Build this RCA-designed, RIAA-equalized high-fidelity stereo preamp for magnetic phono cartridges.
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- Опубликовано: 7 сен 2024
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Warnings and safety precautions!
All vacuum tube circuits operate at dangerous voltage levels, including this project. The dual triodes used in this project and other vacuum tube amplifiers operate at over 300 volts. Accidental contact with an energized circuit of this nature can be fatal.
Working on, testing, and adjusting live tube circuits requires extreme safety. In general, be cautious and have a safety plan in place!
Remember, safety first, always!
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This preamp project is based on a design from the "RCA Receiving Tube Manual" RC-30 edition, page 702, circuit 29-16. The stereo phono preamp consists of a two-stage matched pair of 12AX7 twin triodes, in a common-cathode voltage amplifier configuration. The passive RIAA equalization network is connected between the two amplifier stages.
This network boosts the low frequencies and reduces the high frequencies of audio signals coming from the output of the moving magnet phono cartridge. This is important for achieving the correct equalization curve during vinyl playback and ensuring a more balanced music listening experience. The QA400 audio analyzer's frequency response test result will also show the effect of the equalization curve.
The "New Orthophonic," as mentioned in the book, was developed by RCA in 1954, contributed to the standardization of vinyl record playback, leading to what is recognized at present as the RIAA curve. This standardization was crucial for ensuring accurate playback of vinyl records, allowing analog music to be experienced with the same fidelity that the recording industry intended. 
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Thank you for a nice project. I think i'll try to build and test one soon. Best regards. :)
Thank you. It's a challenge that you'll enjoy.
Muy interesante es mono,me gustarie ver uno estereo.?????
It is in stereo. Thanks.
Note that this preamplifier was meant to have some type of buffering amp between it and the next stage, unless it was mounted on the system preamp chassis. The output is very high impedance, so the cable should be very short and low capacitance as possible. If I were designing this for stand alone use, I would add a 12ax7 buffer.
Thank you. It was also mentioned and recommended in the circuit description of Circuit 29-16 in the RCA Tube Manual RC-30, pp. 702-703, except for the inclusion of a buffer.
Is this the same circuit as 25-17 in the RCA Manual? Uses 12AX7 / 7025 tubes..
Circuit 29-16 in the RCA Tube Manual RC-30, pp. 702-703
sir finished products ani nga amply pila imo baligya
I'm sorry, Eddie. I don't sell kits for any projects posted here or on my website; everything is done DIY (including PCBs).
@@buildaudioamps ok sir thank you kahinumdom paka nako sir eddie kato mo palet unta sa EG wala nadayon kay wa na kompleto ako kwarta c allan JJB nlang ang nipalet ok salamat sa pag reply sir
@@eddieorevillo9269 Thank you
Nice implementation of a vintage project, but I CAN'T STAND THAT AWFUL SOUNDTRACK!