It is possible also to get tubes on EBay. Set up a 'saved search' for "18FX6A tubes" to get notifications. I was able to get quite a few nice tubes, RCA, Sylvania, etc, that way. They are quite a bit better than the Raytheons that came with my version of the kit. All the Raytheons I have used have been quite microphonic.
Speaking of which, here is a five pack of Sylvania tubes.
Speaking of which, here is a five pack of Sylvania tubes.
I've had my SSII for about three years now and it's been chronically plagued by RF noise. It's sporadic and in both channels. I wouldn't call it microphonics.
I've tried numerous tubes, and done my best to troubleshoot without a scope – all to no avail. I can't pin it to my source (interconnects, DAC, etc) or to the powersource.
Hoping someone can recommend a troubleshooting routine I can begin with to root this out.
I've tried numerous tubes, and done my best to troubleshoot without a scope – all to no avail. I can't pin it to my source (interconnects, DAC, etc) or to the powersource.
Hoping someone can recommend a troubleshooting routine I can begin with to root this out.
As I have no Earth in my outlets my SSII was a bit hum-sensitive. Also if my hand came close to the tubes the tubes picked up a lot of hum.
How sensitive is your amp regarding this?
The cure was to screen the tube. I used some quite expensive gold plated bronze shields (it is best to prevent using iron/steel for this). But if your tubes are sensitive if the hands gets close then it could pickup other kind if noise also and then a shield could be a solution. You can see the shields I use in my avatar. My first test was to use a roll of solder to put over the tubes and that helped a lot. Maybe you can try something similar or maybe alu-foil as a test?
How sensitive is your amp regarding this?
The cure was to screen the tube. I used some quite expensive gold plated bronze shields (it is best to prevent using iron/steel for this). But if your tubes are sensitive if the hands gets close then it could pickup other kind if noise also and then a shield could be a solution. You can see the shields I use in my avatar. My first test was to use a roll of solder to put over the tubes and that helped a lot. Maybe you can try something similar or maybe alu-foil as a test?
I tried this. It doesn't seem to do much. The only thing I did differently with this project is that I built a custom case – albeit from the original drawings, so it shouldn't be different in any major way.
Ok, I have built two SSII's and both are very silent.
What is important also is that the pot has galvanic contact with the chassis. I spent some time removing the black anodizing.
Is there a difference between the two modes the amp can run in (anode resistor vs. CCS)?
CCS mode has higher impedance so probably more "noise-prone".
You could try to RF-shield the amp so no RF can get into the amp from "the air" (if you put the whole amp into another metal box).
Also if you ground the input does that help?
If you ground RCA inputs and RF-noise disappears then I guess the noise gets in from the inputs and not via "the air".
Which PSU do you use?
I had problem with one of the 48V PSU's that followed the amp. It caused the tubes to make a strange "buzzing noise". Using the other PSU everything was perfect. After that I purchased a better quality 48V PSU and I use that for the amp.
What is important also is that the pot has galvanic contact with the chassis. I spent some time removing the black anodizing.
Is there a difference between the two modes the amp can run in (anode resistor vs. CCS)?
CCS mode has higher impedance so probably more "noise-prone".
You could try to RF-shield the amp so no RF can get into the amp from "the air" (if you put the whole amp into another metal box).
Also if you ground the input does that help?
If you ground RCA inputs and RF-noise disappears then I guess the noise gets in from the inputs and not via "the air".
Which PSU do you use?
I had problem with one of the 48V PSU's that followed the amp. It caused the tubes to make a strange "buzzing noise". Using the other PSU everything was perfect. After that I purchased a better quality 48V PSU and I use that for the amp.
I'm noticing now that I do not have the washer and nut that connects the pot to the chassis. I had the front plate custom machined and iirc didn't bore out the pot recess deep enough to capture that nut.
If you think that is a problem you can bypass the switch on PCB so it is always powered on. To power off you need to pull the jack connector or implement another switch out of the box. But at least you can try if it helps and change back it if it does not help.
CCS mode is usually more noise sensitive than using anode resistor mode.
CCS mode is usually more noise sensitive than using anode resistor mode.