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Latest update July 9th 2015

VADLYD MD12 MK4

Multicurve Disc preamp

78 RPM and RIAA Record Preamplifier

SUGGESTED RETAIL PRICE: EURO 2,125.- ex VAT

 
DANISH VERSION

			
				
					 
				
			
		

VADLYD MD12 MK4
(in stock now)

and replaces VADLYD MD12 MK3. We are now working with B J Elektronik, Ballerup, Denmark.

There will be a few improvements compared with the mk3 version:

VADLYD MD12 MK4 includes as standard vertical/lateral switch, and switchable inputs for MM/MC cartridges. MC inputs are with 3 switchable load impedances: 50, 100, and 200 ohms.

Recording engineers and serious record collectors know the problem when playing early phonograph records: ordinary RIAA phono equalization does not always match the original recording equalization that was used to make the record.

78rpm records in particular have many different eq settings depending on period, placement, and recording company. Even within the same company, there may be differences depending on which engineer was on job that day.

The VADLYD MD12 MK4 is a product with professional specifications, but it is also useful for record collectors who want the proper playback equalization of early phonograph recordings, particularly 78rpm records.

Overview:


A few words concerning long life of all electronic equipment: most potentiometers can stand severe wear for decades, but dust - and especially smoke - can make them noisy in a very short time. Tobacco smoke is ALMOST as dangerous for a pot as it is for your health!

ABOUT PHONO PREAMPLIFIERS

When playing phonograph records, you might normally use the phono input provided on your amplifier, often called a RIAA (Recording Industries Association in America) phono input.

The RIAA equalization curve specifies two turnover points (a turnover point is where the level changes ħ3dB): one at 500Hz, and the other at 2125Hz. The RIAA playback curve has the following theoretical response:

1. +17dB from 20Hz to 50Hz, then falling about 6dB/octave to
2. 0dB from 500Hz to 2125Hz, and then falling again about 6dB/octave to
3. -13.7dB at 10kHz.

You use the RIAA playback curve to compensate for the RIAA equalization that was originally used to make the record.

Normally this works well on single, EP and LP records, issued from 1955 and later. But with earlier LPs (some record companies didnt use RIAA before 1960), this curve is not correct. The cutting equalizations on all 78 RPMs and LPs before 1955 have been very different. 78rpm records in particular used curves very different from the RIAA curve. For this reason, you should not use the RIAA phono input on your amplifier if you want good quality reproduction of 78rpm records.

I want to thank Roger Wilmut for basic information about reproduction of 78rpm records. For a better understanding of the problems of reproduction of records, read the following articles (with a few edits from my hand) taken with kind permission from Roger Wilmuts home page: ”Reproduction of 78rpm records” - www.rfwilmut.clara.net/repro78/repro.html.

EQUALIZATION OF PHONOGRAPH RECORDS

The simplest form of disk cutter consists of an amplifier, similar to that used to drive a loudspeaker, connected to a cutting head having a stylus connected to a coil, which is placed in the field from a strong magnet (or, more usually in later designs, a magnet within a coil). When the signal is applied to the coil, the stylus moves and engraves a groove in the blank disk. (There is of course a lot more to it than that, but we are considering only the basics here.)

However, because the cutter heads movements translate the amplitude swings of the original signal into velocity - the rate at which the stylus moves during its swings - low-frequency signals would be recorded with a much larger swing than high-frequency signals of the same original amplitude. In order to keep the movements of the groove much the same at all frequencies (given equal level signals) it is necessary to use a circuit to introduce - in the theoretical situation - a 6 dB/octave cut as the frequency decreases - i.e., halve the frequency and you halve the voltage.

In the reverse situation, that of a reproduction head, the principal is that of a wire moved in a magnetic field - it is the rate of cutting lines of force that matters. The cutter head works exactly in reverse, like a simple motor, where increased voltage means increased speed. Therefore, the constant amplitude groove theoretically achieved produces a signal where the bass is low and the treble high: so a 6 dB/octave cut with increasing frequency would be called for.

In the real world, losses in the head with increased frequency complicate the issue. Early cutter heads were highly inefficient, and so, while the bass cut described above was used, the treble trailed away, resulting in equal groove modulations (movements) up to mid frequencies, but decreasing above that.

To compensate for this, the playback characteristic boosted the bass below 200 Hz but left it flat above that - effectively providing a 6 dB/octave boost to the higher frequencies (and the surface noise). With the later improvements in cutters, it was possible to pack more treble onto the records, and so new equalizations provided for a 6 dB/octave cut above a turnover frequency which varied between 3.4 and about 6 kHz, depending on the system.

Boosting the treble during recording had the effect of reducing the surface noise during playback. It was also common to flatten out the bass at the very lowest frequencies to reduce the boost of rumble from the turntable.

Similar techniques were applied to microgroove records, and the final standard, RIAA, provides for a bass boost below 500 Hz and a treble cut above the lower frequency of 2,212 kHz - the latter reflecting the considerably increased amount of treble which can be cut onto an LP.

Therefore playing a 78rpm record using RIAA equalization - all that is available to many people - produces far less top end response than is correct, particularly for the earliest electrical records, where the result is akin to turning the treble control down. (Turning the treble up gives an improvement, but it doesnt touch the important mid-range.)

Use of the correct eq curves when reproducing 78rpm records produces a startling improvement in the sound quality (although admittedly the surface noise can increase).

Many of these older recordings are of surprisingly high quality after all!

STYLUS SELECTION

At the time the format disappeared as a popular format, the recommended stylus size was 60 (0.0025”) conical tip. This would be satisfactory for records made in the final few years, but for the great majority of the time since the beginning of 78s in 1896 the grooves were much wider than the standard, with the result that a 60 stylus skates about in the bottom of the groove, seriously increasing the surface noise.

The basic stylus is conical, with a spherical tip; the included angle of the cone is 60 degrees. Most modern styli are elliptical: i.e. they look the same from the front, but from the side they have a much narrower angle. This enables them to track movements in the groove more easily (as the groove moves from side to side it effectively narrows - not across its direct width but across the diameter of the conical tip, at an angle to the direction of travel: consequently a spherical tip will ride up in the groove).

The illustrations below could apply equally to a spherical tip and an elliptical tip seen from the front: in practice I would always recommend elliptical.

A modern record groove should be a neat 90 degrees, with the stylus making contact at only two points part-way up the groove wall, thus avoiding any debris in the bottom of the groove. (Some modern microgroove styli have a flat section at the contact point, giving a wider area of contact which reduces wear: however it can also increase noise from worn or damaged groove walls and I would be dubious about its use for 78s).

However older 78s were cut to be used with steel needles, on the assumption that the needle would wear down to fit the groove in the first few seconds: when this wider groove is tracked with a 2.5 thou stylus the result is ‘bottoming’ as can be seen here.

 

Here the combination of a larger basic size: 70µ (0.0028”) works on the majority of records, although larger sizes may be helpful with very old records - and the truncated tip (which is spherical down to the contact points but truncated below) result in vastly better tracking. Like LPs, Records in good condition, will be better reproduced If the stylus is elliptical. This brings a considerable improvement in distortion and will be with reduced surface noise and greater analysis. With records in poor condition, you often will have a better reproduction with conical styli.

 

Professional mastering engineers and serious collectors often have a collection of styli sizes, conical truncated as well as elliptical truncated. A good starting point could be:

Records from

Conical truncated

Eliptical truncated

Before 1920:

100µ (0.0040")

100µ x 30µ (0.0040" x 0.0012")

1920 - 1939:

90µ (0.0035")

90µ x 30µ (0.0035" x 0.0012")

1939 - :

70µ (0.0028")

70µ x 25µ (0.0028" x 0.0009")

A good address for buying cartridges and styli, as well as retipping of styli, is

Expert Stylus Company
P.O. Box 3 - Ashtead
Surrey KT21 "QD - England
Tel: +44 01372 276604

 

SPEED SELECTION

Not all 78s were actually recorded at 78 rpm. Even in the late 1920s, English Columbia was still using 80 rpm, and prior to about 1921 speeds were widely variable. Speeds as low as 68 or as high as 84 rpm are not uncommon.

To make matters worse, relatively few 78rpm records state the speed (and when they do its not always accurate). If the work is a classical piece such as an opera aria, it is possible to check the correct pitch against a score or a modern recording. However, as occasionally singers would transpose, even this isn't completely reliable. My best recommendation is to gradually reduce the speed of a record until it starts to sound sluggish, and then increase it slightly (in my experience the ear is much more sensitive to low speeds than high speeds).

Finding a turntable capable of coping with these speeds is often a challenge. I dont know of any normally available turntable which has more than a tiny variation (usually 2 or 3 %), which is nowhere near enough); but electronically controlled turntables may be modifiable. You need a speed range of 72 to 82 to cover most records.

For further information, see Roger Wilmuts web site: http://www.rfwilmut.clara.net/repro78/repro.html. This site contains additional information about 78rpm records.

 

 

HOW TO USE THE PREAMPLIFIER

Front Panel (left to right)

Rear Panel (left to right)

SETTING THE CORRECT EQUALIZATION USING THE PRESETS

Coarse Groove (78 rpm)

SYSTEM

Treble turnover

Bass turnover

Lower bass t/o

Cut at 10 kHz

Boost at 50 hz

Flat

flat

flat




US MID 30

flat

400 Hz

70 Hz

-

16 dB

WESTREX

flat

200 Hz

-

-

15 dB

HMV

flat

250 Hz

50 Hz

-

12 dB

ffrr 1949

6.36 kHz

250 Hz

40 Hz

5 dB

12 dB

Early DECCA

5.8 kHz

150 Hz

-

6 dB

11 dB

Columbia

1.6 kHz

300 Hz

-

16 dB

14 dB

BSI

3.18 kHz

353 Hz

50 Hz

10.5 dB

14 dB


Note that record companies used many different eq settings, and sometimes the same company used different settings depending on which recording engineer was on job.

Generally, there is a difference between American and European 78 rpm recordings: the American records were normally much louder cut with much more bass response and a higher bass turnover frequency. The two American record companies Columbia and Victor had different settings but both used basically the patent from Western Electric.

Since theory and practice are not always the same, always use your ears! This is especially true with records in bad condition, which as a result of wear have often lost much their high frequency response. Unfortunately, many 78s are in bad condition because they have been played many times.

Ideally, use FLAT for old acoustic recordings. Sometimes you will find that you will get a better sound with a little bass lift. Then try one of the other eq settings and use the 80 Hz bass cut filter.

Next eq is US MID 30, which is useful for a lot of American records. Normally you should use it together with the variable low pass filter and find the right settings. Good for American Victor.

Use WESTREX (English Western Electric) for HMV 78s with a triangle matrix code and English Columbias with a “W” Matrix code.

HMV eq is used for HMVs with a square matrix code, and English Columbia with a “C” matrix code, or in both cases with no code (post 1945 up to about 1953).

ffrr 1949 is used by Decca and EMI.

Early Decca are Decca eq setting from 30s.

Columbia is an American Columbia setting used by Columbia since around 1930. But note: this setting is an ideal setting and only useful for records in absolute good condition
.
BSI 78 useful for all post 1953 78s. It can also be useful for some earlier American 78s.

MICROGROOVE (LPs and 45 rpm)

SYSTEM

Treble turnover

Bass turnover

Lower bass t/o

Cut at 10 kHz

Boost at 50 hz

ffrr LP 1953

3 kHz

450 Hz

100 Hz

11 dB

12.5 dB

CCIR

3.18 kHz

500 Hz

50 Hz

10.5 dB

17 dB

NAB

1.6 kHz

500 Hz

-

16 dB

16 dB

RIAA 2.1215 kHz 500.5 Hz 50.5 Hz 13.6 dB 17 dB

Use ffrr LP 1953 for early Decca LPs and for pre 1955 HMV and English Columbia LPs.

CCIR is used by European labels for early LPs and EPs
.
Use NAB (NARTB) for some early American LPs. Use NAB together with the first order 80 Hz bass cut filter for American Columbia LPs.

RIAA is the universal standard (in theory) of all EP/LPs after 1955


.
REPRODUCTION OF PATHÉ AND EDISON VERTICAL CUT RECORDS

Normally mono recordings are lateral, which means ”side to side” in the groove wall. But some of the first recordings were vertically cut, also named as ”hill and dale” recordings. Because of that, a mono cartridge is not able to reproduce a vertical groove signal. But a stereo record is a combination of a lateral cut and a vertical cut record. Thats why you can use a stereo cartridge. You will get the best result with a special costum made stylus for this purpose.
Ask your ”Cartridge Man” for purchasing the right stylus.
For reproduction of Pathé and Edison vertically cut records, activate the ”VERTICAL” switch.


Further references:

International Association of Sound and Audiovisual Archives
http://www.iasa-web.org/

Audio Engineering Society
http://www.aes.org/

Association for Recorded Sound Collections
http://www.arsc-audio.org/

European Broadcast Union
http://www.ebu.ch/en/index.php

Society of American Archivists
http://www.archivists.org/

Grammy Foundation Grants
http://www2.grammy.com/GRAMMY_Foundation/Grants/

SPECIFICATIONS

Power requirements:
90 . 260 V AC
Frequency response: 18 Hz to 54 kHz (-1 dB)
Input impedance: 47 kOhm/47 pF (MM), 50/100/200 Ohm (MC)
Gain @ 1KHz: 50dB (MM), 75dB (MC)
Max out: +24 dBu
Output impedance (normal out) 50 Ohm
Load impedance (normal out): > 600 Ohm
Deviation from RIAA-curve: max. 0.5 dB
Distortion @ +10dBu out (20Hz-20KHz): 0.03%
Noise: -70dBA below 2.5mV in (MM), -70dBA below 1mV in (MC)
Channel separation @ 10KHz: > 55dB
0 dBu = 0.775 V
Balanced XLRs: Pin 1 = ground, pin 2 = hot, pin 3 = cold.

International distributors

France:

Germany:
Phono Passion
Friedrichshof
Im Bohrer 26
D-79289 Horben
Deutchland
att. Andreas Schmauder
Email: phonopassion@t-online.de

USA and CANADA:
MasterDigital Corporation
2614 W. 15th Avenue
Covington, LA 70433
Tel: 504.236.6368

Web: www.masterdigital.com
Contact: www.masterdigital.com/contact

 

Download Users Manual in PDF format

Transferring of 78 RPM and LP's.

Back to VADLYD English Homepage

 

 

For further information:

Please contact

md12@vadlyd.dk

English Homepage - Audio restoration - NoNOISE Pricelist - CD Mastering - Sound Recordings
Transferring of 78 RPM and LP's - 78 RPM and RIAA Preamp
Equipment List and Pro-audio links - References - Relevant Links
Price list - Danish Homepage - Search vadlyd.dk