Well, you haven't looked close enough, as... I did. In fact I use 2 outputs, line and HP, since over a year 
As posted previously and just again very wisely by Hikari1, it all depends on your HP impedance. I have 600R HP and put some 100R between the outputs so it is still a quite easy drive but to avoid Fc being too low I use 100uF at the output.
My HP have quite a high impedance by many modern standards, so you better check, I doubt 30uF will get you anywhere unless you have some very special HP.
As HP amp I found the Korg to be fine, but indeed mainly because I have some high impedance load (and don't need a lot of current). Situation would be very different with low impedance HP, kind of mobile ones, but despite what some predicted my Koss Porta Pro still played some music LOL
As Hikari1 said, IMHO it is all down to the impedance of your HP, but the Korg is not really a HP amp... there are other projects for that, Korg or not Korg based...
All IME
Claude
As posted previously and just again very wisely by Hikari1, it all depends on your HP impedance. I have 600R HP and put some 100R between the outputs so it is still a quite easy drive but to avoid Fc being too low I use 100uF at the output.
My HP have quite a high impedance by many modern standards, so you better check, I doubt 30uF will get you anywhere unless you have some very special HP.
As HP amp I found the Korg to be fine, but indeed mainly because I have some high impedance load (and don't need a lot of current). Situation would be very different with low impedance HP, kind of mobile ones, but despite what some predicted my Koss Porta Pro still played some music LOL
As Hikari1 said, IMHO it is all down to the impedance of your HP, but the Korg is not really a HP amp... there are other projects for that, Korg or not Korg based...
All IME
Claude
Hi, I was listen to music from my PC then suddenly there was a high crash/rumbling sound. I turn the music off, then on again after 30 sec.
Then only sound in right canal, I take cover of Nutube and see left canal is not glowing.
I have not messured things yet, Nutube can crash / fail ?
Frank
Then only sound in right canal, I take cover of Nutube and see left canal is not glowing.
I have not messured things yet, Nutube can crash / fail ?
Frank
Attachments
Same thing happened to me (See https://www.diyaudio.com/forums/pass-labs/313612-b1-korg-triode-637.html#post6598784 and the posts that follow for further info).
I replaced the nuTube.
I replaced the nuTube.
Your twisted wires pairs with cotton "sockets" don't make short contact ? Fragile isolant material..
Best regards
Soundhappy: I dont know about the curent, have not adjusted/checked the Nutube for months. And yes the filament tread/wire is broken ( I can see ).
I messure alitle: T7-20vdc, T8-8.5vdc, 33.2K left side-33K, 33.2K right side-55K. I think I get all kind of crazy messurament with power on and broken filament.
Twisted cables with silk I am 99.99% thats not problem. I have hard twisted interconect cables RCA inn almost all my system, no problem. Ihave already ordred a new Nutube. Make more messurament with Nutube out. chanting: I will look at it. Now that all sound so good with new Accuphase F-20 and all
I messure alitle: T7-20vdc, T8-8.5vdc, 33.2K left side-33K, 33.2K right side-55K. I think I get all kind of crazy messurament with power on and broken filament.
Twisted cables with silk I am 99.99% thats not problem. I have hard twisted interconect cables RCA inn almost all my system, no problem. Ihave already ordred a new Nutube. Make more messurament with Nutube out. chanting: I will look at it. Now that all sound so good with new Accuphase F-20 and all
Attachments
I built one of these preamps a few months back. Really nice unit. Thanks.
My triode is prone to microphonics and can sometimes ring. I've suppressed this as best I can using some methods discussed here..
Recently I put the unit in the Processor loop of another preamp. I adjusted the B1 level to about 12 o'clock position which matches the level thru the main preamp. I noticed that the microphonics are non-existent now? No ringing. Why? The processor loop probably presents about 100kohm load to the B1. Straight into an amp, this is probably 30-50Kohm, so not much different. I can switch the input as hard as I like - nothing.
Thanks for the thoughts ....
My triode is prone to microphonics and can sometimes ring. I've suppressed this as best I can using some methods discussed here..
Recently I put the unit in the Processor loop of another preamp. I adjusted the B1 level to about 12 o'clock position which matches the level thru the main preamp. I noticed that the microphonics are non-existent now? No ringing. Why? The processor loop probably presents about 100kohm load to the B1. Straight into an amp, this is probably 30-50Kohm, so not much different. I can switch the input as hard as I like - nothing.
Thanks for the thoughts ....
some info about the Korg Nutube...
Cheers
Dirk
https://docs.rs-online.com/db3d/0900766b816e68bf.pdf
all info is important - and especially from page 8
Cheers
Dirk
https://docs.rs-online.com/db3d/0900766b816e68bf.pdf
all info is important - and especially from page 8
Preamplifier circuit respect all data sheet parameters, but " geographic map is not a territory ".
Could be after a thousand hours of continuous work some parameters of the filament mechanical structure are altered ?
Maybe some Nutubes was little damaged by transportations, received a shock in the shipping process ?
In Japan Nutube is very popular, many commercial products of Korg use them.
DIY projects included legendary designer Kaneda San who build many variations
of hybride SIC Mosfet with Nutube power amplifiers, DAC's and Phono stages with Korg , check articles in MJ Magasine.
Facts show that is a lot of good evaluations