B1 with Korg Triode

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#8,145
Hi,

Has anyone tried using Meanwell SMPS power supply for their B1K setup?

I am planning to use Meanwell LRS-35-24 (24V 1.5A, this is already the smallest possible in the LRS series) so that I could incorporate the power supply already built-in into the chassis.

https://www.meanwell.com/productPdf.aspx?i=395

To make things clear:
  • YES the stock power adapter (24V 0.5A) included in the DIYAudio Store B1K Essentials Kit doesn't have any problems. I'm just doing this mod more for practical reasons.
  • YES I know that having the power supply out of the chassis would technically be better (isolation), but I would like to have the power supply built-in since I will be making a custom case for the B1K, so I might as well incorporate it inside the chassis
  • NO I do not expect any sonic/noise improvements by upgrading to the Meanwell PS (negligible at best). I plan to use it so that I could also use an IEC socket (for using power cables; easier to plug-in; no more dangling power adapters outside)
  • YES I will be also installing the SMPS DC filter P089ZB kit to suppress any noise (if ever)

Are there any drawbacks/cons to this (noise/sound-wise)? Price is of no concern since the Meanwell is just less than $15 anyway

I appreciate all your feedback/experiences! Thanks!
 
#8,148
I introduced the Korg Nutube B1 into my system with 111dB sensitive horns (Radian without passive crossover, actively crossed), and there was a significant hum introduced (heard via speakers). I did hear the expected microphonics when flicking switches (not too bad with the eraser damping), but hum was unexpected. After rechecking all cables, connections, I still could not get rid of the hum, but then I lifted the Korg B1 and ended up moving it a couple of inches to the side, and the hum disappeared!
I had temporarily placed it right on top of my DAC (Gustard X26Pro) and moved it couple of inches on top of the same DAC, so I guess some sort of EMI/RFI/transformer coupling was going on?
 
#8,153
yeah, clutch-ganged Vol pot would be easiest solution, also using two separate mono Vol pots - easy and convenient when you get used to those

if going another route, say that dedicated balance pot of 100K value should be good

dedicated means proper ones, which are practically open ( not loading the stage/channel) when set to mid position

lazy to search but I remember that Hafler DH101 papers (plenty of sources on net) are clearly showing both implementation and principle

certainly covered on Rod Elliot's too
 
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#8,154
Nelson Pass said:
Try 4.7k and see what you get.

I have made about 10 of these and no encountered that much bias difference.
Click to expand...
I exchanged the 7.5k for 4.7k and now I can set 9.5V on both channles. At the 33.2k I have 3.38 and 3.62V, so the nutube halves are not idenctical, but the sound on both channels seems to be identical.
Thank You so much Papa Nelson for the advice.
B1 sounds incredibly good. Absolutely phantastic.
 
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#8,155
Hmmm, after a good listening session, I took a nap without turning off the system and woke up due to pretty loud high-frequency ringing noise. It sounded like the microphonic pinging noise from Korg B1 except louder and continuous. When I picked up the Korg B1 and jostled it slightly, the noise went away. I've had many tube components that had microphonics but never this loud and continuous. Did my Korg B1 go into oscillation and is there a way to prevent this?
 
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#8,158
drjlo said:
Hmmm, after a good listening session, I took a nap without turning off the system and woke up due to pretty loud high-frequency ringing noise. It sounded like the microphonic pinging noise from Korg B1 except louder and continuous. When I picked up the Korg B1 and jostled it slightly, the noise went away. I've had many tube components that had microphonics but never this loud and continuous. Did my Korg B1 go into oscillation and is there a way to prevent this?
Click to expand...
drjlo, I've built three different variations of preamp/headphone amp/linestage using the Korg Nutube (two of Pete Millett's and Papa's B1K) and any issues I had with ringing, pinging or microphonic noise when touching the units disappeared simply by isolating the Nutube off of the PCB. The most reliable mounting technique is using Pete Millett's "Nutube vibration mount" but one can use other mounting strategies. There are ways of getting it off w/o destroying it but it's just easier to use a new one. I know that trying the anti-vibration mount is now a little late now since you've already soldered the Korg in place. I tried the white erase technique and it kinda worked and it's cheap so try that. My take is that a lot of the noises come from the metal fingers of the Nutube touching the PCB directly. Just my two cents..

Pete
 
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#8,159
Pete Millett's "Nutube vibration mount"

Kind of too late for that, but I think I fixed the (worst) of microphonics by bending the Nutube back up to a position more parallel to PCB plane. I already had the eraser on top of Nutube, but it may have weighed it down and bent the legs too much. I'm surprised the nutube comes with solder pins on one side only, with the other side just floating in air. If microphonics come back, I may wedge some foam pieces between bottom of nutube and PCB..
 
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#8,160
How can I reduce the maximal output of B1K ?
I have two reasons for this. First i would like to reduce the noise of B1 wit system with very sensitive speakers. Second in my system i have "full power" with ALPS around 11 hour it means i am actually using the range between 8:30 and 11, i would like to change it.

On the original Xmas 2019 circuit of B1 at the output is 221 Ohm and 33.2 resistor, now at the output is 100 and 33.2k resistor.
Can i just change the 100ohm resistor for 220, 330 or 470 ?
 
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