Been listening to the Millett SSII for a few weeks now and I love it with Beyerdynamic DT 770 Pro (250 OHM). Input is a skeleton DAC kit from Beezar. This combo is a huge step up for me.
I am getting the itch to build something again and wanted to know how much better the Millett Hybrid Mosfet MAXed is compared to the Starving Student?
Does anyone have any measurements for the various Millett headphone tube amps?
I am getting the itch to build something again and wanted to know how much better the Millett Hybrid Mosfet MAXed is compared to the Starving Student?
Does anyone have any measurements for the various Millett headphone tube amps?
Hi Pete,
Thanks for the swift reply. I can get my order placed now.
This will be my second iteration of the SSII. The first was a DIY store kit. This version will use Dale resistors, Panasonic FC caps and a stepped attenuated. I've been enjoying the standard version for several months now and was curious to see what impact these changes would have.
The case won't arrive until mid July but I'll post some pictures once it's done.
Once again, thanks for the help.
Paul.
Thanks for the swift reply. I can get my order placed now.
This will be my second iteration of the SSII. The first was a DIY store kit. This version will use Dale resistors, Panasonic FC caps and a stepped attenuated. I've been enjoying the standard version for several months now and was curious to see what impact these changes would have.
The case won't arrive until mid July but I'll post some pictures once it's done.
Once again, thanks for the help.
Paul.
I'm curious if you finished your build and how the amp is working with your HE400s headphones? I have the same headphones and I am considering this as my first (DIY or otherwise) headphone amplifier.
Thanks,
Joe
Finished the build a few days ago, sounds great. Before installing the tubes, the voltage at pin 3 of one of the tubes was 20.7, higher than the 19.5 limit suggested, but after many resistance checks I decided to go ahead and install the tubes, and everything worked OK. Is there some reason one of the voltage measurements could be this high in a working unit? The other one was 19.5.
I meant to take some point-to-point resistance measurements before putting it into the case, so that other builders could use them before power-on, but forgot to do so. Perhaps someone else with a working unit could do this before boxing it up.
I really like the case; very elegant.
Now starting a Bottlehead Eros2 to feed my Starving Student ...
I meant to take some point-to-point resistance measurements before putting it into the case, so that other builders could use them before power-on, but forgot to do so. Perhaps someone else with a working unit could do this before boxing it up.
I really like the case; very elegant.
Now starting a Bottlehead Eros2 to feed my Starving Student ...
Update: It's working now and sounds great!
I had missed soldering two relay pins initially. The advice about how you should hear a click a bit after powering the amp on in Starving Student II Headphone Amplifier was super helpful for me narrowing down my search for what was wrong.
I had missed soldering two relay pins initially. The advice about how you should hear a click a bit after powering the amp on in Starving Student II Headphone Amplifier was super helpful for me narrowing down my search for what was wrong.
Hi, the schematic shows a 50k pot in parallel with the 221k grid resistor. When the volume is at the max position the input impedance is 50k, when it’s at the minimum position it’s 40.7k (50k || 221k). For sizing your cap use the lower number.I hope this helps.
Just finished building one of these, and it sounds terrific! Thanks to Pete for the design and to the folks at DIY Audio Store for the kit.
That said, at least with Grado SR-60s (I have not yet tried my Focal Elears), there is WAY more gain than I need. If I turn the volume knob just 45 degrees, it's already plenty loud. Is there a simple way (replacing some resistors, e.g.) to decrease the gain?
That said, at least with Grado SR-60s (I have not yet tried my Focal Elears), there is WAY more gain than I need. If I turn the volume knob just 45 degrees, it's already plenty loud. Is there a simple way (replacing some resistors, e.g.) to decrease the gain?
Any news on that?
I have been thinking about upgrading the pot, etc, as well. Is there an easy way to tell what pins are doing what? I guess maybe reverse engineer it from the pot specs?
There's no easy way to lower the gain. You can attenuate the input - you could insert a resistor between the input jack and the volume control. 50k would drop it 6dB. You can also attenuate between the tube and output buffer by putting a resistor in series with the coupling caps (C4 and C7) - 100k would also get you 6dB.
Pete
So I have been puzzling a bit about how to do this, given that the board is already built, and given what the connectors are like.
Putting a resistor between the input and the pot looks complicated. There isn't anywhere sensible to do that, so far as I can see. I had been thinking about replacing the pot (stepped maybe) AND the jack AND the power switch (necessary if the pot gets replaced), but that is more than I want to do right now. Especially since I'm in the middle of building a case for the board as it is.
Putting a resistor after C4 and C7 looks easier. But that means (a) unsoldering (and replacing) the two caps (since they will then have tiny leads) and (b) somehow wedging the resistor into the circuit. I have thought about wiring the whole thing up to what would then be a "-6dB" switch, but I'm wondering if there isn't an easier option....
Would it be possible to use a shunt resistor off the input to C4 and C7? That would not require unsoldering anything but just wiring the input pads for the caps to ground, through two resistors. If so, what formula can I use to calculate attenuation from different resistor values? I'm thinking this must work like a voltage divider? Please excuse my limited knowledge of electronics. I'm trying to learn here, really!
I'm again thinking about a switch, in case different headphones do or don't want the attenuation. And something like 12dB might be better....
Pursuing a different line of inquiry....
I have been getting quite a lot of microphonics, which I've seen in other parts of the thread isn't expected. E.g., if I tap on the top plate (of my simple home-brewed case), or even tap on the headphone cable, I get ringing. It's not an issue when listening, as the external environment is quiet enough, but it makes me wonder if I've got too much gain for some other reason.
After assembly, I did the measurements suggested, and they were on the high side: Pin 3 to ground was 19.4V in one case and 19.53V in the other. Not way off, but high-ish, yes? Is there something else I should check? I measured every component before installing and measured the resistors again after installing (though some of them measured off, since there was a second path through ground for those).