Amplifier service

Some pictures from a few amplifier repairs. Updated 2011.04.10
This page will be updated continously as often as we have the time!

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We do amplifier repairs on most high quality brands, for example:
KRELL - Copland - NAD - Marantz - Denon - Onkyo - Integra Research and many more...

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Also, our next generation high-end amplifier module is under construction!

Are you interested in joining our way of high-end audio amplifier development?
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Copland CDA823. High-end CD player. What a brilliant piece of work!
This unit will be modified to have an external digital SPDIF input. This makes it possible to use the
superior internal D/A converters with external equipment like a laptop or audio processor.

Back view of the Copland CDA823. Now with the external SPDIF input added.  The switch near the
SPDIF jack select internal or external SPDIF source. We do not do only amplifiers!

Yamaha XP7000 pro audio amplifier. EEEngine output stage failure results in switchmode powersupply failure.

Yamaha XP7000 EEEngine output stage on the bench ready for repair. The trick with EEEngine is
to modulate the magnitude of the output stage rail voltages based on the demands of the
output signal. This improves the efficiency level.

Yamaha XP7000 switchmode power supply repair. Caused by a blown output stage.
Obviously the short circuit protection of the powersupply isn't fast enough to respond...


KRELL KSA-100. This is a pure class A amplifier. Respect. These units are extreme in many ways.
About 500W of powerconsumption at idle. This beast came in for a powersupply problem.
The Krell's are big and heavy, but they are not rocket science in any way.

DENON AVR-2105 multi channel reciever under power amplifier repair.
You really should avoid using speakers with lower impedance than recommended,
especially if you're the kind of person who like to boost the volume from time to time...

Amplifier board repaired and ready for test and bias adjustment

Warwick pro tube IV bass amp. Service after a hard life with the band "Barbados"... :-)

NAD 7155. Repair of preamp section. Routine work...

Don't remember the brand of this amp, but I do remember the design was from the 80's and very special.
Heat pipes was used for effective heat sinking for the MOSFET output transistors.

ROTEL RB-980BX at service of a blown amp channel. Very nicely built amplifier.
Unfortunately this model has a high frequency oscillation, with a very small amplitude,
so some kind of design error has been made. I would suspect a too small phase margin.

Car audio amplifier at service of a burned class D output filter.
Don't remember the brand of this amp, these designs are very similair.

KRELL 150 amplifier. Heavy Hi-Fi! Class A is heavy and expensive! This beast came in for service
of the output stage which had a few shorted transistors. Interesting design. Massive heatsinks!

This picture shows two of our own designed amplifier modules. Each module is capable of 250W
into 8 ohms, though in our guitar amplifier we run them at 170W/8ohm. Each module has its own
protection features like overtemp, DC detect and delayed startup. Completely silent during on and off!

Guitaramplifier TRAYNOR YGL3. A complete "bird nest" completely without circuit board.
Most of the components are fitted to a wooden plate. To the left in the picture to output tube
sockets are visible. Not a single transistor in this buddy!

RODEC mixer for service of a burned driver for the XLR outputs.

JBL car audio amplifier for service. We do much of repairs to car amplifiers of different brands!
Infinity, HK, Sony, Alpine, Soundstream, Clarion are other examples of brands we service!

QSC EX1600 for repair. Nice professional power amplifier from the 90's.

Ampeg SVT pro 4. A high-end 1600W bass amplifier. Very nicely built amp with tubes in the preamp section
and IRFP240/IRFP9240 MOSFET transistors in the output stage. This one had a problem in the temp-protection circuit.

e get lots of different stomp boxes in for repair. Common faults are broken jacks or other mechanical wear.

This is a Laney Plexi in for repair. After curing the problem the customer wanted to have it modified
for adjustable bias. Since he didn't want us to drill any new holes in the chassis for the bias
potentiometer, we decided to use one of the speaker output jacks.

The Laney Plexi waiting for its happy owner to arrive...

Soundstream Tarantula XXX-10000D. This is a very high power car audio amplifier which delivers
10kW of burst power. This unit came in with an almost completely blown power supply.
Remember that this amp will draw over 800A from a 14V source during a 10kW burst!

The XXX-10000D uses a class D output stage to increase the efficiency. The above picture shows the
secondary reservoir capacitors and the big inductors to the left is part of the class D output filter.

Heavy duty terminals for power source and speaker outputs. As can be seen, the installation
has to be done inside the amp. Be sure not to forget any tools inside the amp!!!