Are there any preamps that can work with 2 amps and a sub woofer?

Use a Line Out Converter to go from one power amp to the sub. 

I use the freya+ to power and control volume for  2 amps, a powered sub, and have 1 output leftover. I love it. 

Just get 4 of these and plug to together to give 3 outputs, and tryit you won’t hurt anything, don’t do it if your preamp is a tube it'll run for the hills.
https://www.wish.com/product/5b0d6b80c0d6f4651b819647?hide_login_modal=true&from_ad=goog_shoppin...

Cheers george

OP look for a good preamp. Don't spend a fortune. I love Mac. BUT I'm not stuck on stupid either. There are a lot of good preamps..

I have an older Krell 5.1 HT that I really like the build quality. Great stereo playback too. The cool thing, complete sub control and one of the best made remotes on the planet. Class A type circuits. Older DAC and HT but it is a Krell. I paid 350.00 for it 6 years ago.. You can get a 7.1or2 for close to the same now.. Same great playback in stereo..

Speakers and a GREAT preamp, everything else ebbs and flows.. My case more EBB and less flow.. Yes my cup runneth over.. LOL

Regards

Is your sub self-powered? If not, I would advise selling it and getting a self-powered sub with built-in equalizer.

Sub receives l and r from pre-amp, takes the low bass, sends only upper bass, mids, highs out to amp. Importantly it's volume is controlled by the preamp.

Adjust Sub's crossover point; adjust Sub's volume control to match your main's at your most frequent listening level. Now any volume change at preamp goes to sub and amp(s) cohesively.

If in the used market check any of SF line preamps, 4 outputs, 2 balanced, 2 single ended.

G

Are there any preamps that can work with 2 amps and a sub woofer?

Sure. Its not the number of outputs on the preamp, its whether the preamp can drive the combined impedance of all the amp inputs in parallel.


Since your main amps have balanced inputs I would use a balanced preamp. Since subs are usually single-ended input, if the balanced preamp does not have single-ended outputs, I would use a Y adapter for one set of outputs and use the other set to drive a set of Jensen subwoofer transformers to make the conversion from balanced to single-ended (this will also insure that you don't get hum in the subs). The Jensen subwoofer transformers are line transformers that are optimized for subs and so have response to 1Hz to insure there is no phase shift at 20Hz and well below.

3 sets outputs if you use the tape out, that would be a way for many others

https://www.ebay.com/itm/Audio-Research-Reference-6-Tube-Pre-Amp/324525777594?hash=item4b8f3e62ba:g:...

Tape outs are fixed, the output won't change with your volume control.

McCormack MAP-1?

Are you happy with the way your current setup sounds and performs? If so, consider a REL Airship. For around three hundred bucks, you would hook up the transmitter box using the supplied speakon connection to your speaker taps on your amps and then the receiver would connect to your Krell subwoofer. Then your sub is wireless as well as the bass quality would improve since it will take on much of the flavor of the amps.

@ernie00 I just bought the CODA 07x and I believe it has all the features you require (have not received the unit yet). It definitely can support 2 amps and I am considering getting a second amp. With regards to subwoofer, there is a RCA L/R output that I imagine can be used with a sub. I never used a sub so I am not sure. My KRELL dealer said I could use the KRELL’s RCA variable output on my integrated for a sub so the same logic should apply to the CODA.

“Both sets of balanced receptacles on the left side are identical stereo outputs suitable for connection to multiple amplifiers. The two sets of balanced receptacles on the right side are separate input channels.”

Here is the CODA dealers response to me.

If you're looking to biamp, it allows you to send the signal to both amps without the need for a splitter cable (which is what most preamps require and result in a drop in signal).

It can also be used to connect to another amplifier that is powering an entirely separate audio system.

Both sets of XLR outputs are always active. If you'd like to connect a second set of speakers, it is recommended that you power off the amplifier you're not currently listening to, as the amplifier is the device with the power draw.

Some time back I also asked a similar question on this thread.
https://forum.audiogon.com/discussions/preamps-with-dual-xlr-outputs

SST Ambrosia  2 single ended, 2 balanced

PS Audio PCA-2 has four outs: 2 XLR, 2 RCA

xaak

I wondered about tape out volume, it's been a while, thanks for clarifying that.

With pres offering both RCA & XLR outputs there’s a good the output voltage will be different between them, and they may not necessarily be intended to be used simultaneously.