Maybe the medical grade version I have is too picky and I should have bought the cheaper version..? Worst case scenario I can use a laptop SMPS brick...
Do
Do
Maybe.. I used the cheaper mean well module and caps listed on the bom. The power supply section is working well. Even with my very ugly soldering of the surface mount components..
I’m keen for you to get yours playing music with the J113 JFETs to prove that section works too. Give me some hope!
I’m keen for you to get yours playing music with the J113 JFETs to prove that section works too. Give me some hope!
@Roo2
I can already tell you that both channels appear to be working fine looking at the scope. How great it sounds is a different story. I will know more later.
Do
I can already tell you that both channels appear to be working fine looking at the scope. How great it sounds is a different story. I will know more later.
Do
Look forward to it Pinocchio. I’ve built a store B1 Korg with J113s and it’s perfect. This board appears to be identical though the amp section. I don’t think my problem relates to the J113 JFETs. Something around the Bourne’s pot.. Just can’t pin it down..
I also built this board with the less expensive power supply on the bom and it works very well. Additionally I built the kit from diyaudio and have both preamps running now. I really wanted to be able to hear a difference between the two but I honestly can't.
Yep, just confirming that the less expensive supply works well. The medical grade one hiccups and does not seem to like all the caps. If I remove a few caps it works well but since the less expensive is working properly, no need to change anything.
Algar, I would omit that medical grade smps from the BoM. I think it must be too borderline for charging the cap bank.
On to the real testing now!
Algar, I would omit that medical grade smps from the BoM. I think it must be too borderline for charging the cap bank.
On to the real testing now!
Spent the last 20min troubleshooting this O/C in the pcb track, pls remember to link it.
I built mine with K170 option, with 392Kohms for R102. Will report back if there is any significant sonic difference when i switch back with 332Kohms later.
It now sings smoothly...
I built mine with K170 option, with 392Kohms for R102. Will report back if there is any significant sonic difference when i switch back with 332Kohms later.
It now sings smoothly...
Is the output of this Nutube preamplifier supposed to be very quiet, or you have a “shhhhh” at moderate level? I’m thinking it could be the LDR volume control instead of the potentiometer that is causing this amount of noise? I’m using a 50K version LDR but maybe it optimal for the Nutube?
@meanie
Please let me know the difference between the 392K and 332K, i would really like to know if it makes a difference. Please also check the output noise between the change.
Thanks
Do
Please let me know the difference between the 392K and 332K, i would really like to know if it makes a difference. Please also check the output noise between the change.
Thanks
Do
Mine is dead silent when output directly through headphones, even on max volume (except for a bit of ringing until the nutube settles after the switch on).
You shouldn't be getting hash noise but it could be from the LDR. Where does the LDR source power from?
I was reading this article regarding noise from an LDR and found it interesting:
Tortuga Audio LDR3 Volume Control: Measurements & Review
Having put my build to one side in frustration some weeks ago I started following the thread again and decided to try the cheaper smps as mentioned recently. Smiley face time as now things switch on; nutube glows blue and voltages are within a smidgeon of the values they should be with T7/8 adjustable with the trimmer. I now need to get it cased and have a listen over the weekend. Thanks Avtech for your previous advice.
@Marra
It was the same issue on my side and the cheaper SMPS got it working. Other SMPS should be removed from the BoM.
@avtech23
I have the same issue with a 23 steps 50K attenuator but I suspect the IPS from my test amplifier causing this issue when coupled to this preamplifier. I will test and report back.
Thanks
Do
It was the same issue on my side and the cheaper SMPS got it working. Other SMPS should be removed from the BoM.
@avtech23
I have the same issue with a 23 steps 50K attenuator but I suspect the IPS from my test amplifier causing this issue when coupled to this preamplifier. I will test and report back.
Thanks
Do
Will let you know once i received and swap the resistors, now finding an enclosure for it.
I didn't crank up full volume to listen for noise yet, but at my normal listening level, it was quiet, i did not hear any "Shhhhhh" noise, only the usual slight hum that is coming from my M2X.
Have you tested it with shorted inputs to verify whether the noise is internal or external?
Any SMPS or CFL nearby? I had awful noise on one amp that was caused by one of those cheapo little plug-in USB charger cubes.
Swapped the 392k for 332k.
I didn't pick up any significant difference between the two. So i just leave the 332k intact.
At max volume, without music, there is a very slight "shhhh" noise, similar to that of a valve set, but a lot hell lower than my valve preamp.
There is something very musical about this preamp as compared to the rests of my sets,
I actually enjoy this set very much.
I didn't pick up any significant difference between the two. So i just leave the 332k intact.
At max volume, without music, there is a very slight "shhhh" noise, similar to that of a valve set, but a lot hell lower than my valve preamp.
There is something very musical about this preamp as compared to the rests of my sets,
I actually enjoy this set very much.
WE have music😀. Had a listen to a couple of cd's yesterday; very pleased with the sound. Will have a proper listen this afternoon through the PMC's.
A couple of pics.
A couple of pics.
Mine too is playing well now. The Nutube can get microphonic if placed to close to speakers though. It needs to be well damped and it is fine. Sounds really nice so far.