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

MEPER 31st March 2019 03:18 PM

Yes, I think it is the place for it. The "relay pack" is unpacked but not jumper sets. I found something similar at RS and will get it next time I order from them.

Jason 1st April 2019 10:52 PM

MEPER: We'll get you any missing parts, the helpdesk will be in touch shortly.

pmillett 1st April 2019 11:08 PM

Quote:

Originally Posted by MEPER (https://www.diyaudio.com/forums/the-diyaudio-store/335476-starving-student-ii-headphone-amplifier-post5746182.html#post5746182)
I unpacked today and there was only one 47.5k resistor and no jumper sets. I checked several times. 47k I probably have in stock…...but jumpers are more tricky....

Are you missing the little blue jumpers (shunts), or the 3-pin headers? Or both?

Both are normally packaged in the "other parts" bag, with the connectors, relay, etc.

Pete

pmillett 1st April 2019 11:31 PM

Quote:

Originally Posted by MEPER (https://www.diyaudio.com/forums/the-diyaudio-store/335476-starving-student-ii-headphone-amplifier-post5746156.html#post5746156)
The supplied Raytheon tubes are "made in Japan". Are those NOS? …..how old?

They are NOS from a large master case. I cannot tell exactly when or where they were manufactured. Probably early 1960's - Raytheon farmed out most of their small tube manufacturing to Japan around then.

In general there was much cross-production and labeling, especially in the 60's, so it's very hard to tell exactly what manufacturer really made what tubes.

I have examples that have just about every tube manufacturer's name (RCA, Sylvania, Westinghouse, Raytheon, etc.) and some made in USA, Japan, and Canada.

They all look and measure pretty much identically...

Pete

cwiseman2a 2nd April 2019 01:46 AM

Input problems?
 
I just got my SSII kit built and testing it now. There is a problem with the input. Plugging in either the right or left RCA connector from source gives me output to both left and right headphone out. Plugging in the other (either left or right) RCA input lead I get the hollow remains of the input source. Wondering if anyone is reporting a similar issue. Source is phase correct and works correctly with my other systems. Headphones also working correctly with other sources.

pmillett 2nd April 2019 02:44 AM

Quote:

Originally Posted by cwiseman2a (https://www.diyaudio.com/forums/the-diyaudio-store/335476-starving-student-ii-headphone-amplifier-post5747944.html#post5747944)
I just got my SSII kit built and testing it now. There is a problem with the input. Plugging in either the right or left RCA connector from source gives me output to both left and right headphone out. Plugging in the other (either left or right) RCA input lead I get the hollow remains of the input source. Wondering if anyone is reporting a similar issue. Source is phase correct and works correctly with my other systems. Headphones also working correctly with other sources.

Problems like this are often an open ground connection on the volume control. Try reflowing those pins.

Pete

aljordan 2nd April 2019 03:28 AM

I've been listening the SSII as a headphone amplifier for a pair of headphones which have an impedance of 300 ohms. It sounds decent, but I have very little adjustment room on the volume control, as it quickly becomes quite loud within a ten degree turning radius. I am wondering if anyone knows of a different volume control with a more usable taper that will fit on the board.

Thanks

MEPER 2nd April 2019 05:51 AM

Quote:

Originally Posted by pmillett (https://www.diyaudio.com/forums/the-diyaudio-store/335476-starving-student-ii-headphone-amplifier-post5747802.html#post5747802)
Are you missing the little blue jumpers (shunts), or the 3-pin headers? Or both?
Both are normally packaged in the "other parts" bag, with the connectors, relay, etc.
Pete



Hi Pete


It was both the 3-pin and blue jumpers. I ordered some locally at RS Components. So now the jumper will become black. Hope that does not change the sound :-) seems spacing is 2.54 mm.
Interesting with those NOS tubes. May get some extras while they are available.

mediumroast 2nd April 2019 03:24 PM

What am I doing wrong?

I'm at step 20 - smoke test.
VT1 pin3 to headphone ground measures 43.3 volts.
VT3 pin3 to headphone ground measures 19.05 volts.

My soldering looks very clean and solid (no bridges or cold joints) so I'm guessing I have a defective or wrong part somewhere.

pmillett 2nd April 2019 04:11 PM

Quote:

Originally Posted by mediumroast (https://www.diyaudio.com/forums/the-diyaudio-store/335476-starving-student-ii-headphone-amplifier-post5748439.html#post5748439)
What am I doing wrong?

I'm at step 20 - smoke test.
VT1 pin3 to headphone ground measures 43.3 volts.
VT3 pin3 to headphone ground measures 19.05 volts.

My soldering looks very clean and solid (no bridges or cold joints) so I'm guessing I have a defective or wrong part somewhere.

The most likely error is that the grounded end of R11 isn't really soldered to ground. It's easy to get a solder joint that looks good, but actually has not flowed onto the grounded pad. It's connected to a large copper area that sinks heat away, so it is difficult to solder.

If this happens, the gate of Q3 is biased to 48V, so the source (and VT1 pin 3) goes to 48V - Vgs(th) or about 43V.

With power off, use an ohmeter to confirm that R11 is 200k, and R15 is 221k. And measure from the grounded end of R11 (on the resistor lead) to ground to see if it is connected.

Also check for solder bridges on Q3.

Pete


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