Month: July 2015

LME49830 Amp build (part I)

Both channels are ready now. Bias set to 750mA instead of 500mA. This is done by adding a parallel 510Ω resistor to RB1 to increase the bias range.

I’m using two pairs of 2SJ201/2SK1530 matched.

Noise is incredibly low and distortion is very low as expected. 10W or more of class A can be achieved from this board with only 24V supply:

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Here’s a quick test of one of the channels:

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It’s very promising. I need to mount the supplies to the chassis and do a bit of drilling work to get this amp completed now.

LCR Phono: design notes (Part II)

Introduction

This is a continuation of my previous blog post. I will try to share my experience through the design process of this RIAA stage through these individual posts with an attempt to spark some interest in others and in return to get some valuable input from the experience and knowledge of others. Hope this works!

First stage

LCR-phono-test5
Here is the initial design version for analysis. I’m working through this step by step and refining the circuit in every iteration. The initial circuit is very simple. The first stage is key. We want to achieve as much amplification as possible from this stage before we hit the LCR network. The choice of the 6S17K-V valve may appear as a surprise to the ones not familiarised with this valve.  Here are some notes from Wavebourn around this valve:

Continue reading “LCR Phono: design notes (Part II)”