My B1 Korg isn’t grounded over and above the 24vdc power supply to the board if that has any? The wall wart is only two pin (active and neutral). Perfect sound, no ringing.
Regarding this, I pulled the 270R resistor and it is fine... so my only guess here is that the Zener diode is faulty. Is that a reasonable assumption or could there be a different reason?
Is your regulator regulating? You need to measure the voltage at the output of the regulator to see if it is varying before assuming it's the B1 Korg.
It is regulated... I've noticed it changes a bit depending on my line voltage. During the day it outputs around 23.9V, at night 24.1V depending on line fluctuation. I'll check if thats valid...
Regardless, the B1 is getting ~24V at the input, with T3 at 22.6V which is within spec.
With these values, T4 is ~11V which leads me to suspect the Zener.
Regardless, the B1 is getting ~24V at the input, with T3 at 22.6V which is within spec.
With these values, T4 is ~11V which leads me to suspect the Zener.
Possibly..
Supply not 'strong enough' current drop too much off the 270.. Try 200 ohm
If using Salas.. Drop the R increase current
Supply not 'strong enough' current drop too much off the 270.. Try 200 ohm
If using Salas.. Drop the R increase current
Good morning sirs, reading again and with more attention Mr Pass article about his Nutube preamp, I dwelt upon this sentences: "...and the R1 values are matched to the Q2 Jfets...the kits are provided with selected J113's, and note that Q1/Q2 are not interchangeable." Then, I confess that during the building on my Nutube circuit, I didn't pay too much attention to this and actually I remember that the Diyaudio store sent me two little bags with the pcb, one with four jfets, the other with four jfets and the four R1 resistors. For sure, I messed up the jfets and therefore I lost the correct matching R1/Q2. Nevertheless, my Nutube is working and it seems working well. Do you think I committ a serious mistake? Is my Nutube preamp not operating as it should?
Thanks in advance,
Gaetano.
Thanks in advance,
Gaetano.
I think he said he is using the Amb Sigma 11 (correct me if I'm wrong).
In that case, it is providing up to 1A so plenty of current available (Korg requires 60mA).
I would check the Zener. I went through a pack of diodes to find one that was even close to the 9.1v spec.
I would pull a leg each of the 7k5 and the 2x 475R resistors to disconnect point H (refer to the schematic) and test T4 to see what the unloaded voltage is.
But do whatever is within your comfort zone / capability.
Actually, the only weird thing I noted is that if I want to read the same voltage in T7 and T8, I have to set the two trimpots at different positions. Do you think that this could be related to my mistake?
Thank you everyone.
Thank you for your answer, but I was referring to a previous post of mine, regarding the mistake I committed building the pcb: I messed the Q1 and the Q2 jfets, ignoring the matching between the Q2 jfets and the R1 resistors, to which Mr Pass refers in his article about B1 Nutube. My concern is that my device is not correctly operating, even if it seems to work well...
Gaetano.
Ok, but supposing that I prefer to leave all as it is (I'm not sure to be able to pull out the jfets without damaging the pcb), do you think that this mistake could have a bad impact on the performances of my B1?
Gaetano
Triode need to be heated for 15 minutes , half hours or more before T7, T8 precise voltage adjustements .
Read voltages differences in cold and hot temperature triode state is normal
0.2V of little difference at the psu output in day & night time is normal..nothing to be worried 🙂
Hay Nelson stay home stay safe enjoy lots of music. Get the feeling US will be hit very hard in the next few weeks because of unwillingness to impose on civil liberties and a president putting profit before people. Almost total lockdown in NZ for four weeks. Still as long as Tidal holds up lots of music will be played through NP gear��
Third week living closed at home almost all time, here in Italy. Luckily in the south. Listening tons of music with NP B1 Nutube and diy gear, of course.
A thought for people which is no longer with us...