【Prototype】　OTOMON LAB 300B drive 300B tube amplifier special made for fullrange, field coil speakers

This prototype version so price is cheaper than order made version. If you see this item was sold out, original price for ordering the same one is 4200USD

This used 300B tube drive 300B tube, output power is 8W, special use for fullrange(bookself), field coil speaker.

1. Could it be used for another speaker than above speakers

Of course it it can be matched with another speaker but compare with my other amps with same power output, it has more energy and special tone as using with full range or field coil speakers.

2. Why is this schematic special for such kind of speakers

2.1. The decision of power tube: fullrange speaker does not need much of power as well as wide range of frequency response from the amp. People like such kind of speakers like its tone, the refresh sound, dynamic and energy that multi drivers speakers dont have. And 300B is one of the best tube that performs the beautiful note and refresh sound. I had a little confuse between 300B and 2A3 because 2A3 has more dynamic sound than 300B, but 2a3 has little power and the fame of tone is not as beautiful as 300B, and one more important things is to drive well such kind of power we need amp with power at least 5W and it is difficult to get such power with 2A3.

2.2.2 I can use another driver tube for example 6SN7 or even 717A to get 10W of power with the same type of this schematic but driver tube 300B was chosen to make the characteristic of 300B stronger, and make more energy for the output. Energy is not the thing you can calculate, you can only feel it.

2.2.3 If I do DC heater for 300B, the hum level of the amp can be dropped down to 0.2mV, but with under 1mV you almost can not hear any hum from field coil or full range speakers, so when you can reduce the hum under 1mV then using AC heater is always the best.

3. Why I dont use interstage transformer to driver 300B. Using interstage transformer will have advantage of gain than cathode follower but in this case I dont need gain, I need much of current from driver stage to get the more energy. The much of current does not bring the much of power but the energy will be better but too much of current will make sound more distortion. Using interstage transformer may have more analog and organic sound but it has limitation in frequency and distortion physically as the current in drive stage raise up. And in this case using a driver choke will bring better low frequencies as well as handle more current in drive stage.