I'm a noob so I'm looking for an opinion of this schematic. There is an amp for sale locally to me that uses it. I've reversed imaged searched it and it appears to be only floating around Japanese and Chinese websites. I'll be looking to upgrade the transformers and other parts but just wanted to know if it would be worth getting first. I'll maybe convert it to a 45 too down the line.
Cheers!
Cheers!
Being a Japanese design, it is engineered properly.
If you read the schematic, bottom right hand corner, it has a switch for bias; 2A3 or 45.
Why are you suggesting upgrading, stuff that it appears, you do not already understand.
If you read the schematic, bottom right hand corner, it has a switch for bias; 2A3 or 45.
Why are you suggesting upgrading, stuff that it appears, you do not already understand.
Thanks everyone. I should have been more clear, this particular amp has a single 2.5k tap on the output transformers. It's my understanding that I'd need 5k for a 45. It's reasonably priced and nicely laid out inside so I'm confident I could swap the Chinese output transformers for some nicer ones in the future. I'd like to use it as a platform to learn more about tubes amps rather than jumping in and building one from scratch.
If you connect 8ohm speakers to 4ohm output, you'll get 5K load for 45 tube.
That's shown in the shematics too, so you don't need primary tap unless your speakers are 4ohm.
But if you think output transformers are not of proper quality, feel free to replace them.
That's shown in the shematics too, so you don't need primary tap unless your speakers are 4ohm.
But if you think output transformers are not of proper quality, feel free to replace them.
Thats good to know thanks. Yes my speakers are 8ohms. So if i'm understanding right I could use the 4ohm output and change the 750ohm resistors to 1.5k and I could run 45s?
The first voltage amplifier section is not sophisticated:
The 250k pot gives variable source impedance: This is 62,5k at middle position. The 6SL7's Miller capacitance is 140-150 pF. The result is the 0 to 10 microseconds time constant (worst case under 20kHz -3dB).
The pot isn't enough safe alone at grid (contact drop). I suggest the redundant R (grid to earth).
The 250k pot gives variable source impedance: This is 62,5k at middle position. The 6SL7's Miller capacitance is 140-150 pF. The result is the 0 to 10 microseconds time constant (worst case under 20kHz -3dB).
The pot isn't enough safe alone at grid (contact drop). I suggest the redundant R (grid to earth).