noob stab in the dark - riaa preamp

[JZatopa]

I freely admit that I am nothing close to an EE but I know enough about electronics to know I don't know enough. I drew up a circuit which I think might work but I need to know if I am on the right track. Could someone take a look and tell me if this would work?

http://farm9.staticflickr.com/8414/8706257890_fa1274a5fe_c.jpg


What I am doing is trying to take part of this circuit and make it a dual rail/push pull circuit semi based on the F5 amplifier.

I am not sure this is a circuit worth building but I would like to know if I came up with something that would at least work if I were to try it.

 

[bear]

that will likely not work well... also RIAA requires two separate "curves".

You could use the "F5" type circuit as a gain stage and then do what is called "passive EQ" where the EQ goes inbetween two or three gain stages. In that case the gain stages can be thought of as blocks of "gain" or as "opamps". One issue with the standard F5 amp's design (even set up for lower power) is that it has limited gain and also requires hard to find jfets - they're hard to source now.

It also has poor PSRR, so you will need very very clean rails, which means very very good regulation...

For phono use, especially with MC carts, noise floor is an issue.

Depending on if you want to work on design or want to have a working RIAA, you have two directions to go in - work on design, use LTSpice or similar to get in the game, and in the ballpark with a design, or follow one of the working RIAA designs already published, many here.

_-_-

 

[JZatopa]

bear, thanks for the help. when you say it wouldn't work well, could you tell me if it would work at all? I have played around with LTspice but I never can quite get it to do what I want.

The booze hounds preamp is 2 jfet gain stages with a passive riaa filter in between. All I was trying to do was use a push pull jfet front end ala F5 and a push pull jfet output. Honestly I may just be needlessly complicating things but thats how I learn sometimes.

Would any of your comments about this design still hold true for the booze hounds design?

 

[bear]

I have not seen the other design.

but there is a difference between putting the EQ in the feedback and in series with two stages.

You don't appear to have two jfet stages or a jfet and mosfet stage with a passive RIAA inbetween.

The way to start with LTSpice is to take an example out of the library, run it, see what it does - the schematic is known to work - then edit the schematic to change it to what you want, then run that.