TM preamp design

I just ordered a used TM5 head for 299. It's my first ever H&k product. Is there any recommendations for tube replacement? Also what design is the preamp built after? Or is it unique just to the TM?

Hi Dropdew.  Welcome to the forum.

Valve recommendations are always a difficult topic here thanks to me.  I, for one, have no belief that they make any real difference at all and when others recommend something exotic which will give you a brand new amp with just a simple plug in, (albeit an expensive one), I point people towards proof that they are actually, guess what, pretty much if not all exactly the same.  I know this prevents people from discussing this in the best internet "no proof just opinion" fashion nowadays but, to my mind, if there is a difference then there MUST be accessible proof which you can gather to show that that is so.  There is absolutely no value in saying "It's obvious, I can hear it".  You can't under anything like normal valve swapping conditions.  With the time that must be spent turning off the amp, pulling the old valve, replacing it with the new one then warming the amp up again, your ear has reset and has become incapable of accurately remembering the first sound. From that point on you are telling yourself to hear what you are already looking for.  This can be shown to be absolutely true in properly conducted tests.  There is even a hifi site I once found which has a similar test set up to demonstrate to yourself just how easily fooled the ear and brain are in these terms.  To come up with proof means producing accurate measurements which can be demonstrated at any time.  If there is a difference between valves this should be absolutely a piece of cake for an engineer to do with today's equipment.  No one ever has.  Ask yourself why!

My own proof for the lack of any difference between valve types is now available in this dedicated thread:  Valve Differences, (or not).  Before you go ahead and buy into the latest big thing flavour of the month valvewise I urge you to read that then actually go to the site in the links and look at the results for yourself.  This is not my work and results, it is independet of me entirely and, surprisingly, these guiys were actually proving that valves do sound different (in order to sell some to you).  Ask yourself what differences you can see from their own evidence.  That's not the frigged stuff with its pretty valve pictures and colours and sound descriptions, the only bit of real work and accurate meaningful results are in the single graph at the foot of the page where each valve is compared in the same reference frame.

You see, that is the difference between my engineering stance and that of most other people.  I believe I can hear no difference.  I therefore look for proper independent repeatable evidence to support that claim.  Those who claim they can hear differences do just that, "claim" that they can and they stop there.  That test in the link which shows there are no differences was originally set up to prove there are differences, and when the results show so blatantly that there aren't they just made up a way of displaying the findings to make it look like there are.  It's downright scurrilous lying marketing at its most magnificent!  Tell people something is true even in the face of evidence which shows it isn't and most of them will just believe you because they want what you say to be true.