The Klimo Lar is an MM/MC phono preamplifier that is part of the Klimo product line, a brand well known for its excellence in the world of high-quality audio. The Lar was designed to complement the Merlino line preamplifier, offering a more accessible option for passionate audiophiles. However, despite its more affordable price compared to other products from the same manufacturer, the Lar delivers exceptional sonic performance and high-quality handcrafted construction.

Design and Construction The Klimo Lar features an elegant and refined design, with compact dimensions (44 x 11.5 x 27 cm) and a black finish with a chrome knob for switching between MM and MC cartridges. The rear panel provides connections for the MM input, MC input, and output, along with a power socket. The preamplifier is supplied with a high-quality Klimo power cable, which helps improve dynamics and sound transparency.

The interior of the Lar is a testament to build quality. Two toroidal transformers are housed in a shielded compartment to reduce unwanted electromagnetic fields. The preamplifier features two separate boards, one for each channel, elastically suspended to reduce tube microphonics. The heart of the Lar consists of six tubes, all double triodes, with two ECC88 dedicated to the MC stage and two ECC88 plus two ECC81 for the MM-RIAA stage.

Sonic Performance The Klimo Lar delivers outstanding sonic performance. It is remarkable for its attention to detail and tonal accuracy. Instrument and vocal timbres are reproduced accurately and engagingly, without the typical colorations of old-school tube designs. The preamplifier offers exceptional high-frequency extension, rich in harmonics and detail, while the midrange is smooth and full-bodied, with extraordinary microdynamics. The low end is powerful, articulate, and authoritative.

The Klimo Lar is tonally neutral and succeeds in capturing the emotional essence of a recording, without sacrificing detail or dynamics. It is a preamplifier that pairs perfectly with high-class cartridges, ensuring superb sonic reproduction.

The repair

A client came to me with a Klimo Lar that was producing an annoying hiss on both channels, with one channel noisier than the other. After opening the unit, I discovered that it had been tampered with, and that this modification was directly related to the noise issues.

The modification involved the cartridge load resistor, which is normally soldered directly onto the PCB. However, someone had added two RCA connectors on the rear of the preamplifier to allow easier swapping of the load resistor. This modification introduced significant noise problems, since the circuit area affected by the RCA connectors is sensitive to very weak signals. The cable connecting these connectors picked up interference and noise, further compromising audio performance.

To solve the problem and restore the Klimo Lar to optimal performance, I removed the modification and reinstated the load resistor by soldering it directly onto the PCB. This operation eliminated the interference and unwanted noise that had entered the circuit due to the tampering.

In addition, I carried out a thorough tube check using a computerized curve tracer, reselecting and matching the same tubes already owned by the client. The result of these repair operations was excellent. The output noise of the Klimo Lar was significantly reduced, dropping to only about 5/10 mV peak-to-peak. The preamplifier returned to delivering sound free from annoying noise and interference, restoring the purity and audio quality one expects.

Some curiosities about the measured tubes…

The Psvane ECC81 tubes, new and measured by me, show curves that appear to diverge from the typical curves found when measuring any NOS ECC81, as highlighted in the two comparison plots.

Psvane	NOS

The following images show the graphs of some ECC88 tubes, which display significantly distorted curves (current production tubes). It is interesting to note that, despite not being in perfect condition, they would still work in a circuit. The graphs highlight how the use of a curve tracer can reveal unexpected aspects. This is because, when these tubes are measured on a typical tube tester, even a high-quality transconductance tester, measurement at a single static point may make the tubes appear to be in excellent condition or show only negligible current differences. Then you look at them with a curve tracer, and they appear like this:

The Advance Acoustic Tube DA Converter 24bit 384kHz DAC – MDA503 fits into the entry-level segment, presenting itself as a DAC converter with SPDIF and Toslink inputs. At first glance, it gives the impression of a fairly striking design, with solid front panels and a generously sized remote control that performs its task efficiently.

What immediately catches the eye, according to what is reported online, is the luminous display with graphics resembling a circuit diagram that adorns the front of the DAC. However, the actual chassis of the DAC conveys a sense of cost-saving.

Despite the mixed opinions found online, sometimes even negative, the MDA503 DAC demonstrates its ability to reveal a respectable level of detail, offering a tonally balanced performance without noticeable emphasis in either the high or low frequencies.

Personally, I was faced with a completely non-functioning unit, with burned power transformers and original spare parts that were impossible to find. In the following article, I will share my experience, showing how I tackled this challenge by calculating and replacing the power transformers to bring this device back to life.

During my experience with the MDA503 DAC, I noticed a particular aspect that deserves closer examination. Despite the modest declared total power of 20 watts, the two toroidal transformers present in this device seemed to follow the classic Chinese approach of saving every possible cent.

These transformers, probably characterized by an undersized core and, more likely, by a limited amount of copper inside, tended to overheat significantly due to the high magnetic induction they were subjected to. Over time, the materials used in their construction deteriorated, eventually leading to a short circuit in the primaries and the consequent blowing of the main fuse.

In a clumsy attempt to make the unit work, the owner replaced the original 500mA fuse with an 8 Amp fuse, completely burning the transformers to the point of driving them into insulation breakdown. Fortunately, this misguided attempt did not cause serious damage to what was connected to the secondary windings. However, this episode raises important considerations about component quality and improvised maintenance practices that can further compromise equipment over time.

Fortunately, the electrical schematics provided the AC voltages of the transformer secondaries, making it easy to trace back the currents being drawn. With this valuable information, I was able to easily calculate two new transformers using common EI-type laminations, possibly even smaller than the original toroidal ones. This raises questions about the level of induction those toroids were subjected to, leading me to wonder how unhealthy a mindset it must be to compromise quality and long-term durability so severely just to save that single euro.

Replacement transformers for MDA503

I am pleased to inform you that I have created two new replacement transformers for the MDA503 DAC, designated models 23S70 and 23S71. If you own one of these DACs with damaged original transformers, you now have the option to obtain a pair of high-quality transformers to restore proper operation of your device.

The new transformers, specifically designed and calculated to ensure optimal performance, represent a reliable solution for anyone who needs to replace the burned components of their MDA503 DAC.

It is important to note that the cables with the connectors required for installing the new transformers must be recovered from the original transformers. If you wish to order a pair of transformers 23S70 and 23S71 or would like further details about the replacement procedure, I invite you to contact me directly. I will be happy to assist you in restoring your DAC’s performance and ensuring excellent audio quality.

In addition, it is important to emphasize that my replacement transformers, models 23S70 and 23S71, offer a significant advantage over the originals. Unlike the stock transformers, these new components are designed to ensure higher efficiency and reduced heat generation. You will benefit from cooler operation and greater energy efficiency, improving the overall longevity and performance of your MDA503 DAC.

Since the new 23S70 and 23S71 transformers have a different shape compared to the original toroids, a specific installation procedure must be followed. First, the support bracket of the old toroids must be removed. Next, the two new transformers can be installed following the orientation shown in the photographs. It will be necessary to drill four holes with a small drill and then secure the transformers with four screws, reusing the same screws previously used to fix the bracket, adding four M4 nuts. This procedure will ensure a secure and reliable fit of the new transformers, while guaranteeing proper operation of your MDA503 DAC.

During the inspection process, I identified additional faults inside the MDA503 DAC. Among the damaged components, I found a transistor, an electrolytic capacitor located after an exploded rectifier bridge, and a damaged resistor in the high-voltage supply.

This image provides a clear view of the internal configuration of the DAC during operation.

To complement this, I included a demonstration video showing the DAC in operation. In the recording, the digital source used is a computer, and to enable the connection I used a USB to SPDIF converter based on the PCM2707. To listen to the audio output from the DAC, I used my old and reliable “Calimero” project, previously presented in a past article.

In conclusion, the repair journey of the MDA503 DAC proved to be a fascinating path through technical challenges and solutions. From replacing the transformers to correcting the damaged transistor, capacitor, and resistor, each step was carried out with dedication and attention to detail.

The final result is a repaired and optimized DAC that, in addition to bringing the device back to life, introduces significant improvements over the original configuration. The use of transformers 23S70 and 23S71 not only ensured cooler operation, but also highlighted our dedication to quality and efficiency.

I was entrusted with the task of overhauling and measuring the Line Magnetic Audio LM210IA tube amplifier. In the vast world of tube amplification, this model stands out, particularly for its use of the 300B. The 300B, originally introduced back in 1933, has a rich history, first used in telephone repeater stations and later adopted in the audio industry as the reference tube for hi-fi systems. Line Magnetic Audio, a company based in Guangdong province, China, stands out for the passion of its two founding brothers for Western Electric theater amplifiers. Their activity began with the repair and restoration of these amplifiers, then evolved into the design of their own amplifiers, mainly using Western Electric tubes.

The LM210IA model, which is the subject of my attention, represents a combination of tradition and modernity. Its imposing aesthetics, with a robust aluminum front panel and high quality controls, are matched by a tube layout that includes the 300B for output, the 310B for input, and two 12AX7 for the input stage. The variety of inputs and the multiple impedance speaker terminals reflect a continuous commitment to producing high quality audio equipment.

The repair journey of the Line Magnetic Audio LM210IA amplifier began when the customer, an audio enthusiast, purchased it used online. Brought into my laboratory for a careful inspection, the amplifier showed some issues, including a pair of banana speaker terminals that had come loose and required tightening of the retaining nut. In addition, I noticed that ECC82 tubes were installed, contrary to what was specified by the manufacturer and shown in online images, which indicated ECC83 tubes. The seller claimed that the amplifier originally came new with ECC82 tubes installed, but the quality of the supplied tubes raised doubts. As a result, the customer requested an analysis of the circuit to confirm whether it was designed to accept ECC82 or ECC83 tubes.

After carefully examining the inside of the amplifier, I noticed that the anode load resistor of the ECC8x tube was 220k, while the cathode resistor was 3k. This configuration suggested a bias at an extremely low current, even for an ECC83. Without any doubt, the circuit was designed to accept ECC83 tubes. Installing an ECC82 would have forced the tube to operate under extreme conditions, at the edge of cutoff, causing heavy distortion and probably a roll-off of the high frequencies.

In addition, I would like to point out how often some audiophiles make random modifications to their equipment, such as replacing tubes without proper understanding, compromising the performance of the device.

In search of the most faithful distortion, TATTARATAAAA…

Certain individuals in the audio world, perhaps driven by the pursuit of an elusive “improvement”, end up manipulating elements without fully understanding their implications. In this case, it appears that the seller who sold the amplifier provided incorrect information and could have negatively influenced the customer’s listening experience. It is essential to emphasize the importance of deep knowledge and careful maintenance in order to preserve the integrity of audio equipment and ensure an optimal listening experience.

When evaluating the architecture of this amplifier, a critical consideration emerges regarding the internal layout. Contrary to the traditional arrangement that places transformers on top of the chassis, creating a more compact and accessible design, the current configuration of this amplifier seems to follow a more unusual approach.

Looking inside, one encounters a real labyrinth of components, with transformers located inside the chassis. This approach of stacking elements in an intricate way, in addition to compromising accessibility, raises concerns in the event of maintenance needs. Imagine the challenge of replacing one of those Chinese quality electrolytic capacitors, hidden among the folds of this layout, having to reach in with one hand to grab the component and the soldering iron in the other. In such a scenario, one would face a real challenge, enough to make you want to cry.

A more orderly and accessible design would not only have made maintenance operations easier, but would also have improved the overall efficiency of the device, ensuring greater practicality for those working on the equipment. Functionality and accessibility, in fact, should be priority aspects in the construction of devices intended for long-term use and, inevitably, for periods of maintenance and repair.

Let us now move on to the measurement of instrumental performance, using the tubes originally installed in the unit, which, although not new, still maintained good efficiency. I therefore confirm that the 8 watts declared by the manufacturer are indeed present, with the possibility of reaching even 9 watts under deep clipping conditions. The maximum undistorted power recorded is 6.23 watts RMS without feedback and 6.85 watts with feedback engaged. As for damping, it measures 2.4 with the selector set to zero feedback and 4.3 with the selector set to 3 dB of feedback. Below are the graphs related to the two operating modes.

BP Zero Feedback	BP with Feedback
THD Zero Feedback	THD with Feedback
Square wave 100Hz zero Feedback	Square wave 100Hz with Feedback
Square wave 1kHz zero Feedback	Square wave 1kHz with Feedback
Square wave 10kHz zero Feedback (I mistakenly set a different time scale).	Square wave 10kHz with Feedback

Once again, I would like to point out that, even though the power is set to 1 watt, at zero feedback the distortion is always higher compared to the feedback condition. This once again highlights that it is not true that the presence of feedback increases distortion at low power levels. I can also inform you that, when the customer delivered the amplifier to me, he stated that when set to zero feedback, the bass sounded bloated, loose, and annoying. Certainly, with the presence of the ECC83 and a damping factor of just over 2, this characteristic can only persist. Therefore, if you want to use it with zero feedback, it is advisable to use loudspeakers that naturally roll off the low frequencies, such as single-driver speakers, horns, and similar designs.