You could try NICMAC here on diyaudio, he sells them.
Don't know if he has them with that spec.
Trying to understand harmonic distorsions on the B1 KORG
I couldn't find any precise graphs, but I let's take some figures for the example.
Not sure if in the right ball park, but assuming recommended Papa setting, not inverting output cables, so being at 9.5V positive phase 2nd harmonic set up and of course that 16dB gain.
Say that at 1V pre amp output we have mainly -35dB 2nd harmonic (sounds quite high, but seems not too far off?) and -40dB 3rd harmonic.
Is my understanding correct that now taking a 100mV preamp output, this becoming the new 0dB level, harmonic distorsion values are reduced a great deal while though keeping their "harmonic profile through the harmonic orders", leading roughly to now 2nd harmonic at -50dB and 3rd harmonic at -55dB?
If so, if one likes the harmonic profile of the pre at 9.5V (2nd harmonic over 3rd) but would like say less harmonic distorsion, a possibility could be to reduce preamp output level (having more power amp gain).
Or is the relation between fundamental and harmonic always the same if not playing with the pots, regardless the fundamental level, which on the other side would make sense in term of consistency for music?
Thanks for your help
Claude
I couldn't find any precise graphs, but I let's take some figures for the example.
Not sure if in the right ball park, but assuming recommended Papa setting, not inverting output cables, so being at 9.5V positive phase 2nd harmonic set up and of course that 16dB gain.
Say that at 1V pre amp output we have mainly -35dB 2nd harmonic (sounds quite high, but seems not too far off?) and -40dB 3rd harmonic.
Is my understanding correct that now taking a 100mV preamp output, this becoming the new 0dB level, harmonic distorsion values are reduced a great deal while though keeping their "harmonic profile through the harmonic orders", leading roughly to now 2nd harmonic at -50dB and 3rd harmonic at -55dB?
If so, if one likes the harmonic profile of the pre at 9.5V (2nd harmonic over 3rd) but would like say less harmonic distorsion, a possibility could be to reduce preamp output level (having more power amp gain).
Or is the relation between fundamental and harmonic always the same if not playing with the pots, regardless the fundamental level, which on the other side would make sense in term of consistency for music?
Thanks for your help
Claude
Nice thing about the harmonics is that for reasonably linear Class A circuits
is that they are fairly predictable.
2nd harmonic decreases with the square root of the amplitude, so that a
1% figure at 1 V becomes .3% at .1V and .1% at .01V
3rd harmonic declines in proportion, so that 1% at 1V becomes .1% at .1V
And so on, with even more decline in higher harmonics.
is that they are fairly predictable.
2nd harmonic decreases with the square root of the amplitude, so that a
1% figure at 1 V becomes .3% at .1V and .1% at .01V
3rd harmonic declines in proportion, so that 1% at 1V becomes .1% at .1V
And so on, with even more decline in higher harmonics.
Many Thanks Papa for your kind and quick answer, very clear and very instructive... as ever.
Out of curiosity to be able to carry the calculation, do you remember what the "starting point" at 1V output was with 9.5V - eg how many 2nd harmonic distorsion and how many 3rd order distorsion for 1V at your recommended 9.5V setting?
Many thanks again!
Claude
Out of curiosity to be able to carry the calculation, do you remember what the "starting point" at 1V output was with 9.5V - eg how many 2nd harmonic distorsion and how many 3rd order distorsion for 1V at your recommended 9.5V setting?
Many thanks again!
Claude
Thanks ichiban.
I contacted him already. He has not exactly what I want.
Following Nelson instructions and available options, I choosed to buy a lot of the good and cheap Fairchild FQP3p20 and make some matches.
I think I can share the informatin I received :
"You can use a part like the Fairchild FQP3p20 (attached sheet) or
the IRF9620, 21, 22 as made by Harris. They are actually superior
to the IR parts.
The FQP is available for less than a dollar, so you can buy enough to
get some matches.
You could possibly try the Jfet inputs, also see attached, but this is for
the adventurous. I leave you to decide...."
Nelson Pass
The reference was 1% 2nd harmonic at 1 volt out. I recall 3rd harmonic is
in the area of .1% at the same voltage.
I took typing in high school, too. When I went into my postgraduate training in New Orleans, I would type stuff on the office typewriters. That kind of thing in the South at that time made people consider that a male was of dubious sexuality, so I stopped doing it after getting strange looks from both men AND women, like I had broken some sacred social code.
My B1 Korg has been tootling along for a long time now, and sounds really purty. Can't believe I got the darn thing to work.
So I'm new at the Audiophile Kit thing. My ACA full kit will arrive tomorrow and I'm already on the list for this Korg preamp kit when it's available. Hopefully things will go well and I won't need to bug you folks much, but looking through this and the ACA thread, it seem like this is a great community and it's the main reason I decided to try this. Thanks for that! Soldering station plugged in and fingers crossed...
I started with an ACA which instantly let to a second ACA bridged.
Now I am collecting parts to build an F6.
Words of wisdom.....
Be prepared for the inevitable slippery slope that will follow your first ACA build.
Words of opinion.....
If you have a Preamp I suggest holding off on the B1+Korg+ACA.
I have tried a number of preamps + ACA including B1+Korg.
My ears say B1+Korg+ACA is too much of a good thing,
B1+ACA is just right.
Happy Building,
-BB
I fully expect another ACA will be purchased. But I have a pretty high-end primary system. This will be an experimentation project just for fun. I can see it getting totally out of hand though!
Can you expand on "Too much of a good thing" comment. Too valve sounding? I'm actually wanting to experiment with Valve hardware just to see if I'll like it this time. I've experimented with some Liner Tube Audio hardware in the past and really didn't like it as well as SS. But would like some diversification on a secondary system. Plus the wife hates the light bulb farm look. Thought this could be a good way to go.
It is my experience that usually it is best to use a trick like 2nd harmonic
once in a system, and even then in modest amounts.
But not always......
I find Mr. Pass replying to a post a bit intimidating. 
Plus this is getting a bit off topic, but if the admin's OK with it...
But let me wade in with both feet. My main system utilizes a Lyngdorf 2170 "Digital" amp. It is the total opposite of Valve sound and wouldn't know 2nd order if you beat it to death with it. So I'm really diverging from my norm with this build combination. Valve + Class A. But I like to experiment. If I didn't I wouldn't have discovered the Lyngdorf. Plus I like to build stuff anyway. So even if I don't like it, half the fun is getting there.
Plus this is getting a bit off topic, but if the admin's OK with it...But let me wade in with both feet. My main system utilizes a Lyngdorf 2170 "Digital" amp. It is the total opposite of Valve sound and wouldn't know 2nd order if you beat it to death with it. So I'm really diverging from my norm with this build combination. Valve + Class A. But I like to experiment. If I didn't I wouldn't have discovered the Lyngdorf. Plus I like to build stuff anyway. So even if I don't like it, half the fun is getting there.