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-   -   Starving Student II Headphone Amplifier (https://www.diyaudio.com/forums/the-diyaudio-store/335476-starving-student-ii-headphone-amplifier.html)

Logic800 30th October 2019 03:30 PM

Will this amp work OK with 250 ohm headphones?
 
Hi, thinking of buying the complete kit - can anyone confirm that the amp is OK powering 250 ohm headphones? Thanks.

aljordan 30th October 2019 03:54 PM

Quote:

Originally Posted by Logic800 (https://www.diyaudio.com/forums/the-diyaudio-store/335476-starving-student-ii-headphone-amplifier-post5960029.html#post5960029)
Hi, thinking of buying the complete kit - can anyone confirm that the amp is OK powering 250 ohm headphones? Thanks.

I am using it on a set of 300 ohm Sennheiser HD 650 without any problems. I wish I had a little less sensitivity at the low end of the volume control, but my DAC has a rather high output level.

aljordan 30th October 2019 03:58 PM

Quote:

Originally Posted by srgny (https://www.diyaudio.com/forums/the-diyaudio-store/335476-starving-student-ii-headphone-amplifier-post5958140.html#post5958140)
I recently received the tube set for the Starving Student II Headphone Amplifier. All were received promptly and in good shape. I have switched out the original Ratheon tubes for the Sylvania, RCA, GE and Standard Brand tubes. All work flawlessly. Unfortunately, I can not hear any difference in sound quality among the lot. I am using Sennheiser HD565 headphones and an Apple iPod for input (FLAC files). Is this just because I'm an old guy with bad hearing or am I missing something?

When I first built the kit, I picked up a few pairs of different tubes. I agree that their was very little difference between the sound of the different tubes. I heard far greater differences when running different source DACs into the unit.

Logic800 30th October 2019 08:34 PM

Quote:

Originally Posted by aljordan (https://www.diyaudio.com/forums/the-diyaudio-store/335476-starving-student-ii-headphone-amplifier-post5960047.html#post5960047)
I am using it on a set of 300 ohm Sennheiser HD 650 without any problems. I wish I had a little less sensitivity at the low end of the volume control, but my DAC has a rather high output level.

Thanks, that is useful feedback.

PapillonJack 29th December 2019 11:05 PM

LEDs on pcb not lighting up
 
The LEDs under the tubes light up, but the other 2 LEDs do not. The amp is producing decent sound. What is wrong with the unlit LEDs?

MEPER 30th December 2019 10:17 PM

The LEDs under the tubes are voltage ref. for the tube. The two others are voltage ref. for the CCS transistor. So if you run the amp in anode resistor mode it may work fine. It will be my guess that amp is not working in CCS mode?
The best guess is that you have reversed the diodes for the CCS?
You can measure voltage over the diode. If you measure 48V it indicates that diodes are reversed. Think you should measure about 3V or so over blue led if it is conducting.

PapillonJack 30th December 2019 11:41 PM

Quote:

Originally Posted by MEPER (https://www.diyaudio.com/forums/the-diyaudio-store/335476-starving-student-ii-headphone-amplifier-post6026524.html#post6026524)
The LEDs under the tubes are voltage ref. for the tube. The two others are voltage ref. for the CCS transistor. So if you run the amp in anode resistor mode it may work fine. It will be my guess that amp is not working in CCS mode?
The best guess is that you have reversed the diodes for the CCS?
You can measure voltage over the diode. If you measure 48V it indicates that diodes are reversed. Think you should measure about 3V or so over blue led if it is conducting.

It is working in CCS mode. I will attempt to measure the voltage across the LEDs and report back.

PapillonJack 31st December 2019 12:50 AM

Stupid me! My bad. I took the bottom cover off to check voltages and the LEDs were lit. Sorry for the confusion. :o I didn't see them lit during the smoke test and I cannot see their light through the bottom cover vent holes. Thank you for the fast reply and help.

MEPER 31st December 2019 08:46 AM

Ok....good it works :-)


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