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Vadlyd MD12 Mk4 78 rpm & RIAA Phono Preamplifier

The Mk4 replaces the Mk3, and has the following improvements:
click images to enlarge
Vadlyd MD12 Mk4 Small Front Panel

Vadlyd MD12 Mk4 Small Back Panel

Features | Specifications | Rear Panel Description | Front Panel Operation
Phonograph Records | Phonograph Preamplifiers | Phonograph Equalization
Stylus Selection | Speed Correction | Setting the Correct EQ | Vertical Cut Records

The Vadlyd MD12 Mk4 is a high quality, custom built phono preamplifier designed for optimal playing of virtually all disk recordings. Combined with the proper stylus and turntable, the unit is designed for professionals and serious collectors alike to provide uncompromised reproduction of disk recordings. The unit was designed by Jørgen Vad and Bjarne Jelsborg, B J Elektronik of Denmark after years of research. See Frequently Asked Questions (FAQ).

To download the current edition of the Vadlyd MD12 Mk4 manual, right-click here. Except as noted, the photos and information on this page describe the Vadlyd MD12 Mk4 model.

Purchase




Item Price
Vadlyd MD12 Mk4
78RPM and RIAA Phono Preamplifier		 $2,285.00 total
(2,250.00 + 35.00 UPS ground insured-US)
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Features

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Specifications

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Front Panel Operation

Use the pushbutton on the extreme left to select either Phono Input 1 or Phono Input 2. An LED lights when selecting Phono Input 2.

The next two pushbuttons select either MM (moving magnet) or MC (moving coil) cartridges for each input. An LED lights when MC is engaged, in which case load impedances of 50, 100, or 200 Ohms can be selected using the appropriate toggle switch above each pushbutton.

Equalization curves are selected with the rotary switch, and the currently active curve is indicated by the appropriate LED. Always change equalization curves slowly to minimize pops (the unit was designed to minimize or even eliminate annoying pops by switching slowly).

Both the 80 Hz Low Cut Filter and the High Cut Filter (which is continuously variable from 1.6 kHz to 12 kHz) are engaged by pressing individual pushbutton switches, which causes the appropriate LED to light. Both filters are first order designs.

Three pushbuttons allow you to select Vertical Cut, Left or Right channel only, and Mono/Stereo modes.

  1. Pressing only the first button enables you to hear Vertical Cut records played with a stereo cartridge as the mono function is automatically engaged.
  2. Pressing only the second button enables you to hear Left Channel (inner groovewall) alone in both speakers.
  3. Pressing only the third button enables you to hear Right Channel (outer groovewall) alone in both speakers.
Pressing both the second and third buttons together lets you hear both groovewalls in mono. With neither button pressed, the Vadlyd MD12 Mk4 is working in normal stereo mode.

Next is the volume control for the XLR flat outputs, the main volume control, the stereo balance control, the headphone volume control, the stereo headphone jack, and the power on/off switch.

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Rear Panel Description

The preamp has two identical inputs, so two turntables may be connected directly to the unit. For example, one input might be connected to a turntable for 78s, and another might be connected to a turntable for LPs.

A high quality grounding screw is between the two inputs. With most turntables, connecting to a ground screw on the preamp will result in the best signal to noise ratio.

Outputs are balanced XLRs with pin 1 ground, pin 2 hot, and pin 3 cold. Professional users will be familiar with this. An additional pair of outputs with RCA Phono connectors is available for consumer equipment. For serious archival work, an additional pair of balanced XLRs are provided with flat outputs.

There is a ground lift switch.

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Phonograph Records

All recording engineers and serious record collectors know the problem playing 78s and early LPs. Ordinary RIAA equalization simply does not match the recording equalization.

78s especially have many different eq settings depending on date, location, and recording company. Even within the same company, there may be differences depending on which engineer was working that day.

This custom-built preamp is a product with professional specifications; the preamp is also useful for record collectors who want the right equalization of their records.

Note: Most potentiometers can stand severe wear for decades, but dust - and especially smoke - can make them noisy when operated in just a couple of years. Tobacco smoke is ALMOST as dangerous for a pot as it is for your health!

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Phonograph Preamplifiers

A regular phono input on a preamplifier usually includes the RIAA (Recording Industries Association of America) equalization curve.

The RIAA equalization curve specifies two turnover points (a turnover point is where the level changes ±3dB): one at 500Hz, and the other at 2122Hz. 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 2122Hz, and then falling again about 6dB/octave to
  3. -13.7dB at 10kHz.
You use the RIAA playback curve to compensate for the recorded equalization.

Normally, this works well with single, EP and LP records issued from 1955 on. But with very early LPs (some record companies didn’t use RIAA equalization before 1960), this curve is not always correct.

Various cutting equalizations were used on all 78s (and pre-1955 LPs), and the cutting equalization on 78s are different from the RIAA equalization curve. For that reason, the RIAA phono input is not suitable to reproduce 78s.

Thanks to Roger Wilmut for basic information about reproduction of 78s and allowing the use his equalization settings. For a better understanding of the problems of reproduction of records, read the following articles taken with kind permission from Roger Wilmut's home page: www.rfwilmut.clara.net/repro78/repro.html.

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Phonograph Equalization

The simplest form of disk cutter consists of a 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 head’s 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 off, 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 6dB/octave cut above a turnover frequency which varied between 3.4kHz and about 6kHz depending on the system. This meant that the surface noise became less obtrusive. 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 RIAA provides for a bass boost below 500Hz and a treble cut above the lower frequency of 2,120Hz - the latter reflecting the considerably increased amount of treble which can be cut onto an LP.

Therefore, when playing a 78 with RIAA equalization (which is all that is available to many people), it produces far less top end than is correct - particularly for the earliest electrical, where the result is akin to turning the treble control right down. (Turning it right up gives an improvement, but doesn’t touch the important mid-range.)

Use of the correct curves when reproducing 78s produces a startling improvement in the quality (although admittedly the surface noise can become a problem); many of these recordings are much higher quality than you might suppose.

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Stylus Selection

At the time 78s disappeared from commercial production, the recommended stylus size was 60µ (0.0025”) conical tip. This was 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 wider than the ’standard’, with the result that a 60µ 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.

ideal groove tracking
 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.
standard stylus in old 78 groove
truncated elliptical in old 78 groove

 

 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.

Serious mastering engineers and collectors often have a collection of styli sizes, conical truncated as well as elliptical truncated. A good starting point could be:
Date Conical Truncated Elliptical 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")
After 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

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Speed Correction

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 78 rpm records state the speed (and when they do it’s 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: but 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 don’t 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 rpm to cover most records.

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Setting the Correct Equalization

MD12 EQ viewAlways use your ears when selecting the presets. Record companies used different eq settings, and sometimes the same company used several 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 cut much louder, with much more bass response and a higher bass turnover frequency. In the US, Columbia and Victor had different settings but both used basically the patent from Western Electric.

Theory is one thing and practice is another, especially when cutting high frequencies. Besides, records in bad condition have lost a lot of the high frequency response. Many 78s are in bad condition because they have been played many times.

78 rpm Eq Settings
Eq Curve Treble
Turnover 		Bass
Turnover 		Low Bass
Turnover 		Cut at
10 kHz 		Boost at
50 hz
1 Flat flat flat      
2 US MID 30 flat 400 Hz 70 Hz   16 dB
3 WESTREX flat 200 Hz     15 dB
4 HMV flat 250 Hz 50 Hz   12 dB
5 ffrr 1949 6.36 kHz 250 Hz 40 Hz 5.0 dB 12 dB
6 Early DECCA 5.80 kHz 150 Hz   6.0 dB 11 dB
7 Columbia 1.60 kHz 300 Hz   16.0 dB 14 dB
8 BSI 3.18 kHz 353 Hz 50 Hz 10.5 dB 14 dB
  • 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.
  • US MID 30 is useful for many 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 (after 1945 and up to about 1953).
  • ffrr 1949 is used by Decca and EMI.
  • Early Decca is used by Decca from the 1930s.
  • Columbia is an American Columbia setting used by Columbia since around 1930. But be aware: this setting is an ideal setting and only useful for records in absolute good condition.
  • BSI is useful for all post 1953 78s, and it can also be useful for some earlier American 78s.
LP and 45 rpm Eq Settings
Eq Curve Treble
Turnover 		Bass
Turnover 		Low Bass
Turnover 		Cut at
10 kHz 		Boost at
50 hz
9 ffrr LP 1953 3.0000 kHz 450 Hz 100 Hz 11.0 dB 12.5 dB
10 CCIR 3.1800 kHz 500 Hz 50 Hz 10.5 dB 17.0 dB
11 NAB 1.6000 kHz 500 Hz   16.0 dB 16.0 dB
12 RIAA 2.1215 kHz 500 Hz 50 Hz 13.6 dB 17.0 dB
  • Use ffrr LP for early Decca LPs and for pre 1955 HMV and English Columbia LPs.
  • Use CCIR for early LPs and EPs on European labels.
  • Use NAB (NARTB) for some early American LPs.
  • Use NAB with the first order 80 Hz bass cut filter for American Columbia LPs.
  • RIAA is the theoretical world standard for all LPs and EPs after 1955.
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Vertical Cut Records (Pathé and Edison)

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 this, a mono cartridge is not able to reproduce a vertical groove signal; however, you can use a stereo cartridge for a vertical groove record because a stereo record is a combination of a lateral cut and a vertical cut record. You will get the best result with a special custom made stylus for this purpose. Ask your ”Cartridge Man” for information on purchasing the right stylus.

For reproduction of Pathé and Edison vertical cut records, just press the Vertical pushbutton switch.


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