Super Priboj Clasa A

8/10/2019 Super Priboj Clasa A

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MODIFY Priboj FOR valve sound

I did a find in a grocery store. Among the rubble behind the counter, I saw an old rrhck the brand

Priboj-50, which I managed to buy for 60,000 Rubles (about 200). Dragged it home, picked from the

output transformers which I connected to a pair triodkopplade EL34's and said - "Not bad at all." And sowas born the idea to make something more of Pribojen. Thanks to its designer, Volodja Starodubtsev,

has a pair of output transformers of extremely high quality.

Anyway hemmapulare offered to pick up a new Priboj 50 UM 204 GB of parts from an old (including

output tubes), and thus the opportunity to get their own arguments in the discussion of the tubes any

excellence across the transistors.

What then is to modify off transistor sound? I list the following elements:

Ping Cup schedule must be made easier (in all things, including the number of components and wires).

All components, including resistors, capacitors, connectors cables (and SOLDER!) Including also thepower supply must be carefully selected to maximally harmonize with each other for good sound.

The amplifier must not be motkopplad matter how small negative feedback than could possibly be.

The output must be active and not dependent on the instantaneous value of the signal and not exceed

half the nominal speaker impedance (this criterion only a triodfrstrkare working in Class A).

Each channel shall have a separate power supply to be able to provide power supply free from any

interference and hum. (This is especially important for precisely triodfrstrkare compared with

pentodsteg)

For entry into the "two-stroke Paradise" we have to make some sacrifices.

When the pipes 6P3C triodkopplas and is in Class A lost about 3/4 of the possible output power.

Therefore, regardless of "softclipping" by oversteer, DELIVERING NOT MODIFICATION OF YOUR

SPEAKERS HAVE A SENSITIVITY LESS THAN 90dB/W/m!!

According to the textbook, we have the following efficiencies for different amplifiers

Pentode Class B -78%

Triod Class B -35.3%

Triod Class A -25%

Unfortunately, these values are also theoretical because non-ideal anodkaraktristika. For Pribojens6P3C-pipes, we lack curves when the pipes are as triodes. Therefore we connect quickly up a tube to

obtain the required parameters. We have in mind that the max anodfrlust Pamax = 40W and maximum

gallaerfrspnning Ug2amax = 300V.

Between the anode and screen grid is a resistance on 1Kohm. Taking up the parameters takes no longer

than necessary. We are currently just the ratio Ia / Ua (anode current / grid power) at UG1 = 0 (at 0V

grid voltage). See Figure 1. The major changes in the anode current relationship seems linear with a


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slope equal to the pipe internal resistance Ri = (Ua / Ia) = 200ohm, and mild changes non-linearly (at Ia


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we obtain turnovers near the ones we were looking for. We connect a load to 4ohms 8ohmsuttaget we

have a

turnover in 1300. Quite close to the ideal. And if we connect an 8ohms load to 4ohmsutaget where

we connected in parallel windings, we obtain an equally perfect alignment.

After these theoretical excesses, we can simply restart the modification of our amplifiers.

The diagram shown is based on ideas from the 40-50 century, but meets practically all performances

if the pipes superiority over the transistor.

Short on schedule. The thick lines in the figure and the components should be connected as close

together as possible, and the other completely behind schedule. cable between A and B, but also to

output transformers shall be selected map high sound quality. The same also applies to C2,

C3 and C4.

Although the output transformer seems completely symmetrical it can be connected between the pipes

anodes and speaker connections in several ways. With regard to the correct phase, different

connections tested and test for the best sound.

For the amplifier to get two separate 225V power supply, power adapter must be made of

some. Thus: Parting 192v windings (links 1-4) and 115V windings (15-16).

The windings of bias (50V), primary (220V) and filament (6.3 or 12.6V) should not be touched. We have

now

two windings with respective 96V or 57.5V. Each bobbin wound now at 30 turns of copper wire (I

used 0.8mm - went to about 9m/bobin) giving additional 11.5V. Connect the three windings

(96V, 57.5V, 11.5V) on each spool - with the right phase, to thus get two 165V voltages. These

rectified and filtered, and then receives two 225V DC voltages.

(One tip is to use the PSU board and the rectifier is there, cut copper tracks and drag

new wiring. Bias voltage is not used at all, but keep an eye on voltages glow! Same

method can be used to assemble each amplifier. clear the cards gently from

components and use the existing wiring pattern as far as possible. Z. A.)

When the amplifier is ready, do the following: connect a resistor of hgtalaranlutningen, and set

amplifier next to a turned-on television.

If the light does not go off or the TV is disturbed out after you press the "ON" position, relax and verify


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that tensions do not differ more than 5%. Measure the data if you like. So it looked like to me:

Frequency Response, 4ohm 6Hz - 40kHz

8ohm 15H-45kHz

Put at 10% THD 12W

S / N 95dBA

Sensitivity 400mV

Input 500Kohm

After completing his subjective measurements, we can now listen. But I'm wary of reviews, because I do

not want to take the blame on me by readers, for having promised way to "stroke-paradise." But I hope

that first impressions still be that the base has become more energetic and better articulated, to human

voices become more physical, natural and a significant broadening dynamics.

The great work remains after the onset of the amplifier. The most difficult thing now was to achievetonal balance, after carefully trimming and balancing of the components and cables. The output tubes

and transformers still gives a certain coloring of the sound, especially in the midrange. But you'll still feel

satisfied - amplifier consider all the benefits far its disadvantages.

Finally, I hope that hemmapularen should not fear that modding is not too difficult. With good touch

with a soldering iron and a bit of basic education - as Peter Kvartrup successfully demonstrated - all will

succeed.

A.M. Likhnitsky and Audio Magazin SPb, Russia

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Super Priboj Clasa A