Adding daring front in amplifier ----- Vacuum Tube Preamplifier

Package in the amplifier, Vacuum Tube Preamplifier Keywords: adding fare-order in the amplifier Package in the amplifier Author: Ren Tail Using the free position of the free position in the amplifier, the amplifier can improve the sound quality and improve the grade. Choose a small seven foot tube 3A5 for the pre-level very suitable for the machine, it is small, the power consumption is low. The dynamic range is large, the sound is extremely bright, but it will encounter some troubles in practice, mainly the exchange of exchanges, many people are expected. The author designed a front stage circuit (as shown). As long as you pay attention to the following critical. It can be quite satisfactory. 1. The filament is required to supply power separately, and the current should be clean. The filtered capacitance used is large, and the quality is good. I use the ruby ​​electrolytic capacitor, C7, C8 to be installed on the power supply output and the filament portion, and the intermediate is connected to one end of the shield line. Avoid high frequency radiation interference. 2. High voltage part, in order to save space and reduce heat generation, the bile duct rectification and choke filter are taken. But the sound quality can still be satisfied. C3, C4 is the Philips Blue Hexagon Electrolytic capacitor. C5 is an EC metal thin film capacitor. Output capacitor CL can be used for MKT, MKP capacitance, and C2 is CBB capacitance. The above capacitors have a greater impact on the sound quality. In order to protect the tube, a high pressure delay circuit is added, and R7 is a bleed resistor, R8 is a large current buffer resistor. 3. Be sure to concentrate on the grounding of a unit, avoid dispersion, close, and string. Try to avoid using jumpers, non-useless, use shield lines. 4.3A5 tube is high, slightly vibrating, the speaker will echo (microphone effect - editor note). Tiny AC oscillations in each transformer core in the machine. Will make 3A5 beat (with special shields for this manner). I took the upper fixing hole into the plate to be large, and the rubber is matched with the m3, and then secured to the casing bottom plate, and the original volume potentiometer is connected at the output terminal when the M3 screw is fixed. Several cookers can sing.

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