I put my 5 watt MP-1 into my Spider II 15 Watt combo. It will distort at a medium gain. I put the gain low on the MP-1, like a 3 or 4. Then use the amp's power to louden it up. I mostly use the clean channel of the Spider. I find mixing two distortions ify and time consuming, but sometimes put it on crunch at a low gain usually on the MP-1's clean patches. That's what I do and it doesn't sound like it's doing any damage. You might check the wattage on your preamp to make sure it's not too strong.