Installing RCA jacks in the back chassis of the VTA Amps

Good afternoon everyone.

I believe that I have heard it mentioned here in the forum of installing RCA jacks in the back of the VTA Amps ?

If so.... I have also thought of doing the same.... Bob is absolutely correct... Doing this modification you have to be very careful when placing RCA jacks from the front of the driver preamp board to the back of the chassis so you don't induce a noisy signal from the transformers into the signal path of the front stages of the preamp driver board.

After I get through building my VTA 120 I am going to install everything originally and leave the front RCA jacks where they are. Without drilling any holes in the back of the chassis to mount the new RCA jacks I'm going to temporarily solder in two separate Right and Left shielded RCA preamp cables from the front to the back of the chassis to see if there's any noise being induced into the shielded cables from the transformers into the front preamp stages.

If all is quiet and there's no noise being introduced into the shielded cables from the transformers I plan to install RCA jacks in the back of the amplifier. This way I'll be able to plug-in my gear in the back and also from time to time if I decide to plug-in my iPhone for playing YouTube it will be very convenient to just plug it into the front RCA jacks without having to unplug anything from the back.

Have a good day and stay safe everyone. I hope this was helpful.

I think I might be in the minority when it comes to disliking the original chassis. So many compromises were made to keep prices low and for convenience. I prefer to make my own chassis. DIY. I can then have all connections where I want them including a jack for a detachable power cord.

corndog71 wrote:I think I might be in the minority when it comes to disliking the original chassis.  So many compromises were made to keep prices low and for convenience.  I prefer to make my own chassis.  DIY.  I can then have all connections where I want them including a jack for a detachable power cord.  

"jack for a detachable power cord"

corndog71, I also plan to do this mod as well. I also plan to install a beefier power switch in the back.

corndog71 wrote:I think I might be in the minority when it comes to disliking the original chassis.  So many compromises were made to keep prices low and for convenience.  I prefer to make my own chassis.  DIY.  I can then have all connections where I want them including a jack for a detachable power cord.  

It's no problem installing an IEC input at the back of a vta-70/120.
See VTA70 w/ IEC

Replacing the fuse with an IEC that has a fuse. What's hard is to make the hole !

IEC on the rear of an original Dynaco is simple because the sheet metal is 18g
Not so easy on an newer 16g chassis. I've broken a couple of tools trying to make that hole.
EZer to make a pigtail connection.

tubes4hifi wrote:IEC on the rear of an original Dynaco is simple because the sheet metal is 18g
Not so easy on an newer 16g chassis.   I've broken a couple of tools trying to make that hole.
EZer to make a pigtail connection.

On my VTA70 i actually had a friend with a numeric milling machine do the job before building it. Milling after build is a risky job as small pieces of steel gets everywhere.

peterh wrote:

tubes4hifi wrote:IEC on the rear of an original Dynaco is simple because the sheet metal is 18g
Not so easy on an newer 16g chassis.   I've broken a couple of tools trying to make that hole.
EZer to make a pigtail connection.

On my VTA70 i actually had a friend with a numeric milling machine do the job before building it. Milling after build is a risky job as small pieces of steel gets everywhere.

Yes.... I would definitely take the chassis to a machine shop and never attempt doing it myself. My eyes are just not that good anymore to do that kind of precision work.

Wnen moving power switch to front of amplifier, where do you run the power wires or does it not matter.

Rbertalotto wrote:Wnen moving power switch to front of amplifier, where do you run the power wires or does it not matter.

The ST70 chassis is not ideal for doing this. You would have AC running near the plate and grid wires which could add hum.

Since I'm building a cabinet for my ST120, there will be 3/4" under the chassis. I'm going to run the wires there. Hoping the chassis bottom plate affords enough shielding. Might us a piece of 2 conductor shielded cable and ground one end of the shield to the chassis....

Rbertalotto wrote:Wnen moving power switch to front of amplifier, where do you run the power wires or does it not matter.

Even better : install a SSR relay to control the amp remote, a few mA 12V from the pre will do.

An example :
https://www.digikey.com/en/products/detail/panasonic-electric-works/AQA411VL/2364684