I haven't posted enough on the forum to be able to start a conversation, but I have a couple of Starving Student II pre-amps and would like to get some tubes from pmillett. If someone can have pmillett start a conversation with me I would really appreciate it!
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.
I think this may be the culprit.
I placed the power switch on the back of the chassis. My guess is the hum is from this connection.
Any tips on shielding this?
I placed the power switch on the back of the chassis. My guess is the hum is from this connection.
Any tips on shielding this?
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.
I am sad to say I have hit a wall.
I am currently getting 19.1V on VT1 and 19.0V on VT2. I was stoked, plugged up and no sound haha.
Read through the forms here and reflowed my diodes, as like others I do not hear my relay clicking after power has been turned on.
Wondering if someone could help me confirm some voltages?
Currently measuring across each device I have:
13.6V across D5 and D6
3.3V across D4
13.6 V across D2
20.4V across D3
3.2V across R6
3.2V across R1
I have no voltage to ground on any of my relay pins.
I am at a wall and would buy anyone who could lend a hand a coffee at this point haha.
Cheers gents and thanks for reading.
Edit 2:31 EST
Well boys...... like most things in life I fixed this one with a smoke break. Came back and stared at the board under the magnifying glass and I found a single pin I missed on the relay like a dunce haha. Turns our Pete's troubleshooting guide had my answer all along lol.
Going to case up and see how she runs. I was getting sound but it was hit or miss becuase my RCA cables were backing out,
I am currently getting 19.1V on VT1 and 19.0V on VT2. I was stoked, plugged up and no sound haha.
Read through the forms here and reflowed my diodes, as like others I do not hear my relay clicking after power has been turned on.
Wondering if someone could help me confirm some voltages?
Currently measuring across each device I have:
13.6V across D5 and D6
3.3V across D4
13.6 V across D2
20.4V across D3
3.2V across R6
3.2V across R1
I have no voltage to ground on any of my relay pins.
I am at a wall and would buy anyone who could lend a hand a coffee at this point haha.
Cheers gents and thanks for reading.
Edit 2:31 EST
Well boys...... like most things in life I fixed this one with a smoke break. Came back and stared at the board under the magnifying glass and I found a single pin I missed on the relay like a dunce haha. Turns our Pete's troubleshooting guide had my answer all along lol.
Going to case up and see how she runs. I was getting sound but it was hit or miss becuase my RCA cables were backing out,
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Swapped RCA cables and struggled for a minute until I realized I did not have my jumper at JP1 and JP2 installed. Just a heads up to anyone else if you build it and get clear, but very quiet sound.
Super excited to have this one complete. Thanks Pete for the great documentation and thanks to everyone who commented on the forum. Reading all your discussions was a big help.
My first DIY down!
Super excited to have this one complete. Thanks Pete for the great documentation and thanks to everyone who commented on the forum. Reading all your discussions was a big help.
My first DIY down!
Shortly, I hope to be building a SS II for a friend. This isn't my first go at Pete Millett's designs, as I have bought numerous kits from him in the past. After recommending the Hi-Fi Man headphones as a good place to start, I then told my friend that this may not be the end of things as far as sound from the phones. That conversation quickly jumped to what sort of headphone amp 'would be best' with these headphones. I clench my teeth when people ask that kind of question about anything. Define best. Ok, so I said to him that it is also a good idea to let build this kit for him and see what happens. Of course, I expect that he will be thrilled with the results. As always, you can spend more and maybe get more, but at this price point, I bet this satisfies quite well.
Yah, I will be posting photos and possible questions as it all starts.
Yah, I will be posting photos and possible questions as it all starts.
One more thing. Since I already have an Amy Alice board, is that something that would be recommended to use with this kit?
Well, I am only adding the photo as proof... so there's that. Let me say that I didn't refer to the build guide expect for the LEDs just to make sure. Wasn't going for a record either, but I built it in a couple of hours. That is all good and well, but the sound. Isn't that why we buy? Ok. I listened a short time and am honestly saying that my friend will fall down dead when he hears this. These damned little tubes all have that special sound to them, like it or not. Yes, of course, I am a huge fan of this sound. Listened to George Winston on piano, and immediately was struck by the harmonics in that recording. Then I went to a Bad Company CD and like it a little less. Went from there to using the preamp for its volume controlled output instead of using the tape out. This is important. The HI-FI Man 400SE phones that I have are really efficient and so the volume control on the SSII doesn't have much range at all. If on the other hand you use the preamp volume control to feed the SSII then of course you have a better chance. Overdriving this HP amp is well just like you would expect, nasty. When these tubes don't get blasted with signal they make their best sound. OOH OOH, I have to mention something cool. The tubes sent with the amp are Sylvania and not Raytheon. So, you can even tap the tubes themselves and nothing happens, like microphonics. Hmmm.
Next time around, I want to build the Whammy.
Next time around, I want to build the Whammy.
