"Fluxion NT-6, Can You Explain?"
- Thread starter Newjin
- Start date
FlaCharlie
Super Member
I haven't looked closely at the other stuff he has for sale but when he told you "Some of my amps don't have variable resistors to protect amps", he apparently meant that some of his designs use cathode bias, which is not adjustable. And the owners don't complain about the lack of adjustment.
That's fine, but if an amp can be adjusted owners need to know how.
If he's worried about damage from mis-adjustment he should realize that this is much more likely to happen if an owner decides to start adjusting things without any specific instructions.
It would be much less likely to happen if he provided written instructions with an explicit warning such as: When using 845s bias must be adjusted to xxV +/- xxV or damage may occur and warranty will be void. And same for the 211s.
If he's not willing to do that he should only sell amps that are cathode biased.
Newjin
Active Member
Thanks so much to all you guys for taking the time to answer and explain.
yeah once I get some more time this up coming week I'll push again to try to get mr Young to provide me with at the vary least his bias points and safe operating parameters.
The power supply schematic shows a negative bias supply (so not cathode bias), but the video describes different operating conditions for the two tubes. This likely means that the switch on the front to select each tube sets the correct bias voltage for that tube, not sure if it also alters the plate voltage as well. So it certainly would make sense that the way he shipped it is his ideal operating point for his circuit for each tube.
Safe to say I wouldn't buy something from someone that won't tell me the design bias conditions, but it seems that changing nothing is the best choice here.
Safe to say I wouldn't buy something from someone that won't tell me the design bias conditions, but it seems that changing nothing is the best choice here.
Last edited:
Newjin
Active Member
I agree and I obviously know more now so when I re read the email thats exactly what I thought. I am talking about this amp not your other builds.
I'm just looking for information on said amp like everything else you buy must come with safety operating instructions especially when dealing with high voltage equipment audio or not .
Thanks Charlie I really do appreciate you and everyone else
Newjin
Active Member
I don't understand why if something is so specific why not have a write up describing what you did and why you choose to go that route as to make your amp's different from others.
I am tempted to send this off to a reputable builder and have him or her reverse engineer it and get me a proper spec and schematic to this power amplifier.
Its frustrating having paid good money for something and not really feel like its yours.
Thanks for explain what was going on there Dave
FlaCharlie
Super Member
You would not have to reverse engineer the whole amp. You could just open it up (and if you do please post lots of detailed pics) and measure the voltages on the pins with each type of output tube.
Since you would now know the plate voltages too, it will then be easy to calculate the plate dissipation which the designer considers to be the ideal for each tube type. Doing so would not be difficult.
It would also tell you exactly what changes are made when the amp is switched to use the different tubes. Does it only change the bias voltage or does it also change the plate voltage?
Newjin
Active Member
Thanks Charlie
I'll give another try another try with reasoning with him before I try to get in there .. also I'm still not vary confident in my knowledge of SE tube amplifiers although it is growing everyday.
My brother is an electrical engineer, and now I understand thats not the same as electronic audio engineer at least I would feel much safer getting into it.
But I have been taking notes and like any of my hobbies i learn as much as i can and won't stop until i fully understand it before doing anything drastic as i still feel noobish .
would be looking to many of you for help if and when I do have to get digging into the
nt-6.
maxhifi
Addicted Member
Take some good photos of the under side of the chassis... but be warned that there is probably about 1000V under there while it is working, and some of that will still be present after it is switched off unless he has bleeder resistors on the filter capacitors.
So be super extra careful. The 845 requires voltages which are much more dangerous than usual tube amps. I would let it sit unplugged for a day before opening it just to be sure.
So be super extra careful. The 845 requires voltages which are much more dangerous than usual tube amps. I would let it sit unplugged for a day before opening it just to be sure.
Newjin
Active Member
that's my understanding when popping the hood capacitors and transformers stay charged holding lethal amounts of voltage that can shock let alone kill if you complete the circuit big no-no.
i wont be doing anything like that until i have someone here to guide me through ..so don't worry fellas thanks for helping good maxhifi
rudolfo
Super Member
any luck?
trainbuftony
Electron Herder
I'm going to guess that bias is not adjustable and that he doesn't want you adjusting it.
I'd also hazard a guess that the amp is simple enough that a tech could glance at it and see what's going on without a schematic . Dudes who strive for simple "best practices" style amps tend to build such that any tech who looks at it can make an accurate diagnosis and repair.
For example:
If you get a flat tire on the highway, you don't need to call Toyota Motor company and demand directions on how to change a tire.
You either change the tire or call AAA. If calling the manufacturer crosses your mind, you're out of your element.
It's a case of: you're either familiar with the body of knowledge, or you aren't.
Not trying to offend anyone, the schematic for this amp is probably so basic, so simple that he probably makes the assumption that you don't have any business messing with it.
How about a photo of the under side.
Perhaps the seasoned heads here can shed some light on things...
I'd also hazard a guess that the amp is simple enough that a tech could glance at it and see what's going on without a schematic . Dudes who strive for simple "best practices" style amps tend to build such that any tech who looks at it can make an accurate diagnosis and repair.
For example:
If you get a flat tire on the highway, you don't need to call Toyota Motor company and demand directions on how to change a tire.
You either change the tire or call AAA. If calling the manufacturer crosses your mind, you're out of your element.
It's a case of: you're either familiar with the body of knowledge, or you aren't.
Not trying to offend anyone, the schematic for this amp is probably so basic, so simple that he probably makes the assumption that you don't have any business messing with it.
How about a photo of the under side.
Perhaps the seasoned heads here can shed some light on things...
The Youtube vid linked early on shows 70ma for the 845 tube, which should measure 0.7 volts across the 10 ohm cathode resistor. Shows the math right on screen, so thats not me just making assumptions about what resistor is there. 211 tube is listed as 55ma, or 0.55 volts by the same math.
also shows a bias adjustment pot sticking out the back and test points on top, so it seems like you are meant to be able to adjust it.
assuming unit in the video is the same as the one we're talking about at least.
also shows a bias adjustment pot sticking out the back and test points on top, so it seems like you are meant to be able to adjust it.
assuming unit in the video is the same as the one we're talking about at least.