vikingboy
New Head-Fier
- Joined
- May 6, 2004
- Posts
- 38
- Likes
- 11
Hey guys, I need to check something because Im not sure Im understanding right here and I dont want to shell out $$$ before getting my facts right.
Some basics first to check my understanding of the theory and electronics math behind this subject.
Replacing the caps in the IPOD with the diyMOD enables us to improve the quality of the audio ultimately going to our headphones. The ones on the curcuit board are small and "poor" quality thus degrading the sound quality more than larger ones.
Mounting large caps outside of the case is possible before feeding the signal into our headphone amps. The Frankenstein IPOD thread over at http://www.head-fi.org/forums/f15/fr...d-here-254531/ shows some crazy large caps outside the case. What puzzles me is why use such large uF caps?
If the headphone impedance is 10k ohms, I find that the -3db point (essentially the lowest frequency that will pass te cap) is as follows per uF of cap.
EDIT: Using the formula =1/(2*PI()*AmpImp*(0.00001*DacOutCap))
AmpImp(Ω) - DAC Output Capacitor (μF) - Lowest Frequency (Hz)
100000.115.91549431
100000.27.957747155
100000.35.30516477
100000.43.978873577
100000.53.183098862
100000.62.652582385
100000.72.273642044
100000.81.989436789
100000.91.768388257
1000011.591549431
100001.11.446863119
100001.21.326291192
100001.31.224268793
100001.41.136821022
100001.51.061032954
100001.60.994718394
100001.70.936205548
100001.80.884194128
100001.90.837657595
1000020.795774715
100002.10.757880681
100002.20.72343156
100002.30.691978013
100002.40.663145596
100002.50.636619772
100002.60.612134397
100002.70.589462752
100002.80.568410511
100002.90.548810149
1000030.530516477
Using a 6.x uF cap seems like total overkill.
Assuming the frequency response of hearing is circa 20hz and the Shure earphones go down to 18Hz (taken fromthe shure site)
Technical Specifications:
* Speaker Type: Triple TruAcoustic MicroSpeakers
* Sensitivity (1mW): 119 dB SPL/mW
* Impedance (1kHz): 36
* Frequency Range: 18Hz – 19kHz
* Cable Length/with Extension: 18 in. / 45cm (54 in. / 136cm)
Why not use a smaller, and cheaper cap, something like a 0.1uF would facilitate a -3db at 15hz.
What Im curious about is do I totally misunderstand this and if not, what is the curve from 0db to the 03db point like, how steep is it, essentially meaning how large a cap do I have to use to ensure at my headphones lowest freq range Im within 0db range still.
I hope those are sensible questions, if not....redicule away my friends!
thanks in adv
Ian - aka 'n00b'
Some basics first to check my understanding of the theory and electronics math behind this subject.
Replacing the caps in the IPOD with the diyMOD enables us to improve the quality of the audio ultimately going to our headphones. The ones on the curcuit board are small and "poor" quality thus degrading the sound quality more than larger ones.
Mounting large caps outside of the case is possible before feeding the signal into our headphone amps. The Frankenstein IPOD thread over at http://www.head-fi.org/forums/f15/fr...d-here-254531/ shows some crazy large caps outside the case. What puzzles me is why use such large uF caps?
If the headphone impedance is 10k ohms, I find that the -3db point (essentially the lowest frequency that will pass te cap) is as follows per uF of cap.
EDIT: Using the formula =1/(2*PI()*AmpImp*(0.00001*DacOutCap))
AmpImp(Ω) - DAC Output Capacitor (μF) - Lowest Frequency (Hz)
100000.115.91549431
100000.27.957747155
100000.35.30516477
100000.43.978873577
100000.53.183098862
100000.62.652582385
100000.72.273642044
100000.81.989436789
100000.91.768388257
1000011.591549431
100001.11.446863119
100001.21.326291192
100001.31.224268793
100001.41.136821022
100001.51.061032954
100001.60.994718394
100001.70.936205548
100001.80.884194128
100001.90.837657595
1000020.795774715
100002.10.757880681
100002.20.72343156
100002.30.691978013
100002.40.663145596
100002.50.636619772
100002.60.612134397
100002.70.589462752
100002.80.568410511
100002.90.548810149
1000030.530516477
Using a 6.x uF cap seems like total overkill.
Assuming the frequency response of hearing is circa 20hz and the Shure earphones go down to 18Hz (taken fromthe shure site)
Technical Specifications:
* Speaker Type: Triple TruAcoustic MicroSpeakers
* Sensitivity (1mW): 119 dB SPL/mW
* Impedance (1kHz): 36
* Frequency Range: 18Hz – 19kHz
* Cable Length/with Extension: 18 in. / 45cm (54 in. / 136cm)
Why not use a smaller, and cheaper cap, something like a 0.1uF would facilitate a -3db at 15hz.
What Im curious about is do I totally misunderstand this and if not, what is the curve from 0db to the 03db point like, how steep is it, essentially meaning how large a cap do I have to use to ensure at my headphones lowest freq range Im within 0db range still.
I hope those are sensible questions, if not....redicule away my friends!
thanks in adv
Ian - aka 'n00b'