For Sale, eight blank (un-populated), printed circuit boards, for you to construct, assemble and test

This new design offering is featured in chapter four, second edition of Bob Cordell's "Designing Audio Power Amplifiers" book,  available at Amazon. The amplifier is capable of > 150W/ch/8ohm, this depends on the PS construction.

A reference design was constructed based on the original design. A 3Ux300mm HiFi2000 Modushop Dissipante chassis was used in the construction of the amplifier. A 50-page document was written which includes the original chapter 4, describing the circuit design theory and the concept design. Expanding on the original text, all the construction details have been included plus numerous photos are provided using a cloud link which you receive with each purchase. The design has been constructed and verified by Bob Cordell himself plus the pcb designer, a couple of beta testers so far, in order to review the documentation, go through the build process and provide feedback.

You are required to purchase all the components, we will not be selling any components other than this set of blank pcb's.

You are required to do all the mechanical work involved or have it done by someone else. The chassis supplier offers machining services. Mechanical drawings are available on the cloud.

When you purchase this set of eight blank boards, at the time of shipping, you are provided with links to the Mouser shopping carts to order the bulk of the parts. Mouser supplies the parts in individual bags, with reference designators assigned, allowing easy component identification for assembly. Excel spreadsheets of each BOM are also available on the cloud. A couple of parts are only available at Digi-Key or similar. Any design of this quality, buying one of parts is expensive, you are looking at ~$900USD all said and done. The chassis and transformer make a big chunk of the expense.

This method allows for you to save a great deal of money in building a high performance amplifier. It also makes for a fun project when you do most of the work, in soldering the boards and testing them out. 
The design uses all through hole components, current production parts.

You will receive,

1. Eight blank (un-populated) pcb set, for both channels. 
  • Two of AFE (Amplifier Front End), mirror imaged pcb's
  • Two of OPS (OutPut Stage), mirror imaged pcb's
  • One PS pcb
  • One AC inlet, switch, soft-start relay, earth isolation
  • Two protection pcb's
2. Links to the electronic document web pages, including the detailed build guide, schematics, assembly drawings, BOMs, many pictures showing installation steps in detail. Theory of operation and performance testing.

3. Links to the Mouser shopping carts, to order the parts kit. It is setup so that Mouser will provide separately labeled bags for you, with pcb references printed on the labels for easy component identification, sorting and ease of assembly.

This design was also presented by Bob Cordell at the Burning Amp Festival (BAF) in 2019, which is available on the web.

The book is reviewed using this youtube link
/watch?v=Q5nO9QZx37w

Also there is an Audioxpress.com magazine article, reviewed By Jan Didden
/article/book-review-a-look-inside-bob-cordell-s-designing-audio-power-amplifiers-2nd-edition

You can also visit the cordellaudio web site

The features of this new design are numerous, to name a few:

  • The design uses all modern day, current production parts which are readily available. Precision metal film and metal oxide resistors are specified. High grade capacitors are used. Pcb's are double sided FR4 with LPI solder-mask, silk-screen legends for easy component installation and location.
  • Gain set to 28 (29dB) so that 1Vrms generates 100W into 8W
  • Complete input, feedback and output networks
  • Quasi-differential input/feedback network
  • Diode clamps across the feedback network capacitor for fault protection
  • Diode clamps across input differential pair for transistor protection
  • Diode clamps across the InPut Stage (IPS) differential outputs for cleaner clipping
  • ULGF increased to 1MHz
  • VAS (Voltage Amplifier Stage) output Zobel network for increased stability
  • Dual Vbe multiplier bias spreader with bypass/reservoir capacitor
  • Current limiting diodes from bias spreader to output rail
  • Output transistor base stopper resistors
  • Fast output transistors (MJL3281/1302)
  • Reduced output emitter resistor values to 0.22W
  • Rail clamp diodes added to amplifier output
  • Rail reversal protection diodes
  • Progressive rail decoupling
  • Comprehensive Amplifier and Loudspeaker protection circuits
  • Power on/off muting
  • AC Input line surge current limiting
  • Test points are included at the top of the OPS pcb in order to measure & set the OPS bias current conveniently with your DMM.
  • Usage of multiple pcb's in key positions, minimizes wiring
  • Terminal Blocks and connectors are specified for ease of assembly and repair
Specifications:
  • >=150W into 8W load with ±65-70V power supply rails
  • THD+N 0.0006% at 1kHz, 0.007% at 20kHz                       
  • ~9 nV/ÖHz input-referred noise
  • Un-weighted S/N of -100dB in 80kHz noise bandwidth
  • A-weighted S/N of -105dB (2.83V, 1W/8Ω)
  • Slew rate >48V/µs
Notes:
  1. This assembly is for customers who have previous experience in electronics, built, repaired stereos and amplifiers in the past to obtain this experience. You must understand how to read a schematic, assembly drawings, bill of materials. You should be able to identify components/polarities/markings, be familiar with assembly tools, troubleshooting, have the know how to use the required test equipment. Assembly, soldering and testing these new boards requires a fair bit of skill, experience and patients. We say this because we want to make sure that it is within the capabilities of customers who buy them. We do not want to discourage you but also want to make sure that a build is successful and within your capabilities. We can offer some support, but if you have problems, it will be in most cases an assembly error for which you need to review and inspect your work very carefully. Having the necessary tools are essential. It is involved, not intended for a first timer constructing electronics. We have to emphasize this is a task for experienced constructors. Cables have to be constructed.
  2. Selling assembled and tested boards adds a huge expense, since it is a very time consuming task. We are not setup for manufacturing in large volumes. The savings are made when the boards are assembled by the customer. 

Thank you for your interest and support in making this fine design available.