McIntosh MX 119 Preamplifier vs Adcom GFP 750

The 750 is quite old now, devices eventually drift out of spec.  I would avoid that.

If you're looking to spend 800-900, there should be some pretty good options.  I'd suggest a brand new option.  If you know anything about crosstalk, SNR and other specs, the Freya + by Schiit Audio has stellar performance.  

It's also a tube preamp, but it has two other modes of operation in which the tubes are not engaged.  The sound is so transparent its jaw dropping at times.  I've got it with a solid state amp and the combo is end game.  

How long do the tubes themselves generally last ?
Do they all degrade at the same rate and just replace all of them when its time.
The other solid state I'm considering is the McIntsosh C47.
thx 
for info

It doesn't have any tubes, so they should last forever.

Speaking about the Freya + by Schiit Audio

Many, Many Tubes generally last 10,000 hours. Military Specs much longer.

http://blog.hughes-and-kettner.com/does-it-pay-to-regularly-swap-tubes/

"Here’s a little arithmetic for the worst-case scenario, or as we musicians call it, gigging life:

Two rehearsals a week lasting two hours each + two gigs a month lasting three hours each = 22 hours of operation a month. Let’s round up to 25 hours a month just because we like to play. 12 x 25 = 300. Now we have a rough idea of how many hours a year those tubes get toasty.

The 10,000 hours of expected tube life is of course an estimate, but not an unrealistic prospect. If we divide this life expectancy by 300 hours of service a year, we get a useful life of 33 1/3 years."

......................................

IF you listen 2 hrs per day, 14 hrs per week, 56, say 60 hrs per month. 12 x 60 = 720 hrs per year. 10,000 hrs = 14 years!!!

Having confidence in your tubes is not easy at first, after years, you ’get it’.

I have a big expensive tester, and small inexpensive tester. The big tester has always agreed with my inexpensive tester.

I highly recommend a simple inexpensive tester, which not only reveals problems, it gives confidence about your existing tubes, and reveals that the ’matched’ pair or quad are indeed matched.
...........................................

Rolling Tubes: Tubes definitely can sound different, i.e. my amp came with 6550’s. After a while, I bought KT88’s, and like them better. I have the 6550’s for spares, which gives me time for research if/when a KT88 goes.

Point is: IF you go for tubes (I highly recommend them), research first, and budget some money for trying something else, unnecessary, but can be fun.

............................................

Many of us highly recommend Brent

https://www.audiotubes.com/

............................................

Check for Bias Method.

Some tube equipment has EXTERNAL bias adjustment, some include built in meters. I wish my tube amp had this, it’s adjustment is internal. I have used tube amps for many years without ever checking/adjusting bias, but, if easy, that’s a nice feature to have, especially if you try different tube types.

How long do the tubes themselves generally last ?
Do they all degrade at the same rate and just replace all of them when its time.
The other solid state I’m considering is the McIntsosh C47.
thx
for info

I think they would wear at the same rate, generally speaking.  The Freya+ doesn't have a phono section though, you'd have to get a phono preamp separately if you're into that.  

Your choice of cables with it ?

That might be speaker dependant, but I've got silver solid core IC's from the freya to the amp, and Morrow silver plated copper on the cd player.  With the tube section engaged, it gets really captivating.