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Printed Circuit Boards by Emissionlabs.

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EE51 Moving Coil Board

Introduction

This high quality board is available as ready build version, but without the transformers on it. The possible transformers to use are, LL1636, LL1678, LL9226 or LL9226XL. These can be ordered with the board separate. If wanted, we mount them for you at the board. EE51 features two step up factors per transformer, a ground lift option, and adjustable needle damping. Depending on the transformer, gain can be set: 10x, 20x, 16x or 32x.

EE51

EE51 Order Number: 310-051-09. What is pictured here, is what you receive.

Transformers must be ordered separate. If wanted, we solder the transformers on the board for you. Then the board is ready to use.

Features:

Picture of EE51 with LL1636

Picture of EE51 with LL1678

Picture of EE51 with LL9226XL

Dimensions:

Gain settings

LINE
P/N
Low
High
 High Gain: Set jumpers H1, H2, remove Jumper L.
Low Gain: Set Jumper L only, remove Jumpers H1 and H2.
Ground Lift
Frequency
01
LL9226
LL9226-XL
 1:10 1:20 General purpose, Cobalt core, amorphous transformer. recommended Closed
5 Hz -- 100 kHz +/- 1.5 dB
02
LL9226
LL9226-XL
 1:10 1:20 Larger version of LL9226(or XL), with slightly less loss, and even higher frequency range. recommended Closed 4 Hz -- 90 kHz +/- 1.5 dB.
03
LL1636
 1:10 1:20 Cobalt core, amorphous transformer with internal shield. Lundahl's only MC transformer with internal Faraday shield. Best product for environment with a lot of mains hum. Closed or open. If open, shield is activated. 10 Hz -- 90 kHz +/- 1.5 dB
04
LL1678
 1:16 1:32 High Gain, Cobalt core, amorphous transformer. recommended Closed 10 Hz -- 35 kHz +/- 1 dB
Explanation page: To choose between MOVING COIL transformers LL1636, LL9226(or XL), LL9226(or XL)-XL and LL1678

Ground Lift Setting

Ground lift is needed in rare cases, but since we had one jumper connector free anyway, we implemented it. The GND Links are normally inserted, giving primary and secondary a common ground, and no ground lift is established. This is the normal use, probably for 98% of the cases.

In some cases, a set up suffers from hard to find hum. The place to solve it, is where the hum is generated, and this is not the EE51 board, but more likely a grounding error between various elements of the chain, also referred to as ground loop. It is worth a try to cut the signal ground between record player and RIAA amp, to see if this helps. Removing the "ground lift" Jumpers (these are two) will cut this ground connection. We do not say this will help, but it is possible.

In addition, the ground lift option has an interesting function with failure finding. This procedure is described further down in this text. For now, just insert both ground links. (Left and Right channel)

Needle damping Setting

Correct needle damping is important for good sound. I prefer for this the comparison with a car on a bumpy country road. Wheel contact is reduced when the shock absorbers are worn out. In such a case the wheels would make movements of their own, and road contact is poor. Good shock absorbers, will greatly improve road contact, which means nothing else, than the tires making the same vertical movements as the road itself.

It is exactly this what we expect from the MC needle as well. Regards the groove the bumpy road. We want the needle to follow this pattern exactly, and not shake and jump by itself. The answer to this is: Damping.

A first part of the damping is achieved by the manufacturer, inside the cartridge. This is a rubber part in which the cantilever is mounted. A second part is done by the phono amplifier, which is a load to the cartridge. The third and final part of the damping is done electrically, by an electrical load. The manufacturer specifies for this, the so called minimum load resistance. This means, any value from no load at all, to this minimum load value is possible. Which value exactly is case dependant. For this, EE51 has some resistors, which can be connected in a eight different ways, but such fine steps are not needed, and we advise those 5 step as in the table.

Best damping is found this way

As an example, let's look at the DENON DL103 cartridge, below here in the cartridge table. For best output signal, it needs 1:20 gain. Also you can see, DENON specifies a minimum load of 100 Ohms. In the jumpers table, when looking in the 1:20 column, we see there, the VERY SOFT setting gives 118 Ohms. Probably this is a good setting for the DL103. It depends however also on the tone arm, and needle pressure you have chosen. So it is recommended to try also the setting SOFT, resulting in 98 Ohms. The setting MEDIUM would probably mean too much damping, but as said before this is very individual, and you need to try it. Whereas HARD and VERY HARD is probably too much damping.

Too much damping gives loss of high frequency, and loss of stereo information. That is because faster needle movements (as needed for high frequency) get damped a lot more. (The stereo information is coded in the vertical needle movement, which get damped just as well)

Not enough damping leads to reduced groove contact during loud sound parts, which is a form of distortion, and loss of stereo information. In severe cases it can even cause the needle to skip some grooves with very loud music parts. This is mistakenly judged sometimes as a bad adjustment of the tone arm.

You just need to find the golden middle by hearing tests.

Not mentioned in the table, but a useful help, is simple remove the Jumper A, in any of the other settings. If A is removed, the damping is always "Very soft". Like this you can switch for instance from Hard (A+B+D) to Very Soft, by only remove Jumper A.

 

Damping

A
B
C
D
GND
Cartridge Load at 1:10
Cartridge Load at 1:16
Cartridge Load at 1:20
Cartridge Load at 1:32
Very soft
X
470Ohms
184Ohms
118Ohms
46Ohms
Soft
X
X
390Ohms
152Ohms
98Ohms
38Ohms
Medium
X
X
X
320Ohms
125Ohms
80Ohms
32Ohms
Hard
X
X
X
X
280Ohms
109Ohms
70Ohms
27Ohms
Very Hard
X
X
X
X
190Ohms
74Ohms
83Ohms
19Ohms

PART2. Building instructions:

 

These PCBs fit exactly into Hammond case, type 1590B3. This nice box, you can order it in five colors. Or, take any other box you like.

Never test an MC transformer with an Ohms meter. This will magnetize the core permanently, sound will be distorted. For this reason, buying second hand MC transformers, is generally not a good idea.

 

Drilling holes for the connectors

Before soldering parts on the PCB, it can be used as a template. Above each connector is a dummy hole in the PCB. This can be used as template for the drilling holes. Here is a hint you may like: When drilling holes in Aluminum, use alcohol as a lubricant, and then drill at low speed. This gives a much nicer drill hole. You won't believe this if you have never tried it.

After drilling, the result should look like this.

 

Grounding:

The PCB is double sided grounded, and the two mounting screws are also the ground connections. In general, screws of PCB's tend to get somewhat loose over the years. To prevent a bad ground connection by this, there is also a soldered ground connection. This should be connected with a wire, to the ground plug of the metal case. If the chassis is colored or surface treated (such as passivated aluminum), remember to clean the metal beneath the screw.

In addition to the four RCA Connectors, the metal case needs also a ground screw at the outside, which connects to the record player, with a simple single wire. Since Dec 2023, this ground screw is also provided, a nice gold plated version.

Settings for some cartridges

The EE51 board works with most cartridges needing a gain from 10x to 32x.

The table which is linked here, will quickly assist with the choice.

If a box is green, this is the recommended setting.

If a box is black, so no number is visible, the output signal is much too high or too low.

Special Situation, blue boxes. This may be useful for noisy pre amplifiers. A blue box generates an output signal above normal, thus improving signal to noise ratio. However it gives higher load to the cartridge, and needle damping becomes higher. This may be compensated by choosing the lowest possible damping. In case you want to go this way, ideally you can choose a green and a blue box. So in case the blue box generates too much damping, you can still go for the green box.

Here are some examples, considering the choices.

  1. Denon DL103. One of the most popular cartridges ever. LL1678 would be possible to use 1:16, it gives 3.9mV. Using 1:32 setting would give a theoretical 8.8mV, but it doesn't work well, otherwise this box would have been blue. The 8.8mV will not appear, because load on the cartridge is very high. Also it will give high frequency loss. So LL1678 makes only sense for DL103 when you already have a pair, and you want to try if it works perhaps. A better choice is the LL9226-XL transformer and set it for 1:20. This gives a nice 4.4mV, which is very good, and cartridge load is optimized, as with all green boxes.
  2. Fidelity Research FR-1 Mk3F. In the table, it has a blue box with LL1678 and 1:16. If your pre amplifier is too noisy, this by itself is the real problem. It may be solved however by choosing this blue box, and get 7.4mV signal. However there is some risk, because when it appears wrong, there is no green box setting. The official, recommended use for this cartridge is 1:10 with the transformer LL9226-XL This gives even 4.8mV which is even a very good value. So here, the recommended choice is LL9226-XL. Or, use LL1678 which has higher needle damping as intended for the cartridge.
  3. Benz Wood M2. It has only a blue box, and it is the only option anyway for this curious cartridge. Using a blue box means the damping may be higher as expected. From our side, we can only say it is a little bit risky to have only a blue box. Ask at Benz company if they advise this.
  4. Benz Micro Reference S Copper. This is a nice one for noisy pre amplifiers. In that case use the LL1678, and try it for 1:32. Though 32x gain is quite a load for the cartridge, it can take this because impedance is an incredible low 5Ohms. Even so, minimum load is low, with 40 Ohms. This is why the blue box is highlighted. In case some high frequency is lost, you can still go for the green box and get 4mV, which is a nice value. Some other brand cartridges give only 3.2mV and these are also good.

Complete table.

Fault finding hints

This MC unit designed to work right away. If there is hum however, the EE51 board has a some modes for fault finding

Fault finding methods.