Kenwood KR-V6050 Amplifier

The KR-V6050 is an Audio Video Receiver manufactured by the Kenwood Corporation of Japan. This is a high specification amplifier with Pro Logic 3, RDS tuner radio, and servo volume control. This is a 5-channel amplifier, providing a surround sound experience. The front (left and right) channels produce 65 W each in surround sound mode. The centre channel is 65 W, and rear (left and right) channels 20 W each. In stereo mode, where only the front (left and right) channels are active, the power output is 100 W per channel, at 1 kHz, 8 Ω DIN.

There was also the KR-V7050, which had DSP/DSP Logic, which the KR-V6050 did not have. Both models were identical for the most part with slight differences in the way the speaker impedance selector switched worked, and remote control design.

Designed and manufactured in approximately 1992, this amplifier does not have Digital Theatre System (DTS) decoder, nor does it have 5.1 Channel RCA DVD input sockets, however what it lacks here, it makes up for with a superb sound quality and bass reproduction.

All five channels are Class A circuits consisting of complementary transistor pairs: 2SB1531 + 2SD2340, 2SB1493 + 2SD2255, and 2SB1470 + 2SD2222 in a TOP-3L-A1 package.

This is a rugged amplifier measuring 440 mm × 147 mm × 403 mm and mass 11.4 kg. Part of the reason for the size and weight is the huge conventional transformer employed within the power supply section. It is a lovely bit of robust electronic engineering from the 90s, which would be hard to find today.

Servo Controlled Volume

Amplifier experts will be interested in the master volume control, which is servo driven by a d.c. motor.

When new, this amplifier comes with a RC-R0600 remote control, which operates the servo driven volume control.

Protect Mode

This amplifier has one of the best protection circuit designs, and together with the heavy-duty power transistors, it would be difficult to damage it. However, in the event that you manage to short the speaker outputs, the amplifier will flash PROTECT on the front display panel. If your amplifier is flashing protect, then it is best to disconnect all the speaker wires from the back sockets to make sure a faulty speaker does not cause it. You should also ensure that the volume control is set to zero level. If the volume is set to full then it may also display the protect error. If you find that your amplifier is still showing the protect error, then chances are that you have damaged the internal circuitry and power transistors, and it will require repair by a qualified engineer.

The transistors used in this amplifier are very hardy and it would take a lot to damage them. The 2SB1531 + 2SD2340 pair have collector current rating (Ic) of 10 A. The 2SB1493 + 2SD2255 pair have Ic rated at 7 A, and the 2SB1470 + 2SD2222 pair have Ic rated at 8 A.

Bass and Treble

The bass and treble analogue circuits provide a response of ±10 dB. The treble is noticeable when you turn it up, as you will hear a high frequency hiss which is a good sign. Compared to the Sony STR-DEXXX range I think that this Kenwood amplifier has better bass and treble response.

The two-channel stereo from the front speakers is out of this world and even with a cheap pair of test speakers, the sound is noticeably better.

This amplifier allows you to connect two sets of speakers for the front (left and right) channels. You can then select between Set A or Set B, or both. An internal relay does the switching for the speaker sets.

Problems and Repair

This is a complex amplifier and it will take an engineer few hours to take apart, diagnose the fault, and replace the components. Kenwood make very detailed Service Manuals, so repair is possible by a competent engineer. However, these are getting difficult to find as well. It is worth getting this amplifier repaired if you have the money. However, this might also be a good opportunity to buy the latest audio video receiver. Some of the latest ones have more functions, better sound, more buttons to fiddle with, and are low cost.

This is a multi-page article showing the inside engineering of one of these amplifiers so sit back and enjoy the rest of the pages and the photographs.

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