Petrof P 135 K1 Upright Piano


P 135 K1 upright piano is ranked in to the highest, master built upright piano series. These are upright pianos with the greatest sound potential and that are therefore favourites of demanding professional pianists. They are suited not only to apartment interiors and music schools, but also piano recitals within an orchestra or in different public stages.
The instrument provides wider possibilities for a player to control the sound. The upright piano is handled by 3 foot pedals and a hand lever.

Technical description of the PETROF 135 K1 upright piano
PETROF 135 K1 upright pianos are designed by and produced in PETROF company in the Czech Republic. P 135 K1 upright piano is the highest upright piano model with the greatest equipment and is fit for demanding players, for professional use, for specialized music schools. As with all PETROF upright pianos, the P 135 K1 is marked a „European Excellence“ label, which guarantees the European origin of the instrument.

Technical parameters of the PETROF 135 K1 upright piano


Robust construction from spruce, 5 vertical posts, made in PETROF company.

The solid stable rim supports the tuning stability of the instrument and ensures its total stability. The special constructive modification of soundboard mouldings enable clear and long-lasting tone of upright piano.

Iron plate

PETROF construction, harp shape, agraffe construction, robust, made from grey cast iron in the Czech Republic. Plate working is done in PETROF factory on special CNC machines. Top finish is consistent with surfacing of grand piano plates.

Agraffe construction of the iron plate enables exact scale of strings and is the sign of the most advanced upright piano construction.

Hardware fittings

Massive polished brass, lacquered. Made in the Czech Republic.

Hardware fittings are lacquered, corrosion resistant and do not require any maintenance.


Special beech plywood type Multiplex. Original veneer thickness 2 mm compressed to the density 800 – 850 kg/m3 (= 6 veneer layers/cm). High moisture resistant glue.

The pinblock is highly resistant to atmospheric changes (e.g. humidity). It guarantees high stability of tuning.


The soundboard is made from solid spruce wood in PETROF company. It is shaped into wedge block. Its active surface is 1,2222 m2.

PETROF sound boards have to go through a special long term moisture conditioning and care during the whole production process which guarantee their exact and equal moisture content. This process increases its resistance to cracking due to climate changes. Surface treatment with PUR lacquer raises its resistivity against climate changes.


The ribs are circular shaped and are made from European spruce wood in PETROF factory. The cross rib is produced from beech wood. The board is enforced by 10 ribs.

The ribs from European spruce supports a crown stability of the sound board.


The bridges are made from solid beech wood in PETROF company.


Agraffe construction in the whole range of 88 tones.

The agraffe construction enables the exact scale of strings and is the sign of the most advanced upright piano construction.

Tuning pins

Steel, nickeled. The pins are produced with high exactness in the Czech Republic.

The tuning pins are corrosion resistant.


Steel wire Mapes USA, Röslau Germany.
Copper winding Degen Germany.
Made in PETROF factory.
Longest string 1135 mm.

The strings are made from string wire of the world´s finest quality.

Hammer heads

There are used top German hammers Renner or Abel in the P 135 K1 upright piano.

Hammer heads are voiced for romantic rounded tones, characteristic for PETROF instruments.


Renner original action.
Petrof moderator.
Action is installed and regulated in PETROF factory.
Prolongement function controlled by a middle pedal.
Moderator controlled by a lever (left, underside of key bed).

Renner action is very quick, with good repetition, enables good control in creating tones, provides great feeling from play. It is raited as the world wide best.


Renner original dampers.
High quality special French felt (Laoureux).
70 dampers.


Keys are produced from the finest spruce wood in PETROF factory.
White and black acrylic tops – Polyplex Sweden.

The keys are carefully individually balanced for 48 – 52 g. The keyboard provides very good feeling from play.

Key bed

Robust spruce sandwich board, two-sided covered by thin chipboard and counterveneer.
Key bed is fixed to cheeks from below by analogy to grand piano key bed.

The key bed is highly resistant to deformation which is a prerequisite for stable regulation.


Pedals are made from solid brass, produced in the Czech Republic.
The upright piano is equipped with 3 pedals: the right lifts the dampers, the left draws the hammers closer to strings, the middle controls prolongement.
Moderator is controlled by hand lever, placed left underside of key bed.
Assembly, regulation, voicing of the upright piano

Whole production and assembly of the P 135 K1 upright piano is held in PETROF factory in the Czech Republic.

Mechanism of the upright piano is carefully and repeatedly regulated for standard values so that regulation is stable in the long term, upright action provides good feeling during play, characteristic for European upright pianos.

Hammers are voiced for soft romantic tone, characteristic for PETROF upright pianos.