1875 tent amplifier

1875 tent amplifier

CG negative feedback input power amplifier circuit,

Upgrade based on the original factory drawings,

The use of negative feedback input improves the sound quality to a certain extent, simplifies the circuit, and eliminates the decoupling circuit part.

The power has also been improved to a certain extent.

The original picture shows 20W power, which is increased to 25W power.

There are certain requirements for the selection of capacitors. The input coupling capacitor is generally 2.2uf. The better quality ones include German Weimar capacitors. It is a good choice for mid-range and high-pitched sounds.

The secondary filter capacitor is selected from 22uf to 1000uf. Generally, it is enough to choose one with small internal resistance, and the conditions can be better. Those 1875 power amplifiers that sell for 400 to 500 yuan on Kuaishou also take off the capacitors (they won’t tell you what capacitors to use). You can make a few yourself to try the effect. There are no strict regulations on this parameter. I personally use it twice. The filter is 220uf, and the mids and highs are very warm, making it easy to feel sleepy and intoxicated.

Large filter capacitors are generally large, and 10000uf is enough for me.

The power of the transformer should be larger, 100~220W is enough, and the power supply should be dual 18V.

Output speaker impedance

The 8R speaker has a warm sound, which is fine for listening to songs. The distortion is small, and its shortcomings are difficult to recommend.

4R speakers have high power and good sound quality. They are easy to drive, but have the disadvantage of large distortion.

I have tested both speakers. For "Yao Yingge's Album", I think the 8R speaker performs well. The sound is extremely penetrating, which is very good.

The PCB is not drawn well. I personally think the sound of the tent is nice.

This is made from the original factory diagram (it has a decoupling circuit and pin 1 input)

the image is only a reference

I spent a day re-creating the scaffolding diagram of the input circuit of the negative feedback circuit.

It's a bit ugly

the image is only a reference