either a fairly generic R-core based Chinese 24V linear power supply or... something else.
What are folks here using? To save me trawling through >500 pages can anyone please recommend a DIY power supply build suitable for a newb-ish?
TIA, Haden
My B1 Korg is in daily use at home and bringing much joy - dialed in at around 9.5V on T7 and T8 with phase inversion corrected at the speaker terminals.
I'm using the recommended Meanwell SMPS but it's started humming so I'm looking to replace with either a fairly generic R-core based Chinese 24V linear power supply or... something else.
What are folks here using? To save me trawling through >500 pages can anyone please recommend a DIY power supply build suitable for a newb-ish?
TIA, Haden
Papa's original PS spec is the Triad WSU240-500
https://www.mouser.com/ProductDetail/Triad-Magnetics/WSU240-0500?qs=B4sXYbYweUrXL53rqcMV9w==
https://www.mouser.com/ProductDetail/Triad-Magnetics/WSU240-0500?qs=B4sXYbYweUrXL53rqcMV9w==
