Keep in mind that the TD-1 was primarily designed to be an over the top DI box and offers the most flexibility in that mode (twin topology - tube or SS, variable impedence, transformer in and out). The addition of the preamp channel was originally to be an extra purchasable option but was added in on the rollout. The arrangement was so popular that it stayed with the product. However, you cannot switch in the tube circuit for the preamp -- it is SS only. Which is fine for most people as near as I can tell. Many of the comments on the full boat twin topology units seem to say that they usually use the SS channel. The unit also has reamp. I have a pair of these and they are great little workhorses. You might want to go to DOT's site (the Listening Sessions I think) and check out how they sound. Very detailed and clear. I use the preamp primarily for acoustic instruments and the DI for everything.