[Patrick Turner]

Ian Bell wrote:

Arny Krueger wrote:
"Ian Bell" wrote in message

Eeyore wrote:
Ian Bell wrote:

Since there are untold preamp designs with unregulated
supplies
Bad preamps you mean ?

Graham


You tell me. I have the schematics for many broadcast
consoles and professional music mixers from the 50s that
use unregulated supplies.

Standards for audio were a lot lower in the 50s, if you didn't ever notice
when you listened to a lot of recordings from that time. There are some
exceptional recordings that still sound good, but in general, it was not a
good time for quality sound reproduction.



I would not say they were a lot lower. The flat bandwidth extended only
from 50Hz to 15KHz but elsewhere the specs were close to today's. An RCA
broadcast console achieved a 68dB S/N ratio with a -60dBm input signal
which implies an equivalent input noise of -128dBm - and that would not
be achievable with the LF noise I am seeing right now. Maybe they had
better conditioned mains supplies for studios or maybe there was just
less crap on the mains in those days.

"Mains conditioning" for audio studios in the 1950s is not something I
have ever seen described in any tech journal. There were however mains
regulators based around saturable reactors.

Much audio gear was made to work OK without excessive filtering, and
when being fed by fairly irregular mobile mains power supplies.
BBC vans were full of gear that would try to minimise power losses and
use only battery power. Not much damn noise with batteries.

The BBC could afford batteries. The dc to tubes was at lowish voltages
and anode loads were chokes.

And mains noise has always been bad.

Much quality gear in 1950 had B+ regulation. Countless designs of tubes
oscilloscopes had a regulator using a 6080 and a pentode.

Much domestic audio gear was atrocious because design was by
accountants. The item was not built up to a quality, but down to a
price.

Cash strapped dudes who wanted perfect audio in 1950 were not able to
have the quality they yearned for because they were forced to feed the
large families of the time. No Pill. My father's generation knew the
Depression of the 1930s, and WW2, and having a few extra mV of noise at
an amp output was the least of their concerns.

Many used alcohol to overcome all problems, including those of poor
audio, hence the drink cabinets supplied in deluxe radio-grams of 1950.
Manufacturers knew the best way for punters to accept their terrible
creations was to encourage boozing and smoking. Radio and audio
manufacturers had cousins in the drinks and smokes supply businesses.

Blokes rooted the missus between drinks and smokes and arguments over
money, thus creating today's baby boomers.

Domestic survival each night in 1950 was a challenge. Bliss was a
rarity.

Patrick Turner.



Cheers

Ian