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Original price $ 25.00 - Original price $ 25.00
Original price
$ 25.00
$ 25.00 - $ 25.00
Current price $ 25.00
in stock, ready to be shipped

Please note we have F6 parts / transformer kits now available (which include a pair of these PCBs).

These F-6 Clone Boards use the same circuit as the Nelson Pass / diyAudio FirstWatt F6 described in the diyAudio FirstWatt F6 thread thread.

This set of circuit boards will make a MOSFET version of the F6 amplifier of Nelson Pass. This amplifier is a new and interesting development from his creative mind, where a small collection of parts comes together to make amazing, beautiful music. This creativity and solid engineering has kept Mr. Pass, and his companies, Pass Labs and FirstWatt, at the forefront of specialist audio engineering and construction, where new and wonderful creations are made.

The original amplifier utilized extremely rare power JFET from SemiSouth, which will never be made again, and are all gone. Be warned, any eBay sources claiming to have the SemiSouth devices are fakes. If you happen to already have the power JFET, they can be used with this PCB.

Populate these boards with your components, then add your own power supply, chassis and heat sinks to complete the amplifier.

Circuit description

The F6 is a Class-A MOSFET power amplifier, with a JFET driver stage. It utilizes a small-signal transformer for phase inversion, so both the output MOSFET are N-channel. This transformer greatly contributes to the overall sonic character of the amp which is very highly regarded and considered to be similar and having all the benefits and positive characteristics of a tube amp... making some observers speculate that much of the positive 'tube amp' sound is the transformers, not the tubes. The F6 is a regular kind of amp - a voltage source amplifier, requiring nothing out of the ordinary from the preamp or the speakers.

Output power

As with most of the FirstWatt amplifiers the power output is 25WPC into 8 ohm. More into 4 ohm.

PSU requirements

A Bipolar power supply of (+/- 24V) is required. This will require an 18V+18V (or 36V Center Tapped) transformer from 300-400VA, (shielded transformers are preferred) and PSU capacitance of at 60,000uF per rail or more. A PSU for the F4, F5, or similar will be appropriate. See the F6 build guide for details.

Chassis (heatsink) requirements

The 4U 'Jack of all Chassis' is ideal for this amplifier. If making your own chassis a good rule of thumb is at least 25sq inch (160sq cm) of finned heatsink per output transistor. (More is always better.) The diyAudio "Universal Mounting Spec" (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 the diyAudio store, 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.

Build Guide

An Illustrated build guide showing all sorts of useful information on how to build the F6 can be found here -- F6 Build Guide


Dimensions 250mm x 50mm
Mounting holes UMS Heatsink Compatible
Number of boards included 2
Layers 2
Board Revision 2.0

Customer Reviews

Based on 24 reviews
Mark P.

Looks and sounds incredible. The kit is no longer available, so I had to source the parts from several different suppliers. I highly recommend this amplifier. Thanks Nelson and DIY Audio.

Radoslav P.
First Watt F6

The sound is great.Easy to build. Super !!!! Thanks Nelson.

F6 built like a tank Photos

Part two

Roger S.
F6 vs F5

I decided to build the F6 after doing and listening to the F5 for a few months. Although the F5 is a fantastic sounding amp I somehow found it a tick too bright and flashy...
Now the F6 seems to be a completely different beast (in a positive way) as it sounds darker and rounder.
Only a few hours of listening but I guess I'll stick to this one ;-)
Absolutely fantastic service from DIY as always.

F6 built like a tank

This is my first custom built amplifier but with a difference:
I've used high end parts replacing the kit from Audio-Note Caps and TAKMAN resistors carbon film.
Also Overkill PSU cap 33000uF * 8 and soft-start & speaker modules.
Awaiting to have time hear it to the fullest.

Sheldon S.
F-6 is astonishing

Finished my F-6 a few weeks ago. Truly amazing amp and not that challenging for a semi-beginner. Plenty of things I had to decipher but helps me learn. Nothing blew up and still no smoke or electrical fires after several weeks, probably a good sign. Fantastic level of detail with my Klipsch Fortes and more than enough power. Trying it now with totally rebuilt DQ-10's--much harder speaker to drive but sounds luscious and sensual in a way that the Fortes can't quite do. Gets loud enough for me with the DQ-10 but if I keep these speakers I'll probably tackle the F5T at some point. Now just waiting on my nutube kit we'll see what that does.
What a fantastic hobby this is but potentially highly addictive. Be warned.