How is the audio affected?

It looks like something is breaking down in the right tube. See if you can mooch a tube tester off of someone and see how it tests.

What's the tube number? You can probably source one on AES or something for a pretty good price.

The filament overheating the cathode.
Maybe vacuum loss, maybe voltage problem.

Purple glow most often means air leak, just like in an incandescent light bulb the filament will burn much hotter and brighter when there is air inside, just before it pops.

Take out both tubes, test the filament resistance (cold) in both tubes.
Do you run 12vDC or 6.3vAC on the filaments?

This is the place to ask questions like that:
http://www.diyaudio.com/

It's not the tube. If I swap the tubes it's fine. But the other tube will do it. It's completely random and something with the right channel The tubes are 19j6 and the sound does not change with it happens.

As for the voltage, I don't quite recall, I want to say 12v, I'll have to look at it. I made it a few years ago.
Maybe both tubes are going bad? Or something is bad with the right channel.

Do you have the schematic?
Be careful when you open a tube amps, the caps can kill you.

I do, I made the amp my self. And I work on CRT's TV's so yeah I know what I'm dealing with. I have one TV wit ha flyback that outputs upto 2kv at 20amp. Or so that tag on it says. 🤣 Kind of unrealistic

I found out the problem, tube is on it's way out. I reversed the tubes and the problem came back. Oh and I did find one cap that imploded. 😵
I may need to add a small fan or better heat sinks as it does get tribally hot.

Output buffered by a source follower which is biased by the filaments... 😲
This amplifier is a delicate balance of interdependent components, not the most reliable way to do things but certainly the cheapest. 😎

In this configuration a short in the filament may take the mosfet along to its grave.

Yeah, it's not the best amp, but it's cheap and sounds good. I think I had like 15-20$ in it not counting the tubes.

I think I'll make a new/better amp.

Jade Falcon wrote:

Yeah, it's not the best amp, but it's cheap and sounds good. I think I had like 15-20$ in it not counting the tubes.

I think I'll make a new/better amp.

You make tube amps?

Is a replica of Dynaco Dynakit III hard to build? How difficult is it to find appropriate components, especially transformers? And how much would it cost, approximately?

Kreshna Aryaguna Nurzaman wrote:

Jade Falcon wrote:

Yeah, it's not the best amp, but it's cheap and sounds good. I think I had like 15-20$ in it not counting the tubes.

I think I'll make a new/better amp.

You make tube amps?

Is a replica of Dynaco Dynakit III hard to build? How difficult is it to find appropriate components, especially transformers? And how much would it cost, approximately?

I never made a amp like that. I only ever made newer cheaper tube amps for headphones.

That being said, an amp like that would not be hard to make, just time consuming and or costly.
I believe a lot of parts are still being made for that amp but they aren't cheap.
I saw a old one sold for parts on flebay or like 300$ Not long ago.

Right now I'm working on a new headphone tube amp that uses old tv tubes.

Jade Falcon wrote:

I never made a amp like that. I only ever made newer cheaper tube amps for headphones. […]
Show full quote

I never made a amp like that. I only ever made newer cheaper tube amps for headphones.

That being said, an amp like that would not be hard to make, just time consuming and or costly.
I believe a lot of parts are still being made for that amp but they aren't cheap.
I saw a old one sold for parts on flebay or like 300$ Not long ago.

Right now I'm working on a new headphone tube amp that uses old tv tubes.

I see.

It seems tube amps tend to be simple, that it's easier to DIY than solid-state amps. Correct me if I'm wrong though.

Not necessarily. BJT based solid state amps are extremely simple to build as their response is quasi linear between saturation and cut-off. FET amps, like tube amps, have inherent non-linearity in their response which requires feedback to correct.