KR Audio Electronics P135-MC Pre-amplifier

[KR Audio P135-MC]

A hybrid pre-amplifier for the 21st century

[Italian version here]

Product name: P135-MC
Manufacturer: KR Audio Electronics
UK Distributor: Gpoint-audio
Cost: 5,900 plus 750 for phono stage. (Currency conversion)

Reviewer: Mike Cox - TNT UK
Reviewed: December, 2017

If I had a feature check list for a pre-amplifier the KR Audio Electronics fulfils all my needs. It is a modern looking design with remote control selection of the 4 inputs and volume adjustment.
It has a phono stage capable of handling moving coil cartridges that is quiet and matches well my Benz Micro Wood.

The design uses 45 type valves for the output stage via transformers and has balanced as well as single ended outputs, very handy for the long interconnects to my Emotiva power amplifier. As supplied for the review the P135-MC came with KR Audio type 45 valves, these look beautifully made and feel very solid, I would be surprised if they suffer from microphony.

As you can see from the picture above I setup the P135-MC on top of my vinyl storage cabinets next to the Pre-Audio turntable. I then used long phono cables from my DAC that sits next to the power amplifier and long balanced xlr cables from the pre-amp to the Emotiva power amplifier. It would have been better to use balanced cables from the DAC to pre-amp, but I only had one set.

[KR Audio Pre-amp]
KR Audio P135-MC close up

For the first time I have a system that I can completely control from my sitting position and this is very nice, if only the turntable would operate automatically! The P135-MC was a pleasure to use, it is very quiet with no valve warm up dramas.
The pre-amp is microprocessor controlled with the outputs muted until the processor is satisfied that the valves are operating correctly. The processor also continuously checks the valve operating conditions and will shut the pre-amp down when anything abnormal is detected.

The output stage is driven by a JFET input stage working in class A, with the inputs controlled using reed relays managed by the processor. On the rear there are 3 pairs of phono sockets plus a pair XLR for inputs. There are another pair of XLR for output along with a regular pair of phono sockets. The volume control is motorised from ALPS, it is very smooth and quiet in operation.

There is no safety cover for the valves, they are not very hot when operating, so if you do touch them whilst you will know about it, no serious injury should occur. If you own an amplifier like this you will know to keep young children away. This means the design is very simple and neat, the valves seem to rise organically from the top making a sculptural look.

[KR Audio Pre-amp]
KR Audio P135-MC rear view

Listening in

The KR Audio P135-MC settled into my system very quickly with the remote making my life very easy. My regular digital source is a Chord Hugo TT fed from a PC running Audiophile Linux with all the music stored on a network drive, the music appeared from an inky black back ground. This pre-amp seems very quiet whatever the source, all it does is add that wonderfully natural triode harmonic texture.

The Hugo DAC is one of the most neutral, none digital, sounding DACs I have heard and the P135-MC lets it all flow through, there is no digital harshness here. Compared to my MFA Classic pre-amp there is no doubt the MFA is neutral, it is just missing that wonderful valve tonality the P135-MC delivers and many of us crave. What the P135-MC does provide is great drive and rhythm, the MFA seems slow in comparison.

Playing the Gregory Porter album "Liquid Spirit", Gregory's voice sounds three dimensional, hanging in space between the speakers as if a bubble when using the P135-MC. At the same time the P135-MC was able to keep pace with the agile bass line, a tough challenge that some components fail to deliver. It may be that the P135-MC is better able to handle the long interconnect cables as it has a lower output impedance than the MFA Classic.

The KR Audio P135-MC delivers a more convincing musical experience whilst the MFA is more neutral. The P135-MC is able to handle the long interconnects with ease, losing nothing along the way. When you compare the price, the MAF Classic along with the Whest PS-30R phono stage are about the same as the P135-MC with the optional phono stage.

Turning on the turntable and spinning up some vinyl, the phono stage is very quiet and seems to match well with my Benz Micro Wood. I have no way to measure the frequency response, it does sound accurate, with no particular part of the audio spectrum emphasised. Playing my usual selection of vinyl from Ella Fitzgerald through Mary Black and Dave Brubeck it was all delivered with a wonderfully quiet background and lots of detail.
I enjoyed all my vinyl using the P135-MC, whilst the phono stange is solid state with the 45 valves driving the output it delivers a nice balance of the virtues of both technologies.

[KR Audio Pre-amp insides]
KR Audio P135-MC inside view

Switching source again to my Revox A77 and the studio master tapes from Analogy Records the combination was breathtaking. Whilst the P135-MC adds the valve magic it does not seem to colour the sound in the way some valve designs do. This colouration is liked by many but it is not as intended by the artist and their producer.
The music has that wonderful analog, natural sound whilst avoiding the inevitable background noise, clicks and pops, that are a feature of most vinyl recordings. The 45 valve as supplied is beautifully constructed with a solid glass envelope.

Sometimes valves can feel delicate, the KR Audio 45s feel very robust and there is little sign of microphony when tapping the glass. Poorly constructed valves ring like a church bell when tapped, I would expect a long life from the KR Audio 45s.


This is a wonderful pre-amp and the KR Audio 45 valves are superb, adding that beautiful valve magic. The 45 valve is a new addition to the KR Audio line up with the P135-MC designed to exploit it to the full, and the pairing really sing. The pre-amp is a pleasure to use, has real presence, setting off your system through a simple and elegant design while allowing the music to shine through. The audio system should be a means to play music and should not dominate the musical experience, the P135-MC seems to be invisible whilst delivering a high end musical experience.

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