One we had was a TV aerial type input, a shielded cable but very early.
Buy with care & don't expect it to be modern sounding.
As the years go on, this eliteness fades as readership will have been small.
To us, we found the book a little dull & skipped through a bit.There are 4 pages of Amplifiers with Control Units & Power Amplifiers in the same section.To list all amps of minor wattage after the Valve era isn't going to happen, go buy the books. Our Aim with these pages..to try ALL the 40w-50w amps we can with ones pre 1972 with the cleaner sound can sound good up to 65w, later ones of over 45w can sound rough from too many transistors in the design.We're not too interested in ones with ICs in the Tone-Flat stage & certainly an IC power amp as some ghastly late 1970s 100W ones dare to use won't get our interest.This year appears to only show high quality items & the list is only to be an impressive one, but in 1956 HFYB only listed ones they rated as worthy, actually narrowing their readership a lot, so we'll list the lot.
As noted on the Quad, AZ Senior CU/A 20w £40; AZ Junior Mk II 10w EL84 £22, Three Channel setup: CU/A Bass 22w KT61 , Treble 1.5w ECL80 & Centre(Midrange? The earliest appearance of this idea we don't like, phase errors abound.; That was interesting. Gives the idea only high power ones were sold, but there will have been plenty of the 3w type & Kits in this era.
A true Retro sound like a big 1950s Jukebox, fun factor high, fidelity soft.
Not to buy & try to upgrade, to get working to the old spec is the wise thing on these as buyers won't like you hacking holes for Phono Plugs & 4mm speaker sockets if there are none.
Power ratings may say 10w in 1956 but beyond that no definition of 10w of peak, music, RMS, or into which ohms rating.
So research these elsewhere to see the ratings we'd use today, but from the 1956-57 ones the ratings look like RMS so only later did the USA type misleading ratings begin. If noted in the book, output valves that are still favoured today are noted: EL84, EL34, KT66 & KT88.
For Valves 10w was actually a high power in 1958 so 10w minimum unless an early Integrated.