Mission DAC 5 - capacitor service and upgrades

Another superb English DAC, in for a service and some upgrades. 

A few capacitors lost over half of the capacitance and some had high ESR. All replaced with quality caps, and solid Panasonic caps on the DAC power supply lines. 

The unit also got newer audio grade op-amps, OPA134, gold plated sockets installed, and the mute transistors were removed. 

Micromega Duo DAC - capacitors service and upgrades

A superb audio Dac, in for a service and upgrades. 

A few capacitors were out of spec, everything was replaced with quality parts. Since it was on the bench, opamps were upgraded to highes spec audio grade OPAs. 

Bose SoundTouch 300 – Power Supply Repair and Common Faults

 If your Bose SoundTouch 300 soundbar has suddenly gone completely dead, no lights, no signs of life don’t panic just yet. This is a widespread issue, and the fault almost always points to the power supply board. 

WARNING-  this work requires knowledge of electricity, safety and the dangers presented on mains-powered equipment. DO NOT TAKE THIS ON  if you don't have the basic knowledge on safety. 

Over the years, I’ve repaired a few of these, and the pattern is always the same: the SMPS (switch-mode power supply) fails, usually taking out the UCC28630 driver IC, the main switching MOSFET, and a couple of nearby resistors in the process. Sometimes on the mainboard, there are 5V regulators that short out, easy to identify by part number ( they are not op-amps 😉). There are some SMD capacitors around the chips. If you find a short on any of those caps, you remove the IC and the short goes away... the chip is dead. 

What actually happens

Parasound Zamp v3 - in service

Superb little amps with big sound. On the bench for a service: recap, and board resoldered. These amps suffer from the same issues as many others, another clear example is NAD: great circuits but cheap electrolitics. 

After a full recap and some bad solder joints, it truly sings. 

Audiophiles and Sound – Why Our Brains Don’t Like “Perfect”

 

The Idea

There’s a funny thing about sound: the more time you spend chasing perfection, the less music you actually enjoy.
After 20+ years of building, repairing, and listening to audio gear, I’ve come to a simple conclusion: our brains don’t actually like perfect sound.

We like character, colour, and a touch of imperfection that makes the music feel alive.
Before the purists start throwing cables at me, hear me out.

The Myth of Perfection

In theory, the perfect audio system would reproduce the signal exactly as recorded — zero distortion, perfectly flat frequency response, no noise, no phase errors.

In practice, that kind of sound is boring. It’s analytical and cold, and after a few minutes, your brain starts wandering off.

What keeps us listening for hours isn’t clinical precision, it’s texture, warmth, dynamics, and the subtle imperfections that make the music human.

I’ve heard expensive systems that were technically flawless but emotionally empty, and modest systems that made me smile from the first note.

 The Human Brain and “Pleasant Errors”

Our brains are not precision instruments. They’re pattern recognisers that constantly fill in gaps and add feeling to what we hear.

That’s why valve amplifiers, with their harmonic distortion, sound so inviting; they produce even harmonics that our brain interprets as musical warmth.

On paper, they “measure worse” than a cheap op-amp.
But to our ears? They sound better.

Think of it like photography: a perfectly noise-free digital image can feel sterile, while a slightly grainy film photo feels alive.

Marantz PM 151 repair - full service

A super dirty Marantz PM 151, in for a service.  These are great little amps, with a specific mellow sound. This is a "warm" sounding amp. 

After a full service and calibration- it sings nicely.

- recap with Elna and Panasonic

- sound path Nichicon Gold

- main filter caps upgraded to 10k uF 

- phono preamp opamp upgraded from 4558 to 5532

- pots and switches cleaned

- bias calibrated

Technics and Class A amplifiers

 Another crazy discussion, this was debated many, many times, no harm in presenting my experience with Technics amps that claim Class A in one form or another.

 First of all, No… Technics did not manufacture any Real Class A amplifiers (I never saw or heard about one), but they had a unique design that was quite good.

Technics used a variable biasing circuit that will somewhat modify the class of operation based on the input level.  Simple explanation: first few Watts are delivered in a Class A operation. Increasing the volume will switch the amp to class AB, and the rest of the power will be offered as a Class AB amplifier.

  Does it work?  Yes, although Technics did not focus on high-end, some of their equipment is very good. And they also have a few rare high-end series that are more Matsushita Signatures than Technics/ Panasonic consumer units.

One of the favourite amplifiers here at Audiophile Repairs is the Technics SU-V707, or for other markets the SU-V7, a 90W/ch tank that has all you ever need, sounds amazing and will drive anything. I can already hear the purists screaming about someone liking Technics, I should be hanged, right? 

Not all Technics units marked with a form of Class A operation are the same; the SU-V707 is an amp that I highly recommend to any beginner and even advanced audiophile. They require a service due to age, but the results are amazing. 

-        The unit has a small CPU that will read the speaker impedance, will preheat the output transistors and control the bias.

-        The first 10-15W  are purely amazing, it gives you the feeling that is so powerful it will blow your speakers, but once you go past that point, it just cools down and behaves normally.

The amp was the main listening and test amp for 1 year, and sometimes I miss the sound of that unit. The first time it arrived, everybody was a bit  “meh”, just another Technics. After it was recapped and calibrated … WOW,  that Technics can sing. The smaller brothers SU-V303/505 ( as above, in some markets it might be V3 or V5)  are also amazing.