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Millett "Starving Student" hybrid amp
May 14, 2015 at 4:30 AM Post #6,931 of 7,277
I'm thinking to buy the "Starving Student" hybrid amp kit and i have some questions:
1. If you compere the "Starving Student" amp to other tube amp witch it would be?
2. I didn't understand the the point that i must "warm up" the amp b4 i plug my headphones and unplug b4 im done>why?can someone explain me?
2.1 How long do i need to warm up?
confused_face_2.gif
 Coz nowdays i don't use an amp and mu headphones plugged directly to my "Roland quad capture".
3. What do you think is worth to invest in a tube amp with k702 headphones?
 
May 14, 2015 at 7:43 PM Post #6,932 of 7,277
1. It's sort of like the Millett Hybrid MiniMAX, but a bit less refined/featureless and with much more current capability.

2. See above.  One of the lack of "features" on the Starving Student is a headphone relay-delay.  Upon turning an amp on, a relay-delay keeps the headphone jack disconnected until the output coupling capacitors have had a chance to charge up.  Tubes are biased above a DC voltage of zero.  In the case of the Starving Student, 18VDC are on the headphone jack until the capacitors charge up and start blocking the DC.  Interestingly enough, this usually coincides with how long it takes the tubes to warm up.  So ... once warmed up, it should be safe to plug the headphones in without worry of exposing them to direct DC voltage.

This situation is common to all OTL tube amps and most tube hybrids.  Unless a relay-delay is employed, you could perhaps damage your headphones if you had them plugged in when you turn the amp on.

2. 30-45 seconds is safe.  When you see the orange glow as very bright in the center of the tubes, that means the heaters have heated up fully and the tube is warmed up. Again, it's really whether the capacitors have charged, but you can't "see" them. So we look at the tubes, instead.

3. I don't understand the English in this question.  Are you asking how much should you invest in a tube amp for the K702?  Or are you asking whether it's worth it to invest in a tube amp for the K702?
 
May 17, 2015 at 9:57 AM Post #6,934 of 7,277
slimswaly said:
  3. Im asking Whether it's worth it to invest in a tube amp for the K702? and if yes how much should you invest in it?
Click to expand...

 
Well if I was really a smart*ss, I might say ... "Yes - $10,000" and leave it at that.
 
That wouldn't be very nice, but it does sort of make a couple of points:
  1. No one should tell you what makes a truly worthy investment or how much to invest - in anything.  Even qualified financial consultants present recommendations that are full of disclaimers and caveats.
  2. There's an opinion that's widely shared: the AKG K7-series of phones are one of the truly great headphones.  Before the advent of $1000+ headphones, there were three series that stood at the top of the world: AKG K7-series, Sennheiser HD580/600/650, and Beyer DT880 (impedance ranges).  It's safe to say you can throw ever-increasing quality amps at these phones and they will respond with ever-increasing improvements.  As with most things, you end up in a diminishing returns condition that at some point will reach the limit of your financial capability.
 
You should be careful with tube amps concerning the AKG K7-series, though.  IMHO, OTL tube amps are not appropriate.  This is because the K7-series is known for needing a lot of current.  An OTL (output transformer-less) tube amp will be very limited in current capability.  A output transformer-coupled tube amp will work well, as will a tube hybrid, such as the Starving Student.  The Starving Student has enough current to power even the most stubborn planar headphones, much less the K701/2/12/etc.
 
May 17, 2015 at 10:04 AM Post #6,935 of 7,277
tomb said:
Well if I was really a smart*ss, I might say ... "Yes - $10,000" and leave it at that.

That wouldn't be very nice, but it does sort of make a couple of points:
  • No one should tell you what makes a truly worthy investment or how much to invest - in anything.  Even qualified financial consultants present recommendations that are full of disclaimers and caveats.
  • There's an opinion that's widely shared: the AKG K7-series of phones are one of the truly great headphones.  Before the advent of $1000+ headphones, there were three series that stood at the top of the world: AKG K7-series, Sennheiser HD580/600/650, and Beyer DT880 (impedance ranges).  It's safe to say you can throw ever-increasing quality amps at these phones and they will respond with ever-increasing improvements.  As with most things, you end up in a diminishing returns condition that at some point will reach the limit of your financial capability.

You should be careful with tube amps concerning the AKG K7-series, though.  IMHO, OTL tube amps are not appropriate.  This is because the K7-series is known for needing a lot of current.  An OTL (output transformer-less) tube amp will be very limited in current capability.  A output transformer-coupled tube amp will work well, as will a tube hybrid, such as the Starving Student.  The Starving Student has enough current to power even the most stubborn planar headphones, much less the K701/2/12/etc.
Click to expand...


If you double/triple etc csthodr followers in an OTL you can, in theory, provide massive currents :) but it takes up too much current from transformer to heat more tubes

I wanted to build an amp with 4 12AU7 per channel, but that went downhill lol

Anyways, the K7__ series is fantastic. When I owned mine, I didn't find any tube amps that worked well, but the Starving Student seems to be a good option. I wasn't DIY capable at the time. I think the SS is a good project because of its simplicity and relatively low voltages, so it is easier to work with. The SS uses a MOSFET as a follower (like a tube cathode follower) to provide current, which will allow the K701 to pair well, since it has plenty of current and a low output impedance, which is crucial since the headphones are only like 62ohms
 
May 23, 2015 at 1:57 PM Post #6,936 of 7,277
Hello,
 
Recently I upgraded my setup with Objective2 amplifier :p
 
Since I am a new "audio enthusiast" I want to build Starvig Student as well.
 
As far as I looked on the net, I saw only great reviews about this amp.
 
 
My question now is:
 
Is it possible to get a PCB somewhere ?
 
I texted user Fred_fred2004 about buying few PCBs, but he didn't replay.
 
 
Regards,
Z
 
May 24, 2015 at 12:34 AM Post #6,937 of 7,277
I am selling the original Starving Student that was based on Pete Millett's design. It uses the 19J6 tubes as in the original. The PCB was designed by dsavitsk of ECP Audio.

However, I am only selling full kits, not separate PCBs. The kits were last sold in 2010. It's taken that long to find enough 19J6 tubes to make it worthwhile to sell kits again - but the stock is limited. When these run out, it could be another 5 years before they're offered again, if ever.
 
Jun 13, 2015 at 11:55 PM Post #6,938 of 7,277
I'm considering this for my first DIY tube amp project. I'd prefer not to purchase tubes as I already have a ton on hand; would any of these models work? (I checked for dual triode/heater current and narrowed the field based on that.)
 
14B6
12AU7
12AU7A
12SQ7GT
 
Jun 14, 2015 at 10:24 AM Post #6,939 of 7,277
adevriesc said:
  I'm considering this for my first DIY tube amp project. I'd prefer not to purchase tubes as I already have a ton on hand; would any of these models work? (I checked for dual triode/heater current and narrowed the field based on that.)
 
14B6
12AU7
12AU7A
12SQ7GT
Click to expand...

The 12AU7 and 12AU7A are simply different versions of the same tube.  The 12AU7 version of the Starving Student is fairly well known at this point and is documented here:
http://diyforums.org/SSMH/SSMHvariants.php
 
Jun 16, 2015 at 6:08 PM Post #6,941 of 7,277
Jul 17, 2015 at 10:22 AM Post #6,942 of 7,277
Hello again everyone.

A while back I built a rather ugly ECC82-based variant of the amp on stripboard and put it in a little project box. It was a bit noisy thanks to poor shielding but worked well otherwise.
amp_proto.png


I recently rebuilt the amp using a PCB Fred_fred2004 kindly offered me (quite some time ago). I found a nice enclosure, shielded the inside and installed everything.
amp_03.png


I now have an absolutely excellent amp that's about as silent as I can detect when there's no input. I'm really pleased with the results. :)

Many thanks again to everyone on the forum who helped with advice and good humour.
 
Jul 30, 2015 at 11:45 AM Post #6,944 of 7,277
I've been poking through this thread for days...
 
I built mine and it is working (sort of).  I get good sound, but I am reading voltages that, to me, seem a bit low and the tubes aren't quite heating up as warm as they should.
 
1=27v
4=8v
6=27v
 
Are these values right? - I am using the 12AU7 schematic here: http://diyforums.org/SSMH/SSMHvariants.php
 
EDIT:  Found the problem.  I was putting the led resistor between R1 and R2 which was pulling that voltage down.  I realized it when I noticed that when I plugged in the LED, the voltage at Pin 1 of the IRF510 was dropping on that side.  I move the resistor to a spot on my stripboard before C1.  All is now right with the world.  Thanks.
 
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