Inner groove distortion - Revision history

Petr at 15:30, 30 May 2026

2026-05-30T15:30:46Z

← Older revision		Revision as of 17:30, 30 May 2026
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	== Does 45 RPM partially solve the problem compared to 33 ⅓ RPM ? ==		== Does 45 RPM partially solve the problem compared to 33 ⅓ RPM ? ==
	[[File:33 vs 45 rpm comparison.png\|thumb\|Groove modulations at 33 ⅓ vs 45 [[RPM]].]]		[[File:33 vs 45 rpm comparison.png\|thumb\|Groove modulations at 33 ⅓ vs 45 [[RPM]] ]]

	At 45 [[RPM]], the record spins faster, so more groove passes under the stylus per second. This gives the playback stylus more physical room to reproduce the same signal. It can help reduce the inner groove distortion compared to the same audio cut at 33 ⅓ [[RPM]].		At 45 [[RPM]], the record spins faster, so more groove passes under the stylus per second. This gives the playback stylus more physical room to reproduce the same signal. It can help reduce the inner groove distortion compared to the same audio cut at 33 ⅓ [[RPM]].

Petr at 15:28, 30 May 2026

2026-05-30T15:28:51Z

← Older revision		Revision as of 17:28, 30 May 2026
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	These side-to-side undulations in the groove are called '''groove modulations.'''		These side-to-side undulations in the groove are called '''groove modulations.'''

			[[File:02_modulation_packing.png\|thumb\|Groove modulation of the same sound on the outside and the inside of the record]]

	In order for the music to stay at the correct pitch as the stylus moves toward the center, the same amount of audio time occupies a shorter section of groove. In simple terms, the modulations become more tightly packed, like a squeezed accordion. The music does not slow down, but it becomes harder for the stylus to trace the groove perfectly.		In order for the music to stay at the correct pitch as the stylus moves toward the center, the same amount of audio time occupies a shorter section of groove. In simple terms, the modulations become more tightly packed, like a squeezed accordion. The music does not slow down, but it becomes harder for the stylus to trace the groove perfectly.

	~~[[File:33 vs 45 rpm comparison.png\|thumb\|Groove modulations at 33 ⅓ vs 45 [[RPM]].]]~~

	A stylus can trace wider, more open modulations more easily than very small, tightly packed ones. When it cannot follow the groove accurately, distortion or loss of clarity can occur.		A stylus can trace wider, more open modulations more easily than very small, tightly packed ones. When it cannot follow the groove accurately, distortion or loss of clarity can occur.

Petr at 15:19, 30 May 2026

2026-05-30T15:19:05Z

← Older revision		Revision as of 17:19, 30 May 2026
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	In order for the music to stay at the correct pitch as the stylus moves toward the center, the same amount of audio time occupies a shorter section of groove. In simple terms, the modulations become more tightly packed, like a squeezed accordion. The music does not slow down, but it becomes harder for the stylus to trace the groove perfectly.		In order for the music to stay at the correct pitch as the stylus moves toward the center, the same amount of audio time occupies a shorter section of groove. In simple terms, the modulations become more tightly packed, like a squeezed accordion. The music does not slow down, but it becomes harder for the stylus to trace the groove perfectly.

			[[File:33 vs 45 rpm comparison.png\|thumb\|Groove modulations at 33 ⅓ vs 45 [[RPM]].]]

	A stylus can trace wider, more open modulations more easily than very small, tightly packed ones. When it cannot follow the groove accurately, distortion or loss of clarity can occur.		A stylus can trace wider, more open modulations more easily than very small, tightly packed ones. When it cannot follow the groove accurately, distortion or loss of clarity can occur.

	On top of that, a normal pivoting tonearm is only perfectly aligned at a couple of points across the record. Toward the inner grooves, tracking angle error can become more noticeable, so the stylus may not sit in the groove at the ideal angle.		On top of that, a normal pivoting tonearm is only perfectly aligned at a couple of points across the record. Toward the inner grooves, tracking angle error can become more noticeable, so the stylus may not sit in the groove at the ideal angle.

	~~<center>~~
	~~<gallery widths="300px" heights="200px">~~
	~~01 groove speed.png~~
	~~02 modulation packing.png~~
	~~</gallery>~~
	~~</center>~~

Petr at 15:12, 30 May 2026

2026-05-30T15:12:35Z

← Older revision		Revision as of 17:12, 30 May 2026
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	</gallery>		</gallery>
	</center>		</center>


	== Does 45 RPM partially solve the problem compared to 33 ⅓ RPM ? ==		== Does 45 RPM partially solve the problem compared to 33 ⅓ RPM ? ==

Petr: /* Why Does It Happen? */

2026-05-30T15:12:14Z

Why Does It Happen?

← Older revision		Revision as of 17:12, 30 May 2026
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	On top of that, a normal pivoting tonearm is only perfectly aligned at a couple of points across the record. Toward the inner grooves, tracking angle error can become more noticeable, so the stylus may not sit in the groove at the ideal angle.		On top of that, a normal pivoting tonearm is only perfectly aligned at a couple of points across the record. Toward the inner grooves, tracking angle error can become more noticeable, so the stylus may not sit in the groove at the ideal angle.

			<center>
			<gallery widths="300px" heights="200px">
			01 groove speed.png
			02 modulation packing.png
			</gallery>
			</center>

	== Does 45 RPM partially solve the problem compared to 33 ⅓ RPM ? ==		== Does 45 RPM partially solve the problem compared to 33 ⅓ RPM ? ==

Petr at 14:59, 30 May 2026

2026-05-30T14:59:16Z

@@ Line 1: / Line 1: @@
 '''Inner groove distortion''' ('''IGD''') is a physical limitation, where the audio quality degrades as the stylus (needle) reaches the innermost tracks of a vinyl record, often causing harsher sibilance, distortion, and a loss of clarity.
@@ Line 11: / Line 17: @@
 These side-to-side undulations in the groove are called '''groove modulations.'''
 In order for the music to stay at the correct pitch as the stylus moves toward the center, the same amount of audio time occupies a shorter section of groove. In simple terms, the modulations become more tightly packed, like a squeezed accordion. The music does not slow down, but it becomes harder for the stylus to trace the groove perfectly.

Petr at 09:53, 30 May 2026

2026-05-30T09:53:42Z

← Older revision		Revision as of 11:53, 30 May 2026
Line 24:		Line 24:

	On top of that, a normal pivoting tonearm is only perfectly aligned at a couple of points across the record. Toward the inner grooves, tracking angle error can become more noticeable, so the stylus may not sit in the groove at the ideal angle.		On top of that, a normal pivoting tonearm is only perfectly aligned at a couple of points across the record. Toward the inner grooves, tracking angle error can become more noticeable, so the stylus may not sit in the groove at the ideal angle.


	== Does 45 RPM partially solve the problem compared to 33 ⅓ RPM ? ==		== Does 45 RPM partially solve the problem compared to 33 ⅓ RPM ? ==

Petr at 09:32, 30 May 2026

2026-05-30T09:32:06Z

← Older revision		Revision as of 11:32, 30 May 2026
Line 26:		Line 26:

	== Does 45 RPM partially solve the problem compared to 33 ⅓ RPM ? ==		== Does 45 RPM partially solve the problem compared to 33 ⅓ RPM ? ==
	[[File:33 vs 45 rpm comparison.png\|thumb\|Groove modulations at 33 ⅓ vs 45 RPM.]]		[[File:33 vs 45 rpm comparison.png\|thumb\|Groove modulations at 33 ⅓ vs 45 [[RPM]].]]

	At 45 [[RPM]], the record spins faster, so more groove passes under the stylus per second. This gives the playback stylus more physical room to reproduce the same signal. It can help reduce the inner groove distortion compared to the same audio cut at 33 ⅓ [[RPM]].		At 45 [[RPM]], the record spins faster, so more groove passes under the stylus per second. This gives the playback stylus more physical room to reproduce the same signal. It can help reduce the inner groove distortion compared to the same audio cut at 33 ⅓ [[RPM]].

Petr at 09:31, 30 May 2026

2026-05-30T09:31:31Z

← Older revision		Revision as of 11:31, 30 May 2026
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	While a record spins at a constant [[RPM]] (rotations per minute) during playback, its outer edge moves faster under the stylus than the inner area, because the length of a circle on the outer edge is almost twice as long as a circle near the center label.		While a record spins at a constant [[RPM]] (rotations per minute) during playback, its outer edge moves faster under the stylus than the inner area, because the length of a circle on the outer edge is almost twice as long as a circle near the center label.

	At the outer edge of a 12-inch LP at 33 ⅓ RPM, the record groove travels under the stylus at about 50cm/s. By the time the needle reaches the inner grooves, that linear velocity is reduced to roughly half.		At the outer edge of a 12-inch LP at 33 ⅓ [[RPM]], the record groove travels under the stylus at about 50cm/s. By the time the needle reaches the inner grooves, that linear velocity is reduced to roughly half.

	That matters because sound is encoded as side-to-side movement in the groove. A loud or bright sound requires fast, detailed movement. Near the outside of the record, there is more physical groove length available to draw those movements. Near the center, the same musical information has to fit into a shorter length of groove.		That matters because sound is encoded as side-to-side movement in the groove. A loud or bright sound requires fast, detailed movement. Near the outside of the record, there is more physical groove length available to draw those movements. Near the center, the same musical information has to fit into a shorter length of groove.
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	02 modulation packing.png		02 modulation packing.png
	</gallery>		</gallery>
	'''Constant RPM, different groove speed.''' ''The platter turns at the same speed everywhere, but the outer groove is almost twice as long as the inner one so it passes the stylus about twice as fast. Less speed on the inside grooves means less room for detail.''		'''Constant [[RPM]], different groove speed.''' ''The platter turns at the same speed everywhere, but the outer groove is almost twice as long as the inner one so it passes the stylus about twice as fast. Less speed on the inside grooves means less room for detail.''
	</center>		</center>

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	[[File:33 vs 45 rpm comparison.png\|thumb\|Groove modulations at 33 ⅓ vs 45 RPM.]]		[[File:33 vs 45 rpm comparison.png\|thumb\|Groove modulations at 33 ⅓ vs 45 RPM.]]

	At 45 RPM, the record spins faster, so more groove passes under the stylus per second. This gives the playback stylus more physical room to reproduce the same signal. It can help reduce the inner groove distortion compared to the same audio cut at 33 ⅓ RPM.		At 45 [[RPM]], the record spins faster, so more groove passes under the stylus per second. This gives the playback stylus more physical room to reproduce the same signal. It can help reduce the inner groove distortion compared to the same audio cut at 33 ⅓ [[RPM]].

	However, groove modulations near the center are still more tightly packed than modulations near the outside of the record, so fidelity will still generally be highest at the outer diameter.		However, groove modulations near the center are still more tightly packed than modulations near the outside of the record, so fidelity will still generally be highest at the outer diameter.

	Since the record spins faster at 45 RPM, there is less [[Playing times\|playtime]] available. Once the side length goes beyond the [[Recommended playing times\|recommended playing time]], the cutting engineer might have to cut quieter, use narrower groove spacing, reduce bass, reduce level, or push the music closer to the center. At some point, many of the 45 RPM advantages can disappear.		Since the record spins faster at 45 [[RPM]], there is less [[Playing times\|playtime]] available. Once the side length goes beyond the [[Recommended playing times\|recommended playing time]], the cutting engineer might have to cut quieter, use narrower groove spacing, reduce bass, reduce level, or push the music closer to the center. At some point, many of the 45 [[RPM]] advantages can disappear.

Petr: /* Why Does It Happen? */

2026-05-30T09:05:59Z

Why Does It Happen?

← Older revision		Revision as of 11:05, 30 May 2026
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	02 modulation packing.png		02 modulation packing.png
	</gallery>		</gallery>
	'''Constant RPM, different groove speed.''' ''The platter turns at the same speed everywhere, but the outer groove is almost twice as long as the inner one so it passes the stylus about twice as fast. Less speed on the inside grooves ~~mean~~ less room for detail.''		'''Constant RPM, different groove speed.''' ''The platter turns at the same speed everywhere, but the outer groove is almost twice as long as the inner one so it passes the stylus about twice as fast. Less speed on the inside grooves means less room for detail.''
	</center>		</center>

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	On top of that, a normal pivoting tonearm is only perfectly aligned at a couple of points across the record. Toward the inner grooves, tracking angle error can become more noticeable, so the stylus may not sit in the groove at the ideal angle.		On top of that, a normal pivoting tonearm is only perfectly aligned at a couple of points across the record. Toward the inner grooves, tracking angle error can become more noticeable, so the stylus may not sit in the groove at the ideal angle.


	== Does 45 RPM partially solve the problem compared to 33 ⅓ RPM ? ==		== Does 45 RPM partially solve the problem compared to 33 ⅓ RPM ? ==