F-5T

This set of circuit boards is used to make the F-5 Turbo power amplifier from the mind of DIY hero and audio genius, Nelson Pass.

One set of PCBs will make a stereo F-5T v2, or a single monoblock F-5T v3.  This is the third revision of the boards, which has nothing to do with using them to make a V2 or V3 F-5T!

Please read the F-5 Turbo Article written by Mr. Pass to familiarize yourself with the different versions.

Illustrated build guide

An Illustrated build guide showing all sorts of useful information on how to build your F5Turbo can be found here - Illustrated Build Guide

Circuit Description

The F-5 Turbo is a Push-Pull, Class-A power amplifier. Esentally a scaled-up F5, with more output devices and a higher voltage power supply. The F-5 Turbo is a voltage source amplifier, requiring nothing out of the ordinary from your preamp or speakers.

The F-5 Turbo is the biggest offering in the Nelson Pass/Firstwatt DIY series of amplifiers. The v3 will handily drive 100Watts into 8ohm, and much more into 4ohm. This circuit also has the ability to scale up to truly amazing power levels.

Populate these boards with your components, then add your own power supply, chassis and heat sinks to complete the amplifier. The mounting hole spacing is compatible with the diyAudio Universal Mounting Specification mounting pattern found in the Deluxe Chassis.

Output Power

• F-5T v2 - 50 Watts per channel into 8ohm
• F-5T v3 - 100 Watts into 8ohm. (The v3 should be built as monoblocks.)

Power supply requirements

A stereo F-5T v2 requires a bipolar power supply of (+/- 32V). This will require an 24V+24V (or 48V Center Tapped) transformer from 600-800VA, and PSU capacitance of 80,000uF per rail or more. The DIYaudio Universal PSU v3 was made with the requirments of this very amp when it was designed.

The F-5T v3 will require two of the above PSU. (One for each monoblock)

The amplifier has the ability to use a higher voltage PSU for more power, but you must 'cascode' the driver stage of the amp to protect the input Jfets. (And have even more heatsink.) See the article for more details.

Chassis suggestions

This is a high-wattage Class-A amplifier. It has lots of excess heat that needs to be dealt with. The 5U Chassis is of suitable size and disipation for a Stereo v2 or a mono v3.

The 5U Deluxe amplifier chassis makes a great home for this amplifier, and has pre-tapped holes that match the circuit board and transistor mounting positions.  The diyAudio "Universal Mounting Specification" (UMS) is a common mounting pattern between the amplifier PCB and the heatsinks. The new revision driver board will fit on the heatsinks, between the output boards.

Helpful Links

• F-5 Turbo Article by Nelson Pass
• F-5T v2 Bill of Materials
• F-5T v3 Bill of Materials
• Support discussion thread for these boards
• Please note that while these boards are marked as "V3" that refers to the fact they are the third revision of the boards, and nothing to do with their suitability to make a v2 or v3 F-5T.  You can use these boards to make either a v2 or v3 F-5T.

Other Notes

• The F-5 Turbo, an F-5 on steroids, with outputs up to 100w per channel
• With these PCBs you can make a 2 channel amp, or a massive monoblock depending on the output desired, PSU voltage, and the heatsinking available! Either way it should be used with the 5U x 400 chassis. You could also make a smaller monoblock using the 4U x 300 chassis, and only 2 of the output boards.
• For questions about the PCB itself and myriad links to the original article, discussion threads and build threads, please see the F-5T boards support thread
• This is not a beginners project
• These boards are the newest revision, having a new layout of the Front-End board featuring many new solder pads, and rationalized labeling and numbering across all the PCBs. The layout has been only slightly modified, but it is different from the v2 PCB.