I noticed that there´s quite little info about this module on the web although it´s probably the most sought after transistor preamp from WSW/Siemens Austria.
The UA module was produced in a fairly large quantity in the 1960ies and 1970ies for broadcast companies - foremost Austria´s own ORF, but also other countries e.g. Yugoslavia. In the 1990ies large quantities of it were dumped. The guy in the ORF surplus storage reported about hundreds having been thrown in the trash just there.
The UA preamps were never used in a console´s channel strip like Neve 1073 and didn´t attract any attention by the time they were sourced out. With the simple ELA M-grey frontplate they look very unspectacular. Surviving specimen of the 811403 preamp are very rare. It´s an excellent sounding module - easily one of the very best transistor preamp modules ever made. The large and heavy transformers are of outstanding quality. The module offers three different input impedances that result in different sound coloration and gain range.
The rack type for this module system is called "Wiener Wanne" and is a proprietary heavy duty non-19" format, not suitable for modules by any other makers or german Siemens modules.
DIYing this preamp might be virtually impossible as the transformers were manufactured in house by Siemens Austria and are not available. Probably they are to a large degree responsible for the sonic character of the module. Resistors are VTM metal film 1% tolerance. The transistors might be quite difficult to source today.
Here are some pics:
Input transformer
Output transformer:
This is one of mine. Seems to be a later example. It also has been recapped professionally - maybe by ORF-service or Siemens directly because it has an unusual quality control sticker from the Siemens-Prüffeld on the outside.
