Getting an exact 24.0 V with the AMB s11 is a matter of choosing three components more carefully. A higher precision zener, such as the BZX55B12 can be used at D5. Then 0.1% 10k resistors could be used at R8 and R10. Or you could hand select the resistor values. R8 needs to be 10k in order to work properly with the 220 pF compensation cap at C16.
If you wanted to be extra meticulous, you could use a matched pair of higher Beta NPN transistors at Q3 and Q4.
If you wanted to be extra meticulous, you could use a matched pair of higher Beta NPN transistors at Q3 and Q4.
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I usually socket s11 D5 and R10 and get 10 diodes that I measure. Quick and easy to achieve 24.0V output by D5 trial, or reconfigure to an entirely different voltage later. I’ve repurposed the s11 in the pic several times already. Using a little 7VA Amveco transformer from my parts drawer here.
BK
BK
OK....I will read a bit more on this site:
The σ11 regulated power supply
…..to learn a bit more about the circuit and how it regulates.
I have found D5 and R10 in schematic.
The σ11 regulated power supply
…..to learn a bit more about the circuit and how it regulates.
I have found D5 and R10 in schematic.
no smoke.
A question of gain;
so, my 11 yr old son and I recently built the ACA kit. What a great experience. He is all in...and fantastic sound. When I use it with my "big" preamp, we can drive the pretty inefficient speakers to a reasonable level. (like Goldilocks, just right). But when we use an iphone, ipod, etc. directly, it is good for background music.
From what I can tell, these portable devices will only swing 1V.
So, I was looking at the B1 Korg as a next step project and a way to get a little more gain to the ACA. Looking at Mr. Pass' original paper on the OP, and the comments in the thread, looks like there is about 10db of gain. But the distortion curve shows a minimum at about 50mV with linearly increasing distortion after that crossing 1% at about 1V.
So, even if the design will deliver 10db - 14db of gain, should I think of this as relative gain? Effectively a max useful output of 1-2V which is basically unity gain?
I know - it's a buffer, but a few db of useful gain could help me a lot.
so, my 11 yr old son and I recently built the ACA kit. What a great experience. He is all in...and fantastic sound. When I use it with my "big" preamp, we can drive the pretty inefficient speakers to a reasonable level. (like Goldilocks, just right). But when we use an iphone, ipod, etc. directly, it is good for background music.
From what I can tell, these portable devices will only swing 1V.
So, I was looking at the B1 Korg as a next step project and a way to get a little more gain to the ACA. Looking at Mr. Pass' original paper on the OP, and the comments in the thread, looks like there is about 10db of gain. But the distortion curve shows a minimum at about 50mV with linearly increasing distortion after that crossing 1% at about 1V.
So, even if the design will deliver 10db - 14db of gain, should I think of this as relative gain? Effectively a max useful output of 1-2V which is basically unity gain?
I know - it's a buffer, but a few db of useful gain could help me a lot.
Hello,
My Nutube is ready and singing but...
The sound is very grainy, saturated, something is wrong.
Everything measures well, accordingly to the manual.
I am not using the recommended psu...
Instead, I use a psu that was almost forgotten in a plastic box.
This psu has 5A current(!!!!!). I thought that to much current would be just a waste but would not have a negative effect. May be I was wrong... Can you please help me here?
I suspect that everything will be ok with the 24V Triad. Thank you!
My Nutube is ready and singing but...
The sound is very grainy, saturated, something is wrong.
Everything measures well, accordingly to the manual.
I am not using the recommended psu...
Instead, I use a psu that was almost forgotten in a plastic box.
This psu has 5A current(!!!!!). I thought that to much current would be just a waste but would not have a negative effect. May be I was wrong... Can you please help me here?
I suspect that everything will be ok with the 24V Triad. Thank you!
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A much higher current rating than you need is no problem. The most important is how "clean" the 24V is. I also use a 4-5A PSU. A Meanwell which is now the standard for the ACA kit. I made some additional filtering for it to be sure I have not switching noise. The distortion measurement showed very low noise. I can recommend objective measurements before any listening test. Then you know if everything is up to expected specifications. Guessing what is wrong is always difficult.
MEPER :
I understand, but I measured everything and it was ok. I can not measure distortion and it's hard to believe that the problem is so much noise from such a psu. This psu is supposed to be better than the recommended one. I used a few before and they are not high end psus but they are good nevertheless. Again, and as you said, I am guessing... May be I will have to try another psu if I have no other clue. May be you're right.
I understand, but I measured everything and it was ok. I can not measure distortion and it's hard to believe that the problem is so much noise from such a psu. This psu is supposed to be better than the recommended one. I used a few before and they are not high end psus but they are good nevertheless. Again, and as you said, I am guessing... May be I will have to try another psu if I have no other clue. May be you're right.
@polaron
Unfortunately, your attached image will not load for me. I've build two B1 Korgs and they are anything but grainy. There is definitely something wrong. As you suggest, try a different power supply, but it would help if you could confirm all of the voltages at the test points are in order. You will enjoy this preamp one you get past this initial problem.
Unfortunately, your attached image will not load for me. I've build two B1 Korgs and they are anything but grainy. There is definitely something wrong. As you suggest, try a different power supply, but it would help if you could confirm all of the voltages at the test points are in order. You will enjoy this preamp one you get past this initial problem.
If there is clear audible difference from "clean sound" then something must be wrong and in these cases measurements can show it. First thing to check is always PSU. You could check using a DMM how much AC there is on PSU output. It may give an indication if PSU has noise (DMM set to mV AC). Korg Nutube has correct color…..blue?
polaron,
That's the impression I got. I borrowed member 6l6's version of the nutube. It's signature was almost identical to a 12ua7 preamp I had for awhile.
However I can't help but wonder how much those micro-phonics affect to sound, it was much worse than I imagined. After some tone bursts I could hear ringing for 10 seconds later, with the unit in a damped isolated area. I still use my version of the B1 as the reference of neutrality and musicality.
That's the impression I got. I borrowed member 6l6's version of the nutube. It's signature was almost identical to a 12ua7 preamp I had for awhile.
However I can't help but wonder how much those micro-phonics affect to sound, it was much worse than I imagined. After some tone bursts I could hear ringing for 10 seconds later, with the unit in a damped isolated area. I still use my version of the B1 as the reference of neutrality and musicality.
Ok, I just re checked all the measuring points.
Psu out gives exactly 24V.
All points are ok.
The most critical are
T5 with 0,6827 volts,
T6 with 0,6833,
T7 with 9,495 and
T8 with 9,468.
May be not very accurate but not dramatic.
The Nutubes are GREEN!!!!
Note that some resistors have much less than 400mw. I made a mistake and bought some much less powerfull, they are very tiny, but very accurate, good quality Koa Speer :
all of those 332K are the tiny ones.
I may have to check the resistors values, but then I have to take them out. Arrrgghhhh!!
Psu out gives exactly 24V.
All points are ok.
The most critical are
T5 with 0,6827 volts,
T6 with 0,6833,
T7 with 9,495 and
T8 with 9,468.
May be not very accurate but not dramatic.
The Nutubes are GREEN!!!!
Note that some resistors have much less than 400mw. I made a mistake and bought some much less powerfull, they are very tiny, but very accurate, good quality Koa Speer :
all of those 332K are the tiny ones.
I may have to check the resistors values, but then I have to take them out. Arrrgghhhh!!
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