Supratek Owners Thread

@couger4u ,   start with no inputs (no sources plugged  in) and only the output connected to your amp.   If you have a couple shorting plugs you can use on the  'selected' input use them. With the vol. dwn if the amp is quiet and there is no more hum from the speakers (there will always be a tiny bit due to the tubes) then your issues lies a source component and the connection between the pre and that/those components.  If you still have the same hum with the vol down and no inputs connected there is an internal issue somewhere in the circuit.   If it is quiet,  try raising the vol (with no inputs connected).  With a non-terminated (no shorting plug) input you will get some increasing noise with an increase in volume knob,  this is normal (with shorting plugs this would be gone).  You should not hear any loud or disturbing hum though.   Once you have confirmed that it is quiet as described above,  start adding components to the inputs,  1 at a time.  .  Your issue is most likely a grounding issue between the 2.     Any 'mechanical' hum you are hearing from the PS is a completely separate issue.   This can be caused (as mentioned earlier) by wall power or its grounding  or also by the grounding from other components that are connected to the same circuit (breaker).   The PS will always have a little hum.  Nothing you should hear from a seat 8-10 feet away though,  however if you get your ear next to the unit you will hear a little or faint buzzing or hum.  Alot of times this is the rectifier (buzz)  or transformer (hum). Some rectifiers are quieter than others but their perceived noise is also very dependant on the wall power in general as well.   Use the supplied regulators and use a good 5AR4 for the rectifier when testing and listening.   While other tube compliments can work,  it is easy to get some interesting results and subsequent mechanical noise (not from speakers) with other tubes.   Hope this helps a little.  Best,

I have resolved my hum issue by re-routing the umbilical between the power supply and preamp, along with power cords to other equipment and other signal wires. I didn't take a scientific approach to figure out what was causing what. I just fiddled with it until the hum stopped, then "secured" the position of various bits to keep things positioned so the hum was gone.

Hope your efforts are successful.

I just got a set of Linlai 101D hifi series to replace my older set of TJ 101D Mesh plate. These TJ 101Ds have been on the Supratek Cabernet for more than 10 years which I used very sparingly over the years.

For the price ($100 a pair from aliexpress) they perform very well to my years. They have a very sweet and full sound for vocals and less muddy than the old set (which really should have been replaced long time ago). I like them particularly with voice and the Eva Cassidy album Live at Blues Alley had a very euphoric quality to it. The amplifier I used was Cary Audio 120s by the way. I replaced all the 6SN7 tubes with some RCA and Sylvania NOS on both units. 

Getting the tubes to run at the full potential do take some effort however. TLDR is the tubes archived -70dB THD after tuning the voltages on both channels. If I play at low volume it could even archive -80dB THD wihch mostly 2nd harmonic. This is quite good for a tube design.

I attached an analyzer to the balanced output with 1k input to RCA. I first tuned the 6SN7 bias voltage then adjusted the plate voltage of the 101D and then finally the grid voltage of 101D. There seems to be a feedback in the design and the voltage takes a little while to stabilize after each adjustment. I was watching the FFT of analyzer and voltmeter during the tuning.

After some experiments I found the highest gain setting have the lowest distortion. Lowering the gain will gradually increase distortion for the same output level. I hope this information is useful for those who wonder the effect of the gain on the sound.

Comparing the FFTs of the Linlai and the TJ mesh plate I had the appreciation of the TJ very much. The TJ had very low 60Hz noise and mostly only 2nd harmonic distortion. The Linlai however is quite a bit noiser with 120hz and higher order harmonics of the power noise. The 3rd harmonic distortion is also quite high. I should probably get a set of TJ while it is still available.

Sorry for late response, been busy at work. I think there is something wrong with the umbilical cord for the preamp. I started by turning on the power supply and could not hear any hum coming from it. Then I attached the preamp with umbilical cord with no RCA in or out and I could hear the hum from the power supply. I have asked for a new umbilical cord from Mick and will test it again when I receive it. I also googled the cord and found Revelation Audio Labs makes one. Will also ask them in future to make one for me if it works in resolving the issue. Has anyone tried them?

Brad is supposed to make great cables but from what I have heard on other forums pay no attention to his promised delivery times as they are mostly make believe.