Hello…both my pots are maxed…one side (T7) is very close the other (T8) I can only get to 12.06v.
T4=9.48
T1=23.98
T2=23.17
T3=22.37
T5&6=.65
How do I get more range in those pots?
Thanks for the help
T4=9.48
T1=23.98
T2=23.17
T3=22.37
T5&6=.65
How do I get more range in those pots?
Thanks for the help
Attachments
In the paper written about this preamp, it states that the voltage at T7/T8 should be adjusted to 10 volts and then allowed to set a few minutes until the tubes warm up. 12 volts might be the maximum setting for this test point. Looks like 9.5 volts is the starting point and then voltage is adjusted within a unspecified range to determine 2nd and 3rd order harmonics. Distortion will also be affected by this adjustment.
Thanks for the feedback. I let it run for about 5 min…no change…pots are both maxed to one side….the 12.3 vdc (side) just goes up from there adjusting the other way. Hummmmmm
The other day when I was building one these kits the T7/T8 voltages were way up at 19 volts! No way, so I quickly dialed them back to 10.
FWIW, in this next B1 kit, I am using a 4 turn pot instead of a 1 turn pot. Of course the value is the same at 10K, and ultimately it won't make a difference, but I will have more turning room to work with.
Note: I am starting to wonder if the value your pots are 10K or otherwise.
FWIW, in this next B1 kit, I am using a 4 turn pot instead of a 1 turn pot. Of course the value is the same at 10K, and ultimately it won't make a difference, but I will have more turning room to work with.
Note: I am starting to wonder if the value your pots are 10K or otherwise.
to Monk55
Hello Monk55,
why do you want to go higher than 12 Volts on T7/T8? You have zeroed out
2nd harmonic at around 12 V....
- so,very dominant 3rd harmonic.
I would start at around 9.5 - 10V and would only adjust very slightly.
And depending on your setup - invert polarity at speakeroutput (the B1 NUTUBE pre is phase inverting) to test what sounds better. If you flip your speakercables - please turn off the amps.
And you know - the DIY-NUTUBE-pre has a turn-on-thump...
Only some thoughts....
Cheers
Dirk
Hello Monk55,
why do you want to go higher than 12 Volts on T7/T8? You have zeroed out
2nd harmonic at around 12 V....
- so,very dominant 3rd harmonic.I would start at around 9.5 - 10V and would only adjust very slightly.
And depending on your setup - invert polarity at speakeroutput (the B1 NUTUBE pre is phase inverting) to test what sounds better. If you flip your speakercables - please turn off the amps.
And you know - the DIY-NUTUBE-pre has a turn-on-thump...
Only some thoughts....
Cheers
Dirk
Attachments
Ixnay & Dirk
Thanks for reaching out….the NuTube acted funny on first start….glow then no glow…reflowed. More jumpy…all voltages spot on. I matched all components on both sides. After a tedious NuTube extraction (fortunately I had a backup) I replaced. Fired right up…able to set both at 9.5…it’s still running. Been about 10 min. I’ll let it go. No doubt a bum tube from the get go.
Thanks for reaching out….the NuTube acted funny on first start….glow then no glow…reflowed. More jumpy…all voltages spot on. I matched all components on both sides. After a tedious NuTube extraction (fortunately I had a backup) I replaced. Fired right up…able to set both at 9.5…it’s still running. Been about 10 min. I’ll let it go. No doubt a bum tube from the get go.
Attachments
Request for help
Hello everyone.
I kindly ask your support to fix my B1.
Been in use for months without any issue. Yesterday i started to notice some "static" like noise from the right speaker, first quite low and almost not noticeable... then within about 1 hour grew louder until the right channel died.
I had the B1 connected to my tv phones output - while troubleshooting this i connected the rca from tv to my ACA just to test and had a lot of "static" like sound also in speakers - here i suspect the tv phones output is bad.
5 minutes ago i have opened the B1 and found the nutube only lights up on the right side - no light on the left side.
Upon closer look i see the fine filament across the device is broken on the left side.
Can you please help me troubleshoot this to know if its the nutube damaged only or not before i order a new one?
Would like to prevent replacing and damaging another nutube.
Thank you in advance.
Hello everyone.
I kindly ask your support to fix my B1.
Been in use for months without any issue. Yesterday i started to notice some "static" like noise from the right speaker, first quite low and almost not noticeable... then within about 1 hour grew louder until the right channel died.
I had the B1 connected to my tv phones output - while troubleshooting this i connected the rca from tv to my ACA just to test and had a lot of "static" like sound also in speakers - here i suspect the tv phones output is bad.
5 minutes ago i have opened the B1 and found the nutube only lights up on the right side - no light on the left side.
Upon closer look i see the fine filament across the device is broken on the left side.
Can you please help me troubleshoot this to know if its the nutube damaged only or not before i order a new one?
Would like to prevent replacing and damaging another nutube.
Thank you in advance.
Last edited:
Hello
Thank you for your reply.
I am going to power it up and measure everything, take notes and look at them.
I have very basic electronics understanding thus this forum is an invaluable source for me.
Just want to do all i can to make sure when i replace the nutube it will not get damaged due to some problem elsewhere.
Thank you for your reply.
I am going to power it up and measure everything, take notes and look at them.
I have very basic electronics understanding thus this forum is an invaluable source for me.
Just want to do all i can to make sure when i replace the nutube it will not get damaged due to some problem elsewhere.
I know there is such thing as the “broken review” síndrome: you go to Amazon and read reviews, but most people only review that which they have had problems with (and only very few post reviews if everything is just working!), so you i understand there is a disproportionate amount of negative reviews that don’t necessarily reflect the “true” amount of people with problems.
That could very well be the case with this Korg Tube, but the amount of tube failure claims here do create a certain concern in me. Obviously all other projects may have failures as well, and you could be a lucky one and never have an issue with the tube, but there seems to really be an additional chance of failure with these type of devices.
I could be wrong, of course.
Rafa.
That could very well be the case with this Korg Tube, but the amount of tube failure claims here do create a certain concern in me. Obviously all other projects may have failures as well, and you could be a lucky one and never have an issue with the tube, but there seems to really be an additional chance of failure with these type of devices.
I could be wrong, of course.
Rafa.
Rafa,
You have a valid point. When I used to working telephone repair, it seemed like all I ever saw was trouble and wondered sometimes how we even got dial tone to the customer to begin with. The reality was quite different in that day (remember the Bell System?).
I would say that I have built maybe 8 different NuTube kits of various types and 2 or 3 three had tube issues of some sort. Usually it was excessive ringing or even oscillation. None of them completely failed as described above.
You have a valid point. When I used to working telephone repair, it seemed like all I ever saw was trouble and wondered sometimes how we even got dial tone to the customer to begin with. The reality was quite different in that day (remember the Bell System?).
I would say that I have built maybe 8 different NuTube kits of various types and 2 or 3 three had tube issues of some sort. Usually it was excessive ringing or even oscillation. None of them completely failed as described above.
A channel is failing in my NuTube preamp build now. Havent been able to dig into it yet. Ran fine for almost 2 years. I already have a replacement on hand. One could complain, but I'd be willing to bet most of us have dropped 50's on way less responsible things that lasted far less than two years....
Edit: I still love how the NuTube sounds and will repair it without question. Running my dac straight into my vfet amp still sounds good, but just doesnt have the same sweetness to it.
Edit: I still love how the NuTube sounds and will repair it without question. Running my dac straight into my vfet amp still sounds good, but just doesnt have the same sweetness to it.
