Chinese Tube amps

[JohnnyAudio]

Anyone using this amp? I am... it's not perfect but with proper input voltage and decent tubes, it's not bad.
Just wondering if the output transformer can be upgraded> Anyone have any idea's on this?
Also the caps.

Nobsound Hi-Fi 300B Mono Vacuum Tube Integrated Split​

 

[mhardy6647]

Well, of course the OPT could be upgraded -- is it worth the expense, time and effort?
I suspect (!) you'll end up in a "Stone Soup" or "Nail Broth" situation -- change absolutely everything but the chassis and the knobs, and you can make a pretty good amplifier. I would assume that the passive components (capacitors, resistors, and chokes, at least) are of very low quality unless you know otherwise with certainty. A quick googling suggests some (ahem) interesting circuit design choices and questionably-rated parts (e.g., capacitors with working voltage ratings below actual circuit voltage). It's possible that's been fixed, but I'd be very skeptical.

If you feel like sinking money into them, buy a set of superior quality new or NOS vacuum tubes (I believe each uses a 6SN7 voltage amp/driver, 5U4 full wave HV rectifier, and of course the 300B direct heated power triode) for each of them and call it a day. Even that is probably not a terribly fiscally prudent investment.

_______________
* Nail Broth

first ca. 9 minutes
Trigger warning: It's a needle drop, on a battered LP.

 

[amirm]

Pretty boxes!

As far as changing parts, unless you can measure the performance before and after, you will never know if you wasted money or did something good.

 

[JohnnyAudio]

Pretty boxes!

As far as changing parts, unless you can measure the performance before and after, you will never know if you wasted money or did something good.

Hi Amirm,

Yes, they look nice and with proper tubes, sound decent, just driving old ESS rock monitors, everyone says they sound nice.
BTW, just joined your fine place.

 

[mhardy6647]

Probably wouldn't be hard to extend (measurably) the high & low frequency response with improved output iron. It would not be inexpensive, though. That said, I am not sure who's making good SE 300B OPTs any more. Electra-Print is gone, and Magnequest's Mike LaFevre passed away in March of 2023. Looks like One Electron is moribund, as well (only one choke listed at Antique Electronic Supply, which is their dealer for consumer purchases).
EDIT: Hammond SE OPTs might even be a step up from whatever's in these amps as supplied. If nothing else, the Hammonds are inexpensive enough. They have several models with a primary impedance that would be OK for a single 300B output per channel.