DIY audio blog for projects, schematics, PCB's, designs, electronics, mods


Crossfeed Headphone Amp With BUF634. The X-Feed

In this post I’m about to show my new BUF634 based headphone amp which also has a crossfeed filter. This gives a better listening experience. The BUF634 IC from TI is an exceptional piece of technology and offers excellent performance. It is very suitable for headphone applications. I have used it in another of my projects with very satisfactory results. For my application the amplifier will have the task of providing some hefty voltage swings because I use 600 Ohm headphones, namely the Sennheiser HD 540 Reference. These are simply gorgeous and I do love them. Check out the HD540 at Head-Fi.

6SN7 Preamp With DN2540N5 or IXCP10M45S

Here is an article to show how I designed my 6SN7 preamp with CCS based on DN2540N5 or IXCP10M45S D-MOS transistors. The article is an addition to my design which showed a 6SN7 tube in parallel connection. Here I will continue to develop the schematic. I will introduce a popular solution for a reliable constant current source.

6SN7 preamp. DN2540N5 or IXCP10M45S. PCB 3D rendering.

6SN7 Preamp With Parallel Sections + CCS

Here is my design of a 6SN7 (6N8S) based preamp with parallel sections of the tubes. I plan to use just two tubes, one for each channel. As we all know 6SN7 is a double triode and for my design I will tie the two sections in parallel. The main design parameters fall into three points – low-distortion, low-gain and low output impedance without using a output buffer/cathode follower. In order to achieve some of these goals I will be using an active load – constant current source(CCS).

Setting the bias point

First of all lets begin with the obvious – setting the tubes into the desired operation point. Lets consider a fairly typical power supply voltage of around 300V and a 30kohm plate resistor which results in a plate current of 10mA. From these three values it’s easy to draw the load line, so here’s what it looks like:

6SN7 Load line and biasing
6SN7 Load line and biasing

Tektronix SG505 low-distortion audio oscillator

The Tektronix SG505 instrument is an ultra-low distortion and low-nose oscillator intended for testing of audio grade electronic products. This one came to my possession as a non-working unit and I set-out to fix it.

Front view. Tektronix SG505
Front view

The LPRO-101 DIY Rubidium Clock Generator

The DIY LPRO-101 ruibidioum clock generator. This box together with some additional electronics on a separate PCB will transform this LPRO unit into stand alone equipment. I’ve always wanted a good and affordable frequency standard for my home lab. Searching the eBay one might find quite a lot of solutions. The good thing is that nowadays we have plenty of options.

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