Rörförstärkare PhonoGraph 60 

Idea which inspired the creators of phonograph PG60, was to build a classic amplifier based on proven designs and technical solutions of the highest quality components, so as to obtain the orthodox and sound quality, which was marked by a solid tube devices manufactured in the 50s of the twentieth century. Task reckless and admirable, but the design Phonograph PG60 proved to be a success - so far several dozen copies of the amplifier, which found consumers both in Poland and in Germany, the Netherlands and the United Kingdom.

A few words about Williamson amplifier design and the phonograph PG60

Williamson amplifier is described by D.T.N. Williamson in 1947, Wireless World high quality amplifier. His power level has a characteristic structure, gave a very significant contribution to the development of the art hi-fi. It is one of the first embodiment described in the literature aimed at obtaining a construction as best performance sound reproduction. It can be considered as a first-class amplifier hi-fi.

Technical advantages of the Williamson are:

- Very low harmonic distortion and intermodulation output stage with high energy efficiency.
- Low internal resistance, high resistance to changes in load impedance. This is of great importance in today's loudspeakers, which have complicated switches and their impedance varies strongly as a function of frequency.
- Redundantly designed transformers, increasing the true weight of the device, but allows for excellent low frequency transmission.

PG60 phonograph amplifier consists of four basic functional blocks. And the degree of pre-inverter (phase inverter) are constructed on the lamp 82 degree initial ECC is directly coupled to the operating phase inverter load shared system characterized by a very high symmetry. The signals from the phase inverter are not given directly to the output stage, but used an intermediate step in the system symmetric differential amplifier built on the lamp ECC 99 (the driver). This guarantees delivery to the degree of the output signal of large amplitude, and low distortion.

The output stage is built on the legendary tetradach streaming 6L6GC and works in class AB1 (first grid work only in the negative voltage). For output power 10 W lamps work in pure Class A. The output stage is coupled to the output transformer in ultra-linear system (ultra-linear).

Ultralinear system was patented in 1936 by Alan Blumlein, and first applied practically in 1951 by D. Hafler and HI Keroesa. Its characteristic feature is the local feedback loop by connecting the screen grid to tap the primary winding of the output transformer. Unhook is positioned so that the grid gets a 20 - 50% of the variable component of the anode voltage. In this way, the lamp operates in an intermediate mode between the triode (100% shielding grid signal) and pentode (0% of the signal on the mesh shield). This arrangement provides a very low harmonic distortion and intermodulation and low internal resistance only slightly worse than the triode with incomparably higher energy efficiency.

Output transformers are performed on the multi-layered moldings of a suitable coupling EI core cross-section that provides high transmission of both low and high frequencies.

Lamps final degree work with automatic constant current of rest (auto bias) which ensures stable operation of the amplifier in the whole period of operation by eliminating entirely the need for any regulation and control by the user throughout the period of the so-called. lamp life. Assembly technology is based on a combination of spatial and assembly of printed circuit techniques. This ensures complete repeatability produced amplifiers.

Electrical audio track has been designed as a pure tube technology dual-monoblock, which eliminates crosstalk and interference between channels penetration. Semiconductors have been used only in soft start circuit transformer and power delay lamp output stage of the amplifier. As the coupling elements have been applied polypropylene capacitors MKP.

The power supply of the amplifier, in order to achieve the correct impulse response, the battery runs low impedance (LOW ESR) electrolytic capacitors with very high capacitance of 2000 mF.

Appreciation

Phonograph PG60 is a beautiful audio. Housing is not like traditional tube amps, but rather a first-class design type Marantz. The housing is made of laser cutting technique entirely of pickled steel sheet steel polished - it looks very monumental. At the same time it is a fairly large device (430 x 375 x 120 cm - without lamps) and extremely heavy (30 kg). Front is thick asks steel - cut two vertical cavities in which the blue clearances installed with lighting (from the inside). In this way, these two vertical slits lit a gentle blue light during operation of the amplifier.