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Preamp photo
Build a stand-alone, High-precision
Vacuum-tube Phono pre-amplifier

This is a "stand-alone" implementation of the preamplifier design used in my "RA-100" integrated amplifier. It uses a novel design approach, in which modern op-amp design techniques are combined with classic vacuum-tube knowledge to produce a circuit that represents a significant improvement over most classic audiophile- level tube designs. As detailed here, it is configured as a RIAA phono preamplifier for magnetic or ceramic cartridges.

How does it sound? In a word, great. Download listen to an actual recording made from a test record at our Sound clips page.

This project is recommended for intermediate electronics experimenters. A basic electronics knowledge is assumed, and at least some experience with vacuum tube projects is highly recommended before building this project. The information provided here is believed to be correct, but the author and Dogstar Music assume no liability for damages incurred through use or misuse of the information provided herein.

With the disclaimer out of the way, I can only add that if you're looking to build a precise, clean, and reliable phono preamp, you've come to the right place. The project can either be built using a point-to-point approach as shown in the illustrations on this site, or on a printed-circuit board for a cleaner look.

  • Magnetic (high-gain RIAA) or Ceramic (flat, gain=5) inputs
  • Precision RIAA implementation via negative feedback
  • High linearity, low distortion
  • Simple, self-contained power supply from common parts
  • Uses readily-available vacuum tubes and other components
  • Very low power consumption
Copyright Notice:

All contents of this website, including all schematics, text, diagrams and photographs are Copyright ©1998, ©2001 by Fred Nachbaur, Dogstar Music. All rights reserved. This site may be freely linked, but none of the contents may be posted anywhere else without express permission of the copyright holder.

The information presented here may be used for personal, non-commercial use only. Any commercial applications of this design or any part thereof requires previous licensing arrangements with the author and copyright holder, Fred Nachbaur.

Article Index:

Note: the pages on this site contain inline images to aid in understanding the operation of the project. Most such images (with a border) can be viewed in an enlarged version (1200 pixels wide) by clicking on the image. Alternately, you can right-click to open the enlarged image in a new window.

For best results, this site must be viewed at a screen resolution of 800 x 600 or better (1024 x 768 recommended).

If you are running 1280x1024 resolution or greater, you can switch to high-resolution mode, with larger inline images, by clicking on the link below:
Click here for 1280x1024 version

1: Introduction

2: Design Philosophy

3: How It Works

           0: Overview
           1: Differential Input Stage
           2: Output stage
           3: DC Feedback
           4: AC Feedback
           5: RIAA Phono Networks
           6: Power Supply

4: Construction hints

5: Parts List

6: Other Preamp Applications

7: Wav and MP3 sound samples


Following is a listing of available resources (schematics and other diagrams) necessary for construction of the stand-alone pre-amplifier. These are provided as GIF files, intended to be printed to letter-size paper, Portrait layout, with an image size of exactly 7.5" x 10".

The complete RA-100 amplifier project (of which the stand-alone preamp is a subset) as published on this website is also available in PDF format (Acrobat Reader required).

Also available (in PDF format) -is the original article from which this portion of the site was derived. This was originally intended as a magazine article, but for various reasons I decided not to publish this in the printed medium.

The "Figures" are not embedded, as I've found this can cause trouble on some printers; you will still need to download the GIF images. The "Artwork" (PC board layouts) is also available as a single ZIP file containing the needed images.

Document: Figure: Filename:
Full RA-100 Article N/A amptext.pdf
rev. 12 Feb 01
Original Preamp Article
(previously unpublished)
N/A phono.pdf
August 1987
Artwork (PCB layouts, templates) N/A sapart.zip
rev. 9 May 01
Phono Preamp Section Figure 2 phono-l.gif
Power Supply for Standalone Preamp Figure 5a prepwrsl.gif
Preamp Gain vs. Feedback ratio Figure 6 pregainl.gif
Preamp Frequency Response Figure 7 prefreql.gif
Other Preamp Applications Figure 8 premodsl.gif


You may contact me regarding this project at fnachbaur@netscape.net. I'd be happy to hear from you, and any bug reports or suggestions for improvement are always welcome.

To find out what other kinds of trouble I get into, check out my sites listed below:

Back to Tube Projects Main Page
My main Dogstar Music site
Fred's ZX81 retro computer page
My Theremin Exploits

Original music on IUMA.com

Point-to-point version
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