Introduction:

The popularity of "ZEN" project points out very simple and interesting linear circuits. They are intended to fuel this interest. ZEN bride and ZEN son have been exploring how much objective and subjective performance can be achieved through a single gain level. This extreme simplicity has an aesthetic appeal, which shows the purist Audiopile and hypothesis that simple circuits sound better. At least one "objectivist" complained that the project did not measure more complex amplifiers. This is usually true, but it doesn't matter. Various literature and store shelves are full of multistage amplifier circuits using a large number of negative feedback. This is a single-stage amplifier. It is an excellent technical challenge to obtain good performance from a single gain stage. I will say who will design and build more complex circuits at an appropriate start. Simple circuit has special value as DIY project. They are easier to understand, they are more likely to be tried, and they are more likely to work well. So, is this the expected bride of the son of ZEN? Yes, I think it is. It has the same topology and is very suitable for driving ZEN's son, but this circuit has many uses. It also acts as a good balance or unbalance to balance converter. Like ZEN bride and ZEN sub-project, this circuit performs linear amplification without negative feedback. As for many pros and cons of using negative feedback, I do not recommend that debate be included in this article. It happens that we will get quite good performance without it (negative feedback).

 

Sound sense: thick and moist, not dry and flat, rich in water, with both resolution and dynamic.

Balance circuit features:

Let's review why balancing is desirable. The audio circuit works in the environment of electrical noise, including crosstalk from other channels, grounding circuit, magnetic pickup of transformer, power ripple and other noises. In a balanced circuit, two opposite belief signals exist on two other identical input lines. The input balance circuit of has positive and negative polarity, and the circuit also has a+and -. The balance amplification circuit will amplify the difference between the two inputs and display the difference signal at a larger output. What the circuit does not do is as important as what it does; It does not amplify any part of the signal and is the same on both inputs. Ideally, it completely suppresses common input signals. This is called common mode rejection ratio (CMRR), which indicates how many common input signals pass. Since the noise picked up from the environment is usually common in two input lines, it is suppressed at the input end of the balance circuit.

 

Therefore, the noise problem is much smaller. The actual home audio system usually has about 1/10 background noise and buzzing noise when using balanced interconnection. Another reason for using the balanced gain stage is that the high-end DAC design provides balanced output, where a separate DAC circuit is used for each of the two output phases. Using a separate balanced DAC circuit can reduce random noise by 3 dB. If they are connected in parallel, common noise will be reduced by a larger number. There is also potential to reduce distortion and such methods, but to achieve the full performance of these circuits, there must be a balanced input at the stage below the gain level.

 

Summary results:

This is a particularly good sound circuit. I think it sounds obviously better than ZEN bride, although I can hardly explain why. It seems to be more moist and deeper, while Boz is a little dry. The reason may be the distortion cancellation in the balance circuit, or it can provide a larger dynamic range through quieter balance operation and higher output swing. As always, I encourage you to build it and make your own decisions.

 

Input voltage: AC 0-65V (not less than 0.3A), AC 0-65V (not less than 0.3A).

Gain: 20dB -100dB (default setting is 50dB. If you want a higher gain, you can replace the * resistance value on the PCB. The higher the resistance value, the greater the gain)

PCB Size: 161mm*91mm (PREAMP), 90mm*90mm (PSU)

 

NOTE: We have DIY kit or finished board (Optional)