Home theater and 2 channel setup from same speakers?

I deleted my previous 3 posts. about using the Receiver’s inputs

My understanding is that , only a Receiver, with a HTB ( if there are such Receivers ) could be connected to a external preamp.

p.s. : an AVR is a Receiver ; wihich  is not the same as a Processor

The OP owns a Receiver

@maxwave
I believe that the HT AVR (receiver) or AVP (processor) supplies either RCA or XLR outputs to the amp(s).
It is shown in the white section on photo 5 of 8 on here:

RCA inputs could take in a TT or AM/FM tuner, or something else…
But I think that the OP wanted the HT output to go THROUGH the preamp.

Then they may want RCA to XLR depending on the preamp and amp(s).
Mine are XLR from the HT, XLR at the preamp bypass, but the existing amps are RCA. Ideally those amps would be XLR.
 

@holmz

I thought , the OP wanted the Tube preamp to go THROUGH the Receiver.

Then , being able to use the same speakers he already owns.

If he uses the RCA outputs , to the preamp ; the OP will have to buy

a power amplifier. and a speaker , A/B switch for using the same spreakers.

I have an Acurus ACT4-20 Processor. I am less familiar  with Receivers.

In my knowledge, there is no Receivers with a HTB ( input)that allows to bypass

the preamp section of the Receiver; and then allows , only an external preamp;

and using that way ,only the amp section of the Receiver.

https://cdn.shopify.com/s/files/1/0562/5390/7003/products/TXRZ50_4_1300x.jpg?v=1643250423

Back in the prehistoric days of Dolby Prologic, I bought a B&K HT preamp and two extra amps (one for the center channel and one for the rear speakers channel).  I ultimately gave up on HT and stuck to developing my 2 channel stereo.