The F5 is a Push-Pull, Class-A power amplifier. It is unique in that it has no capacitors in the amplifier circuit. The F5 is a voltage source amplifier, requiring nothing out of the ordinary from your preamp or speakers.
The F5 is probably the most popular amplifier being built on DIYaudio these days. It is simple to make, sounds fantastic, and has similar gain to many commercial amps.
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 the same as all other diyAudio Version 2 UMS boards.
25WPC into 8ohm
Power supply requirements
A Bipolar power supply of (+/- 24V) is required. This will require an 18V+18V (or 36V Center Tapped) transformer from 300-500VA, and PSU capacitance of 30,000uF per rail or more. The PSU for the F4, F5, and Aleph J are all essentially identical. See the F5 build guide for details.
The 4U 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. If you utilize the UMS on your heatsinks or use one of the pre-drilled chassis from diyAudio, you will be able to quickly and easily mount different amplifier boards in the same chassis. For example, a 4U 'Jack of all Chassis' with a 400VA, 18V+18V transformer and PSU board, will give you a power supply and chassis where you could try the F4, F5, F5C, Aleph J, and other Pass/Firstwatt amps in the future merely by swapping the amp PCB. The investment in Chassis and PSU needs only be made once.
Please see the F5 thread in the store support forum for any questions you might have and a definitive list of relevant links and resources.
- Initial release
- Updated to suit UMS
- Change to F5 schematics from F5 Turbo article
- Minor diagram change in NTC and limiter sections
- P3 added to adjust N/P variations to reduce distortion
- Relabelling of resistors to match schematics
- JFETs moved further away from current traces
- Hole for OUT moved to other edge of board to make it prettier and increase symmetry
- Middle mounting holes removed
V3 information (the current board is V3)
- Please note: The F5 V3 boards use the part numbering from the F-5 Turbo article, which is the latest official version of the F5.
- The P3 is optional and only used for advanced builders with advanced equipment - you can leave it out if you don't have this equipment.
- diyAudio F5v3 Build Guide
- V3 Schematic (Included in the F-5 Turbo Article) (PDF)
- V3 Schematic itself extracted from the F-5 Turbo Article (JPG)
- diyAudio Store F-5 Helpdesk Thread
V2 information to be used for reference only
- Bill of Materials (V2 for reference) (PDF) Please note - the current board is V3, we do not currently have a BOM for V3
- V2 Schematic (V2 for reference) (PDF) Please note - the current board is V3
- Dimensions (V2) (PDF)
- diyAudio F5 Build Guide (old information from 2013, mostly pertains to V2)
|Dimensions||170mm x 50mm|
|Mounting holes||UMS Heatsink Compatible|
|Number of boards included||2|
I replaced an ancient NAD 2150 with this and am very happy with the result. My system consists of a DIYINHK DAC driving the amp, and a pair of Linn Keilidh speakers.
The circuit boards are high quality and the assembly is straight forward. I went with the deluxe chassis, universal power supply, and the soft start/speaker protection boards. The build guide and help thread were very helpful.
I can find no flaws with the sound quality. It is very clean and clear. Voices in particular stand out. Bass has plenty of punch. Complex musical passages with lots going on remain clear. It has plenty of power to drive my speakers to above reasonable listening levels.
My compliments to Nelson Pass for the circuit design, and to the DIY Audio Store crew for making it possible.
Very good board.
I modified the F5 board to F7.
1-Cut 3 places (orange line).
2-Add 2 resistors back face.
3-Cross drain pin & sorce pin of power mos-fets.
So last night I finished my F5 amplifier.
It uses these boards and is a text book build; everything went to plan, and it sounds great.
A 300 watt Toroidy Audio Grade transformer is being used, which seems fine.
1 - when soldering R7 & R8 think about how you will attach your multi meter during the bias setting stage. I have them standing off the board a little, and my test hooks clipped on easily and safely.
2 - when setting P1 and P2 to zero, triple check that the resulting resistance across R5 & R6 is low not high. This could require clockwise OR anti clockwise adjustment depending on how you position P1 & P2 on the board. When setting bias for the first time, expect no change for a few turns, then a rather sudden increase in voltage.
Top quality boards. Top service and fast shipping. Build zhe F5 and Im truly happy with the sound. Thanks Diyaudio store!
Absolutely love these boards! Very nice quality board, and the layout is superb. DIY Audio never disappoints!
excellent quality thank you for stocking these boards ,can't wait to start my build *
Usual amazing quality of DIYAudiostore products. All faultless and as specified. And of course great service from the Store answering queries. Thanks.
Excellent very helpful staff when I stuff up order
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