Has been debated and explained many times in the past...
Short answere is NO - no roll off relevant for HIFI purpose with these values at these locations
Claude
Short answere is NO - no roll off relevant for HIFI purpose with these values at these locations
Claude
Good. I do have some used boutique caps lying around at these lower values I can try for fun..
Hi Claude,
Can you direct me to the post where you explained these? Sorry I can't seem to find them
Advanced search function is your friend, look for my posts in this thread, over a year ago... I am afraid you will have to do it.
If too time consuming for you, these caps associated with the corresponding R form a (in fact 3 as 3 different locations) high pass RC filter which Fc (cut off frequency) isn't difficult to calculate by all means.
Goof luck either way
Claude
If too time consuming for you, these caps associated with the corresponding R form a (in fact 3 as 3 different locations) high pass RC filter which Fc (cut off frequency) isn't difficult to calculate by all means.
Goof luck either way
Claude
I need some help. I have one problem with my B1. Sound is very good, channels are very equal, soundstage is great, i think that B1 is soldered absolutely properly, i checked everything three times.
1. I measured voltages, tried three different 24V ps.
t1 23,94
t2 23,18
t3 22,4
t4 8,65
t5 0,58
t6 0,6
So, t1 to t6 are ok, maybe t4 should be little higher.
The problem is t7 and t8
t7 10,5 - it is minimal possible voltage, i can't go below 10,5
I measured the whole available range at t7 - it is 21V to 10,5, when the potentiometer is at 12 i have 18,5V
t8 9,25 - it is minimal possible voltage, i can't go below 9.25, but it is most probably ok, as most people use 9.5-9.8
I measured the whole available range at t8 - it is 20,5 - 9,2, when the potentiometer is at 12 i have 17V
Is it possible, that the potentiometer for the left channel (t7) is broken ?
Any hints ?
1. I measured voltages, tried three different 24V ps.
t1 23,94
t2 23,18
t3 22,4
t4 8,65
t5 0,58
t6 0,6
So, t1 to t6 are ok, maybe t4 should be little higher.
The problem is t7 and t8
t7 10,5 - it is minimal possible voltage, i can't go below 10,5
I measured the whole available range at t7 - it is 21V to 10,5, when the potentiometer is at 12 i have 18,5V
t8 9,25 - it is minimal possible voltage, i can't go below 9.25, but it is most probably ok, as most people use 9.5-9.8
I measured the whole available range at t8 - it is 20,5 - 9,2, when the potentiometer is at 12 i have 17V
Is it possible, that the potentiometer for the left channel (t7) is broken ?
Any hints ?
My Korg Nutube popped a left channel filament after months of enjoyment, reading back on this thread it seems to be the fourth left channel that's popped while in service.
Hopefully not a trend for the future, ordered another one and should be back up and running again soon.
Hopefully not a trend for the future, ordered another one and should be back up and running again soon.
Measure the voltage at the 33.2k resistor after the pot. Are the voltages at maximum and minimum pot settings the same for both channels?
@BenMah Apologies that my description was not more clear. You got it though "connected the volume pot right channel output to the Nutube board left channel and that worked. Then you connected the volume pot left channel output to the Nutube board right channel and the output was low."
I measured all R1's and here's what I got-
Left Channel:
R1 input side: 0.92v
R1 output side: 0.98v
Right Channel (no sound):
R1 input side: 0.148v
R1 output side: 0.106v
Is this a sign that JFETs may have been damaged?
Thanks again for the help!
I measured all R1's and here's what I got-
Left Channel:
R1 input side: 0.92v
R1 output side: 0.98v
Right Channel (no sound):
R1 input side: 0.148v
R1 output side: 0.106v
Is this a sign that JFETs may have been damaged?
Thanks again for the help!
Yes, it does point to bad jfets. I am not sure how the bad amplifier blew them, but it does look like they need replacing.
Thank you so much for your answer Ben 🙂
I measured the voltage, on both channel it is nearly the same.
Left channel at 33.2k is from 0,0 to 3,38V and the right channel is also from 0,0 to 3,39.
Then i set the voltage for t7 and t8 for both channels at 14,6 and measured on 1k resistors on both channels
Then i measured the voltage on 1k resistor before q1 and it is on both channele 14,3 -14.31.
Any ideas why i can't get lower voltage on t7 ?
The voltages are identical so that leads me to think that the two halves of the Nutube are not identical.
As a last check, if you haven't checked 332k resistors at the Nutube anodes, then check to make sure that they are 332K.
As a last check, if you haven't checked 332k resistors at the Nutube anodes, then check to make sure that they are 332K.
Hi Ben,
I set the pots on max, and on 332k at the Nutube anode i have 9.2 and 10.5, it means that two halves of the Nurube are not identical.
Thank you so much for you support.
I bought B1 as a kit from diyaudio. Will they exchange it ?
You can't see it on the picture, but two halves of the Nutube have different green light intensity and my soldering work is not so bad.
I set the pots on max, and on 332k at the Nutube anode i have 9.2 and 10.5, it means that two halves of the Nurube are not identical.
Thank you so much for you support.
I bought B1 as a kit from diyaudio. Will they exchange it ?
You can't see it on the picture, but two halves of the Nutube have different green light intensity and my soldering work is not so bad.
Hi.
maybe check the standard specs of the nutube to see if within factory specs. All products have tolerances
quickly found this https://docs.rs-online.com/200b/0900766b815db1b5.pdf but maybe ahve a look at the korg ntube website
Does the preamp sound different left and right?
maybe check the standard specs of the nutube to see if within factory specs. All products have tolerances
quickly found this https://docs.rs-online.com/200b/0900766b815db1b5.pdf but maybe ahve a look at the korg ntube website
Does the preamp sound different left and right?
The sound is identical on both channels, but i can't set both channeles for negative H2 at 9,5V. When both pots have the same maximum setting, than after the pot on 33.3k i can measure 3,38 and 3.39V (1% difference) and on Nutube anodes (332k) I can measure 9.2 and 10.5V. It is nearly 15% difference between two halves of the nutube.
I wrote two emails to diyaudo shop describing the situation.
Nobody is answering ...
I wrote two emails to diyaudo shop describing the situation.
Nobody is answering ...
The store is not set up to give any sort of technical advice. Assuming that there are no other issues,
it looks like one channel of the Korg is off. I would try lowering the value of the 7.5K resistor that feeds
bias to both Grid controls and see what happens.
it looks like one channel of the Korg is off. I would try lowering the value of the 7.5K resistor that feeds
bias to both Grid controls and see what happens.
I was not asking the store for technical advice, i described the problem and asked for another nutube with equal halves ...
Is 15% difference between Nutube halves normal ?
Papa Nelson, thank you for your advice. Should i try 5k resistor instead of 7.5 ? Or 6.2 ?
Is 15% difference between Nutube halves normal ?
Papa Nelson, thank you for your advice. Should i try 5k resistor instead of 7.5 ? Or 6.2 ?
Try 4.7k and see what you get.
I have made about 10 of these and no encountered that much bias difference.
I have made about 10 of these and no encountered that much bias difference.