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A Super-Simple 6DJ8 Headphone Amp - Page 6

post #76 of 490
I got my PCB after a week and a half of winning the auction. It is beautiful, and nicely sealed in plastic. Already ordered the tube and the socket, now ordering the components and enclosure. I'm very excited, this is my second amp (the first was a Starving Student).
post #77 of 490
Since I'm still a newbie at this, I decided to put together a BOM so I can get all the parts straight in my head. I used suggestions from this thread and borrowed some part #s from other DIY projects. I've attached the Excel file to this post.

Any suggestions are welcome, especially since I'm not 100% sure whether everything will exactly work.
LL
post #78 of 490
Thread Starter 
C102/C202 need to be boutique-ish electrolytics; you can bypass them with other caps - PIO might not fit very easily, but anyway... the parts in your list will work, but might not fit very well - the board has holes for 15mm caps with 7.5mm lead spacing, and I think yours are 12mm caps with 5mm lead spacing.

C103 is the power reservoir - low ESR electrolytic, bigger is probably better, all other things being equal. The board will accept a 20mm part with 10mm lead spacing; the part in your BOM is a 16mm part with 7.5mm lead spacing.

C101/C201 are a spot where it would/could make sense to use boutique film caps, like PIOs; I can confirm that K42Y-2s will fit, though it's tight.

Everything else, at first glance, looks like it'll probably work just fine.

$83 USD, huh? (Really more like $103 or so once you figure in shipping, alas.) Didn't realize this was such a pricey undertaking; I guess the fact that the parts come from a lot of places, and I had a lot of the bits laying around already, made it seem cheaper than it really is.
post #79 of 490
I never even considered spacing on the PCB, thanks for the pointer. Just like my Millett SS, this is just an experiment. I plan to get the parts and fiddle with it until it works right.

If you consider the price of the populated board and power supply from 8audio is $95 shipped, $103 is not so bad for a complete product with an enclosure and a power supply (not to mention high quality parts of your choosing and the excitement of putting it together).
post #80 of 490
Didn't get it together this weekend. I got some 1watt resistors and was able to gt a couple of the values I wasn't able to before. I'm just waiting for the fets STILL. Total bummer. Maybe next weekend!
post #81 of 490
I got the heatsinks today from HK, only problem is I remember buying 4, and got 16. Must have been 4 sets of 4 each. Guess I'll have to build some more.

Only things missing now are the PCB, FETs and case.
post #82 of 490
I found a place for to buy 2sk310, 2sk117 and lmt317t. They have a very high minimum order, I guess I'm buying 10 or 15 of each....
post #83 of 490
Hi,
I breadboard this circuit last night, but got couple questions.

1. I used NOS 6DJ8 tube. The filament voltage measured was 5.5v, not 6.3v
2. The current to 2sk117 was only 0.1mA, and won't change much if I trimmed the 1kohm pot.
It looks to me the 6DJ8 didn't drain current from 2sk117.

Is any idea what I'm missing?

Thanks,
post #84 of 490
I don't think your gonna see an incredible amount of current going through a 6dj8 with less than 24v on the plate, and nothing on the grid.
5.5V will work for the filament, but more voltage and heat will mean more electrons will be flowing.
post #85 of 490
Does the 2sk117 act as a CCS? and bias current should be around 0.5 -1mA?
I'm new to tube amp. My knowledge is more on transistors and may not apply to tube.
Could some one explain how the 6DJ8 diased here?
It looks to me this is more like a self biasing:
the current on cathode creates a negative voltage on grid, how the CCS (2sk117) used here? limiting the plate current?
The question confusing me is if we set trim pot(R110) to have 1mA current, 1mA x 100ohm(R102) = 0.1v = -Vg, but will 6DJ8 will give 1mA plate current when Vg=-0.1v?
post #86 of 490
It turns out the place where I ordered the fets is out of business: I never received them, they did not reply to my emails, and paypal reimbursed me as soon as I filed a claim.

So I now need to source them from somewhere else: any of you have a set to sell me, or trade for a NOS 7dj8 tube?
post #87 of 490
B&D Enterprises has both, the K310's are $3.59 ea. and the K117's are $1.59 ea.
There is a $15 minimum order in the states and I think a friend recently told me that it's minimum $50 international.
Maybe you could figure out some suitable and easily obtainable replacements. I think an LM317 would work great in place of the K310.
You might find these on ebay(the K117/310).
post #88 of 490
Yes, and B&D has very expensive shipping. On ebay they are 10 euro each plus shipping. For that price I'd better sell the PCB and use the parts for a different project.
post #89 of 490
Here is a link for the K117 in ebay, 3 for $1 plus $2 shipping. That's $1 ea. shipped.

LittleDiode shows the K310's for $16 ea. and $5.99 shipping. Highway robbery
post #90 of 490
I've had 2 different results on Google suggest that replacements for the 2SK310 would be:
BUZ60
BUZ76A
IRF710/720/732
MTP3N40
The pages state clearly that these are just suggestions. They also have links for Drop IN Replacements.
link
link
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