I just read a review on a just released phono preamp that retails for $US45,000 and it uses 12AU7,12AX7 tubes!!!
12AU7, 12AX7 tubes were designed for use in televisions , but became used in audio as similar replacements for 6SN7 and 6SL7 tubes, which were genuine audio tubes.
The 12 series were cheaper, but nowhere near the quality of the 6 series tubes.
Substitute a 6SN7 for a 12AU7 and the difference is day and night, but for reasons of economy and ease of supply the 12 series tubes caught on and became widely used in the audio industry.
I first used 12AU7 and 12AX7 in a phono circuit about 30 years ago- the popular RCA tubebook circuit.
It used feedback EQ and sounded ok, but couldn't drive a long cable let alone a power amp without the easiest of a load.
I wouldn't even use a 6SN7 and 6SL7 in a phono, although I have built a few phonos to prove it coudn't be done.
Well, actually it can be done, and again they sound ok, but there were some fantastic tubes released at the end of the tube era which are near perfect for the needs of a phono preamp, and are high gain and have good drive - these tubes give very high definition , accuracy and transparency.
The 12 series tubes are wimps in comparism and give a bloated ,warm "romantic"and "tube" sound , ok if you like that sort of ting but I guarantee you will soon tire of it.
My LCR and Standard Cortese use 6688 and 6H23 frame grid tubes in the phono section.
The soon to be released phono only LCR preamp uses 6688, 6688, and 6E6P tubes.
These are combined with the fantastic enveloping LCR circuit and state of the art circuit design to produce a circuit you will never tire of listening to and enjoying.
Classic cosmetic appearance, finest sound and $5500 for the LCR Cortese.
Against $45,000 for 30 year old technology , and another $10,000 for a SUT so you can use your MC cartridge - flabbergasting!!!
