tube phono stage with multiple 78rpm EQ

[mambaum]

Hello Folks


I have a nice collection of 78rpm Tango records.

I'm working on a Garrard-401 with SME 3009 and Stanton 681ee for 78rpm and Hadcock gh-228 for the time being with Audio Technica 450e. I also have a Thorens 126 mkIII with Ortofon om-20 (and 78rpm) and Shure M44c.

I'm playing through a modded Audio Innovations 500, that doesn't have a nice phono-stage, so I'm looking for a tube based phono pre amp that can do multiple RIAA-like corrections like stated on http://sound.westhost.com/project91.htm. The phono pre amp there isn't tube based and I don't want to cut down on options: so 9 bass options and 7 treble options.
I did find some nice 78rpm tube-based designs, but those do not meet all requirements like http://members.myactv.net/~je205d/mono.htm

I did some googleing but I hardly found a tube-design that has made the bass and treble independent and I couldn't find the filtering sections for the award roll-offs.

This one is the closed I could find: http://www.hagtech.com/pdf/monogram.pdf

Any other great idea's?


De Groenten
Martin

[Horexx]

Some further ideas you can get here:
http://ingoschroeder.de/dphono.htm

it is a symmetric phono pre with valves and a detailed description of switchable time constants (in German).

Regards Peter

[mambaum]

Mei....what a work...but leaving the MC stage out makes it do-able. But it doesn't have the independent bass and treble.

Going through the links I found the mono-amp that used variable frequency/time-constants setting...that's something I will think about. That also contained a mono-schematics that can do independent bass and treble.

I'll look into it....putting it in LTspice.

[mambaum]

Just saw that the Hagerman is a mono design. Need two to get stereo...will become to expensive unless I completely build it myself. To cut on cost I have a few questions:
-if I build a stereo version can I do with one 12AX7 or is there a special reason for the dual 12AX7 stage in the beginning?
-can't I skip the last section and do all with 2 stages instead of 3? I should be able to get enough gain in 2 stage or not? How should I change the design then?
http://www.hagtech.com/pdf/monogram.pdf