$10 tube preamp kit to headphone amp

[jwin615]

Saw this on Hackaday and a light bulb clicked on. Well, it flickered a bit. So I thought I would share.
It's a cheap Chinese tube preamp kit using 2 6J1 tubes. Found this one on Ali.

GitHub link

I haven't seen the exact transformer listed but I'm guessing it's like these 1300:8 ohm E14 sized. They mention that the transformer is killing the bass response some and an upgrade may be in order. Maybe a pair of these for $15 would suffice. Edit:just saw that these don't ship free.

7k or 10k to 8 or 4 ohm.
Anyway, the light bulb. I'm sure there are much better circuits to utilize but it would be kind of cool to have a little 2 tube headphone amp dressed up as a mini amp head. A mains to 12v transformer , a pair of tubes and 2x 2.5 inch output transformers mounted externally. Just a random idea that I'll never follow through on but could be a cool project and done for probably <$50 in Chinese parts.

 

[rossbalch]

Hey so I have something similar to this and it's kinda interesting. Apparently there is some kind of voltage pump on board and the tubes actually run at 200+ V. I have this version (https://www.aliexpress.com/item/1005006132468731.html#nav-description) which has a DC input. I actually jumpered one side into the other and it was still clean as a whistle, but very high volume output. Good for an output stage then maybe. Would there be a significant volume loss going down from 10k to 8 ohm?

The other thing you could do is combine it with this circuit as the preamp

This one runs at a lower plate voltage and distorts quite nicely in my opinion. Both would run off the 12AC source using your original link.

As an aside, this guys channel is actually a gold mine if you're trying to learn about tube stuff.