Supratek Owners Thread

@gryphongryph   you should not hear any hum from the supply or speakers, save for a touch of tube rush/hum that is normal for a DHT. That hum/rush will be a touch more than on the SN7 output.  Should really only be heard with ears next to the speakers.   Supply (PS) should be almost dead quiet (again) save for some very slight mechanical hum only heard from a foot away (or closer)..  nothing should be heard from a seated position.   Mick was unfortunate with a small batch of bad transformers.  Only 4 I believe.   I helped repair one,  and while it left my bench and system dead quiet (after 20hrs of listening),  it showed up at the owners with noise again.  Turns out he had a bad umbilical cord that did not present a problem to me at all.  I suspect one of the connectors was a lemon.  Mick's soldering is as good as you'll find anywhere.   Mick sent the customer a new cord and the unit is now reported to be quiet and trouble free.     Try this,... completely remove the umbilical  (unattached at both ends, very important)  and if you have a dental pick or large sewing needle (or something similar and metal),..  wedge it in between each metal contact and the plastic shell hole of the connector.  This will help ensure that there is adequate contact tension.   May help,  may not, but it would be a good place to start trying something to see if it makes a difference.   I also think that sometimes in the manufacturing process a little oil gets left inside the contacts and can cause some light resistance issues as well.   Generally some purposeful plugging/unplugging back and forth a bit with connector pin wipe down (rubbing alcohol) can help that too.    
    In regards to the gain.   A gain switch can be added to the SN7 circuit if need be.   I'm in the middle of a move between states right now so my bench is down for the next 6 weeks,  but would be happy to look at adjusting for you if needed when I'm back up and running.   Best,  Johnny

Thanks for the reply Johnny, interesting points you make, unbelievable the hum suddenly disappeared last weekend and has not come back yet, although I have not had time to listen since Sunday evening, I have not done anything to the system for at least a week before, where I have been trying everything I could think of, like the fase on the pover cables, tried 4 pairs of different rca cables and 2 pair of xlr cables, also unplugged various other units like dac, Mac mini that is on separate mains, but nothing helped, then suddenly it’s gone, I am a bit perplexed of it all, Mick is sending me an other power supply, which I am grateful for as it would make me feel more comfortable with the purchase in the long run.
When I got it, there was no hum at all, although I thought the power supply could be more quiet, the hum came after 1-2 weeks.

I need to clarify a thing, when using the 300B output the gain is okey, although I have to turn it way down, it sounds quite good after using it exclusively for over a week now, but, I still like the 6SN7 output better, if not for the gain.

Maybe a better pair of 300B tubes would give me more clarity while keeping the warmth.

Yes, I am not a fan of the biblical cord between power supply and pre, seams unnecessary stiff and unwieldy, a softer cord would be preferable, will check both connections if, or probably when the hum comes back, as I suspect it will.
Now I hear only a slight hiss from the speakers, but I have not tried it with the 6SN7 output since the hum disappeared, unfortunately I am swamped with work all week and probably weekend too, so no testing until sometime next week.

There is a big difference in sound between a standard 300B and say a TJ Full Music meshplate.Almost like a different preamp.With the meshplate you get beautiful airy treble,much better timbre and a much more holographic soundstage.If you have heard the difference between say the really good Dynaudio speaker models and the next tier down it is that sort of difference.The difference between good and great.

On the Cab Dual Mick recommended to stay away from the mesh plate tubes, was it the current draw?