Can I Bench Test an Integrated Amp with Just the FNIRSI 2D15P? | Review Part 2 ~ Real World Testing

"FNIRSI sent me this 2D15P free of charge in return for an honest assessment.

Disclosure: Some of the links below are Amazon affiliate links, which means I may earn a commission at no extra cost to you. As an Amazon Associate, I earn from qualifying purchases.

🛒 FNIRSI 2D15P (Amazon affiliate link):
https://amzn.to/3KLtLoV

💸 Use coupon code ZVRJDMEP to get a discount through Dec 28, 2025

🛒 Related tools and accessories (Amazon affiliate link):
https://amzn.to/49hzbRJ

Just getting started in audio repair and looking for some guidance? Check out my Patreon page for in depth diagnostic, repair, and restoration examples:
  / novaluxstereophonic  

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In Part 1, I covered the technical features, interface, and limitations of the FNIRSI 2D15P.

Part 1 Video Link:
   • This One Tool Can Start Your Audio Repair ...  

In this follow-up video, I put the 2D15P to work in a real bench-testing scenario to see how far a beginner can realistically go using just this one device.

For Part 2, I attempt to fully bench test a vintage Sansui AU-20000 integrated amplifier using only the FNIRSI 2D15P, a dummy load, and basic cables — no full bench of test gear. The goal is to answer a simple question:

Can a beginner meaningfully troubleshoot and evaluate an audio amplifier with this tool alone?

What’s covered in this video:
Initial inspection and safe power-up of an unknown amplifier
Separating and testing the preamp and power amp sections
Using the 2D15P to:
Inject test signals
Compare left/right channel behavior
Identify dirty controls and switching issues
Square-wave testing of tone controls and filters
Phono stage verification using low-level square waves
Use of an inverse RIAA network to validate phono stage frequency response
Power amplifier testing into dummy loads
Output voltage measurement and power calculations
Identifying the limitations of the built-in sine wave generator
Verifying results with a standalone bench signal generator

Key takeaways:

The FNIRSI 2D15P performs very well for preamp and phono stage testing, especially when using square waves. It makes it easy to:
Compare channels
Spot control issues
Verify overall signal flow
Perform meaningful diagnostic work as a beginner

Where the device falls short is standalone power amplifier testing. The internal sine wave generator lacks the cleanliness and fine amplitude control needed to accurately detect clipping and channel balance at rated output power. In this case, a dedicated signal generator is still required for precise power amp evaluation.

Final thoughts:
While I wasn’t able to perform a complete amplifier bench test using only the 2D15P, I came surprisingly close. For someone just starting out in audio repair, this device covers a lot of ground at a reasonable price, with an intuitive interface, solid oscilloscope and DMM functionality, and excellent usability.

As long as you understand the limitations of the signal generator — and plan to add a standalone generator later — the 2D15P remains a strong beginner tool.

Chapters:

00:00 Introduction
00:32 Visual Inspection of the AU-20000
01:29 Setting Up the 2D15P For Audio Testing
03:20 Separating the Preamp & Power Amp for Isolated Testing
04:29 Preamplifier Testing
09:09 Affiliate Link Call Out
09:24 Phono Stage Testing
13:01 Power Amplifier Testing
29:07 Does the D215P Pass the Test? Summary of Results
32:29 Closing Thoughts

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