As a complete rookie it would be so much easier to wait on a kit but I may see what I can piece together. Thanks for the reply.
This pre-amp generates such little heat, I’m tempted to just leave it on all the time. The Korg website says it should last “30,000 hours of continuous life expectancy” (~4 years continuous). If it sits powered on but idle 90% of the time, would that extend tube life or should I expect to replace the tube every ~4 years?
Personally, I think it sounds better left on. I leave everything but the power amp on all the time. Also, it keeps me from inadvertently powering down/up the Korg while the power amp is on. Also, Iam lazy and my korg b1 has no power switch.
I have some components like a sals phono stage that have been on for literally years.
I have some components like a sals phono stage that have been on for literally years.
I don't know about the nutube itself but it's thought that SS designs (like the buffers in the Korg B1) sound better when left on. Pass uses a standby switch in the power amps to leave the front end circuitry powered on and the output stage powered down. So, my thought is it will sound better if left on all the time.
And, turning tubes on-and-off in an ideal fashion isn't all that easy. Here is a summary of a longer article I found discussing tubes:
The above gives an overview of often-discussed issues. If you want to know more about factors determining tube life, Tomer’s book would be a good read. Audio Discussions #4 also has many tips and tricks related to tube life throughout the book. To wrap up the most important points:
• High voltage should preferably be switched on only after the cathode has reached operating temperature, and this is especially important when using solid-state rectifiers. (that would be us)
• To avoid higher anode voltages at switch-off, it is recommended to first switch off the high voltage, then after discharge of the high voltage capacitors, switch off the heaters. This may depend on the actual equipment, possibly thermal inertia of the anode structure is enough to discharge the high voltage capacitors while the anode current peters out. Here is one case where excessive rectifier filter capacitance is a disadvantage.
• The preferred heater supply is AC, unless there is an insurmountable hum issue. Heater voltage should be nominal or a bit lower like -5% for maximum tube life. Consider running the heaters at 50% in standby, never turning them off, to avoid turn-on current surges and insure quick turn-on of the equipment.
• Make sure that an operating tube has sufficient air circulation around the envelope to avoid high temperatures. The tube will get hot, but the surrounding air should not, and should be able to flow unobstructed.
• Keep an eye on heater-cathode voltage differences — even below the specified limit, leakage and noise may increase. If you do switch the heaters completely off, consider limiting heater turn-on surges with an NTC resistor or something similar. But consider where to mount it — an NTC under the chassis may generate enough heat to cause reliability issues on itself. When debating the use of fixed or auto bias for the grid and the screen, also consider the impact on equipment reliability.
This article was originally published in audioXpress, August 2020.
I would think the reason was that the circuit is designed to operate when the parts are at, uh, operating temperature, and that takes some time to reach. That's certainly audible with power amps. It takes 30-60 minutes, usually, for my amps to sound their best. I'd guess something similar would be true with a pre-amp. So you can just turn it on an hour before you want to listen, if you want the absolutely best sound. But the difference probably wouldn't be that huge anyway.
Does anyone have any experience with an audio device that simply reduces power to the tube heaters and leaves everything else on when turned "off"? Would that modification solve or reduce the Korg's switching thump and also extend the life of the tube? If the life is extended, then by how much?
The power switch used in the Korg kit could be repurposed simply to reduce power to the heaters when turned off. Maybe replace the switch with an ON-OFF-ON switch to retain the "completely off" capability in the middle position?
The power switch used in the Korg kit could be repurposed simply to reduce power to the heaters when turned off. Maybe replace the switch with an ON-OFF-ON switch to retain the "completely off" capability in the middle position?
The Nutube does not have a heater that would be conveniently switchable like a traditional tube.
If you switch your amplifier on after the Nutube is powered up, and the amplifier off before the Nutube is powered down, the thump is not an issue.
The Nutube has a finite life, it's likely best if you power it on when using it, and off when you are not.
If you switch your amplifier on after the Nutube is powered up, and the amplifier off before the Nutube is powered down, the thump is not an issue.
The Nutube has a finite life, it's likely best if you power it on when using it, and off when you are not.
The Nutube does not have a heater that would be conveniently switchable like a traditional tube.
If you switch your amplifier on after the Nutube is powered up, and the amplifier off before the Nutube is powered down, the thump is not an issue.
The Nutube has a finite life, it's likely best if you power it on when using it, and off when you are not.
Ha. Shoulda seen that from the schematic, but I don't speak "tube" very well. What about reducing or removing power from the cathode? Would that shut down the tube so that it doesn't age while not in use? And what kind of thump would result when power was restored to the cathode?
Sorry to beat this horse, maybe it's dead and I should give it up. I have a pcb on order that includes delayed connect and instantaneous disconnect at power on/off so I'm not worried about the power thump but I would love to baby the tube for maximum life and I could easily modify my board to handle practically any power sequence.
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If you moved your B1 with Korg NuTube to a new enclosure, you could install a new rotary switch on the new front panel. This switch could conceivably have quite a few more than two positions, corresponding to quite a few more options than simply POWER_OFF and POWER_ON. You might envision a four position switch, with these settings. The first item in the list is the max-anticlockwise rotation, and each subsequent item in the list is one click clockwise beyond its predecessor:
Now you, the human operator, can turn the rotary switch as quickly or as slowly as you like. To turn your B1 with Korg NuTube ON, switch from position 1 to position 2 and wait 15 seconds. Then switch from position 2 to position 3 and wait another 15 seconds. Then switch from position 3 to position 4 and the music comes on with no thump. Reverse the process to turn your B1 all the way off. It mutes instantly, as soon as you switch from #4 to #3, but you control how quickly the power is withdrawn.
Or, decide that you will operate your own NuTube without ever switching to position 1. For you, the "No Longer Playing Music" switch position will be #3: always powered up, always at thermal equilibrium, but output relays muted so thumps are eliminated. Or you could imagine that it extends the life of the NuTube to choose your "No Longer Playing Music" state as switch position #2. Half voltage thus less power, but still drawing juice from the SMPS and hopefully reducing or eliminating Hiccup Mode when you turn on again.
You'd need to design and fabricate an output muting relay board (including control circuitry), and find a convenient place to mount it in your new enclosure. Near the output jacks, I imagine. If you implemented the control circuitry using a microcontroller + firmware, you might be able to use a two position toggle switch on the front panel again. Let the microcontroller programmaticallly step through the four step sequence, as quickly or as slowly as you prefer.
edit- and of course you can have the control circuitry illuminate more than one front panel LED, to show the power state currently selected. You can have one front panel LED per state, perhaps in different colors. Or you can use bicolor or tricolor LEDs to indicate the power state with fewer "bulbs". Finally, you can also add blinking (or "breathing") to your repertoire: state1=LED_OFF; state2=LED blinking red @ 50% brightness; state3=LED blinking green @ 50% brightness; state4 = LED steady green @ 100% brightness.
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- 1. OFF: zero DC voltage applied to all circuits, zero DC current everywhere, output muting relays MUTED (output shorted to ground thru relay NC contacts)
- 2. WARMUP: 50% DC voltage applied to active circuits, output relays MUTED
- 3. ON_BUT_MUTED: 100% DC voltage applied to active circuits, output relays MUTED
- 4. ON_AND_OPERATIONAL: 100% DC voltage applied to active circuits, output relays NOT MUTED
Now you, the human operator, can turn the rotary switch as quickly or as slowly as you like. To turn your B1 with Korg NuTube ON, switch from position 1 to position 2 and wait 15 seconds. Then switch from position 2 to position 3 and wait another 15 seconds. Then switch from position 3 to position 4 and the music comes on with no thump. Reverse the process to turn your B1 all the way off. It mutes instantly, as soon as you switch from #4 to #3, but you control how quickly the power is withdrawn.
Or, decide that you will operate your own NuTube without ever switching to position 1. For you, the "No Longer Playing Music" switch position will be #3: always powered up, always at thermal equilibrium, but output relays muted so thumps are eliminated. Or you could imagine that it extends the life of the NuTube to choose your "No Longer Playing Music" state as switch position #2. Half voltage thus less power, but still drawing juice from the SMPS and hopefully reducing or eliminating Hiccup Mode when you turn on again.
You'd need to design and fabricate an output muting relay board (including control circuitry), and find a convenient place to mount it in your new enclosure. Near the output jacks, I imagine. If you implemented the control circuitry using a microcontroller + firmware, you might be able to use a two position toggle switch on the front panel again. Let the microcontroller programmaticallly step through the four step sequence, as quickly or as slowly as you prefer.
edit- and of course you can have the control circuitry illuminate more than one front panel LED, to show the power state currently selected. You can have one front panel LED per state, perhaps in different colors. Or you can use bicolor or tricolor LEDs to indicate the power state with fewer "bulbs". Finally, you can also add blinking (or "breathing") to your repertoire: state1=LED_OFF; state2=LED blinking red @ 50% brightness; state3=LED blinking green @ 50% brightness; state4 = LED steady green @ 100% brightness.
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As it happens, I've already done most of the work -- an addon pcb that handles everything you mention except for partial-power to the pcb which could be partial power just to the Korg and leaving the FETs full powered. It's fully automatic but I could add a switch control with three way off-standby-on positions using an on-off-on switch. the muting relay would operate on it's automatic delay sequence based on the switch position.
I have two spare pins on the programmable chip I'm using which could control a high-side FET to deal with power to the Korg cathode or cathode and anode.
My first design (pictured) is enroute from China now, should be here in a week or two.
I have two spare pins on the programmable chip I'm using which could control a high-side FET to deal with power to the Korg cathode or cathode and anode.
My first design (pictured) is enroute from China now, should be here in a week or two.
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All this talk about the NuTube wearing out has gotten me thinking. I took some measurements of my speakers the other day and there was a 10db roll off from about 2k to 20k. I just bypassed the B1 Korg going straight from my DAC to a F6 that is my main amp. I notice that the highs came back, music is more dynamic etc...
I was using the DAC as a source originally. I wonder if the tube is wearing out a bit. I have had it on most of the time for about a year now (bad habit I know) and have adjusted the bias back up to 9.5v a couple of times.
I remember one of my favorite things about the preamp was it's beautiful highs. My initial impressions were that I was really impressed with the B1 Nutube so I know there must be something wrong with it.
I think I am going to go ahead and order a tube. Does anyone know how to test if the tube is wearing out? It isn't any more microphonic than it was when I got it originally.
Also, if anyone has any suggestions on a good solid state preamp to build, I want something dynamic and clear. Not too concerned about the harmonic distortion. I like the voicing of the F6 already.
Thanks!
I was using the DAC as a source originally. I wonder if the tube is wearing out a bit. I have had it on most of the time for about a year now (bad habit I know) and have adjusted the bias back up to 9.5v a couple of times.
I remember one of my favorite things about the preamp was it's beautiful highs. My initial impressions were that I was really impressed with the B1 Nutube so I know there must be something wrong with it.
I think I am going to go ahead and order a tube. Does anyone know how to test if the tube is wearing out? It isn't any more microphonic than it was when I got it originally.
Also, if anyone has any suggestions on a good solid state preamp to build, I want something dynamic and clear. Not too concerned about the harmonic distortion. I like the voicing of the F6 already.
Thanks!
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Boyz, you're overengineering it
no tube is made to be constantly on, same as it isn't made for often cycles of powering on and off
that includes little puny calculator screen tubes too
also, as tube doesn't care for decreased anode voltage, it does care about heater voltage being lower than declared in datasheet - practically all tubes form Yore were made to be happy with +/-10% fluctuation of heater voltage , being direct result of mains fluctuation
all you need to know about proper approach to tubes is - take a look at few Tectronics scopes from tube era; when real engineers made professional thingie, there are rare timers, soft starting, soft stopping and other audiophool discoveries
you'll find these things in Pro gadgets dealing with higher currents and voltages, so using tubes with specific construction and thus much more expensive
examples are ........ say ........ Mercury rectifier tubes, feeding Xenon lamps in Cinemas (who's old enough for that?), triode tube based radio and TV xmitters
so, in short - if you know that you don't need your KB1 in next hour or so - power it down; you'll prolong its life .......
there is hardly any current/power inside , to justify even thinking of warming up time ........ I mean - JFets are going to get working temp in 5mins or so , and that's it
no tube is made to be constantly on, same as it isn't made for often cycles of powering on and off
that includes little puny calculator screen tubes too
also, as tube doesn't care for decreased anode voltage, it does care about heater voltage being lower than declared in datasheet - practically all tubes form Yore were made to be happy with +/-10% fluctuation of heater voltage , being direct result of mains fluctuation
all you need to know about proper approach to tubes is - take a look at few Tectronics scopes from tube era; when real engineers made professional thingie, there are rare timers, soft starting, soft stopping and other audiophool discoveries
you'll find these things in Pro gadgets dealing with higher currents and voltages, so using tubes with specific construction and thus much more expensive
examples are ........ say ........ Mercury rectifier tubes, feeding Xenon lamps in Cinemas (who's old enough for that?), triode tube based radio and TV xmitters
so, in short - if you know that you don't need your KB1 in next hour or so - power it down; you'll prolong its life .......
there is hardly any current/power inside , to justify even thinking of warming up time ........ I mean - JFets are going to get working temp in 5mins or so , and that's it