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UREI / Universal Audio 1176LN compressor for 200 € The proof! Do-It-Yourself Test & Review Part 1 / 3

How you can make it as electrical layman a hi-end studio equipment such as the UREI 1176LN build.
but now I have decided early this year from my
SAE Institute Berlin
with the vintage best grade 1.3 (97%)
excellent thesis



"The comparison of non-professional replicas of classic studio compressors with their original example of the UREI 1176LN to check the fidelity"


free and fully , ie including all images, sound samples, circuits, statistics and sources (see attached) to be published here on this blog
in three parts.



part 1:
basics and background to the devices

part 2:
The comparison, analysis, summarized


part 3:
survey statistics, audio samples, references , building instructions


complete thesis in PDF format (without audio)


complete thesis in PDF format (including audio)



Part 1 - Basics and background information on the devices
first Introduction
countless audio engineers, musicians, producers and sound people who are interested have probably already asked the question, why all the costs related to major studios such equipment assets. Is that not better? Are they worth it at all? Can not do by myself? Does that then just like the original? How much does something like that and what we must achieve in order to observe all acceptable results?


In this thesis is to prove that it is possible for electrical lay with remarkably little financial means acceptable and comparable results to achieve when it comes to replicas of famous studio equipment.


The basis for this study, the compressor
1176LN UREI
the company was chosen. Because of its more than 40 years without change its popularity, its unique sound and its impressive price accordingly, he is an excellent example for many other projects, such as equalizers, mic preamps or other classic analog devices.

for this compressor is needed in principle no more than 88
resistors, 42 capacitors, 14 transistors, 10 diodes, some other components such as amplifiers, transformers, cables and a little soldering artwork
. With a little time and training can be almost all analog studio equipment rig up yourself at home, so the idea that it is checked.

Nevertheless, this thesis is no instructions or exact description of placement and wiring of the said compressor, though this takes some parts of the outline.
(Note: Additional information such as

building instructions are in my references listed in Part 3
)

more but it is therefore to look at, or better yet to hear whether a replica can also meet the high standards which they are put in the original. Therefore, with the two devices processed signals to published survey purposes, because in the end is hearing the most sensitive instrument of man. In this listening test is in the broadest sense to include relevant items such as timbre, dynamics, controls and control behavior, but also subjective perception.

was built for this thesis by the author by using the internet published schematics and commercially available components, a copy of the
UREI 1176LN
to the feasibility and checking the cost of such a project. This is a maximum budget
of € 200 was set. This so-called clone was used to as the test object and comparison to one of the company Universal Audio 1176LN
produced.

The company Universal Audio has been found after the dissolution of the company UREI the task to connect their heritage under the leadership of the Sons of
UREI
founder Bill Putnam.


second The compressors

2.1 UREI 1176LN

He is certainly one of the most common devices in analog recording studios around the globe. Later in this thesis attempts to explain and explain why this is so, what technology is behind it, what distinguishes them and how it works.



Figure 01: An open UREI 1176LN Revision H (SN: 7652 + ...)

2.1.1 Historical background
It was Bill Putnam himself, the founder of Universal Audio
later UREI , who in 1966 was responsible for the original Design of
1176.
(FET) in various configurations to reduce the level of the compressor. He began to use the FET as a voltage-dependent resistors, in which the resistance between drain and source terminal of the transistor gate is connected by a voltage controlled.
Figure 02: A field-effect transistor as a voltage-dependent resistance His biggest challenge was to ensure it that the distortion of the FETs can be minimized and they are working within a linear operating range.

accommodate After several unsuccessful attempts, the FETs in gain reduction circuit, the Putnam decided to it directly from the input amplifier installed in a voltage divider.
the output of the 1176
takes a carefully manufactured Class A line level amplifier that was designed to with the later standard of 600 ohms
to work. The heart of this circuit portion is the output transformer, whose design work and a critical matter. Its primary function is the internal circuit of the unbalanced 1176 in a balanced line output and transform the output impedance 600 Ohm adapt. These two tasks are realized through the primary and secondary winding turns ratio also determined that the impedance ratio.

This transformer is a critical element of what the fact is debt that he has a few extra coils to provide a kind of feedback, which makes him an integral component in the output amplifier. Putnam spent much time perfecting the design of this extraordinary transformer and to sensitize the few capable suppliers.
The first major modification was the 1176
Brad Plunkett developed with the intention to reduce the noise of the circuit. The birth of the 1176LN whose LN for Low Noise stands. Numerous design changes followed, resulting in a total of at least 13 revisions of the 1176
.

2.1.2 Circuit and functional analysis
originally constructed in
Putnam
was built in 1176, an input transformer, this was later replaced by an electrical balancing by an operational amplifier.


Figure 03: Input of the original 1176 (with input transformers)
Figure 05: Gain Reduction control circuit of the 1176LN
The manipulated input signal is now used as a control voltage for the compressed audio signal FET. Increase the input level, the control voltage proportional closes the gate of the FET, the signal is compressed. This is done according to the set ratio.



Figure 06: Gain Reduction circuit of the 1176LN


Another highlight of the 1176
is its Class A output stage. It "is also reflected in the successful
UREI 1108 and is based next to the lavishly produced output transformer on the arrangement of two transistors (2N3053

) as a so-called Darlington Pair."

2.1.4 Tonal characteristics

"The 1176LN makes his special sound, which is characterized by its distinctive bite, instruments and voices and assertive presence in the mix"

The most characteristic features and the statements of renowned engineers 1176LN
seen as a strong organization crisp and involved compressor. He does not seem suitable for a full, soft compression to achieve, as it claims, for example from the LA-2A
. Rather, it is used for rock voices, cutting bass and drums as the effect of compressor rooms. Here are some opinions of recognized Engineers:
"They have an equalizer kind of effect, adding a coloration that's bright and clear Not only do they give you a little more impact from the compression, they then sort of clear things up. , maybe a little bottom end gets squeezed out or maybe they are just sort of excitingly solid state or whatever they are The big thing for me is the clarity, and the improvement in the top. end. " Jim Scott


" If you turn the knob fully counterclockwise until attack it clicks, the 1176 cease to be a compressor and acts only as an amplifier. Sometimes this is the perfect sound for a vocal. And of course the unit can be driven over, adding another flavor of distortion in case your plug-ins are maxed out! "
Ken Kessie
2.2 The replica

Figure 07: Photo-built replica of the
2.2.1 Historical background
addition to the familiar, mostly commercial 1176-clones such as the Purple Audio MC77
, Edward the Compressor
or
Empirical Labs Distressor
, try all the way to their unique sound and features such as the all-buttons-in mode to imitate the original, there are no commercial tests to implement this product yourself.

The most famous version is by the Dane Jakob Erland

that parses through this site
http://www.gyraf.dk
several different devices, including well-known equalizer and preamp, expanded and published his schematics. Developed by
Erland
design
1176 based on the F Ein geöffneter UREI 1176LN Revision H (SN: 7652 + ... ) revision of the original. The study in this work is based principally on the circuit Erland was, however, extended by the Australian
Mako Natsume
revised and with a range of alternative placement. The material used for the reconstruction
Printed Circuit Board (PCB) is also from Natsume
and was by him directly imported from Australia for the purposes of this thesis.

2.2.2 Circuit and functional analysis

The reconstruction is designed to point out exactly how to work as a beacon, which is expressed in the same manner and the same control signal flow. Deviations can be found at the used components. While the FET of the type used BF245A is still the same, are applied by European standards, instead of the other transistors 2N3053 pair use. take over the task of the output amplifier in the replica of the transistors of the type
BD135 and BD136
.
2.2.3 Special characteristics of the circuit
The aforementioned alternative placement options in Version Natsume, make this flexible circuits to a and project-cost entry. The most interesting possibility is to replace the original transformer provided the company
Lundahl LL5402
type
cheaper by the company Oxford Electronic Products Ein Feld-Effekt Transistor als spannungsabhängiger Widerstand (
OEP). This applies to both input and output transformers. Input transformers are optional instead of the original op-amp used.
developed by
Mako Natsume
circuit has been further optimized for hum elimination. This is done by a skillful centralization of all mass points. This prevents ground loop already within The circuit can develop.

For cost reasons, it was considered in this work for the reconstruction no need for a transformer at the input. The original was originally

Lundahl transformer in the main be replaced by alternative
OEP
assembly.

2.2.4 Forecast of phonetic differences
Since the reproduction of the aforementioned lower-cost OEP output transformer type A262A2E were used is to assume that this saving in the different frequency response is expressed. Especially in the high frequencies will occur losses since coil block for high-frequency signals. This is likely enhanced by components of inferior quality, since in this case the processing quality matters most. not
Because due to difficulties in procuring installed the exact values for the attack and release potentiometers, and putting it coupled capacitors 10 to 20% deviation from the nominal value are not uncommon, it is assumed further that the control times of planting slightly from those of the original are different.


Thanks to the complexity of the internal wiring and outstanding quality seemed processed components of the original is in the Construction of the replica, using commercially available components is not always possible to minimize any interference enough, so can a lower-noise ratio and large background noise in comparison be considered the original.

2.2.5 manufacturing the compressor Probably the most time during the manufacturing of the compressor took the component procurement. Most of the items could be purchased from local distributors in Germany, because this work has, however, also set a financial framework that had sometimes longer for cheaper alternatives, such as in obtaining a suitable housing, be searched. It was during production of the replica set a high value on accuracy of processing. This manifests itself on the one measure it in a very time-consuming process, the matching components. Especially in the choice of the resistors was measured at 0.1% tolerance. It was not uncommon that out of 100 eligible components only five quality characteristics, allowing it to be installed qualifying.


Second, the effort shows in the complexity of lay people quickly degenerated internal wiring of the device. Here was to make sure the correct signal paths sufficient interference sources, such as to isolate the toroidal transformer and thus to minimize interference.
An optimal grounding of the shield of the cable and limited to the minimum cable length also play a significant role in the fight against hum, noise and chirping.

END PART 1
Input des ursprünglichen 1176 (mit Eingangsübertrager)




Blockdiagramm des ursprünglichen 1176 part 1:
basics and background information on the devices



to Part 2: The
comparison, the evaluation concludes




part 3: Gain Reduction Kontroll-Schaltkreis des 1176LN survey statistics, audio samples, references, building instructions



complete thesis in PDF format (excluding audio)
Gain Reduction Schaltung des 1176LN
complete thesis in PDF format (including audio)

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