There was a strange little thing that appeared in Danish magazine Ny Elektronik (New Electronics) in 1989. A very simple preamplifier that used two L63 tubes in Class A with no feedback and it operated pretty much badly out of spec. (It was supposed to though, that was the whole angle of the article.) The article is available here (20MB PDF), for those who understand Danish: http://www.nisbeth.dk/carrotman/files/Bastard.pdf
It was called The Bastard, and gathered quite a following (it got the name because it was a hybrid. The phono stage used transistors for better SNR), and somebody suggested I should try it.
The Bastard was tested by some Danish guys and was found to have 6% THD+N or more. They upped the voltage and added some feedback, and it ended up performing very much better.
*) Measured using Russian 6S2S tubes, more information below.
I made PCBs for this pre (omitting the phono stage and input selector) that incorporates the higher voltage and feedback, and designed a regulated DC power supply to go with it. Both have been built and tested, and the preamp is sounding pretty sweet.
The full Bill of Materials and a Mouser shopping cart is available here: https://hackaday.io/project/16944-the-muffsy-bstrd-valve-preamp/log/49757-components-bill-of-materials
You can find more info about these measurements on Hackaday.io.
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I offer complete preamplifier kits for turntables. There are currently four kits available:
- A phono preamplifier for MM and HOMC cartridges
- An MC head amp that lets you use LOMC cartridges with any MM phono stage
- A power supply for the two preamps
- A back panel for the two preamps
The kits are complete with all necessary components, easy to build with detailed step-by-step instructions, affordable and customizable.
See https://muffsy.com for more information.