1920s baloon valves stash

Just found a box of old radio spares ,  a few old triodes , an  interstage transformer , caps and pots/rheostats ,
'Balloon' valves , stunningly beautifull  bright chrome  gettering ,  transformer 3.5:1 ,  looks like theres easily the makings of  a preamp and also spares to help renovate my Marconiphone preamp .

Loudspeakers of the time were typically a very tiny headphone speaker  attached to  the conventional horn type apparatus found on a gramaphone , around 500 mW output power with  2 or 5% distortion was sufficient ,the drive units were usually in the range of 1-2kohms ,these era of audio transformer should work fairly well into a modern mic input or  10k balanced load ,  it will be fun to test what the cores in these very first generation audio transformers.

Very cool.  Some of those old bottles are very, very linear. 

Almost like vacuum tube makers laxed off a bit after Harold Black's discovery of negative feedback?

Have fun.

Nice find .  I want some 01’s or 201,301s. There not so much a linear sound as a liquid sound to the point of an effect.  Someday I’ll put a 2 ch together.

Heres the spec on the transformer included in the lot ,
I havent recieved the stuff yet so I don't know if the primary is intact or not .
It will be interesting to try  CJ's inductance tests on the 1920's core materials ,
Feranti claim performance up with the best modern technology could offer at the time ,
I wonder how far off what we expect from sound now will the 1920's components be capable of ,
I see some frequency graphs of that range of transformers showing  flat to 8khz but that might have
been the response in conjunction with the ear piece drive unit into a horn ,

This transformer seems to be aimed at an AM detector-- note remarks about rectification.

So an anode to grid step up ,
Maybe it can match a triode of a few thousand ohms into 20 k balanced for me ,
It weighs in at well over 2 lbs ,that seems like a gigantic core for the amount of power their passing under normal opperation.

And some more ,

I made the journey to hand collect the items  ,

AF-5 Transformer secondary o/c by the looks of it , the primary is still there ,measured about 2.6k with multimeter .

Included was a beautiful pair of the BTH B4 tubes ,BBC stamped, stored in their boxes but dusty
One of the desirable grid mesh versions of the 41M.P.
Three other triodes as well as the assorted coils , rheostats  vernier drive capacitances and odds and ends you see below .
I'll have a closer look tomorrow .