DIY Audio Projects Forum

12J8 Headphone Amplifier
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Author:  ILoveHiFi [ 19 Feb 2019, 02:43 ]
Post subject:  Re: 12J8 Headphone Amplifier

If its only 0.5w on such high power tubes I wouldn't really even worry if I had 12ax7s in there running at 0.7w and having the holes blocked.
Given the electornics parts arent ran supper hot and built very close to max power ratings.

Author:  ILoveHiFi [ 19 Feb 2019, 02:48 ]
Post subject:  Re: 12J8 Headphone Amplifier

My listening shows hotter running valve means the electorns flow more smoothly and freely, it does what likes doing better.
It sounds more warm and theres is more valve taste and colour.
Its simliar to how you can change tubes to fancier ones and get better sound with the specs being same.

Its similar to heating up your tubes more by overvoltaging your heaters for better sound but your doing it a way where the tube will last longer by pushing more power in plates.

Author:  BowToEd [ 19 Feb 2019, 02:51 ]
Post subject:  Re: 12J8 Headphone Amplifier

ILoveHiFi wrote:
The heat from the tubes is also in the form of heat as like air, so air should help it cool down.
Most of the heat should be in the form of air, not infared/light radiation.
Not sure where your getting the idea of air cooling only helps elecotnics cool but not tubes.
Air blowing on the glass bottle will also help to some extent.

The tube is full of nothing. They are called vacuum tubes for a very good reason. This means nothing exists to conduct or convect heat away from the plate itself. That's where infrared comes in.

Sure, blowing air on the glass will keep the glass cool, but it does little for the plate. Transmitting tubes needed forced air on the envelopes to keep the seals from melting, not to cool the plate. The only way the plate gets rid of heat is by converting it to IR.

As Matt already pointed out, the IR passes right through the air and affects solid objects. It's the same mechanism whereby sunlight warms the earth through 93 million miles of vacuum.


Author:  BowToEd [ 19 Feb 2019, 02:53 ]
Post subject:  Re: 12J8 Headphone Amplifier

You can believe what you will. I hope you'll understand when I don't listen to your advice, which seems mainly based in opinion and listening tests. I'm am engineering student and an avionics technician. I have enough experience in electronics to know a thing or two.


Author:  ILoveHiFi [ 19 Feb 2019, 02:58 ]
Post subject:  Re: 12J8 Headphone Amplifier

I designed many innovative amplfiler schematics and I had innovated stuff that smartest guys failed to do in the many past years.
Not just tiny bit better but everything diffrent and wheel reinvented to do absolute better.

Author:  BowToEd [ 19 Feb 2019, 03:05 ]
Post subject:  Re: 12J8 Headphone Amplifier

Okay. Do whatever you want. Just don't expect me to take your advice without some kind of evidence. Being honest, I don't trust your claims besides using vent holes, which is a good idea. The other ones don't convince me.

Also, look up the data sheet for 12J8. Most of the power is going to be in the heater, and that heat might endanger electrolytic capacitors I'll be using to filter power. The B+ will be close to 13 volts which means the plate will be hard pressed to overheat.


Author:  ILoveHiFi [ 19 Feb 2019, 04:12 ]
Post subject:  Re: 12J8 Headphone Amplifier

LED lights and infered LEDS are close to a source of perfect infared/light emiting device.
If you own led lights you know how bright they get with very little power.

Does the infared from leds make you hot, no it dosen't.
How bright is a tube, not very bright. Neletible infared led emission.

Infared from electctrons? I don't think so as its flowing from plate to cathode, if it was to leak evey where the valve would not work.

The vaccum is acting more like a sheild locking the heat inside the valve.
Most of the heat should still be in form of standard heat like from transitors.

I wanted to say that earlyer but I didn't want to hurt your feelings.

Author:  BowToEd [ 19 Feb 2019, 08:59 ]
Post subject:  Re: 12J8 Headphone Amplifier

You obviously don't understand this as well as you think. Read up on black body radiation like I suggested earlier, as it's a known property of physics. That's the principle at work here. I know what I'm talking about.


Author:  ILoveHiFi [ 19 Feb 2019, 13:44 ]
Post subject:  Re: 12J8 Headphone Amplifier

Thers zero radation so theres nothing for you to argue about.
Using black to get more absorbtion dosen't work.

It hate it when guys are being disrespectfull and trolling.

Author:  BowToEd [ 19 Feb 2019, 14:00 ]
Post subject:  Re: 12J8 Headphone Amplifier

Any object that is above 0 degrees Kelvin radiates some infrared energy. How do you think thermal energy works. As the temperature rises, the frequency of the photons change and the glow shifts to the visible range. This is why really hot objects glow red. Although tube plates aren't designed to glow, they do put off energy by radiating light in the IR spectrum. It's also why they show hotter in a thermal imager.

Using black works as was pointed out before by the other gentleman. I'm sorry you don't want to believe our statements but you also show no interest in looking up the principles I suggested to see what I'm talking about. The information is there if you choose not to ignore it.

And, talking about trolling, this is a thread started by me to discuss a project I am actively working on. You showed up to offer suggestions and are acting like I'm the petulant one because I expect some kind of justification for what you're saying. I don't rightfully care about your experience and work success. I think your statements should stand on their own merit and this one has failed to do so.

I challenge you to take your assertions to your own thread and discuss it. If you really are that confident in your position, you should have no problem defending it against the collective knowledge of the group.

With that, I'm asking you to leave. You're not going to make unsupported claims on a thread about my project and then act like I'm unreasonable when I challenge your claims. It's up to you to convince me, and you don't do that by talking about your listening tests and what Electrons like to do.

Are any of the moderators paying attention to this exchange? I'd love to hear from you.


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