YARC yet another RIAA circuit

[kjunom]

I haven't seen this topology, but I didn't do an extensive search (sorry moderator).

I couldn't get it into gif, so I zipped it. It's a dxf file.

I used some non descript transistors, not what is on the schematic. I also am using 20 ohm instead of 200 ohm degenerator resistors.

I added an opamp to buffer the second stage, not shown. Good place to set overall gain.

Not shown, but much needed are good supply filtering (poor PSRR, even with only 20mv ripple) and a servo.

Filter resistor values were changed as calculated for the measured filter capacitor values.

It's a proto board rats nest, only one channel, no expensive parts, but it souncs quite nice. The bass seems quite strong. Just using an inexpensive cartridge for now and it is listenable. Would have liked to try JFETs on the input, but don't have any.

[Onvinyl]

Can't read your file

[peranders]

Originally posted by kjunom
It's a dxf file.

DXF is not a common file format for normal people

You could download LTSpice (freeware) if you want to draw a schemtic.

http://www.linear.com/designtools/so...gistration.jsp

[cukkurullo]

Originally posted by peranders

DXF is not a common file format for normal people

You could download LTSpice (freeware) if you want to draw a schemtic.

http://www.linear.com/designtools/so...gistration.jsp

Hi,

is this software the best one? Does it provide optimized board layout?

thanks
cukkurullo

[peranders]

With LTSpice you can do:

Draw schematics

Make transient analysis

Frequency response

FFT, distortion analysis

With this program you can check fairly good if a circuit has any chance to work.

[CheffDeGaar]

A more readable pdf version...

[kjunom]

I use MicroSim PSpice for simulation and PCAD for layout, and Corel, Autocad and Adobe Illustrator when needed. DXF files are pretty interchangeable between them. At least for me, dxf files are ordinary but gif is not.

I liked using the filter as a load for the first stage and the following buffer also as a gain stage for the second filter. Using bipolars for the differential transistors gives quite a bit of gain and the gain for the second and third stages are pretty low. When I try JFETs, I hope to only change some resistor values. Seems to be a pretty simple circuit. The freeware spice simulators are great for small circuits.

The input offset voltage for the parts I threw together was pretty low, so I didn't worry about offsetting the cartridge.

If there is any interest I could do a more compete schematic using the recommended LTSpice. There are two opamps. I don't know if that is a problem. I'm sure there is room for improvement (resistors setting opamp gain could be increased to reduce input bias current mismatch, but the effects on performance may be minimal), but it's a pretty simple circuit.