Perancangan Penguat Awal Menggunakan Tabung Hampa Pada Aras Tegangan Rendah
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Abstract
Vacuum tube amplifiers have been known as softly-cliping audio amplifiers, as opposed to solid-state based amplifiers which exhibit hard-cliping properties. However, vacuum tubes are operated in high voltage level. Meanwhile, in order to work in low voltage level, a vacuum tube amplifier must employ step down transformers that leads to complexity. This study aims to make use of vacuum tubes in a pre-amplifier working on 12 VDC level. First, several measurements were done to obtain graphics of characteristic of triode 12AT7 in low voltage level. Common-cathode topology was cascaded with a common-anode topology to realize such amplifier. The results show that the preamplifier has an input impedance of 1.11 MΩ, output impedance of 3.5 kΩ for the right channel and 3.2 kΩ for the left channel. Maximum Total Harmonic Distortion of 1.7% occurs on frequency of 4 kHz. Voltage gains of 20.08 dB and 20 dB were obtained for the right and left channels, respectively. This pre-amplifier also shows sensitivity of 212 mVrms, maximum output level of 2 Vrms, and relatively flat frequency response within 60 Hz–20 kHz with ripple of ± 0.5dB. This pre-amplifier can be alternatively used in two modes, namely linear mode and distorted mode.
Keywords : Pre-amplifier, Vacuum Tube, Linear Mode, Distorted Mode
Abstrak
Penguat tabung hampa telah dikenal sebagai penguat audio dengan sifat soft-clipping, dan tidak seperti penguat transistor yang bersifat hard-clipping. Tabung hampa umumnya merupakan suatu komponen aktif yang bekerja pada aras tegangan tinggi (ratusan volt), namun pada aras tegangan tinggi penguat tabung membutuhkan transformator keluaran untuk menurunkan aras tegangan isyarat keluaran. Penelitian ini bertujuan untuk merancang penguat awal dengan menggunakan tabung hampa pada tegangan kerja 12 VDC. Untuk merancang untai tabung hampa pada aras tegangan rendah, telah dilakukan pengukuran untuk mendapatkan grafik karakteristik trioda 12AT7. Untai tabung hampa direalisasikan dengan topologi katoda bersama yang dikaskade dengan anoda bersama. Dari hasil pengukuran didapatkan spesifikasi penguat awal yaitu impedansi masukan sebesar 1.11 MΩ, impedansi keluaran 3.5 kΩ pada kanal kanan dan 3.2 kΩ pada kanal kiri, THD maksimal terjadi pada frekuensi 4 kHz di kanal kanan yaitu sebesar 1.7%, bati tegangan 20,08 dB pada kanal kanan dan 20 dB pada kanal kiri, sensitivitas 212 mVrms, aras keluaran maksimal 2 Vrms, tanggapan frekuensi yang rata pada rentang 60 Hz – 20 kHz dengan fluktuasi ± 0.5 dB. Penguat awal ini dapat digunakan secara bergantian dalam dua ragam, yaitu ragam linier dan ragam cacat berupa efek flanger.
Kata Kunci : Penguat Awal, Tabung Hampa, Mode Linear, Mode Distorsi
References
[2] Aitchison, M. & Fenton, S., Can transistors sound like valves?, Proceeding of Computing and Engineering Annual Researchers’ Conference, pp. 20-26, (2010)
[3] Doidic, M., Mecca, M., M., Ryle, M., & Senffer, C., U.S. Patent No. 5 789 689, 1998.
[4] Hamm, R. O., Tubes vs transistors – Is there an audible difference?, Journal of the Audio Engineering Society, vol. 21 no. 4, pp. 267-273, (1973).
[5] Yeh, D. T., Automated Physical Modeling of Nonlinear Audio Circuits for Real-Time Audio Effects—Part II: BJT and Vacuum Tube Examples, IEEE Transactions on Audio, Speech, and Language Processing, vol. 4 no. 4, pp. 1207-1216, (2012).
[6] “Space-Charge and Other Low Voltage Tube”, diakses dari http://www.junkbox.com/electronics/lowvoltagetubes.shtml, 16 Juni 2013.
[7] Jones, M., Valve amplifiers, ed. 3, Burlington: Linacre House, (2003).
[8] “The Edison Effect”, diakses dari http://www.charlesedisonfund.org/tomedisonbio/ch10.html, 28 Mei 2013.
[9] Ryder, J. D., Engineering electronics, ed. 2. New York: McGraw-Hill, (1957).
[10] Millman, J. & Halkias, C. C., Integrated electronics, NewYork: McGraw-Hill, (1972).
[11] Celi, P., Get More Out of Your Flanger, diakses dari http://www.premierguitar.com/articles/Get_More_Out_of_Your_Flanger, magazine article, September 2012 edition, accessed July 21st, 2014
[12] Smith, J. O. Physical Audio Signal Processing, W3K Publishing, (2010).
[13] International Electrotechnical Commission, IEC Standard 268-3, Sound System Equipment - Part 3: Amplifiers, Geneva, Switzerland, (1988).
[14] Crown International Website, "FAQ: How to record direct? Please explain impedances and levels", diakses dari http://www.crownaudio.com/kb/entry/304/, (2014).
[15] Hi-Fi World ,“Sensitivity”., diakses dari http://www.hi-fiworld.co.uk/amplifiers/75-amp-tests/150-sensitivity.html, (2014).
[16] Mutiarasari, Rina, “Pembangkit Derau Putih dan Merah Jambu untuk Pengujian Elektroakustik dan Audio”, Salatiga, (2006).
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