Supratek Owners Thread

No, it's the fact what you posted is not the norm.

And what about your summary? What are you implying? Your experience with a used piece that was purchased ten years ago is what future new owners should expect to experience? The fact that what you bought was used and is not what most have experienced should make you think.

@alpha_lam  The filament is run from a regulated DC circuit not B+,.  regardless,  there is a small electrolytic at the regulator output (5V assuming a 300b DHT) in PS box,..  if you are referring to a cap seen in the pre (not PS box) directly soldered to the socket pins this would not be an electrolytic cap and would not be for filament power filtering but would be a bypass cap.  As mentioned earlier there would be one on each filament pin.   Just trying to help you out here as what you are describing is not making a lot of sense from a circuit standpoint.  At least not how Mick builds his circuits..

Sorry I admit I'm not familiar with terminologies in tube circuitry. The problem I found was with the DC filament on the right channel. The DC wires from power supply are reversed. Here is a closer look https:/ibb.co/tKXVz4j
On the left channel is correct. Here is closer look for comparison. https://ibb.co/k17Zvdx
The electrolytic cap on the right channel swelled and fell off. I replaced them with Nichicon KG with the same ratings.

I am also disappointed to see power transformers used as output transformers. It is using the Talema 22VAC @ 0.8VA. It's hard to know the effect without some measurements. I might attempt to replace it as well.

I appreciate very much @jslateiv's constructive comment.

Ah, I see,.. I’m pretty sure (without seeing a schematic) that cap is feeding a regulator used to increase the cathode voltage of the DHT. It has nothing to do with the filament V if this is the case. The circuit is direct/DC coupled between the 2 stages (sn7/DHT) and the DHT cathode has to be raised beyond what is naturally generated through the cathode resistor/current alone. That cap is not in the audio path at all and should have no noticeable effect on the sound (provided it is installed correctly and working as intended). Obviously in your case, with it being blown, it was effecting the reg that was helping raise the cathode V so yes, it would have thrown the circuit out of spec.
In regards to the transformers, Mick has been using them a long time and found they sounded more ’real’ than most anything else he has tried and lived with. I had the same misgivings as you at first when I realized what they were, very much wanting to see some ’boutique’ brand like lundhal, etc... I have listened to both and others at this point in my Cortese lcr as I couldn’t resist ’knowing’ for myself and being a constant tinkerer the swaps were pretty easy for me. If it makes you feel any better I ended up with the Blue Talema’s back in there at the end of it all. I felt they really provided a more natural presentation of the music. Everyone hears different though. You very well may like a slightly different sound/presentation that swapping them will provide. I do think that if you make the change you will realize with a little time that the Talema’s are really spot on and excellent when used with Mick’s specific circuits. Best,

Thanks @jslateiv for your feedback. Indeed the electrolytic caps are not on the sound path as they are coming from the 5V DC regulator. These are the Panasonic 10000uf. My guess is they are used for smoothing the DC from regulator. Nonetheless I replaced them with similar equivalent.

Very interesting that you tried different set of transformers. What did you try and was it a drop in replacementm? I might try a set of Hashimoto with similar ratio.