B1 with Korg Triode

What I tried as the last things last night last night was to try other input in Focusrite but with same result. But if I turned up the volume a bit the 280 Hz spike disappeared as the picture shows. Distortion is higher but noise level still very low. Also listening to the amp is a very good experience. Very silent. It is just academic it could be fun to know how the 280 Hz spike was generated. I have a scope that goes to 0.5 mV/Div but think Focusrite is my best measuring instrument for this kind of "findings". I could try the scope.
 

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I will try later using a lab supply which is an old type linear supply. It did not use screened cables inside the box as I thought that inside was very "clean".....no PSU etc. The Arta + Focusrite is a fine tool. I can measure just the noise at the output with input grounded. The 280 Hz spike is the only one I can't explain so far. It is so low that it is inaudible so only a learning experience to try to find out where it comes from.
 
Here is the result using a linear lab supply. It has more 50/100/150 etc. noise which was expected. But no 280 Hz so conclusion must be that the 280 Hz noise comes from the Meanwell SMPS. Meanwell is more clean which is good. The only thing I can think of if I should try to dampen the 280 Hz spike is adding E-caps at the PSU input. The relative powerful Meanwell should be able to handle some uF without going into "protection". I can try and see what happens.
 

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I added 2 x 2200 uF at the PSU input where it was most practical to place them. First I added one. The 280 Hz spike was gone but seems to move down a bit in frequency. Then I added one more and the spike moved further down in frequency. But now it is lower about 110 dB down and I think this is sufficient?

My caps etc. seems to interact with a circuit inside the Meanwell PSU. I think it is looking good now. Most be time for some listening…….
 

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Hello MEPER,


Switch it on, test offset at RCA-output. If everything is o.k. - listen to it.
I am curious about your impressions. I like this little giant!
I have my loudspeaker +/- reversed. Play with the 10kOhm trimpots - slowly.



Have a relaxed Easter-weekend with lots of listening - pleasure! ;)



Greets
Dirk
 
I will listen to it...….and I had a listening experience last night. The problem is that it is MoFo that is in my current setup. Not the best match as MoFo requires a lot of voltage swing but it worked quite well…..a lot better than expected. I will try with reversed speaker polarity…...this evening. First I will go and buy an "Easter egg"....don't know if this is only something we do in Denmark...…often made of chocolate….with something inside.
Maybe I will try to power both pre and power amps simultaneously and see if this works without loud pops in speakers. It works for all my other setups (e.g. BA3-pre + MoFo).
 
to MEPER

I always turn on the source, then the B1 NUTUBE Pre.
I wait a short while (only half a minute or so).
Then the poweramp.
Then I have never pops out of the speaker.


Same procedure (only reversed) turning off:


First the poweramp off ( I wait till the LEDs of the PSU went off)

Nutube off
Source off.


My amps have no loudspeaker protection!


Greets
Dirk
 
I usually have all connected to one power outlet and normally I just switch all on/off at the wall outlet. It depends how slow power amp is to power up compared to pre-amp and how nicely they power up. Let us see what happens :) …..my woofer can handle 1000W and 2000W in peak power and MoFo has output caps….and is relative robust. It was a good test yesterday when both fuses burned in MoFo PSUs. Both mosfets survived the spark from MoFo choke! ….it was good I installed the protection zener.
 
No pops when both Korg and MoFo was powered up from the same wall outlet at the same time. So that is nice. Very nice sound also (I remembered to revers phase at speakers). It is a good learning experience to hear relative large amount of 2nd harmonic. I assume 2-3% or even more.....maybe 5% at peaks. Think I will switch back to BA3-pre for MoFo during the coming days and then start building M2X and use Korg for that.
 
Member
Joined 2004
Paid Member
I see a lot of peeps use this with the M2 clones. I just soldered one up and put it into the 4U case that has been cannibalized twice now (F5 > F6 > M2). I always feel bad about that, but it's *so* easy to do!

Anyhow, I was thinking this NuTube B1 was next, but the M2 says it needs 3V for rated output (and 500mV for 1 Watt). So what level will this drive the M2 to before it loses steam? I have efficient speakers, so it probably won't be an issue. Just curious.
 
I think Dirk use Korg with M2X. As Korg works with MoFo which has no voltage gain then it will work perfect with M2X is my guess. Regarding the standard chassis with 2 x 24 V psu it was also my intention that chassis could be used for other projects. Else all those amps will take up a lot of space and also expensive with new chassis + psu for every build.
 
The one and only
Joined 2001
Paid Member
Depends on the speakers as well as how loud you want it.

Me, I listen at moderate levels to 95 dB loudspeakers. A scope on the
amp triggered for peaks shows about 2 watt peaks unless I am trying
to impress someone. ;)

2 watts is 4 volts peak, which requires about 1 volt from the Korg.

The Korg will reasonably deliver a 3 volt peak before the 2nd harmonic
starts owning the dance floor, and the resulting 12V peak coming
out of the amplifier is about 18 watts.

This would give you the same level I listen to but with an 85 dB speaker.

I think you'll be OK.

:p