Hi.
(1) We could do this simple analysis in dB but it's easier to understand in simple voltage gain.
(2. The highest gain triode I know of is the 12AX7.
(3) Given the above I doubt there would be many takers for such a preamp. However, there is no doubt that some sound would be present but I would not call it Hi Fi.
First off, I appreciate you have shown yr due respect to me in this too-simple a phonostage project that has sent so many tube DIYers headscratching. You are not alone, & in fact I was one of them showing extreme skeptism on how one active stage can make a good sounding phono amp let alone it be theoretically possibe???
Strictly to satisfy my passion for
better quality music, I tried it out against all odds. I think I've succeeded to make it an excellent sounding phonostage that beat any, repeat, any multi-stage phonostage respective of makes & prices,
sonically, IME. It also sonicaliy beats my already excellent sounding upgraded 50-year stock Dynaco PAS-2 phono-preamp which I virually rebuilt inside out by chopping out its entire tone-control linestage, + major circuit upgrading. Now it's a 2-stage RIAA phonostage+passive linestage. I dare say I am the only guy ever upgraded a Dynaco PAS-2 in such 'crazy' way so far, 'cause I am a music-maniac!
(1) Please don't go by the conventional wisdom dictated by the textbooks. Anyone who got some audio electronic knowledge should know the gain so called "Needed" for a RIAA phono amp should be min 40dB (@1KHz) for MM cartridge O/P voltage 5mV & 60dB for MC cartridge O/P 0.3mV... becaue of RIAA equalization loss etc etc. My question is - do we need 40dB/60eB so much gain at all???????????????
I've auditioned so many Hi-end brandname phono-preamps tagged for mega bucks matched with TTs, power amps & loudspeakers of similar mega pricing levels in past years. None of them really impressed me sonically - lacking transparancy, air & music headroom, too pushy due to one common problem, IMO - too much gain!!! The volume control can never go up beyond 9 0'clock. This shows a huge problem, technically & sonically.
So my logic & common sense tell me the 40dB for MM cartridge & 60dB used by the audio industrial in building phonostages is way way too HIGH to reprduce quality music. So why don't we DIYers get out of the box by rectifying such design pitfall??? I've done it & have proved my "less gain for better music" philosophy is correct!
(2) Yes, you are on the right track - we need highest gain triode - 12AX7. A hint - no conventional design!
(3) Yr "doubt" is redunctant as I already built one & have been enjoying QUALITY music for a few years now
- fast, see-thru transparent, micro-detailedl, airy, dynamic & very quiet background - noiseless at max
volume pot setting with TT turning. As I already posted earlier, around 2 O'clokc for high level rock/
pop music & up to 5 O'clock (max volume setting) for some very low level classical music - driving direct
my brandname tube power amp & SS direct-current power amp
Please get out of the box to think more creatively like what I have done.
I want you to do some more research before I tell you the unconventional design used in this too-simple
phonostage.
c-J