Golden Age Project PRE-73 Jr MKII Manual

Golden Age Project Ikke kategoriseret PRE-73 Jr MKII

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W W W . G O L D E N A G E P R O J E C T . C O M

PRE-73 Jr MKII

INTRODUCTION

Congratulations on choosing the Golden Age Project PRE-73 Jr MKII microphone preampliﬁer!

The PRE-73 Jr MKII is a one-channel vintage style microphone- and instrument preampliﬁer. The signal path

uses only discrete components like resistors, capacitors and transistors. The in- and output is transformer

balanced, using two different transformers, each one optimized for its purpose. This is the way audio compo-

nents were built before integrated circuits became available.

Integrated circuits are small and cheap and widely used in most modern designs. It is clear though that audio

components built with modern technology doesn´t always provide the best perceived sound quality or the type

of character that the modern user desires.

On the contrary, the subjective sound quality delivered by vintage equipment is often prefered over the one

delivered by modern units, a situation that is even more obvious now when music is recorded with clean-

sounding digital audio equipment.

This is the reason why so many vintage audio components are cloned and produced again and also why the

vintage originals are often very expensive on the second hand market.

The circuit used in the is similar to the preamp section in the classical 1073 module with a PRE-73 Jr MKII

corresponding sound character that is warm, punchy, sweet and musical. These classic characteristics have

been heard on countless recordings through the years and it is a versatile sound that works very well on

most sound sources and in most genres.

The essence of this sound is now available at a surprisingly low cost, making it available to nearly everyone.

FEATURES

- Vintage Style class-A electronics. No integrated circuits in the signal path. No surface mount components.

- GAIN switch range 20 - 70 dB.

- Selectable two position high frequency AIR boost eq, 3 or 6 dB @ 30 kHz.

- Selectable 6 dB/octave two frequency high pass ﬁlter at around 40 (HP1) and 170 Hz (HP2).

- Switchable phantom power and absolute phase.

- A high-impedance instrument input for any sound module, electric guitar or bass.

- A simple signal LED indicator.

- The output level control makes it possible to do ﬁne gain adjustments and also to overload the main gain stage for more character and then

lower the signal to a suitable level before the output stage.

- Combo XLR/TRS input jack and separate output XLR and TRS jacks for ﬂexible connections.

- Insert jack for inserting EQ´s and other units.

- The circuit board is prepared for the Carnhill input transformer.

- External power supply to avoid interaction with the audio circuits and transformers.

- The small format makes it possible to mount 4 units in our 19-inch rack kit, the UNITE MKII.

- A solid build quality that will last many years of normal use.

W W W . G O L D E N A G E P R O J E C T . C O M

CIRCUIT DESCRIPTION

The signal ﬁrst enters the input

transformer. The primary of the

transformer has two windings

that are connected in series which

results in an input impedance of

1200 Ohms which is suitable for

most mics.

The transformer is followed by the main gain stage using

only three transistors.

The signal then goes to the insert jack and from there on to

the

output level potentiometer and then to the output stage.

This stage again only uses three transistors, the last one in

the chain is a hefty 2N3055 power transistor run in class-A

mode, driving the output transformer.

So, all in all, the complete signal chain only contains a

maximum of six active elements. Compare that to the big

number of transistors that are usually used in one single

integrated circuit!

MODERN VERSUS OLD

It is true that there are some great IC´s available today that

achieves very low levels of static and dynamic distortion.

The simple circuits that the PRE-73 Jr MKII uses, and even

more so the transformers, cannot match the low distortion

speciﬁcations of modern IC´s.

It is the distortion components that imparts a sound char-

acter to the audio signal and, if the distortion components

are of the right type, this is a good thing since it makes the

recorded voice or instrument sound “better”, more musical,

more pleasing to the ear. This is one reason why vintage

style units are so popular today.

This is not to suggest that modern, transparent sounding

audio circuits is a bad thing, sometimes they are prefered

over colored ones. It´s all about taste and it depends on the

genre. For most modern music styles, color and character

is deﬁnitely a good thing.

And doesn´t it feel good to use audio components built

according to the old, minimalistic approach where one can

follow the signal from one discrete component to another?

USING THE PRE-73 Jr MKII

Using a preampliﬁer is not rocket science. Here are some

points though to help you getting the maximum out of the

PRE-73 Jr MKII:

- Connect the cable from the power supply to the 24V AC

connector at the back of the PRE-73 Jr MKII. Power on the

unit with the POWER switch on the back panel.

- Connect your microphone to the input XLR/TRS combo

jack on the back panel.

- Engage one of the positions of the High Pass ﬁlter if you

want to roll off the lower frequency range. Set the switch in

the center position to remove the high pass ﬁlter from the

signal path.

- Engage one of the two positions of the AIR eq boost if you

want to add some level in the upper frequency range. The

center of the boost is at around 30 kHz. The switch center

position = OFF.

- If you want the smallest amount of coloration, always set

the OUTPUT level potentiometer at or close to maximum

and adjust the output level with the stepped GAIN switch.

- If you want more character, turn the OUTPUT level poten-

tiometer counterclock-wise and increase the gain with the

GAIN switch. This will drive the input gain stage harder and

provoke more character from it.

- You can also overdrive the output stage and the output

transformer for even more character, but you will then usu-

ally need a level control after the PRE-73 Jr MKII in order to

reduce the level to the appropiate one. This level control can

be a passive damping device (like the Shure A15AS XLR

switchable pad) or an input level control in the unit follow-

ing the PRE-73 Jr MKII.

The Shure A15AS is also useful for reducing the ouput

level if the PRE-73 Jr MKII is connected to a unit that has a

standard operating level of -10 dBu. The standard operating

level of the PRE-73 Jr MKII is +4 dBu, the output level into a

600 ohm load will be about 1,23V.

- Instruments can be connected to the TRS input at the front

which has an input impedance of about 100 kohm. Press

the DI switch to engage this input. A source at the back can

remain connected.

- Engage the +48V phantom power for any mic that needs

it. It is a good procedure to always disengage the phantom

power and wait for about 10 seconds before unplugging the

mic.

- The phase switch simply reverses the phase by revers-

ing the wires from the secondary winding of the output

transformer. Reversing the phase of the signal is useful on

a number of occasions, one example is phase reversing the

the lower mic of a snare drum to make it sum in phase with

the upper mic.

- There is an unbalanced Insert jack located at the back

panel where you can insert equalizers and other external

effect units that has an operating level of about -10 dbu to

-18dBu.

Send is on “tip” and return on “ring”.

WARRANTY

The PRE-73 Jr MKII is built to last. But as in any electronic

device, components can break down.

There is a 1,0A slow blow fuse located inside the unit. If the

unit dies, please check this fues. If it has blown, replace it

with a new one. You can also try with another 24V AC adap-

tor if you have one available.

If this doesn´t help, or if the unit has another problem, it will

need repair and you should then contact the reseller where

you bought the unit.

The warranty period is decided by the Distributor for your

country. The Distributor will support Golden Age Project

resellers and end users with repairs and spare parts.

REGISTRATION

You are welcome to register your unit at our website:

www.goldenageproject.com

---------------------------

I would like to thank you for chosing the

PRE-73 Jr MKII!

I hope it will serve you well and that it will help you

in making many great sounding recordings.

Bo Medin

Vintage character for modern ideas!

Produkt Specifikationer

Mærke:	Golden Age Project
Kategori:	Ikke kategoriseret
Model:	PRE-73 Jr MKII

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