Old era 78 replay circuitry

[Michael Maurice]

Originally Posted by dseymo1

I remember owning a preamp which offered perhaps half a dozen switchable eq options to suit the various record manufacturers' products. Don't remember now what it was, though.

Probably a Leak Varislope from the early 1950's

[dave walsh]

That Leak Varislope is interesting-I've not seen one of those before. It's a bit similar [in concept anyway] to the EQ units predominant in Hi Fi gear during the 80's with sliders for setting a curve. Peter brought up the fact that everything referred to on here was in Mono of course [p16*]. A recent thread re Quad Electrostatic Speakers illustrated listening to just one of them, in Mono and extolled the benefits.

I've obtained a 1930's copy of Wireless World which arrived today [Friday 8/9/1933] many thanks Boater Sam! The editorial "The Art of Listening..Advantages of Indirect Reception" compares the Concert Hall experience to listening on the Radio and surprisingly, favours the latter. 78rpm recordings aren't referred to but it's all in the same context I suppose. The emininent musician Sir Walford Davies had "boldly stated" [in the Times no less] "Personally I have never in my life enjoyed Beethoven more in any concert room here or abroad than I have enjoyed him 'electrically reproduced' recently".

The Editor suggests that this may be because "In listening through the medium of the broadcast receiver it is possible to suppress all extraneous noises and interruptions". He goes on to say that "the listener must learn to understand his set and to judge whether it's performance is doing justice to the original transmission". This struck me as an early [indirect] reference to EQ [possibly variable via the set]. He's actually trying to promote educating the public about the "capabilities of a modern high quality receiver". I'm not sure why recordings didn't come into it, there is an overlap with 78's and the various standards that came along later. I suppose it is the Wireless World though

Dave

[gramofiend]

Something which may help is a site run by Roger willmut : www.78rpm.org.uk. This contains information about early 78's, equalization curves and some equipment. Software for removing noise By Brian Davies an Australian mathamatics proffessor which is quite impressive (listen to the downloads). offered.

Mike

[Stevie342000]

Originally Posted by barrymagrec

Most of the record companies had their own characteristic for 78s, as they did for LPs until the RIAA standard came in.

Some hi fi units had various settings for different characteristics, including Quad and Leak but if you can get hold of the DTN Williamson / GEC book on high quality sound reproduction it includes a pre amp design with quite a lot of different settings and some description of the characteristics, if I remember correctly, I have a copy but I currently have no idea where it is.

You can download a copy of the GEC book here: http://www.tubebooks.org/technical_books_online.htm

It's under Audio Section.

[barretter]

The GEC book had nothing to do with DTN Williamson (who worked for Ferranti, I think). It's by Messrs Heath, Leakey and Woodville.
There are some graphs on p.106 of the equalisation characteristics available in their Preamplifier Circuit no. 2, but only one refers to shellac discs, something called "The British 78 r.p.m. equalisation characteristic" whatever that means. The others are for tape and "British microgroove" and "American Standard" which differ from each other. As the book was published in 1957 by which time the RIAA standard was fairly universal, these last two presumably refer to pre-1954 equalisation curves but for which labels is unclear. The pre-amp also includes tone controls so basically it's back to "suck it and see".
I wouldn't bother building it.

[barrymagrec]

I think there is more than one book, DTN Williamson certainly worked for GEC / MO valve company where he designed his famous amplifier, he later moved to Ferranti.

I must try and find my book, apart from the preamp and two different versions of the Williamson amplifier, one using PX4s in place of the normal KT66s, it has AM and FM VHF tuner designs and an article on the GEC metal cone loudspeaker which was highly regarded at the time.

[Ted Kendall]

A British Standard 78 curve was introduced in 1955, just in time for the format to go pop. 450/50uS.

[dseymo1]

Originally Posted by Michael Maurice

Probably a Leak Varislope from the early 1950's

It was indeed! Thanks Michael.

[Orakle42]

I may have posted the attached sometime in the past, if so apologies!
The leaflet shows how Maconiphone dealt with the "..treble register.." but I suspect that this was long before 45's & 33's were contemplated.

Orakle42

[Hartley118]

Interesting how, back in the day, the purchaser of this pickup was presented with so much technical circuit detail. I suspect it wouldn't go down too well today!

Martin

[SteveCG]

May I humbly suggest that one of the biggest challenges to explore the differing EQs is to actually find some records of this era (pre RIAA) that have not been already been 'ground down' by weighty tracking and frequent playing...

[Hartley118]

Originally Posted by SteveCG

May I humbly suggest that one of the biggest challenges to explore the differing EQs is to actually find some records of this era (pre RIAA) that have not been already been 'ground down' by weighty tracking and frequent playing...

It's surprising how often one can find classical 78s that are relatively unworn. Some owners were fastidious about only using fibre needles which were not only a great, if extreme, scratch filter, but also caused very little wear. Some specialists have suggested that damage can be cause by the fibre picking up bits of grit from the regrinding sharpening process, but I can't say I've noticed that problem.

Even a steel needle in a post-war pickup is not too unkind to pre-1950 78s that weren't too heavily modulated. More recent 78s were of course more heavily modulated in order to compete on level in juke boxes and they need a compliant cartridge of similar vintage.

I think that much of the record damage we see has has been caused by stiff heavy soundboxes in acoustic gramophones, particularly if a worn out needle has been misused, i.e. removed and replaced in a different orientation, creating an effective groove cutting tool. There was also the damaging vintage of 'permanent' early sapphire tipped needles which could also act as cutting tools in a heavyweight pickup, being so much harder than the record material.

Martin

[Ted Kendall]

Thr idea that fibre needles wreck a 78 for any other stylus type is given prominence in Burnett James' pioneering book "Hi Fi for Pleasure", published in 1956. I must say I've never come across the problem, and I've dubbed a few 78s...mind you, this is a small error in an otherwise very good book.

One of the worst irritations in finding 78s good enough for remastering purposes was wear on peak mod, which causes a burst of noise around the peak, what we used to refer to as a "blatty turn" - sometimes it was confirmed by greying of the groove at this point. With tools such as Retouch, the problem is not as acute as it once was. but still takes time to sort out.

Having worked across the board in terms of repertoire, I really wonder how much most classical 78s were played - wear is pretty unusual, except for horrors such as Eva Turner's "In questa reggia" from 1926, which was so "hot" it was soon re-recorded at a level which was playable on the soundboxes of the day. More likely is crackle caused by storage in damp conditions. Popular stuff, on the other hand, can be difficult to find in good nick, and the biggest hits next to impossible, because they were played to death!

The job which caused most trouble with this was my complete George Formby edition. Despite having one of the best collections to hand, filling the gaps was a frightful chore. Formby's banjolele dominated the last third of most of his sides, and the pickups of the day really couldn't cope with the changes of groove direction, so they just ploughed a sort of democratic mean through the peaks. And Formby discs, once bought, tended to be played...

[rontech]

I inherited four George Formby records from the 1936 / 1938 period. They had been played on a Garrard RC4 autochanger using a semi-permanent sapphire stylus in the magnetic pickup head. From about 1946 this was replaced by a plug-in crystal pickup head ( Garrarsd / / Rothermel / Brush ) which was used with fibre needles. Then seldom played but from 1955 would have been on a BSR autochanger. In the early 1970's I copied most of the family 78s onto cassette using a Garrard401/SME3009/ShureM55 with 78 stylus. Playing the tapes back now on my good modern hifi system I am amazed at the good transient response on Formby's banjolele.
Sadly I disposed of all the original 78's years ago.