5876 is a space age tube in used at MERCURY launch, today NOS price is about $30, quality over the price so much, I try to post this to the tube forum here, but I found out most of the readers reply just replacing tubes to their gear for difference and there no market amp using this tube before, so still in DIY is better, may be not too many DIY amp builders in this site and I did post this to diy.com and got some positive reply.there are two type of DIYERS , one is beside with fun in build but mainly for pay less, they use same value numbers of components to the market made amp design and that is the main in that .com, sometime they can have good result by lucky, but sound quality is count on component's quality, so the other type of DIYERS doesn't mind to pay more for better level, sometime just one out put transformer cost more than the whole system in the market, still amp is only one part of the system if looking for the best need others to support otherwise you don't know how good it can be so I try to post in here. Not all old NOS component must be better than today's make, today's cap and transformer has much better quality than the old time made with new material but tube is different story, especially those made for military industrial and high tech use, and now no more jobs for them in their field but it is over quality for audio, so if you can convert it to use in audio, you will have a super quality parts with small cost, here the circuit in using this tube to drive a 809(NOS$30) transmitting tube to have 8 watts in SE out put, the most simple and less parts amp design but you can challenge any high price 300B amp in the market made but with good quality transformers
