YPOC 1176 - nowoczesny klon kultowego kompresora 1176 o wymiarach 1 rack unit

YPOC 1176 - nowoczesny klon kultowego kompresora 1176

 

YPOC 1176, the start...

It‘s been my dream for several years to own one or two of the classic 1176 compressors but there were always two main reasons against it:

  • - No money available when offered two of these great compressors
  • - Only two different models available when I eventually had the money! Urei made 10 models with different circuits and of course they all sound different. This was not very useful to me for stereo applications.

So, for a long time I spent my money on other toys. However, last year I received a stage rider from a band, the sound engineer, Jens Schwemin required 5 pcs(!) of 1176‘s for his band. So, I now had the choice to sell my beloved Harley Davidson and look for 5 x 1176‘s or find another solution!´So I called him up and said "Hey, I can provide you with a few BSS402 and DBX 160‘s but I can´t get 5 x 1176‘s for your band". " No problem", he replied. "I can bring my 1176 rack with me!" I was a now very curious, who has 5 x 1176‘s in a rack? It was a bit like saying to me: "No problem, I’ll just bring my Rolls Royce Silver Shadow with me and you can drive it around town for a while! He came to the gig with his rack and I found out that his 5 1176 were selfmade "original" copies of the old stuff. But made with great attention to detail and with a lot of knowledge about the differences of the old circuits. From then on I’ve kept in touch with Jens Schwemin and he has provided me with a lot of useful information about the old circuits. He also suggested for me to take a look to the Gyraf website and to study their fantastic copy of the 1176 wich has a lot of useful details in their schematic. So, some months (and hardwork) later, I decided to start making my own 1176 clone. My intention was a more affordable clone of the old device that could bought by most engineers, but with the same sound/character of the old devices (even thought the originals all sound different and have their own particular identity...). Affordable versions are only possible when the main work is done by a pick an place machine which reduces the overal cost. So, I implemented smd devices as much as possible on the board layout and also implemented a small microcontroller with lcd display. The controller switches the four ratio relays and the bypass relay and the lcd indicates the audio levels and the ratio. This was built in a 1U rack unit as space is important to me and as we all know comes at a premium today. However, the 2 boards with all the smd parts and microcontroller include software are available for low money as well if you prefer to build your own clone. Just contact me or one of my distributors for details.

1176 - schematic
The schematic (click it..) or download hi-res

The schematic:

The circuit is based on the old "K version. I found out that the original transistors are very hard to find. So, I used smd transisitors as replacements but also placed thd footprints for the original transistors on the board. So, you can replace the smd transistors with the old „classical“ devices if you wish. However, we couldn‘t hear any real difference with different transistors (perhaps you might). The old transistors had tolerences of more than 60 %(!) 40 years ago and the developer of Urei had to implement a few intelligent parts in his 1176 layout to compensate the high tolerances of the original transistors. A simulation with LTSpice brought the same result. Almost every modern transistor with a near idendical hfe can do the job very well.

Note re the capacitors: I‘ve started with smd ceramic capacitors for the signal and control part of the board in order to keep the cost down. However, I‘ve also added space for polyester capacitors in the analog path that will have a better performance for audio applications. Ceramic capacitors tend to reduce their capacity if there is a dc offset between both pins. After an 1:1 compare between 2 clones with different capacitors I decided to use film capacitors for the future, cause the differences in the sound were easy to note.

About the resistors: I used smd metal film resistors with 1 % tolerances what have less noise floor compared to the old carbon resistors with 5 % tolerances what were used in the old devices.

The microcontroller board switches the „Ratio“ and „Bypass“ relays on the main board. The well known „All Button“ and „1:1“ modes are implemented as well. The „Up“ and“Down“ buttons will change the ratio values. The „Mode“ button will change the 2nd row of the display between „Output Signal“ and „Gain Reduction“. Please be fair and don´t expect too much exactness of the bargraph. The build in fet (BF245) still have some tolerances. “ The original analog display 40 years ago, indicated the level depending of the moon, the temperature and the political climate but not very often the correct level :-)“.

The output transformer of the Ypoc 1176 is one of the essential parts for „original“ sound of the unit. I decided to prepare the layout with footprints for 2 different transformers on the board. The „Lundahl transformers“ sound more „smooth“ and the „Walters transformer“ sounds a bit more like „Rock´n Roll“ (please forgive me these esoterical describtions). A bridge on the pcb board beside the output transformer will connect a 1k resistor load to the output transformer, just in case the desk input impedance is too high for the transformer. The rest of the circuit is almost original. The main transformer also has 3 different footprints on the board in order to use an other available transformers. This also helps to keep the cost down. The original low leakage diodes are replaced with modern BAV99’s that are available in a double sot23 package. I made the drawing of the schematic in a slightly different way so that it was easier for me to read. The drawing of the original schematic looked a bit confusing to me! By the way, the stereo link option is implemented like in the original model. However, you will find some nice add on boards in the internet what will link the Ypoc 1176 better compared to the original.

Specifications:

Physical dimensions: 480 mm x 44 mm x 180 mm
Power: 180 - 230 Volt, 8 Watt power consumption
Frequency response: 20 Hz - 20 kHz +/- 1dB
Connectors: XLR input and output
Power connectors: 230 Volt IEC-60320 socket