This is the exquisite preamplifier that is built in two boxes, one for the power supply and one that includes a tube RIAA and the preamplifier. The tubes are all current source loaded and the pre is parafeed coupled to a 1010/1701b Sowter transformer. The tubes used are 5842/417 for the RIAA and EC8010 for the preamplifier.
The preamplifier pictured above is current source loaded and parafeed coupled to a 1010/1701b Sowter transformer, for the highest sound quality. There are two versions of this preamp, one with a pair of 5842/417 tubes for the made in USA tube admirers and one with EC8010 for the Made in West Germany product lovers.
This beautiful preamplifier with the Sifam Vu meters uses a pair of 417 / 5842 tubes that are parafeed transformer coupled for balanced output, there is also included a solid state RIAA pre. The pre was tested and performs dead flat from 20Hz to 25Khz.
This is another beauty, using a pair of 7788 tubes and it is transformer coupled with LL1671. Note that part of the power supply is in another box.
It also includes driver card with TL074 for the Vu meters and a phono RIAA pre with ICs for vinyl records.
The Preamplifier Project That Was Built On A Shoestring
This peculiar little preamplifier was commissioned on a very tight budget so note that no fancy transformers or exotic parts were used. The 417/5842 pre is plate transformer coupled, there is also the choice of balanced (low Z input) or unbalanced input (high Z) . The measurements were done using the balanced input and the balanced output @ a level of 5 Vrms.
Although there is no frequency correction provision in the pre, note that the frequency response is flat from 30Hz to 30Khz and only @ 17.6 Hz it is down 1.9 db.
Here is the THD @ 5 Vrms output.
PHONO PREAMPLIFIERS WITH RIAA eq
R.I.A.A @ Work using 5755 - 6072 tubes in cathode follower configuration.
R.I.A.A @ Work. This is the new over designed power supply that is tube regulated and employs one GZ32 one 6V6 one JAN5842 and one 5651A.
This is a new radical design for a phono preamplifier with RIAA equalisation, constant current source loaded with a quad of 5842 tubes.
Now that the digital audio technology reached its peak and anything sounds like everything, I felt the urge to step back to the day mono ruled.
It was a resistless affair for me to build this mono phono preamplifier that is based in an old RCA schematic I came across in the net, that includes four different equalisations for old LPs.
Needless to say that no phono preamplifier is of any use without one or two turntables.