B1 with Korg Triode

Sounds great BTW! Testing it out at 9.4v at T7, T8.

:cheers:
 

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In a test bed - all voltages check out and plate voltage adjusted to approximate 1% 2nd harmonic - need to download and install DiAna and see how close this is for me.

You use SMPS for the pre-amp? Do you add a HF noise filter after the SMPS?

I was thinking if a filter like this would be useful if SMPS was used for a preamp:
0-50V 4A DC power supply filter board Class D amplifie EMI suppression 12V 24V | eBay

I assume it is PI filter using HF serial chokes and a large and small "shunt" capacitor before and after the chokes. I was thinking of something like that for the Meanwell 24V SMPS...…..if I am going to try those.
 
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OK.....the SMPS you use may also be a higher quality version than the Meanwell I have which is the one many ACA users use. The PSU requirement for preamp use is usually higher than for a power amp. But let us hear when you get power on the Korg if it is silent……with no "sharp edges". There is filtering on the Korg PCB but that is more for LF ripple rejection than HF noise…...as I see it....
 
OK.....the SMPS you use may also be a higher quality version than the Meanwell I have which is the one many ACA users use. The PSU requirement for preamp use is usually higher than for a power amp. But let us hear when you get power on the Korg if it is silent……with no "sharp edges". There is filtering on the Korg PCB but that is more for LF ripple rejection than HF noise…...as I see it....

Or you can employ a FET CxMx and get rid of all the HF noise.
Very elegant and very simple.
I use a SMPS for a Pearl phono pre, followed by a CxMx and it's dead quiet, with no sharp edges and all that, just silent.
 
Ok.....is that an active circuit using a FET in the filtering circuit?
I was also thinking of instead of one of the 10 ohm resistors on the PCB for the filtering (e.g. the first one) exchange it with a small ferrite core choke and then on the backside of the PCB I could parallel a 100 nF capacitor on each filter cap so the on board filtering also has some HF noise filtering. If the ferrite core choke has thin wire so it also has some ohmic resistance then it would have a double purpose?
 
Quick note for those concerned about microphonics. I previously built Pete Millet’s Nuhybrid and now have the B1/Korg. My Nuhybrid rings like a bell on start up and when I adjust the volume, as described by Pete and others — totally normal, but reality.

I have not heard any microphonics from the Nutube in this B1 build. I haven’t gone around tapping or anything, but in normal application it seems to be a dead quiet tube. I did apply foam tape under the nutube on the board before soldering — definitely recommend that, as it actually sits better with a little elevation underneath.
 
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I have not heard any microphonics from the Nutube in this B1 build. I haven’t gone around tapping or anything, but in normal application it seems to be a dead quiet tube. I did apply foam tape under the nutube on the board before soldering — definitely recommend that, as it actually sits better with a little elevation underneath.

I have also built one of Pete’s NuClassD amps and was very surprised at how microphonic the 6P1 is.
This is good news about the B1 w/Korg Nutube :)
 

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That would be interesting to try!

I'd probably use a common-mode choke before the power input if you wanted to filter any HF noise that the smps might have - SU9V-05020 KEMET | Mouser

That's what Pete used on his NuTube headphone amp power supply. Works beautifully.

But remember that this PSU starts with DC in, has 2 stages of RC filtering, and local RC decoupling at the tube's plate and output buffer. I'm going to try it as designed first. :D
 
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