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Millett "Starving Student" hybrid amp - Page 448

post #6706 of 6853
Quote:
Originally Posted by scorp997 View Post
 

Well I finally built a 12au7 version of this amp, I have been watching this thread for a long time.

 

My brother turned me onto this project and he had built one with the pcb board and is really happy with it. I too purchased a pcb, but once I started looking for a suitable enclosure I changed my mind and went for a point to point build.

 

What I came up with is shown in my avatar. I can't upload photos yet, since my account is too new. I will post more when I can. The box is from a Kenwood CB-44 Dual Amp Balancer I found at a local PC recycle center and the heat sinks are just clamp-on style CPU heatsinks mounted to the sides of the box. The volume pot was already a 50k and the power switch made a perfect location for the 1/8" headphone jacks. The box is very tight and the way it opens makes it somewhat difficult to keep some of the leads short. I know the heatsinks may work better if turned 90deg, but there is plenty of heat rejection and I feel it looks much better this way. Another really cool thing about this case is that the volume knob has a lit ring around it that will work as a power indicator.

 

Using all of the optional components, I found the gain was too high when I use my Shure SE315s and an iPod dock outs as a source. I removed the cathode caps and upped the input resistors to 500k and it seems to be working much better. After removing the cathode caps to floor noise is much less, though there is still a little there.

 

This was a very cool project, thanks to all who made it possible.

 

Great to hear you had fun and enjoy your new amp. The gain is hard to control indeed. I've been thinking about experimenting and adding a little bit of global negative feedback, as some builders in the thread mentioned they had done it and it had worked wonders. You might consider doing the same to help tame this little beast.

 

By the way, as some posters say: pictures of  your amp or it didn't happen. :)

 

cheers!

post #6707 of 6853
Quote:
Originally Posted by the_equalizer View Post
 

 

Great to hear you had fun and enjoy your new amp. The gain is hard to control indeed. I've been thinking about experimenting and adding a little bit of global negative feedback, as some builders in the thread mentioned they had done it and it had worked wonders. You might consider doing the same to help tame this little beast.

 

By the way, as some posters say: pictures of  your amp or it didn't happen. :)

 

cheers!

I'd love to post a couple photos, but each time I try and insert a picture I get the popup "Your account does not have the required permissions to access this page"... I have a request into the moderator to see what they can do about this..

 

As for the negative feedback, is it just as simple as adding a 10K (or so) resistor from the output (pin 1) of the tube to the grid (pin 2), or does it have to be further downstream? I'm still new to tubes, sorry if this is a silly question. I didn't see a definite answer to this when I searched.

 

thanks in advance

post #6708 of 6853
Quote:
Originally Posted by scorp997 View Post
 

I'd love to post a couple photos, but each time I try and insert a picture I get the popup "Your account does not have the required permissions to access this page"... I have a request into the moderator to see what they can do about this..

There's a minimum number of posts before you can post pictures. I think it is 15 posts.

Just put in links to the pics.

post #6709 of 6853

While I am waiting for the PCBs from Fred (the MHSS 12AU7 version), I have a couple of questions. I know that the answers are probably in one of the 6700+ posts but I hope you realize that going thru all that is almost impossible. So  here are my questions:

 

1. Can the heatsink be mounted on the top or on the side of the enclosure and the MOSFET mounted inside the enclosure (touching the heatsink) so it is not visible on the outside? I am just trying to find a solution that will not expose parts outside of the enclosure.

 

2. Is the CISCO power supply still the best power source for the 12AU7 version? I want to add two LEDs to light up the tubes. I know that they are only about 20mA each but the power supply is only rated at 380mA.

 

3. Any problems with grounding in a wood enclosure?

 

Thanks.

post #6710 of 6853

I went through a lot of it, but it is really hard, and its even harder to go back and find something later! If you check the starving student website they explain how to mount the mosfet on the inside of the case: (but it is a metal case so aids in the heat transfer)

 

http://www.diyforums.org/SSMH/SSMHconstruct5.php

 

For the power supply, I personally am having problems getting one for under 30 euros (italy), and I may actauly find it easier to get one shipped from the states!!!

post #6711 of 6853

Quote:

Originally Posted by drabina View Post
 

1. Can the heatsink be mounted on the top or on the side of the enclosure and the MOSFET mounted inside the enclosure (touching the heatsink) so it is not visible on the outside? I am just trying to find a solution that will not expose parts outside of the enclosure.

I can't see why you can't do so, but its probably more efficient for cooling to keep MOSFETs outside so you dont heat air inside of enclosure. My MOSFETs run quite hot even with http://item.ebay.com/390627718088/ those or atleast my heat sinks are quite hot so I think MOSFETs are too.

 

Quote:
2. Is the CISCO power supply still the best power source for the 12AU7 version? I want to add two LEDs to light up the tubes. I know that they are only about 20mA each but the power supply is only rated at 380mA.

That 380mA is @ 48V so you will be ok when your leds take 20mA @ 3.3V or so.

 

Quote:
3. Any problems with grounding in a wood enclosure?

I am using point-to-point with wooden enclosure and I don't have any grounding problems. Only small problem is with volume pot when I am touching it, but it could be fixed by grounding that shaft/knob thingy. There is some posts about that in this thread. For me it is only hearable with very high volumes, that I am not even using so not going to do anything to it. Might be same thing with metal or plastic enclosure not sure.

post #6712 of 6853

Thanks for the replies.

 

One more question (for now): If needed, can I extend the legs of MOSFETs or that's not recommended? Just thinking that if I need to mount them outside, I may not be able to reach the PCB.

post #6713 of 6853

if you are based in the states I have the name of a user on here who had some power supplies, (I am not linked to him in anyway), if you want I can pass you his name, for me the price with shipment worked out slightly more expensive than buying here in Europe so I gave it a miss, up to you, let me know if you want his name...

post #6714 of 6853

In case anyone is looking for some power supplies for this build....I have a post here that should help you out.

 

http://www.head-fi.org/t/698662/cisco-power-supply-for-starving-student-amps

 

 

Thanks!

Dustin

post #6715 of 6853

Another noob question: What tube makes should I be looking for on Ebay? I am new to the tube world so I have no idea what to look for. I want a decent sound out of the SSMH but I do not want to lose the "SS" in the name by paying $50 for tubes.

 

Thanks

post #6716 of 6853
Quote:
Originally Posted by drabina View Post
 

Another noob question: What tube makes should I be looking for on Ebay? I am new to the tube world so I have no idea what to look for. I want a decent sound out of the SSMH but I do not want to lose the "SS" in the name by paying $50 for tubes.

 

Thanks


19J6 tubes are scarce enough that brand is not going to matter.  If you're building the 12AU7 version, note that the 5963 is often a great substitute.  It was designed to work at much lower voltages than the typical 12AU7 and is usually cheaper, to boot.  As you've probably noticed, the 12AU7 is one of the premier pre-amp tubes on the market and the variance is all the way from a few dollars to several hundred.

post #6717 of 6853
Quote:
Originally Posted by tomb View Post
 


19J6 tubes are scarce enough that brand is not going to matter.  If you're building the 12AU7 version, note that the 5963 is often a great substitute.  It was designed to work at much lower voltages than the typical 12AU7 and is usually cheaper, to boot.  As you've probably noticed, the 12AU7 is one of the premier pre-amp tubes on the market and the variance is all the way from a few dollars to several hundred.

I forgot to mention that I am building the 12AU7 version of SSMH. So can I use 5963 tubes without any modifications to the circuit?

 

Though even with those, there are RCA, Raytheon, GE, Sylvania, etc. Any of those are better than the rest or it doesn't matter?

post #6718 of 6853
Quote:
Originally Posted by drabina View Post
 
Quote:
Originally Posted by tomb View Post
 


19J6 tubes are scarce enough that brand is not going to matter.  If you're building the 12AU7 version, note that the 5963 is often a great substitute.  It was designed to work at much lower voltages than the typical 12AU7 and is usually cheaper, to boot.  As you've probably noticed, the 12AU7 is one of the premier pre-amp tubes on the market and the variance is all the way from a few dollars to several hundred.

I forgot to mention that I am building the 12AU7 version of SSMH. So can I use 5963 tubes without any modifications to the circuit?

 

Though even with those, there are RCA, Raytheon, GE, Sylvania, etc. Any of those are better than the rest or it doesn't matter?


Yes, you can use 5963's in a 12AU7 circuit, period.  JMHO, but I'm not sure any of those brands really matter if you're building the amp yourself.  After all, DIY-ing sort of implies that you're not "susceptible" to the marketing BS.  That said, tube rolling is a very fun thing to do with tube amps.  So, if you can get different brands and different tube structures for a decent price - heck, yes - go for it!  That's what makes this hobby fun.  All I'm saying is keep things in perspective.  The 5963 might keep you off of the "audiophile $$$ treadmill" with the Starving Student.  If you can get them cheap (IMHO, <$10 ea), then by all means - give them a shot.  You might find that one-in-a-thousand that "sounds fantastic" tube pair that can keep you happy for a long time. :) 


Edited by tomb - 2/6/14 at 6:57pm
post #6719 of 6853

So I rebuilt my attempt of point to point soldering into a stripboard version and I can get both tubes glowing, one mofset heating up and a buzz out of that channel.
But no audio. I will replace the dead mofset and see if it works but any suggestions for fixing no audio? I checked my cables and headphones and they worked fine.

I would really appreciate any help, this forum is amazing.
thankyou.

post #6720 of 6853

What are people using for the internal case wiring for these amplifiers?  I see references to "silver wire," is that better for wiring up circuits?  I'm still putting together the parts for one of these projects, and wanted to make sure I had everything on hand.

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