ELBERG MD12 MK2
78RPM and RIAA Phono Preamplifier

click images to enlarge

Sorry, this unit is not available. A new version is under development from VADLYD in Denmark.
Check back soon. For further information, please contact us.

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 Elberg MD12 Mk2 is a high quality, custom built phono preamplifer 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 Elberg of Denmark after years of research. See Frequently Asked Questions (FAQ).

Features

• 12 presets enable adjustment to nearly all eq curves, 8 presets for 78s, and 4 presets for 33/45s
• Excellent sound quality (see full specifications below)
• Switches for Stereo, Mono L + R, Mono L or Mono R
• Switch for Vertical Cut records (Pathé/Edison)
• Volume and balance controls, with the ability to drive a power amplifier directly
• Built with many LEDs for easy operation
• Professional, balanced outputs with Neutrik black/gold XLR jacks
• Rack mountable (1 RU) - 1.75"H x 19"W
• Input impedance for Moving Magnet (MM) phono cartridge is standard 47kOhm
• Moving Coil (MC) phono inputs with three selectable load impedances: 50, 100, or 200 ohms
• Custom built in Denmark by Elberg, supplier to Radio Denmark's Elberg mixers
• Improved noise figures, more precise equalization curves, and more noise free switching
• Equipped with two identical inputs, making it possible to have two turntables connected at the same time
• Internal power supply (no wall warts)

back to top

Specifications

Power requirements: 230 VAC 50Hz or 115 VAC 60Hz
Frequency response: 18Hz to 54kHz (-1 dB)
Input impedance: 47k/47pF (MM), 50/100/200 Ohms (MC)
Gain @ 1 kHz: 46dB (MM), 71dB (MC)
Max. out: +24dBu (12.3 V)
Output impedance: 47 Ohms
Load impedance: > 600 Ohms
Deviation from RIAA-curve: max. 0.4dB
Distortion @ +10dBu out (20Hz-20kHz): 0.03%
Noise: -90dBA below 10mV in (MM), -76dBA below 1mV in (MC)
Channel separation @ 1kHz: 66dB
0 dBu = 0.775 volts
XLR balanced out: pin 1 (gnd), pin 2 (positive), pin 3 (negative) - for unbalanced out, connect XLR pins 1 and 3 for ground, and use pin 2 for unbalanced hot
To download the Elberg MD12 Mk2 manual, right-click here.

back to top

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 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. For connecting to consumer equipment with RCA Phono plugs, use pin 2 as hot (connected to the middle pin in the RCA plug), and pin 1 + 3 connected together as cold to the screen.

Next is a voltage selector 230 V AC or 115 V AC (50 - 60 Hz). Be sure the voltage selector is set properly to your power supply voltage and never change the voltage selector while connected to mains!!!

back to top

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. +17dB from 20Hz to 50Hz, then falling about 6dB/octave to
2. 0dB from 500Hz to 2120Hz, and then falling again about 6dB/octave to
3. -13.7dB at 10kHz.

To compensate for the cutting equalization, it is necessary to do the opposite when you play back the records, and that’s why you use a RIAA phono input. The RIAA eq curve is identical to the European CCIR curve.

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.

I want to thank Roger Wilmut for basic information about reproduction of 78s and allowing me to use his equalization settings. For a better understanding of the problems of reproduction of records, read the following articles (with a few edits from my hand), with kind permission, taken from Roger Wilmut's home page: Reproduction of 78rpm records.

back to top

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.

back to top

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.

	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.

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")
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

back to top

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. Some of the audio tracks included in the Music hall section of this site were transferred at speeds as low as 74 rpm, and I have come across records where the speed was as low as 68 or as high as 84 rpm.

To make matters worse, relatively few 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). I’m afraid it’s all rather rule of thumb; and the narrow bandwidth of old records doesn’t make it any easier.

Coping with these speeds is yet another problem. 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.

back to top

Setting the Correct Equalization

Always use your ears when selecting the presets below. 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

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	450.0 Hz	100.0 Hz	11.0 dB	12.5 dB
10	EMI	3.1800 kHz	500.0 Hz	50.0 Hz	10.5 dB	17.0 dB
11	NAB	1.6000 kHz	500.0 Hz		16.0 dB	16.0 dB
12	RIAA	2.1215 kHz	500.5 Hz	50.5 Hz	13.6 dB	17.0 dB

back to top

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 that, a mono phono 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. That’s why you can use a stereo cartridge. You will get the best results with a custom made stylus for this purpose. Ask your ”Cartridge Man” about purchasing the right stylus.

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

back to top

---

For further information on purchasing the Elberg MD12 Mk2 in US and Canada,
contact MasterDigital Corp.