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Millett "Starving Student" hybrid amp - Page 469

post #7021 of 7035
Quote:
Originally Posted by fuens View Post
 

Here another amp :)

Best regards mates!

 

Toni

 

 

All those jacks and the power switch/AC plug are incredible. What are those? I've never seen them.

post #7022 of 7035
Quote:
Originally Posted by vapman View Post
 

All those jacks and the power switch/AC plug are incredible. What are those? I've never seen them.

Hello Vapman.

The AC switch and socket is : Panel Mount Fuse Holder IEC320 C14 Inlet Red Lamp SPST

The audio sockets are: Neutrik NJ3FP6C-BAG 1/4" 6.35mm Jack Chassis Panel Mount, Neutrik NF2D-B-9 Phono RCA Chassis/Panel Female Socket RD and Neutrik NF2D-B-9 Phono RCA Chassis/Panel Female Socket WH.

Have a nice project!

 

Cheers mate

post #7023 of 7035
Quote:
Originally Posted by the_equalizer View Post
 

Ok, so here are a couple pictures from my amp with the CCS mod. Since I built it just as a test it's not very neat and I haven't removed the unused parts from the regular build (cathode bias resistor and bypass electrolytic capacitor). Now that it's working I'll split the CCS board in two and fix each little module between the tube socket and the terminal strip. The location will also help with lead length and I could also use a couple connectors for the wiring so the modules are easy to replace or service.

 

 

 

In the following descriptions I'll refer to the 12A_7 / 17EW8 pins and to right channel parts. The left channel CCS should connect to the homologous points in the left channel; and naturally other tubes (like the 19J6) will have different pinouts.

 

Black wire is ground, brown wire comes from the tube cathodes (pins 3 and 8), red is power (from the junction of R13 and C6) and orange goes to the tube plates (pins 1 and 6).

 

The blue 2K ohm trimpots replace the cathode bias resistors and are simply wired as rheostats. You could maybe do without them but it's definitely nicer being able to dial in the plate voltage and hence get the best sound from the tubes.

 

 

 

Here's the schematic for the CCS. It's just the typical ring of two transistors. The circuit simply replaces the plate load resistor R1.

 

 

I've been listening to the amplifier constantly and I just keep playing album after album. I'm really enjoying the sound from it with all kinds of music I've tried. I'm really glad I decided to build the CCS mod.

 

I hope someone else also tries it. It's fun and it works great!

 

cheers!

the_equalizer - 

Thanks for all your input on this - without you I wouldn't have been able to get as far as I have with this build.

 

I'm trying to wrap my head around this - Can you take a look at this rough schematic I did and let me know if that is right?
http://i.imgur.com/JMt2pPk.png

 

I take it the pot replaces R5?  (I the wrong label in the pic)

Thanks, Man...

 

EDIT

Answered my own question.  That seemed to work.  I'm on my third build now - for funsies - and integrated the CSS into it. Now I'm working on plate voltages...


Edited by GingerBeard - 3/4/16 at 6:30am
post #7024 of 7035

Sorry, a noob question.

I just discovered the Starving Student Amp. While I would like to construct it based on the information on the original post, I have a feeling there are now numerous changes. The almost 500 posts on this thread is pretty intimidating. 

I suspect there's a better version somewhere here.... Can anyone point me to a post(s) that might help me out here?

 

Thanks.

post #7025 of 7035
Quote:
Originally Posted by fuens View Post
 

Here another amp :)

Best regards mates!

 

Toni

 

 

 

 

Beautiful! Details?

post #7026 of 7035
Quote:
Originally Posted by snafu1 View Post
 

Sorry, a noob question.

I just discovered the Starving Student Amp. While I would like to construct it based on the information on the original post, I have a feeling there are now numerous changes. The almost 500 posts on this thread is pretty intimidating. 

I suspect there's a better version somewhere here.... Can anyone point me to a post(s) that might help me out here?

 

Thanks.

 

Here's a summary I wrote up on another forum:

 

Quote:

 

You can get the PCBs from here:

http://www.head-fi.org/t/664191/starving-student-pcbs

They come from Aussie land so it takes a while. You can ptp it as well but I wouldn't necessarily call it a great idea haha.

The main thread for the amp is here:

http://www.head-fi.org/t/319231/mill...ent-hybrid-amp

The original build is here:

http://www.pmillett.com/starving.htm

This site has a bunch of good info but a few dead links

http://www.diyforums.org/SSMH/SSMHoverview.php

Updated schematic for the version I built (The original 19J6 tube is very hard to come by so the community members came together and modified the circuit to use a different tube.) is here:

http://www.diyforums.org/SSMH/SSMHvariants.php

A full Mouser Bom is here:

https://www.mouser.com/ProjectManage...sID=d7adb25dd2

Do me a favor and if you want to use that, make a copy of it into your own account. I posted a different one online on head-fi and someone deleted a bunch of stuff off of it and it somehow populated back to my account. Note that there are copies of the .22 uf caps in there, I ordered two different ones to try. I also included some heat shrink that I used.

Any new or NOS 12AU7, 12AU7A, 5963, or similar (Google is good at finding equivalent tube names) tubes will work. They don't have to be matched but it is best for them to be of the same make/vintage. I prefer vintage tubes to new, it doesn't make sense for something this non-critical not to reuse/recycle what's laying around, it's fun to get something that old and bring it back to life, and it's cheap if it doesn't work out.

I used these tube sockets:

http://www.ebay.com/itm/160580213397...%3AMEBIDX%3AIT

In hindsight I maybe should have gone with something that doesn't have that little edge sticking out around the perimeter. It would have made drilling the holes for the tube sockets in the case much easier. Also, an option to consider is using chassis mount tube sockets and wiring them to the PCB board. That would take the stress of inserting/removing tubes off of the pcb which is something I'm somewhat concerned about.

The PSU is here:

http://www.ebay.com/itm/QTY-1-Cisco-...AAAOSwYIhWjT-K

Not where I bought it, but this is the right model.

Looking at all that all at once I may have underestimated the cost by about $20 in my original post. 

In addition to what I've listed, you'll need a case and a volume knob.

 

Edited by Nathan P - 3/24/16 at 3:48pm
post #7027 of 7035

Excellent! Thank you.

post #7028 of 7035
Quote:
Originally Posted by GingerBeard View Post
 

the_equalizer - 

Thanks for all your input on this - without you I wouldn't have been able to get as far as I have with this build.

 

I'm trying to wrap my head around this - Can you take a look at this rough schematic I did and let me know if that is right?
http://i.imgur.com/JMt2pPk.png

 

I take it the pot replaces R5?  (I the wrong label in the pic)

Thanks, Man...

 

EDIT

Answered my own question.  That seemed to work.  I'm on my third build now - for funsies - and integrated the CSS into it. Now I'm working on plate voltages...


My apologies GingerBeard. "Real" life took over since late 2014 and I don't come around here too often know. I hope you're enjoying your amp. I'd very much like to know what do you think about the amp with the CSS plate loads and which transistors you chose to implement them.

 

Cheers!

post #7029 of 7035
Quote:
Originally Posted by fuens View Post
 

Here another amp :)

Best regards mates!

 

Toni

 

 

I assume that you used the TL783? what kind of transformer did you use?

 

I'm looking into building one with a transformer myself because I don't trust those 48 volt powersupplies off ebay

post #7030 of 7035
Quote:
Originally Posted by GideonW View Post
 

I assume that you used the TL783? what kind of transformer did you use?

 

I'm looking into building one with a transformer myself because I don't trust those 48 volt powersupplies off ebay

Hello mate.
You are right, I'm using a tl783 voltage regulator (see this item http://www.ebay.com/itm/High-Voltage-Adjustable-Regulator-Module-Based-TL783-/130669696724?hash=item1e6c8556d4 )
About the transformer I'm using RS part no. 223-8049 (it's too big but it's what I found)
I will use a little one in my next project RS 223-7995  223-7939  223-7850
I recommend to you use an external and bigger bridge diodes, because when capacitors charge those burn the little bridge diodes. And replace the heatsink for one more bigger.
Also I have a psu (still need to try) RS 466-6890
Have a nice project.

Toni


Edited by fuens - 5/24/16 at 10:16am
post #7031 of 7035

So you are feeding the TL731 with 70 volts, wouldn't things cool down quite a lot if you tried to get closer to your 48 volt output voltage? now you are turning 22 volts @ whatever current you are using into heat. A transformer with 2*18 or 2*20 volt would seem more sensible to me if you can find it, but correct me if I'm wrong.

 

anyhow, thanks for the info I think that I am going to try to replicate your build albeit with a slightly lower voltage transformer :) 

 

 

EDIT:

 

i think that I found a nice transformer:

http://www.tme.eu/nl/details/tst50w_2x19v/toroidale-transformatoren/indel/tst50010/

 

50VA 2*19 volt

 

gives you 53.6 volt after rectification (minus some diode losses) and you only have a 5.6 volt difference between input and output voltage which limits the heat a lot


Edited by GideonW - 5/24/16 at 11:46am
post #7032 of 7035
Quote:
Originally Posted by GideonW View Post
 

So you are feeding the TL731 with 70 volts, wouldn't things cool down quite a lot if you tried to get closer to your 48 volt output voltage? now you are turning 22 volts @ whatever current you are using into heat. A transformer with 2*18 or 2*20 volt would seem more sensible to me if you can find it, but correct me if I'm wrong.

 

anyhow, thanks for the info I think that I am going to try to replicate your build albeit with a slightly lower voltage transformer :) 

 

 

EDIT:

 

i think that I found a nice transformer:

http://www.tme.eu/nl/details/tst50w_2x19v/toroidale-transformatoren/indel/tst50010/

 

50VA 2*19 volt

 

gives you 53.6 volt after rectification (minus some diode losses) and you only have a 5.6 volt difference between input and output voltage which limits the heat a lot

Hello again :)

I tried with an 2x18v 80va, but the maximum dc voltage was around 40v. I don't know why (the theory and the practical was not the same)
Waiting news about your lineal psu.
Best regards

Toni

post #7033 of 7035

I'll have a try after I finish my LM3886 amplifier.

 

the well known endless list of projects needs to be shortened first

post #7034 of 7035

Hey all, I've built this amp using Fred's PCB. It's working except for something is wrong with the left and right channels. Right channel is okay and is outputting just that channel.  The left however, while louder when playing left side sound, is also playing the right side sound. I have gone over everything so many times, everything seems to be in place. Any ideas what would cause this issue?

post #7035 of 7035

Check your Heater Voltage (Pin 4) and your Plate Voltage (Pin 6) on both tubes.  What are they for each tube?

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