Dumb Subsonic filter question.

[Lavane]

So, I finished up my CNC build, then in hind sight, I realized I should have gotten a bigger chassis to fit a subsonic filter board I have. So, since this is a passive preamp with a phono preamp, can the subsonic filter be added between the passive preamp output and amp? This would put it after the volume control. I'm thinking this would be a no go.

 

[rothwellaudio]

Yes, but it wouldn't really be a passive preamp if you did because the output would be buffered. Whether that's a good thing or a bad thing, I'll leave others to debate.

 

[Lavane]

Thanks, that makes sense.

 

[HamboneF18]

Could you not put your subsonic between the phono pre and preamp?

 

[Lavane]

Could you not put your subsonic between the phono pre and preamp?

Maybe, but I've already built the thing. There isn't much room to add the power supply, power supply filter board and subsonic filter board anyway. There isn't any room at the rear to add a quad of jacks, where I could add, or remove the filter using it outboard. I do have other stand alone phono preamps I could use it with though.

 

[HamboneF18]

Looks like you’re a victim of “mission creep!”

I’ve got several Motronix boards in use. I like them! The discreet low noise preamp is quite good, IMO. So is the 70 w/ch stereo amp board.

 

[Lavane]

Looks like you’re a victim of “mission creep!”

I’ve got several Motronix boards in use. I like them! The discreet low noise preamp is quite good, IMO. So is the 70 w/ch stereo amp board.

I'm so guilty of project creep. It happens almost every project. I start with a simple plan, and just keep adding things. This started out as simple input selector box with a volume control.

 

[AudioFeline]

Mount the subsonic board upside-down on the lid of your passive preamp box?

 

[Lavane]

I thought of that, but I like the nice clean look of it, no screw head sticking up.
The top is held on with the four round corner tops.

 

[HamboneF18]

I would think your existing power supply has plenty of voltage/current capacity to run the extra board. Unless it’s voltage output doesn’t support the subsonic filter board. And you don’t have to use screws to mount the additional board.

 

[tjste]

If chassis height allows, is mounting filter boards vertically an option?

 

[Lavane]

I would think your existing power supply has plenty of voltage/current capacity to run the extra board. Unless it’s voltage output doesn’t support the subsonic filter board. And you don’t have to use screws to mount the additional board.

The power supply does, but it has to be adjusted to 10v for the phono board. The filter board needs 15v.
I really only need one more line level input. I could disconnect two sets of jacks on the rear and wire them between the phono board and volume control. Then connect the filter to them as an outboard unit. And either use jumpers if not used, or add a switch.
If I build it as a stand alone filter, I guess I could connect it to the tape monitor of my main system preamp also. Tape out comes right off the selector switch, tape in them goes to the line stage of the preamp. That would put it right after the phono pre before the line stage and volume control. And just switch it in when I need it.
I would have to use an extra outboard selector though. I have too much equipment connected in my main system as is.

 

[gadget73]

maybe modify it into a tape loop. Output from the mode selector to the output jacks, input from another set of jacks to the volume control. Switch to route signal through the jacks or just bridge them together. That would give you the option to run anything you like between the source and the volume control.

 

[Lavane]

maybe modify it into a tape loop. Output from the mode selector to the output jacks, input from another set of jacks to the volume control. Switch to route signal through the jacks or just bridge them together. That would give you the option to run anything you like between the source and the volume control.

Thats what I was thinking. The filter is a project for next month.
I still need to find a chassis I like, and get a few bits along with some .1uf film caps and two inductors for the small power supply filter board. The supply filter board was designed to be used with dual switch mode power supplies like the one I'm using.

 

[AudioFeline]

I thought of that [mounting the subsonic board under the lid], but I like the nice clean look of it, no screw head sticking up. The top is held on with the four round corner tops.

You could mount it upside down using countersunk bolts, so it is flat. You could buy a tin of hammertone copper spray paing, and either paint the top of the countersunk bolts, or cut a plate that could be painted and stuck on top, shaped around the corner mounts.