I built a p-p Aikido pre-amp and it pretty quiet as far as hum is concern but I do have a fair amount of hiss. I'm not to sure where the sourse of it is coming from. Is it my tubes or the way I built it. Its on both channels and swapping tubes does not improve things. Tubes are 6CG7and 12BH7. Are these tubes noisey by nature?
Short of a o-scope, how do I troubleshoot this? Also, what techniques/tips should I incorporate if I were to rebuilt this? TIA...
Short of a o-scope, how do I troubleshoot this? Also, what techniques/tips should I incorporate if I were to rebuilt this? TIA...
Its still hisses when the inputs are shorted. Its also not volume dependent but the hum goes up a bit more at full volume.
I am using a 6X4 in the power supply and was wondering if that could be an issue. I think I read somewhere that this was not the best tube to use but can't remember if that was true or not. Any opinions on this rectifier tube? I could try some SS diode if need be but like the look of that tiny tube. Anybody have any luck with another smallish type tube?
I am using a 6X4 in the power supply and was wondering if that could be an issue. I think I read somewhere that this was not the best tube to use but can't remember if that was true or not. Any opinions on this rectifier tube? I could try some SS diode if need be but like the look of that tiny tube. Anybody have any luck with another smallish type tube?
SY would be one to listen to. My experience is much more limited, but I can tell you that the 6X4 is unlikely to be the issue. It may not be considered the "best" rectifier, but that's probably due to its relatively high impedance. Regarding noise, I've used them with no problems at all.
Sheldon
Sheldon
Based on my own experiences with my dual mono Aikido line stage I formed the opinion that the 6CG7/6FQ7's need to be hand picked for the lowest noise and hiss. I finally ended up using clear top RCA as my input tube of choice. Mind you I still haven't been able to score a pair of NOS 6FQ7's since we started talking about them for the Aikido. It seems that the ebay price has shot skyward since then.
Yes, I have a very slight amount of hiss if I put my head right up next to the speaker and listen. It exhibits no signs of oscillation on the scope.
I have enjoyed mine since I put it together and no issues have come up.
My hand wired 6sn7/6sn7 Aikido has no hiss or noise and I used a 5Y3 as the rectifier tube.
Different thing. In a solid state phono stage using bipolars, the current noise dominates. For tube input stages run well away from grid current, voltage noise dominates. Generally, the high value grid leak resistors are shunted by a much lower driving source impedance so they do not contribute significantly to the noise.
Thanks Sy,
That is my first lesson into the differences between tubes and SS.
You should take the Burnt Diode Festival (Burning Amp Festival) on the road and come to the East Coast! It would be great to meet you and everyone that is involved! You could bring the wine! I'll make the ribs (burnt of course)!
Regards//Keith
That is my first lesson into the differences between tubes and SS.
You should take the Burnt Diode Festival (Burning Amp Festival) on the road and come to the East Coast! It would be great to meet you and everyone that is involved! You could bring the wine! I'll make the ribs (burnt of course)!
Regards//Keith
When I first built my Aikido I had a great deal of hiss.
I was using it with a CDP as source and it was driving a SS power amp.
I had 6N1P/5687 set up. I had way too much gain for this set up with the SS amp.
I played around with the grounding a lot. I changed the input tubes to 6N6P's. I put in a 10K alps with 20K Holco resistors in series to the input.
Now I have a beautiful sound, managed gain and dead silent even playing through Klipsch horns.
I was using it with a CDP as source and it was driving a SS power amp.
I had 6N1P/5687 set up. I had way too much gain for this set up with the SS amp.
I played around with the grounding a lot. I changed the input tubes to 6N6P's. I put in a 10K alps with 20K Holco resistors in series to the input.
Now I have a beautiful sound, managed gain and dead silent even playing through Klipsch horns.
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