Cassette Dubbing Optimizer
Get the right levels and bias settings before you press record. Fewer failed transfers, better sounding tapes.
Works with Type I, II, and IV cassettes. Built for mixtape makers, archivists, and anyone who wants their dubbed tapes to sound close to the source.
Transfer Settings
Highest meter reading on your playback deck during the loudest passage.
Does your deck's meter read high (+1 to +4) or low (-1 to -4)? Set 0 if unsure.
A quick walkthrough for your first dub
Check your source
Play the loudest part of the source tape and watch the peak meter. Write down the highest number you see. If your deck has a peak hold button, use it. For VU meters, the true peak is usually 2–3 dB above what the needle shows on fast transients.
Pick your blank tape
Type I tapes are forgiving but hiss more. Type II tapes give you brighter highs and lower noise. Type IV metal tapes handle the hottest signals but cost more. Choose based on what you have and how important the recording is.
Enter your numbers
Select your source tape type or enter a custom peak level. Choose the blank tape you are recording onto. If you know your deck's meters are off, slide the offset control. The calculator updates instantly.
Set your deck and test
Use the suggested record level as your starting point. If your deck has bias fine-tune, adjust it as recommended. Record 30 seconds of a track with strong highs and listen back. If it sounds dull, reduce bias slightly. If it sounds harsh or distorted, increase bias or lower the record level a touch.
Tape type characteristics at a glance
| Type | Common Names | Bias | Typical MOL | Noise Floor | Best For |
|---|---|---|---|---|---|
| Type I | Normal, Ferric, LN, SLH | Normal (100%) | +2 to +4 dB | Higher hiss | Voice, demos, casual mixtapes |
| Type II | High, Chrome, CrO2, SA, XLII | High (150%) | +4 to +6 dB | Lower hiss | Music mixtapes, archival copies |
| Type IV | Metal, MA, MX | Metal (200%) | +6 to +8 dB | Lowest hiss | Master recordings, critical transfers |
MOL = Maximum Output Level (3% THD at 315 Hz). Values are typical for quality tapes from the late 1980s onward. Older or budget tapes may perform 2–3 dB lower.
Mistakes that ruin a dub (and how to avoid them)
- Recording too hot on Type I tape. Ferric tape saturates quickly. Pushing past +4 dB often adds mud, not loudness. Back off to +2 dB and use your ears.
- Ignoring azimuth. If the playback deck's head is tilted relative to the recording deck's head, you lose high frequencies. Adjust the playback deck's azimuth screw while monitoring a 10 kHz tone, or use a pre-recorded reference tape.
- Using Dolby without level calibration. Dolby encoding and decoding depend on accurate levels. If your deck's meters are off by 2 dB, the Dolby tracking will be wrong. Always calibrate record level with a test tone before a critical Dolby dub.
- Dirty heads. A thin layer of oxide on the record or playback head can drop high frequencies by 6 dB or more. Clean heads, pinch rollers, and capstans before every important session.
- Copying a copy. Each analog generation adds noise and reduces bandwidth. If you must dub a dub, use the best tape you have and keep levels conservative to minimize added distortion.
Quick answers
Why does my dubbed copy sound dull compared to the original?
The most common cause is recording at too low a level on a tape that needs more high-frequency energy. Type II and Type IV tapes typically need a hotter signal and often a slight bias reduction to keep the highs crisp. Check your deck's bias fine-tune if available, and make sure your playback deck's azimuth matches the recording deck.
Can I use this calculator with any cassette deck?
Yes, but the accuracy depends on how well you know your deck's meter behavior. The deck offset control compensates if your meters read consistently high or low. If unsure, set offset to 0 and do a short test recording.
What if my deck does not have adjustable bias?
Focus on the record level suggestion. The bias note is still helpful: if it says "reduce bias slightly," you might pick a brighter tape formulation or accept slightly softened highs. Many fixed-bias decks are optimized for one tape type; using that type gives the best results.
How do I measure my source tape's peak level?
Play the loudest passage and watch your deck's peak meters. Note the highest reading in dB. For VU meters, the true peak is often 2–3 dB above the needle indication. Use peak hold if your deck has it, or rewind and watch several times.
Does the calculator account for different tape brands?
The suggestions are based on typical performance for each tape type. There is variation between brands and even between batches. Treat the numbers as a solid starting point, then adjust by ear. If you dub often, keep notes on which tapes work best with your deck.
About this project
This calculator was built for people who care about how their dubbed tapes sound. It does not replace your ears, but it gives you a repeatable starting point so you spend less time guessing and more time listening. The logic is based on standard recording alignment practices: setting record level relative to the tape's maximum output level, then adjusting bias for flattest frequency response.
We assume your deck is in good working order with clean heads, proper azimuth, and functioning electronics. If your deck needs service, the numbers here will not fix mechanical problems. Always do a test recording before committing to a full tape.
Last updated: April 2026. Settings are saved in your browser for convenience; nothing is sent to a server.