1 KW 6 Meter LDMOS Amplifier by W6PQL
You only need a bit over 1w in for a KW out on this one; the amplifier shown here has an internal 16db attenuator so it can be used with drivers in the 50 to 100w range.
http://www.w6pql.com/1kw_6_meter_amplifier.htm

2SC1957 linear AMP by JF1OZL
The construction of linear amplifier is common interest of our homebrewer. Because all the SSB transmitter has some kind of the linear amplifier. I will inform you one type of my product.
https://www.qrp-ja.net/jf1ozl/2sc1957.html

450 watt 6m 50MHz Ham Radio VHF Amplifier by G3WOS
The amplifier uses transistors that have been designed for VHF SSB operation. The 'HF' aspect is important because, unlike VHF devices, they are considerably more stable and do not have that disastrous tendency to go into VHF' parasitic oscillations.
http://www.gare.co.uk/amplifier/450_watt_6m_amplifier.htm

50 MHz 10 Watt amplifier by PA2RF
I found some info of a 6m amplifier I built in 2007.It uses a VHF transistor 2N4933. I made the unit in order to give the SEM35 radio 10 Watts out instead of 1 Watt. The PA can only be used in FM and CW.
http://pa2rf.blogspot.com/2015/01/50-mhz-10-watt-amplifier.html

50MHz linear AMP by JF1OZL
This is a linear amplifier for 50MHz. This machine uses 3 valves. This machine does not use any power transformer for the plate and heater.
https://www.qrp-ja.net/jf1ozl/50Mlinear.html

50MHz/6m 8877-based DXpedition Amplifier by G3WOS
In September 2001 I had the opportunity to inspect and admire the amplifier built by Dick, K5AND for his 9G DXpedition. This inspired me to get thinking and building!
http://www.gare.co.uk/amplifier/index.htm

6CL6 single 50MHz power AMP by JF1OZL
6CL6 is a famous valve. It is known as a driver tube used in the Collins transceiver. I made a 50MHz QRP power AMP with this valve. This is normal grounded cathode amplifier.
https://www.qrp-ja.net/jf1ozl/6cl6.html

6m amplifier with 2x Gi7b by 9A3MR
This is my contribution to cheap tube amplifier gallery. Idea was to build stable and small power amplifier, suitable for portable and domestic use.
https://www.qsl.net/9a3mr/6m_amplifier.htm

8877 "Lite" A 50 MHz (6m) 20lb Travel Amp by K5AND
As those of you who do expeditions and mountain-top contesting can attest, carrying a kilowatt amp on your quest is SO much fun. Over the years since 1987, I have created 5 travel amps, all for six meters.
http://www.gare.co.uk/k5and/8877.htm

A Compact 8877 50MHz Amplifier and Power Supply by GJ4ICD
The reason for building this amplifier is to conduct Ionoscatter/Troposcatter along with FAI tests, and a good building exercise in producing an amplifier.
http://www.gare.co.uk/gj4icd_8877_amplifier.htm

A Dead Easy 50MHz Preamp by VK3CJS
I modified an old Realistic SSB CB radio for 6 metres. With a bigger PA it got out fine, with reports of good Tx audio. On receive though, it was deaf on account of it's simple grounded-base RF amplifier.
http://www.cgfar.com/vk3cjs/vk3cjs_page7.asp

Mini power Grand grid (GG) amplifier by JF1OZL
In 1993 some projects by 7L1OPH Mr.Yamano about his grand grid amplifier was introduced on the Japanese CQ magazine. I wanted to make such a GG amplifier. But I had no license to use 50W linear.
https://www.qrp-ja.net/jf1ozl/ggamp.html

VHF 6 Meterband amplifier by ON6MU
https://www.qsl.net/on6mu/schemas/vhfamp1.gif