I am quoting myself just to reference that my build is atypical.
I have redone some work. The majority of wiring has been redone. It is cleaner and stays out of the way of the top cover's minimal footprint now (woops). The battery has a 3D printed tray and wires have quick disconnects.
Either through mounting PCBs on rubber spacers or adding voltage dividers, my ringing issue didn't occur (though it briefly happens at turn on thump) in an extended listening session. The original omission of the voltage divider was an accident. As suggested, it seems wise to use voltage divider when not incorporating a volume control.
The voltage divider did take some wind out of the sails. Now I can turn the volume up a bit. Previously, some tracks were too loud with source even at lowest volume. It had amazing bass slam that is dialed back now. However, that could be more a product of the amp being in the 28V-25V range then, and now it was well below that range. Voltage divider byproduct or due to battery voltage? If the characteristics of the amplifier change drastically with voltage, I don't view it as a completely horrible (possibly very cool).
The charge circuit works and works well. Combining the display and charge circuit together was done because I only had three switch positions (amp on, amp off... charge/display). But it works out well since it shows the battery's status during charging. The smart charger correctly stopped around 28V, so the display isn't necessary during charging, but not detrimental either.
The startup/turn of thump... it still scares me. But I can't really add anything elaborate inside the chassis. The Bottlehead Quicksand forum mentioned using a 1W 1Ohm resistor to short the outputs to solve startup thump. I wonder if this is a viable option? If so, would it also solve the turn off thump?
I can report it sounds better than my ACA. Considering the money I spent, it should. Early impressions would suggest it is detailed and does separation very well. Unlike some tube amps I've owned in the past, it does not hide poor recordings. If it's a good recording, it will make it shine though.
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That would make it sound even brighter. I have mounted the NX BG 47 uf a week or 2 ago. Have not listened to it yet. I have a Aleph 1.7 in same enclosure. Maybe I just drop the Nutube in the bin.
Don't you think it's suspicious that you are the ONLY ONE of all the builders who finds it too bright and harsh? With that kind of input, I would suspect that something has gone wrong in build/setup first...
You are totally wrong. I am not the only one. Maybe my system is better and more analytic then most. But it is the same impression both in my place and in the our Hifi Club in Copenhagen. Maybe my input impedance is to high. I use a Tkd 50 kohm potentiometer.
Erlend,
50k pot sounds right so unlikely to be the problem unless it is a defective pot.
Bright sound... no other built seems to match that description, at least for sure not mine... nor have I read such comments here from another builder. So pretty isolated comment among what seems to be now over 100 builts.
Your system better than others- ahem, won't get into that kind of arguments.
I have seen your posts here and there coming back again: you seem sadly stuck since a while. Have you compared your B1 Korg to another one, perhaps one from another fellow builder nearby? That could help isolating the problem - unit or taste? The latter is of course very respectable... that comparative test would perhaps help deciding wether it is worth for you investigating your unit further or not and what to expect from a B1 Korg.
Just thinking loud...
Claude
50k pot sounds right so unlikely to be the problem unless it is a defective pot.
Bright sound... no other built seems to match that description, at least for sure not mine... nor have I read such comments here from another builder. So pretty isolated comment among what seems to be now over 100 builts.
Your system better than others- ahem, won't get into that kind of arguments.
I have seen your posts here and there coming back again: you seem sadly stuck since a while. Have you compared your B1 Korg to another one, perhaps one from another fellow builder nearby? That could help isolating the problem - unit or taste? The latter is of course very respectable... that comparative test would perhaps help deciding wether it is worth for you investigating your unit further or not and what to expect from a B1 Korg.
Just thinking loud...
Claude
Another idea while reading "bright"... are you sure your output caps have the right capacity vs the input input impedance from your power amp? Perhaps they are defective, or perhaps they are under rated?
Again, just thinking loud in hope to be helpful, and having another unit would help
Claude
Again, just thinking loud in hope to be helpful, and having another unit would help
Claude
Can you post photo of the PCB component side? My experience building both the B1K and the Millet NuTube buffer is that "tone" is affected most by changes to the plate resistor value as well as plate voltage. The Millet circuit did not sound really right to me until switching to the recommended B1K plate resistor value of 332K. All the other circuit differences, Mosfet vs Jfet buffers, input caps, power supply filtering and filament regulation, etc. were extremely subtle.
I would double check supply voltage is +24VDC under load, T7 and T8 as approx. +9.5VDC to ground, and if you have a high input impedance meter, check those voltages again right at the tube plates as well. Make sure the plate resistors (the ones to the left and right of the NuTube pins) are 332K, not 33.2K or some other value.
I too think the korg B1 is bright compared to my solid state preamps. Maybe it’s not bright but more diffuse and airy which may translate to “bright” for some.
25k volume pot and lowering the tone arm on my turntable helped. I am still not 100% satisfied with the tonality of mine but Iam 1000% satisfied with the soundstage which is why it stays in my system.
I have polypropylene coupling caps to try next (I have tried silmics and Mylar caps). Hopefully they will be a step in the right direction.
25k volume pot and lowering the tone arm on my turntable helped. I am still not 100% satisfied with the tonality of mine but Iam 1000% satisfied with the soundstage which is why it stays in my system.
I have polypropylene coupling caps to try next (I have tried silmics and Mylar caps). Hopefully they will be a step in the right direction.
Finished PCB’s from the image posted on page 430. These are 4 layer FR4 1oz. A mixture of smd and thru hole. ~ 4 hrs to build a pair.
Input / Output signals routed on top. The plate , filament , & grid supplies are located on the bottom. The inner layers contain the ground plane and the power distribution plane.
