Category: Photo gallery
Grzegorz Makarewicz "gsmok"
Note: 12.02.2012r. added the original diagram of the amplifier
Tube amplifier produced by POLKAT Wroclaw. The design quite controversial when it comes to opinions of holders. Unfortunately, you have to say "let the veil of silence falls on the quality of its assembling". I think, that pictures presented below speak for themselves. I do not mean, of course the damages associated with the normal operation and storage of the amplifier, but the details of construction and the way they are performed by a "qualified" person with blacksmith skills. I think, the best summary of the amplifier can be opinion of Romek (Romekd) presented on TRIODA community:
"Implementation of this amplifier is a complete crap. Photos that have been posted in the Gallery does not provide the full splendor of the primitivism and mediocrity of it's mechanical structure. You simply have to see it with your own eyes, being careful not to hurt yourself during dismantling this technical "miracle". If today, a high school student of electronics want to give any kind of work and it would be done in mechanical terms like this amp, it would not be highly rated. I think that the spiral electric heater is a true masterpiece of grace and elegance when compared to this amp. In addition, electrical design prevents any upgrades and improvements, and the amplifier is characterized by a significant level of hum and noise.
But there is something surprising and magical in this design! First, that after 33 years since the production of this amp it still works, and the measurement of electrolytic capacitors shows their full capacity and overall efficiency (at least in the copy I own). The second is the fact that the properties of the sound of this amp especially when it comes to music reproduction in the low and mid tones (treble tones do not sound quite as good) are pretty decent, not to say that they are very good!
According to several people who listen to this amp, it sounds much better than the modern, recently manufactured home cinema receiver Sony "STR-DB930," which seems almost unbelievable.
It seems even more surprising, given the fact that the design principles of this amplifier are not correct, for example:
- output transformer windings are not divided into sections - hence soprano leaves much to be desired, despite the fact that the core cross section of 17.4 cm2. seems to be large enough for a 25W output power,
- working of the output tubes in pentode mode and applying the typical TV tubes PL500, which will definitely have an impact on the level of harmonic distortion,
- using PCB paths, not a twisted wires to provide filament voltages and thus perhaps 50Hz hum.
Going back to the look of this amp, I think that its appearance had an impact that the amplifiers in those days were not as popular as radio or television sets, which in some cases were a great interior decoration.
However, this amp, despite its primitiveness, inclined me to return to my interests in old devices and tube amps."
So, welcome to the photo gallery. Let's start with a few photographs covering the entire amplifier.
Front view (Fig. 1). The front panel and a wooden enclosure with ventilation holes in the form of narrow slots.
Take off the cover (this requires special "rubber", screwdrivers, help of two friends and a bit of sedatives), and here the amplifier interior presents in all its glory (Fig. 2). I must admit that it looks really impressive. Ordered structure. Input preamplifier section protected with the metal grille. Different copies of "MELOMAN" varied in construction details. I would like to quote here Romek's opinion again:
Read more: Tube Amplifier "MELOMAN 25"