Here is an RIAA phono stage I designed.
If you're not familiar with them the 6F12P is a high mu triode/pentode. The triode has a mu of 100 with 19.5ma/V. When triode strapped, the pentode is similar.
I use the triode connected pentode as an active load, with a split RIAA network. The 6N5P is very close to a 6SN7 at this bias point.
If you're not familiar with them the 6F12P is a high mu triode/pentode. The triode has a mu of 100 with 19.5ma/V. When triode strapped, the pentode is similar.
I use the triode connected pentode as an active load, with a split RIAA network. The 6N5P is very close to a 6SN7 at this bias point.
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Nice!
At one point I was planning to do a 6F12P based design, for fun you might want to check out my Muscovite and Muscovite Mini threads over in analog source. (This thread might be better over there if you want me to move it at some point.)
I'd love to see some pictures and a blow by blow of your development path.
My designs are almost all cascodes and not unsurprisingly not too different in some ways to what you have come up with. The pentode design was ultimately not successful, now working on 6S17K-V based design.
http://www.diyaudio.com/forums/analogue-source/213769-muscovite-6s3p-tube-phonostage.html
http://www.diyaudio.com/forums/analogue-source/273817-muscovite-mini-iii-6n23p-phono-stage.html
http://www.diyaudio.com/forums/analogue-source/246756-muscovite-mini-6-9-6z9p-phono-stage.html
At one point I was planning to do a 6F12P based design, for fun you might want to check out my Muscovite and Muscovite Mini threads over in analog source. (This thread might be better over there if you want me to move it at some point.)
I'd love to see some pictures and a blow by blow of your development path.
My designs are almost all cascodes and not unsurprisingly not too different in some ways to what you have come up with. The pentode design was ultimately not successful, now working on 6S17K-V based design.
http://www.diyaudio.com/forums/analogue-source/213769-muscovite-6s3p-tube-phonostage.html
http://www.diyaudio.com/forums/analogue-source/273817-muscovite-mini-iii-6n23p-phono-stage.html
http://www.diyaudio.com/forums/analogue-source/246756-muscovite-mini-6-9-6z9p-phono-stage.html
You should take signal from cathode instead. Plate is hi Z point, and will worse thd profile when loaded.
I´d put low cap fet on top instead, but that´s just me
Well there will be a couple of changes on the next build of this.
The 200 ohm cathode resistors will change to 100 ohm to increase conduction.
There is also too little gain for my taste. I have remedied this by using Hammond 124B interstage transformers as a stop gap measure until I'm ready to rebuilt this.
As for microphonics I only notice any microphonics if i'm tapping the tubes, otherwise it's quiet and clean.
The pics are too large to show here so I'll post them online and add a link.
This circuit is part of a larger complete preamp that I built.
The 200 ohm cathode resistors will change to 100 ohm to increase conduction.
There is also too little gain for my taste. I have remedied this by using Hammond 124B interstage transformers as a stop gap measure until I'm ready to rebuilt this.
As for microphonics I only notice any microphonics if i'm tapping the tubes, otherwise it's quiet and clean.
The pics are too large to show here so I'll post them online and add a link.
This circuit is part of a larger complete preamp that I built.
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