Millett "Starving Student" hybrid amp
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the_equalizer

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Quote:

Originally Posted by revolink24 /img/forum/go_quote.gif
I've got a puzzle for everyone.

I said earlier that whenever I tapped one of my tubes, there was a very loud cracking sound coming out of the headphones. I swapped tubes, and lo and behold, the other side began cracking, so I ordered some new tubes. 5 of them, in fact. The problem is, that the problem occurs with ALL 5, and only one tube of the seven I now own seems to not do this. I doubt that all of them are bad, and can only hypothesize that the one is very good and there is another problem somewhere. Anyone have any idea what that might be?

Oh, and I'm using a pcb build.



Could be that that particular socket is defective, maybe one of the pins of that socket is very very loose.

It could also be a cold solder joint for one or more of that socket's pins.

cheers !
 
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revolink24

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I've been suspecting that for a while, it's just odd that it would happen to both sockets and not affect one of the tubes. The pins must be bent oddly or something.

Anyhow, I guess I'll deal with what Ive got for now and worry about getting new sockets later. It just happened once without tapping it and I don't particularly want to damage my ears or headphones.
 
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tomb

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Quote:

Originally Posted by revolink24 /img/forum/go_quote.gif
I've been suspecting that for a while, it's just odd that it would happen to both sockets and not affect one of the tubes. The pins must be bent oddly or something.

Anyhow, I guess I'll deal with what Ive got for now and worry about getting new sockets later. It just happened once without tapping it and I don't particularly want to damage my ears or headphones.



It's tough to tell for sure, but it could still be the tube pins. Vendors are dragging the bottom of the barrel for these tubes now and many of them are in very sorry shape when it comes to the pins. I've tested many of them that registered as bad, but then months later went back after wire-brushing the pins and they tested good. It's something you can try, but do it very carefully - then use some alcohol to clean up so there's no fine metal dust to further exacerbate this issue.


EDIT: Heck, I've had some that had so much corrosion on the pins that the pins wouldn't even fit in the socket holes - ugly, green, foul stuff, too.
 
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Logos

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Quote:

Originally Posted by tomb /img/forum/go_quote.gif
OK - the price for this round of kits will be $120.

As stated, the heat sinks continue to increase and the cases are slightly higher than before. Finally, even though the BOM shows $118, there are a couple of hidden costs for me:

1. The power caps are Panasonic FC's. Those are $2.65 each at DigiKey.
(Pricing is based on the Mouser column except for these.)
2. For this round of kits, I am drilling and gluing the tube sockets so that you can use the tube LED's without any additional work.

#2 is a significant added feature, but one many of you have requested.



Well, that is more than fair. I'm surprised you're actually justifying the low cost, and doing all this extra work for the kits. You've got a heart of gold man, a heart of gold.


...Now to get me one of these things...
 
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Llama16

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Yeah tomb,
I can't stop envying your effort. That you are going to make the sockets yourself, wow!
It would be more then reasonable to raise the price just for that.

You're making many happy!
 
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Dunceiam

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I hate to sidetrack the thread with such a meager question, but how else does one learn these things?


I'm doing a PtP SSMH, and looking over the schematic, something caught my eye - why are there resistors/capacitors connecting to ground? (ex. R6, R12, R5, C6, R11, C1 - too name a few). This is one of my first non-stick in hole and solder projects, so excuse me for the quick question.
 
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timmyGCSE

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I won't have the money to order the PCB kit, I'll probably look at doing this in a month or so..but from what I read above it sounds like the tubes are in that short supply that I may not be able to?
I found a place selling the tubes for $4 a piece but haven't enquired about that yet
 
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tomb

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Quote:

Originally Posted by timmyGCSE /img/forum/go_quote.gif
I won't have the money to order the PCB kit, I'll probably look at doing this in a month or so..but from what I read above it sounds like the tubes are in that short supply that I may not be able to?
I found a place selling the tubes for $4 a piece but haven't enquired about that yet



When you do, I bet they tell you they don't have any. If a vendor does have some, they won't be $4 anymore.


Quote:

Originally Posted by Dunceiam
I hate to sidetrack the thread with such a meager question, but how else does one learn these things?

I'm doing a PtP SSMH, and looking over the schematic, something caught my eye - why are there resistors/capacitors connecting to ground? (ex. R6, R12, R5, C6, R11, C1 - too name a few). This is one of my first non-stick in hole and solder projects, so excuse me for the quick question.



Every electronics design has resistors and capacitors connecting to ground. You might refer to some of the many electronics articles and books that have been talked about often in the DIY section. The Search Tool is your friend.
 
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timmyGCSE

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Quote:

Originally Posted by tomb /img/forum/go_quote.gif
When you do, I bet they tell you they don't have any. If a vendor does have some, they won't be $4 anymore.




so I have no other option unless I can just be lucky and source some from somewhere?
 
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Llama16

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I don't know if this is possible on the PCB, but equalizer has gone with the very accessible, cheap and new production 12AU7 guitar tubes.

Check the link for any help. It could be a very helpfull solution, and they don't sound bad either I've heard
.
If you've got any questions contact equalizer, who has showed me as well.
http://www.head-fi.org/forums/6024902-post3873.html
 
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revolink24

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I promised pictures 8 million years ago on this thread, so I've finally made one.




And about that $120 price on those kits, I can't think of anything but the amazing amount of effort you put into this stuff for such little reward. The care with which you treat every order and customer is amazing. Thanks for all your hard work.
 
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the_equalizer

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Quote:

Originally Posted by timmyGCSE /img/forum/go_quote.gif
so I have no other option unless I can just be lucky and source some from somewhere?


Quote:

Originally Posted by Llama16 /img/forum/go_quote.gif
I don't know if this is possible on the PCB, but equalizer has gone with the very accessible, cheap and new production 12AU7 guitar tubes.

Check the link for any help. It could be a very helpfull solution, and they don't sound bad either I've heard
.
If you've got any questions contact equalizer, who has showed me as well.
http://www.head-fi.org/forums/6024902-post3873.html



Well, if you manage to get an adapter tube socket, then it would be easy to use the 12AU7 tubes in the beezar.com PCB SSMH. The only thing you'd need to do is swap R2 and R8 in the PCB for 390Kohms.

Unfortunately I don't think such an adapter exists, even though I know there are adapters for some popular audio tubes (like this one, for example); so this 19J6 -> 12AU7 adapter would have to be custom built.

Then again, as some previous post suggested, there's also the possibility of re-designing the PCB for the 9-pin 12AU7 socket; but that, of course, is not an easy or quick endeavour.

cheers!
 
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the_equalizer

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Quote:

Originally Posted by Dunceiam /img/forum/go_quote.gif
I hate to sidetrack the thread with such a meager question, but how else does one learn these things?


I'm doing a PtP SSMH, and looking over the schematic, something caught my eye - why are there resistors/capacitors connecting to ground? (ex. R6, R12, R5, C6, R11, C1 - too name a few). This is one of my first non-stick in hole and solder projects, so excuse me for the quick question.




Aside from TomB's recommendation on checking electronics articles and books, you might want to read this carefully. It might help you understand what do R5/R11 (the cathode resistors) do in the "Starving Student" Hybrid circuit.
 
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tomb

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Quote:

Originally Posted by revolink24 /img/forum/go_quote.gif
I promised pictures 8 million years ago on this thread, so I've finally made one.


Looks great! Quote:

And about that $120 price on those kits, I can't think of anything but the amazing amount of effort you put into this stuff for such little reward. The care with which you treat every order and customer is amazing. Thanks for all your hard work.


What a nice thing to say! Thank you very much.
 
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