Preamp Chassis Layout Advice

[ChrisM91]

I am building a 12B4 CCS preamp to go between my phono preamp and poweramp.

I have now got the designed finalized and have all the parts ordered. With the major parts already here I have got this mock chassis layout for the preamp.


How does this look?
*not all the parts shown are the actual ones I will be using (i.e. volume pot, power switch, etc.)

1. The RCA jacks will be at the back right corner. 3 pairs of input jacks, 1 pair of output jacks
2. That input/source selector and volume controls will have shaft extenders to bring the controls to the front panel of the chassis.
3. There will be two big film caps and resistors at the front of the chassis where the two electrolytic caps are. This is due to the single regulated PSU. The RC filter will decouple each channel.
4. I have the power switch at the front because it will be an illuminated push button. This does cause a long AC run from the back of the chassis where the IEC is to the front where the power switch is. Not sure if this is a problem? Maybe I should just put a simple power switch at the back?

Any other thoughts or advice?

Thanks!

 

[djn]

Looks good to me. The only suggestion I have is to mount the tubes right under the vents to minimize heat build up. That is a great pre...if you need that much gain.

 

[ChrisM91]

Looks good to me. The only suggestion I have is to mount the tubes right under the vents to minimize heat build up. That is a great pre...if you need that much gain.

Good point

I think for the bottom plate I will have to go this way, just due to space to drill into. I will make sure the top plate has the vents above the tubes though.

Heat does rise after all!

 

[ChrisM91]

Bump

 

[ChrisM91]

Any other thoughts on my layout?

 

[Eli Duttman]

Use a tightly twisted pair to bring the "juice" to the power switch. Shield the twisted pair with metal braid that's connected to the chassis. "Dress" the assembly close to the enclosure's wall.

FWIW, I'm not a fan of IEC power connectors. They are just another set of mechanical connections to make trouble.

 

[HollowState]

FWIW, I'm not a fan of IEC power connectors.

Ah yes, but with it you have the ability to audition various high end audiophile (audiophool?) line cord interconnects to hear which one sounds best.

 

[GlennW]

I recommend DC power for indicator light, rather than AC illuminated switch.

 

[Jeff Yourison]

+1 for GlennW's comment. I've had trouble with hum using an AC indicator on pre-stages, especially high gain. Simple low-voltage DC for LED works well.

 

[ChrisM91]

The illuminated on/off switch is actually LED based and powered by DC (12V)

This is the switch in question:
Light Blue LED Illuminated 16mm Metal Self Latching Locking Power Push Button | eBay

It does look a little small but the specs show that it should be able to switch the 120V AC input fine