Phil Lynott

For a period of time. Phil used a pair of Hiwatt SE4123 cabs, which were powered by the Hiwatt DR103.

Watch closely at 1:16 to 1:24, that's definetely a Marshall super bass on a Marshall 2x15 cabinet left of the drums. Mentioned in 1981 interview with Tony Bacon:

I've had custom-made stuff. I'll tell you one of things I found that was really nice, the old Marshall—well, they were a ripoff of the Fender, you know? I used to use that with an Acoustic, the Acoustic for the throw and that was for the sound down there.

This is either a Custom 100, 200 or (just maybe) 400, I can't tell. However, I think it's a 100 as the 200/400 amp is shaped slightly differently. Anyway, you can see this amp from the start of the video behind Phil on top of a huge silver cabinet. Hiwatt logo and general design is unmistakable.

Phil Lynott used the Ampeg B-15NF Portaflex 30-Watt 1x15" Bass Combo during a live performance with Thin Lizzy at the Sydney Opera House on October 29, 1978. This is documented in the YouTube video "Thin Lizzy – Jailbreak (Live in Sydney 1978) | 4K Remastered," shared by Fabrício Gabriel. The footage clearly shows Lynott with this amplifier, highlighting its role in his live setup.

Phil Lynott is confirmed to have used an Acoustic 150b amplifier, as evidenced in the video titled "Thin Lizzy – Jailbreak (Live in Sydney 1978) | 4K Remastered" provided by Fabrício Gabriel The Channel on YouTube. This video captures Thin Lizzy's live performance at the Forecourt, Sydney Opera House, Sydney, Australia, on October 29, 1978, where Lynott, the band's bassist and vocalist, is clearly seen utilizing this specific gear.

Evidence confirms that Phil Lynott utilized a 1972 Acoustic 135 amp, as demonstrated in a photograph showing him with the gear. This information is supported by visual documentation available through a specific image source.