The Great River MP-500NV preamps arrived a week ago and I have to say they sound awesome! These preamps were designed to be a "modern" take on the Neve 1073 sound which is one of the most sought after sounds in recorded music.
I've had a week to play around with the Great Rivers a bit and I'm really digging them. I have been recording with an API preamp for about 7 years now so I'm really use to that sound. I was almost wondering if I was taking that sound for granted because I'm so use to it. I haven't had a lot of time to compare between the API and the Great River but I did have some listen tests with vocals. Without music I found they sounded relatively similar. When I added the backing music and listened again though there was a big difference. I can definitely hear what people mean now when they talk about the API "push". The API vocal stood out whereas the Great River settled in with the mix. I also found I could add more top end to the Great River vocal sound without it being harsh. I may decide to record most of my instruments with the Great Rivers and the vocals with API so my vocal stands out in the mix. I guess with experimentation all will come clear.
Here's a few other things I've run through the Great Rivers and what I thought of them:
Bass Synth: Nice! Crank the input till see a bit of red and it gives you a really nice thick sound. I know what the expression "running it through iron" now means :).
Bass Guitar: I ran my bass through a sansamp bass driver--->Great River Pre--->Distressor and then into the apogee converters and got the best bass sound I've ever gotten. Very smooth low end with a nice mid/top end presence.
Guitars: Really nice. I'm going to have to figure out what configuration works best for this as API is known for it's great guitar sound too.
In closing the Great Rivers are going to be a great addition to the Morph sound. The great thing about them is that they should compliment the API I already have really nicely. The API is known for it's pronounced mids and the Great Rivers for their wonderful low end/top end so now I have more sounds to work with. I'll write more about these as things progress and I get a chance to use them more.