Project files: The Bas***ds

What is it?
These are the files for my revised version of the “The Bastard” preamp and RIAA design (see blog posts here and here)

How big are the boards?
– Line stage: 2.15″ x 3.90″ (app. 55 x 99 mm)
– RIAA: 3.0″ x 3.875″ (app. 76 x 98 mm)

What is the status of the boards?
The boards are both in version 1.1. Version 1.0 has been prototyped and version 1.1 incorporates some minor tweaks and fixes to the layouts.

Does it use any special/expensive/hard-to-find parts?
Not really. The 6J5 tubes should be possible to find on ebay and similar places. There is also a 12J5 version which, apart from needing a 12VDC filament voltage, should be identical to the 6J5. As for other substitutes, please search online. The caps in the line stage and the RIAA are Mundorf standard MKP types (the white ones).

Anything else I need to know?
Not really, no. The boards take a +37VDC (or thereabouts) main power supply and draw very little power – you can easily use one of the regulated PSUs I have posted here on the site. The Line Stage additionally needs a +6.3VDC filament supply. Current draw depends on the type of tube chosen, but you can use one of the regulated PSU designs as well as long as you use a 6 or 7VAC transformer.

Download design files here

Related information:
Note: Always read the “intro post” for additional important information about my designs.

Link to the original design/build article (in Danish) is here (20MB scanned pdf).

A real Ba****d – Part 2

Second part of my “rework” of the old “The Bastard” – the RIAA-stage. The first was the tube-based line stage which you can see in one of my previous posts and there you can also find a link to the original article from a (long gone) Danish magazine.

This is a discrete solid-state RIAA stage based on fairly standard BC5xx-transistors. I know virtually nothing about RIAA-designs, toplogies, correction curves etc. so I will not comment on that and all I have done is to lay out a new PCB in Eagle. My enclosure parts for this build are currently on order, so I have only managed to listen very briefly to the board but it does sound promising I have to say :). Once it is built I will be listening further and comparing it against the Retro as well (in an “old-versus-new-technology” shootout :D).

A real Ba****d – Part 1

Yes, the name is maybe not so fortunate in today’s english-speaking world, but the design is still interesting – mainly because of its simplicity. Originally published by (long-gone) Danish magazine “Ny Elektronik” (which incidentally means “New Electronics” 😉 ) in 1989, “The Bastard” is a preamp made up of a tube line stage and a solid-state RIAA-stage. The line stage is based on a somewhat unorthodox design with a single 6J5 tube per channel operating at just 40V anode voltage, while the RIAA is a single-supply job based on more pedestrian BC550/BC560 transistors.

This is another design that has fascinated me for a long time, so I have made my own PCB layouts and tried it out. I started out with the line stage and this is what I will be presenting here (the RIAA pcbs have arrived but I need a few “odd-value” parts before I can start assembling them, so they will have to come in part 2 later). The PCB layout was designed to be more or less as compact as possible, with 10cm being the largest dimension (also helps keep the price down at the boardhouses 😉 ) For the tubes I use GE 6J5s in metal cans.

Eagle layout

Silkscreen rendering from the Gerber files. Made with – thanks guys!

I have only had this connected briefly to my desktop amp and speakers and I probably won’t get around to casing it for a while, but it does sound promising. Since I ordered a few extra boards, I may try building two more for a balanced version.

Assembled board with test wiring

Closer view of the assembled board and tubes.

PS: If you want to read the original build article (in Danish) you can read it here (20MB pdf)