Difference between revisions of "THD Sweep Measurement"

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== THD SWEEP MEASUREMENT - USER GUIDE ==
== THD SWEEP MEASUREMENT - USER GUIDE ==
''Master the art of measuring Total Harmonic Distortion with style''
''Master the art of measuring Total Harmonic Distortion with style''
[[File:sweep.png|400px]]


__TOC__
__TOC__
Line 12: Line 15:


---
---
== Install ==
== Install ==


Dowload THD measurement :
Download THD measurement :


[https://partnerzone.digigram.com/s/mqm8BrLDYPz3ZRR THD sweep measurement] April 2026
[https://partnerzone.digigram.com/s/RgiG5JFxNpjG5C6 THD sweep measurement] April 2026


=== Install model===
=== Install model===
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Put the model folder : "THD computation" on model database of NVgate.  
Put the model folder : "THD computation" on model database of NVgate.  
(By default : C:\OROS\NVGate data\Workbook Library\User\ )
(By default : C:\OROS\NVGate data\Workbook Library\User\ )
=== Requirement ===
NVGate V17 or upper.
Option : DC simulated on NVGate front end.


== ⚡ QUICK START - 30 SECONDS ==
== ⚡ QUICK START - 30 SECONDS ==
Line 27: Line 37:
{| style="width: 100%; border-collapse: collapse; margin: 20px 0;"
{| style="width: 100%; border-collapse: collapse; margin: 20px 0;"
|-
|-
| style="background: #f0f4ff; padding: 20px; border-left: 5px solid #667eea; font-weight: bold; width: 50%;" | STEP
| style="background: #f0f4ff; padding: 20px; border-left: 5px solid #667eea; font-weight: bold; width: 10%;" | STEP
| style="background: #f0f4ff; padding: 20px; border-left: 5px solid #667eea; font-weight: bold; width: 50%;" | ACTION
| style="background: #f0f4ff; padding: 20px; border-left: 5px solid #667eea; font-weight: bold; width: 90%;" | ACTION
|-
|-
| style="padding: 15px; background: #fafbff;" | 1️⃣ Launch
| style="padding: 15px; background: #fafbff;" | 1️⃣ Launch
Line 34: Line 44:
|-
|-
| style="padding: 15px; background: white;" | 2️⃣ Connect
| style="padding: 15px; background: white;" | 2️⃣ Connect
| style="padding: 15px; background: white;" | Put the sweep sine on channel 4️⃣ ; put the response on channel 1️⃣
| style="padding: 15px; background: white;" | Put the sweep sine signal on channel 4️⃣ ; put the response on channel 1️⃣
|-
|-
| style="padding: 15px; background: #fafbff;" | 3️⃣ Start
| style="padding: 15px; background: #fafbff;" | 3️⃣ Start
Line 40: Line 50:
|-
|-
| style="padding: 15px; background: white;" | 4️⃣ Monitor
| style="padding: 15px; background: white;" | 4️⃣ Monitor
| style="padding: 15px; background: white;" | Watch 4 metrics update live , THD and frequency will also be injected on channels DC simulated of NVgate
| style="padding: 15px; background: white;" | Watch 4 metrics update live , THD and frequency will also be injected on NVGate channels DC simulated.
|-
|-
| style="padding: 15px; background: #fafbff;" | 5️⃣ Stop
| style="padding: 15px; background: #fafbff;" | 5️⃣ Stop
Line 75: Line 85:
| style="background: white; padding: 20px; text-align: center; border: 1px solid #ddd; font-family: monospace; font-weight: bold; color: #667eea;" | 5.0e-01 V
| style="background: white; padding: 20px; text-align: center; border: 1px solid #ddd; font-family: monospace; font-weight: bold; color: #667eea;" | 5.0e-01 V
|}
|}
=== 💬 Log Console (Bottom) ===
Real-time messages with color coding:
{| style="width: 100%; border-collapse: collapse; margin: 15px 0;"
|-
| style="width: 20%; background: #e8f5e9; padding: 10px; font-weight: bold;" | 🟢 GREEN
| style="width: 80%; background: #e8f5e9; padding: 10px;" | Everything OK - measurement working perfectly
|-
| style="width: 20%; background: #ffebee; padding: 10px; font-weight: bold;" | 🔴 RED
| style="width: 80%; background: #ffebee; padding: 10px;" | Error occurred - something needs attention
|-
| style="width: 20%; background: #e3f2fd; padding: 10px; font-weight: bold;" | 🔵 BLUE
| style="width: 80%; background: #e3f2fd; padding: 10px;" | Information - status updates and details
|}
---


== 🎯 UNDERSTANDING YOUR RESULTS ==
== 🎯 UNDERSTANDING YOUR RESULTS ==
Line 157: Line 149:


</div>
</div>
---
== 📋 TYPICAL MEASUREMENT WORKFLOW ==
=== Pre-Measurement Checklist ===
<div style="background: #fff3e0; border-left: 5px solid #ff9800; padding: 20px; margin: 20px 0; border-radius: 5px;">
Before you start, verify:
* ✓ NVGate is open and ready
* ✓ Sweep is configured (e.g., 10 Hz → 20 kHz)
* ✓ FFT traces are visible on screen
* ✓ Sine generator is active
* ✓ Speaker is connected and working
</div>
=== Step-by-Step Workflow ===
{| style="width: 100%; border-collapse: collapse; margin: 20px 0; background: white;"
|-
| style="background: #667eea; color: white; padding: 15px; font-weight: bold; width: 5%; text-align: center;" |
| style="background: #667eea; color: white; padding: 15px; font-weight: bold; width: 25%;" | PHASE
| style="background: #667eea; color: white; padding: 15px; font-weight: bold; width: 70%;" | WHAT TO DO
|-
| style="background: #f5f5f5; padding: 15px; text-align: center; font-size: 2em;" | 1️⃣
| style="background: #f5f5f5; padding: 15px; font-weight: bold;" | Prepare
| style="background: #f5f5f5; padding: 15px;" | Open NVGate → Set sweep → Verify FFT visible
|-
| style="background: white; padding: 15px; text-align: center; font-size: 2em;" | 2️⃣
| style="background: white; padding: 15px; font-weight: bold;" | Launch App
| style="background: white; padding: 15px;" | Double-click Lancer_THD.bat → Check Connected status
|-
| style="background: #f5f5f5; padding: 15px; text-align: center; font-size: 2em;" | 3️⃣
| style="background: #f5f5f5; padding: 15px; font-weight: bold;" | Start
| style="background: #f5f5f5; padding: 15px;" | Click ▶ START → Watch log for "Starting THD Measurement"
|-
| style="background: white; padding: 15px; text-align: center; font-size: 2em;" | 4️⃣
| style="background: white; padding: 15px; font-weight: bold;" | Monitor
| style="background: white; padding: 15px;" | Watch metrics update → Frequency should increase → THD should be stable
|-
| style="background: #f5f5f5; padding: 15px; text-align: center; font-size: 2em;" | 5️⃣
| style="background: #f5f5f5; padding: 15px; font-weight: bold;" | Stop
| style="background: #f5f5f5; padding: 15px;" | Click ■ STOP → Watch for "Measurement ended" → Note final values
|}


---
---
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* Different DC input addresses
* Different DC input addresses


If you're not sure → Don't change anything. It works. Trust it.
If you're not sure → Don't change anything. It works.


</div>
</div>
The NVgate Model generate a sweep sine on the output, feel free to modify the settings if you need. We recommand to not put a sweep speed more than 0.05dec/s (or less) in logarithme for accurate results


=== How to Access Configuration ===
=== How to Access Configuration ===
Line 243: Line 193:
| style="padding: 12px; background: #f5f5f5; border: 1px solid #ddd;" | Number of harmonics
| style="padding: 12px; background: #f5f5f5; border: 1px solid #ddd;" | Number of harmonics
| style="padding: 12px; background: #f5f5f5; border: 1px solid #ddd; font-family: monospace;" | 9
| style="padding: 12px; background: #f5f5f5; border: 1px solid #ddd; font-family: monospace;" | 9
| style="padding: 12px; background: #f5f5f5; border: 1px solid #ddd;" | 5 (faster), 15 (more detailed)
| style="padding: 12px; background: #f5f5f5; border: 1px solid #ddd;" |
|}
|}


Line 255: Line 205:
---
---


== 🔧 TROUBLESHOOTING ==
== ❓ FREQUENTLY ASKED QUESTIONS ==


=== Issue 1: NVGate Shows "Disconnected" ===


<div style="background: #ffebee; border-left: 5px solid #d32f2f; padding: 20px; margin: 15px 0; border-radius: 5px;">
=== Q: I Have only one channels. Can i take the max marker on windows 1 ?===


'''What it means:''' Application can't reach NVGate
'''A:''' Yes, on this configuration, put windows 1 for window (sweep) and select the good number for the marker.


'''Solutions (in order):'''
=== Q: Is THD 5% good? ===
# Is NVGate actually open? Check your screen.
# Restart NVGate
# Restart the THD application
# Check Windows firewall allows localhost connections
# Call your IT department and cry


'''Reality check:''' 99% of the time NVGate just wasn't open. No shame, happens to everyone.
'''A:''' For a speaker? Excellent! You can be proud of that equipment. 🎉


</div>
=== Q: Why does THD change with frequency? ===


=== Issue 2: Measurement Won't Start ===
'''A:''' Because speakers aren't perfect at all frequencies. Some frequencies cause more distortion than others. That's physics being weird.


<div style="background: #fff3e0; border-left: 5px solid #f57c00; padding: 20px; margin: 15px 0; border-radius: 5px;">
=== Q: Can I use this on any speaker? ===


'''What it means:''' Something blocking the measurement
'''A:''' Yes! Desktop speakers, studio monitors, subwoofers, car speakers - if it's connected to NVGate, we can measure it.


'''Solutions:'''
=== Q: How many times should I measure? ===
# Click '''Run Diagnostic''' - it will tell you exactly what's wrong
# Common causes:
#* No sweep configured in NVGate
#* Markers not properly created
#* Wrong window names in configuration


The diagnostic is your friend. Use it!
'''A:''' Once for curiosity. Three times for reliability. Ten times if you're publishing a paper.


</div>
=== Q: Can I export the results? ===


=== Issue 3: THD Values Show "--.-" (dashes) ===
'''A:''' Yes! Copy text from the log console and paste into Excel, Word, or wherever you need it.


<div style="background: #e8f5e9; border-left: 5px solid #388e3c; padding: 20px; margin: 15px 0; border-radius: 5px;">
=== Q: What if my project has different settings? ===


'''What it means:''' No data is being read from harmonics
'''A:''' Use the Configuration panel to adjust. It's literally made for this.


'''Check these:'''
=== Q: Does this work over WiFi? ===
# Are FFT traces actually visible in NVGate? (Most common issue)
# Is the sweep running?
# Is there audio output to your speaker?
# Are markers properly set up?


Fix one of these and you're golden!
'''A:''' No. It only works locally (same computer or local network). WiFi would add too much latency.


</div>
---


=== Issue 4: STOP Button Doesn't Work ===
===disclaimer===


<div style="background: #f3e5f5; border-left: 5px solid #7b1fa2; padding: 20px; margin: 15px 0; border-radius: 5px;">
1) This program is delivered free of charge for NVGate V12. Support is not automatically provided on this tool.


'''What it means:''' Measurement is shutting down but taking its time
2) For any other requests, please contact your local distributor or the [mailto:customer.care@oros.com OROS Customer Care department.]


'''Solution:''' Wait 5 seconds. Seriously. The app is cleaning up.
---


If it still doesn't respond after 30 seconds:
{| style="width: 100%; background: linear-gradient(135deg, #667eea 0%, #764ba2 100%); color: white; padding: 30px; border-radius: 10px; margin: 30px 0; text-align: center;"
# Close the window
|-
# Restart the application
| style="font-size: 1.5em; font-weight: bold;" | You're Ready!
# Continue with life
|-
| style="font-size: 1.1em; margin-top: 10px; opacity: 0.95;" | Go measure some THD and make your speakers proud 🎵
|}


</div>
== Technical appendix THD Formulas ==
 
---


== 💡 PRO TIPS ==
=== THD Percentage (DC1) ===


{| style="width: 100%; background: linear-gradient(135deg, #fff9c4, #fffde7); padding: 20px; border-radius: 10px; margin: 20px 0; border: 2px solid #fbc02d;"
'''Formula:'''
|-
| '''Tip 1: Start Simple'''
Always use default settings first. Change things later if needed.


'''Tip 2: Read the Log'''
<code>THD(%) = (√(H2² + H3² + ... + H9²) / H1) × 100</code>
The log console tells you everything. It's your best friend.


'''Tip 3: Use Diagnostic'''
Where:
When something's wrong, click "Run Diagnostic". It's like magic.
* H1 = Fundamental amplitude (1st harmonic)
* H2, H3, ..., H9 = Harmonic amplitudes (2nd to 9th)
* √ = Square root


'''Tip 4: Multiple Measurements'''
'''Example:'''
One measurement is interesting. Five measurements is scientific.
* H1 (fundamental) = 1.0 V
* H2 = 0.02 V
* H3 = 0.01 V
* H4 = 0.01 V
* (all others = 0)


'''Tip 5: Document Results'''
Calculation:
Take a screenshot or copy the final THD values. You'll forget otherwise.
* Harmonics RMS = √(0.02² + 0.01² + 0.01²) = √0.0006 = 0.0245 V
|}
* THD% = (0.0245 / 1.0) × 100 = '''2.45%'''


---
---


== ❓ FREQUENTLY ASKED QUESTIONS ==
=== THD in Decibels (DC2) ===


=== Q: Is THD 5% good? ===
'''Formula:'''


'''A:''' For a speaker? Excellent! You can be proud of that equipment. 🎉
<code>THD(dB) = 20 × log₁₀(√(H2² + H3² + ... + H9²) / H1)</code>


=== Q: Why does THD change with frequency? ===
Or from THD%:


'''A:''' Because speakers aren't perfect at all frequencies. Some frequencies cause more distortion than others. That's physics being weird.
<code>THD(dB) = 20 × log₁₀(THD% / 100)</code>


=== Q: Can I use this on any speaker? ===
Where:
* log₁₀ = Base-10 logarithm
* All H values same as above


'''A:''' Yes! Desktop speakers, studio monitors, subwoofers, car speakers - if it's connected to NVGate, we can measure it.


=== Q: How many times should I measure? ===
'''Example from above:'''
* Ratio = 0.0245 / 1.0 = 0.0245
* log₁₀(0.0245) = -1.611
* THD(dB) = 20 × (-1.611) = '''−32.2 dB'''


'''A:''' Once for curiosity. Three times for reliability. Ten times if you're publishing a paper.
Or: THD(dB) = 20 × log₁₀(2.45 / 100) = 20 × (−1.611) = '''−32.2 dB'''


=== Q: Can I export the results? ===
---


'''A:''' Yes! Copy text from the log console and paste into Excel, Word, or wherever you need it.
=== Quick Conversion Table ===


=== Q: What if my project has different settings? ===
{| class="wikitable"
 
|-
'''A:''' Use the Configuration panel to adjust. It's literally made for this.
! THD Percentage !! THD in dB !! Quality Rating
|-
| 0.5% || −46 dB || Excellent (pro audio)
|-
| 1% || −40 dB || Very Good
|-
| 3% || −30 dB || Good
|-
| 5% || −26 dB || Acceptable
|-
| 10% || −20 dB || Fair
|-
| 30% || −10 dB || Poor
|-
| 100% || 0 dB || Unusable
|}


=== Q: Does this work over WiFi? ===
'''A:''' No. It only works locally (same computer or local network). WiFi would add too much latency.


---
---


== 🎓 QUICK REFERENCE ==
=== Three DC Outputs ===


{| style="width: 100%; border-collapse: collapse; margin: 20px 0;"
{| class="wikitable"
|-
| style="background: linear-gradient(135deg, #667eea, #764ba2); color: white; padding: 15px; font-weight: bold; width: 25%; text-align: center;" | ACTION
| style="background: linear-gradient(135deg, #667eea, #764ba2); color: white; padding: 15px; font-weight: bold; width: 25%; text-align: center;" | SHORTCUT
| style="background: linear-gradient(135deg, #667eea, #764ba2); color: white; padding: 15px; font-weight: bold; width: 50%; text-align: center;" | RESULT
|-
| style="padding: 15px; background: #f5f5f5; text-align: center;" | Launch App
| style="padding: 15px; background: #f5f5f5; text-align: center; font-family: monospace;" | Double-click .bat file
| style="padding: 15px; background: #f5f5f5; text-align: center;" | Window appears ✓
|-
|-
| style="padding: 15px; text-align: center;" | Start Measurement
! Output Channel !! Measurement !! Formula !! Typical Range
| style="padding: 15px; text-align: center; font-family: monospace;" | Click ▶ START
| style="padding: 15px; text-align: center;" | Metrics begin updating ✓
|-
|-
| style="padding: 15px; background: #f5f5f5; text-align: center;" | Stop Measurement
| DC1 || THD % || (Harmonics RMS / H1) × 100 || 0 to 100%
| style="padding: 15px; background: #f5f5f5; text-align: center; font-family: monospace;" | Click ■ STOP
| style="padding: 15px; background: #f5f5f5; text-align: center;" | Log shows "ended" ✓
|-
|-
| style="padding: 15px; text-align: center;" | Run Diagnostic
| DC2 || THD dB || 20 × log₁₀(ratio) || −200 to 0 dB
| style="padding: 15px; text-align: center; font-family: monospace;" | Click "Run Diagnostic"
| style="padding: 15px; text-align: center;" | See all [OK] or [FAIL] ✓
|-
|-
| style="padding: 15px; background: #f5f5f5; text-align: center;" | Change Config
| DC3 || Frequency || Sweep frequency at current point || 0 to 40 kHz
| style="padding: 15px; background: #f5f5f5; text-align: center; font-family: monospace;" | Click ▶ Configuration
| style="padding: 15px; background: #f5f5f5; text-align: center;" | Apply changes ✓
|}
|}


---
---


== 📞 BEFORE YOU CONTACT SUPPORT ==
=== Coherence Between DC1 and DC2 ===


Gather this information:
The two THD channels always maintain mathematical coherence. Given DC1 value (THD%), you can always calculate DC2:
* Screenshot of the error message
* Last 5 lines of the log console
* Your NVGate window names
* Steps you took before the error


This helps us help you faster! 🚀
<code>DC2(dB) = 20 × log₁₀(DC1(%) / 100)</code>


---
'''Example:'''
* If DC1 displays 5.5%
* Then DC2 = 20 × log₁₀(0.055) = 20 × (−1.26) = '''−25.2 dB'''


{| style="width: 100%; background: linear-gradient(135deg, #667eea 0%, #764ba2 100%); color: white; padding: 30px; border-radius: 10px; margin: 30px 0; text-align: center;"
This relationship is guaranteed by the software mathematics.
|-
| style="font-size: 1.5em; font-weight: bold;" | You're Ready!
|-
| style="font-size: 1.1em; margin-top: 10px; opacity: 0.95;" | Go measure some THD and make your speakers proud 🎵
|}


---
---


'''Last Updated:''' 2026-04-15
=== Why Two Formats (% and dB)? ===


'''Version:''' 1.0 - User Guide
'''THD %:'''
* Easier to understand for non-technical users
* Direct representation: "5% distortion"
* Useful for product specifications


'''Format:''' MediaWiki
'''THD dB:'''
* Logarithmic scale: easier to see small differences
* Standard in audio/RF engineering
* Used in all standards and specifications
* Better for comparing measurements at different levels


For technical details, see DOCUMENTATION_EN.txt
Both represent the same information, just in different scales.
 
---

Latest revision as of 16:36, 15 April 2026

THD SWEEP MEASUREMENT - USER GUIDE

Master the art of measuring Total Harmonic Distortion with style

 


🎵 THD SWEEP MEASUREMENT
Professional Acoustic Testing Made Simple

---

Install

Download THD measurement :

THD sweep measurement April 2026

Install model

Put the model folder : "THD computation" on model database of NVgate. (By default : C:\OROS\NVGate data\Workbook Library\User\ )

Requirement

NVGate V17 or upper.

Option : DC simulated on NVGate front end.

⚡ QUICK START - 30 SECONDS

STEP ACTION
1️⃣ Launch Launch NVgate in connected mode and load the THD computation model Double-click THD_Sweep_Measurement.exe
2️⃣ Connect Put the sweep sine signal on channel 4️⃣ ; put the response on channel 1️⃣
3️⃣ Start Start the THD_Sweep_Measurement.exe and Click green ▶ START button
4️⃣ Monitor Watch 4 metrics update live , THD and frequency will also be injected on NVGate channels DC simulated.
5️⃣ Stop Click red ■ STOP button

✅ That's it! Your first THD measurement is complete. You're now a certified acoustic engineer. (Not really, but it feels good.)

---


📊 Four Metric Cards

The heart of the interface. These four numbers tell the whole story:

📈
THD (dB) 		📊
THD (%) 		📡
Frequency 		⚡
Fundamental
Harmonic distortion (log scale) Harmonic distortion (%) Current sweep point Signal strength
+5.42 dB 58.294 % 1234.56 Hz 5.0e-01 V

🎯 UNDERSTANDING YOUR RESULTS

THD (%) - The Easy Number

What is it? Percentage of unwanted harmonics in your signal.

Think of it this way:

  • THD 5% = 95% pure signal, 5% noise
  • THD 20% = 80% pure signal, 20% noise

The Quality Scale:

🌟 1% - 5% Excellent - Professional grade equipment
✅ 5% - 15% Good - Solid speaker performance
⚠️ 15% - 30% Acceptable - Consumer level equipment
❌ > 30% Poor - Time for an upgrade 🛠️

THD (dB) - The Technical Number

Same measurement as THD (%) but in decibels (logarithmic scale).

Quick Conversion Chart:

THD % THD dB Quality
1% -40 dB 🌟 Perfect
3% -30 dB ✅ Great
10% -20 dB ✅ Good
30% -10 dB ⚠️ Poor

---

⚙️ CONFIGURATION

When Do I Need to Change This?

Honest answer: Almost never.

The default settings work for 95% of users. Only change if your NVGate project has:

  • Different window names
  • Different marker numbers
  • Different DC input addresses

If you're not sure → Don't change anything. It works.

The NVgate Model generate a sweep sine on the output, feel free to modify the settings if you need. We recommand to not put a sweep speed more than 0.05dec/s (or less) in logarithme for accurate results

How to Access Configuration

Click on ▶ Configuration (section expands)

Important Settings

Setting Default When to Change
Window (sweep) Window2 Your sweep FFT has different name
Window (response) Window1 Your response FFT has different name
Number of harmonics 9

How to Apply Changes

  1. Modify field value
  2. Click Apply Configuration
  3. Log displays "Configuration applied" ✓
  4. Done!

---

❓ FREQUENTLY ASKED QUESTIONS

Q: I Have only one channels. Can i take the max marker on windows 1 ?

A: Yes, on this configuration, put windows 1 for window (sweep) and select the good number for the marker.

Q: Is THD 5% good?

A: For a speaker? Excellent! You can be proud of that equipment. 🎉

Q: Why does THD change with frequency?

A: Because speakers aren't perfect at all frequencies. Some frequencies cause more distortion than others. That's physics being weird.

Q: Can I use this on any speaker?

A: Yes! Desktop speakers, studio monitors, subwoofers, car speakers - if it's connected to NVGate, we can measure it.

Q: How many times should I measure?

A: Once for curiosity. Three times for reliability. Ten times if you're publishing a paper.

Q: Can I export the results?

A: Yes! Copy text from the log console and paste into Excel, Word, or wherever you need it.

Q: What if my project has different settings?

A: Use the Configuration panel to adjust. It's literally made for this.

Q: Does this work over WiFi?

A: No. It only works locally (same computer or local network). WiFi would add too much latency.

---

disclaimer

1) This program is delivered free of charge for NVGate V12. Support is not automatically provided on this tool.

2) For any other requests, please contact your local distributor or the OROS Customer Care department.

---

You're Ready!
Go measure some THD and make your speakers proud 🎵

Technical appendix THD Formulas

THD Percentage (DC1)

Formula:

THD(%) = (√(H2² + H3² + ... + H9²) / H1) × 100

Where:

  • H1 = Fundamental amplitude (1st harmonic)
  • H2, H3, ..., H9 = Harmonic amplitudes (2nd to 9th)
  • √ = Square root

Example:

  • H1 (fundamental) = 1.0 V
  • H2 = 0.02 V
  • H3 = 0.01 V
  • H4 = 0.01 V
  • (all others = 0)

Calculation:

  • Harmonics RMS = √(0.02² + 0.01² + 0.01²) = √0.0006 = 0.0245 V
  • THD% = (0.0245 / 1.0) × 100 = 2.45%

---

THD in Decibels (DC2)

Formula:

THD(dB) = 20 × log₁₀(√(H2² + H3² + ... + H9²) / H1)

Or from THD%:

THD(dB) = 20 × log₁₀(THD% / 100)

Where:

  • log₁₀ = Base-10 logarithm
  • All H values same as above


Example from above:

  • Ratio = 0.0245 / 1.0 = 0.0245
  • log₁₀(0.0245) = -1.611
  • THD(dB) = 20 × (-1.611) = −32.2 dB

Or: THD(dB) = 20 × log₁₀(2.45 / 100) = 20 × (−1.611) = −32.2 dB

---

Quick Conversion Table

THD Percentage THD in dB Quality Rating
0.5% −46 dB Excellent (pro audio)
1% −40 dB Very Good
3% −30 dB Good
5% −26 dB Acceptable
10% −20 dB Fair
30% −10 dB Poor
100% 0 dB Unusable


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Three DC Outputs

Output Channel Measurement Formula Typical Range
DC1 THD % (Harmonics RMS / H1) × 100 0 to 100%
DC2 THD dB 20 × log₁₀(ratio) −200 to 0 dB
DC3 Frequency Sweep frequency at current point 0 to 40 kHz

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Coherence Between DC1 and DC2

The two THD channels always maintain mathematical coherence. Given DC1 value (THD%), you can always calculate DC2:

DC2(dB) = 20 × log₁₀(DC1(%) / 100)

Example:

  • If DC1 displays 5.5%
  • Then DC2 = 20 × log₁₀(0.055) = 20 × (−1.26) = −25.2 dB

This relationship is guaranteed by the software mathematics.

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Why Two Formats (% and dB)?

THD %:

  • Easier to understand for non-technical users
  • Direct representation: "5% distortion"
  • Useful for product specifications

THD dB:

  • Logarithmic scale: easier to see small differences
  • Standard in audio/RF engineering
  • Used in all standards and specifications
  • Better for comparing measurements at different levels

Both represent the same information, just in different scales.

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