Design by Mr. K PPA-01 / PPA-02B passive TVC preamplifier

Design by Mr. K: passive TVC preamplifier in two versions

This passive preamplifier by Design by Mr. K is available in two versions. Choose the version that suits your system's connections from the model options:

• PPA-01 – RCA: three RCA inputs and one RCA output.
• PPA-02B – RCA and XLR: three RCA inputs and three XLR inputs, with one RCA output and one XLR output.

Both versions operate without an external power supply and combine C-Core autotransformers with mechanical volume control in 59 steps. This allows you to connect your source and power amplifier without an additional active amplification stage while easily returning to your favorite volume setting. You can find the connections, gain settings, and weights for each model below.

How does Transformer Volume Control work?

A conventional potentiometer controls the volume using a voltage divider. These preamplifiers use taps on C-Core autotransformers for this purpose. Choosing a different tap changes the voltage ratio and thus the signal level. This magnetic volume control is also called Autoformer Volume Control (AVC) with autotransformers.

What is special is that not only the voltage, but also the impedance is transformed. When attenuating, the effective output impedance can become lower. This can be beneficial for driving the power amplifier compared to a simple passive voltage divider.

Why the ‘cool-melted method’?

The designer opts for a special construction method in which the C-Core autotransformers are assembled without metal stabilization clamps. He calls this the ‘cool-melted method’.

The reason for this choice is to avoid material differences between the transformer and the metal clamps used for stabilization in a conventional construction. According to the designer, such material differences can adversely affect sound quality. By making the clamps unnecessary, he aims to eliminate this potential influence during construction. It is therefore a deliberate design choice regarding the transformers that provide the volume control.

Furthermore, the two autotransformers are positioned at a 90-degree angle to reduce mutual magnetic interference between the left and right channels.

The benefits in your system

• No external power supply: the control operates without a powered amplification stage, thereby avoiding potential noise contributions from such an additional circuit.
• 59 fixed volume steps: accurately and repeatably set your listening level.
• Selectable gain: match the voltage ratio to your system. The settings vary by model and connection. Voltage increase is passive, not through active power amplification.
• Special transformer construction: C-Core autotransformers without metal stabilization clamps, manufactured using the manufacturer's described ‘cool-melted method’.
• Choice of connections: RCA on the PPA-01, RCA and XLR on the PPA-02B. Both versions have separate connections for House GND and Audio GND.

Specifications PPA-01 – RCA

• Design: fully passive preamplifier with C-Core autotransformers
• Volume control: mechanical, 59 steps
• Gain settings: 1×, 3×, 5× and 10×
• Winding ratios according to the product specification: 1:1.00; 1:3.10; 1:4.97; 1:10.39
• Inputs: 3 RCA
• Output: 1 RCA
• Grounding: 1 House GND and 1 Audio GND
• Frequency range: 20 Hz–20 kHz (±3 dB), at 1× gain, maximum volume and a load of 10 kΩ
• Dimensions (w × d × h): 350 × 280 × 80 mm
• Net weight: 4.0 kg
• Gross weight according to the product specification: 6.8 kg

Specifications PPA-02B – RCA and XLR

Do you want to connect sources and a power amplifier via XLR in addition to RCA? Then choose the PPA-02B variant. This model also operates fully passively with mechanical volume control in 59 steps and C-Core autotransformers using the ‘cool-melted method’. The difference lies, among other things, in the connections and the gain settings for XLR.

• Inputs: 3 RCA and 3 XLR
• Outputs: 1 RCA and 1 XLR
• Gain via RCA: 1×, 3×, 5× and 10×
• Gain via XLR: 0.5×, 1.5×, 2.5× and 5×
• Grounding: 1 House GND and 1 Audio GND
• Frequency range: 20 Hz–20 kHz (±3 dB), at 1× gain, maximum volume and a load of 10 kΩ
• Recommended minimum input impedance of the power amplifier: 10 kΩ
• Dimensions (w × d × h): 350 × 280 × 80 mm
• Net weight: 4.5 kg
• Gross weight according to the product specification: 7.3 kg

House GND and Audio GND

The separate connections for House GND and Audio GND provide additional options for tailoring the grounding in your system. The designer describes connecting to an external grounding box or, where appropriate, a connection between both GND connections with a jumper. These connections are not a replacement for the protective ground of connected equipment.

Choosing gain: matching, not simply turning it up louder

The gain choice changes the voltage ratio of the autotransformer. The designer describes different tonal characteristics per setting, but these are subjective descriptions and not guaranteed characteristics. Choose the setting that suits the output level of your source and the sensitivity of your power amplifier; higher gain is not automatically better.

Reviews and listening experiences

The Dutch summaries below reflect the impressions of the mentioned sources.

HiFiReport – listening review of the PPA-02B

The reviewer experiences the PPA-02B via RCA at 1× gain as virtually neutral, with little recognizable character of its own. Any differences are described as a slightly tighter and better defined soundstage, without a harsh character. At 3× gain, he hears a fuller instrument presentation and more spatial depth.

Read the full English PPA-02B review on HiFiReport

Deco Audio – dealer review of the PPA series

The British dealer Deco Audio appreciates the simple, purist design and the finely adjustable volume control in 59 steps. The dealer recommends the default setting of 1× gain for most systems and mentions the other settings as an option when additional voltage increase is needed.

Read the English product review by Deco Audio

Delivery time: 1 to 2 weeks within Europe