Tubes for Schiit Saga

I replaced the default tube in the Vali2 with a Telefunken Black Diamond from Tube Depot and even with this cheap headphone amp ($150) and Fiil headphones the improvement is very noticeable sounding smoother and more musical - more relaxing to listen to. 
Does anyone know who makes the $10 tubes that Schiit uses?

I ended up with a Tung-Sol from Upscale Audio, and am very happy with it ( under$50 )...I just went with their top recommendation...

@jl35 i recently got the safa idk if you are talking about the vali2 or saga but the stock tubes schiit tends to use in the pre amps are VERY neutral . can barely tell a difference. but i just switched to a ken rad vt 231 smoked and the difference is huge. such an upgrade. im also getting the vali 2+ would the tung sol you got fit in the vali 2 or were you talking about the SAGA?

I have the original Saga

@jl35 when you click the button to switch from tube to SS do you notica a large change? mine went from nothing to amazing with a NOS tube