Building your Universal pre-amp with 6sn7’s to go with a Willsenton R8. I upgraded the stock 6sn7’s with Tung-Sol tubes. (Huge improvement in sound quality) So now I have 2 stock tubes left over. My question is: once my pre-amp is done, should I install the Tung-Sol’s in the pre-amp and put the stock ones back into the Willsenton. Some say that when using the PRE input, the 6sn7’s are still used in the power amp circuit. If that is true, would the PRE I put just in reality be another line in? Would appreciate your take on this and your suggestions. PS really like your boards. Easy to work with and strong.