And we're off! Thank you Nelson Pass and bk856er!!!!!!!!!
jphabc54,
you are so quick and lucky!!!!
jphabc54,
you are so quick and lucky!!!!
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.
thanks again Nelson , looking forward to getting it set up to listen to in my system.
..dB
thanks again Nelson , looking forward to getting it set up to listen to in my system.
..dB
Look at T7,T8 and ground on the pcb is the jfet's output probe test points for voltages verifications.
T5,T6 is filaments = cathode voltage points.
Do You know how much Is ?
T5,T6 is filaments = cathode voltage points.
Do You know how much Is ?
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.
Last edited:
From what I have been told and read the filtering you need is already on the board directlty after the 24v input. So you dont need any further filtering.
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....
You have a nice, functional enclosure. Where I could get one from?
Sounds great BTW! Testing it out at 9.4v at T7, T8.
It’s a Galaxy 2U with optional baseplate from Modushop/DIY Audio Store. This one is WxD 230mm x 280mm.
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?
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.
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.
Really? That's exciting, to say the least! I have one of the Millett headphone amps and it sounds absolutely fantastic, but rings as you describe.
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 🙂
What the is current draw of the amp......not much I assume. Less than 100 mA?
Could such a choke be used instead of the 10 ohm resistors in the PSU filter?
B82144A2225J000 | EPCOS Spole med tilledninger 2,2 mH +-5% Ferrit, Max SRF: 800kHz, Q:60, 120mA Idc, 9Ω Rdc | RS Components
Could such a choke be used instead of the 10 ohm resistors in the PSU filter?
B82144A2225J000 | EPCOS Spole med tilledninger 2,2 mH +-5% Ferrit, Max SRF: 800kHz, Q:60, 120mA Idc, 9Ω Rdc | RS Components
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. 😀
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. 😀
Last edited: