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A Super-Simple 6DJ8 Headphone Amp - Page 28

post #406 of 490
Originally Posted by Zigis View Post

As promised, here are schematic with parts numbers and values for those of you, who building amps with my boards.


I got the board a couple of days ago, and it's very well made, thanks a lot for the schematics!


If you make another batch, would it be possible to design it with larger capacitors? In my old build I used the Elna Silmic II, but they are too large for your board.

post #407 of 490

Thanks, KimLaroux.

I have not made A/B tests with and without additional RC filter, however I believe PS filtering and cleaning never can be too much.

What exactly we hear in phones or speakers? We hear PS, slightly modulated with audio signalregular_smile%20.gif, think about it this way.

Even if PS dirt is not listenable as background noise, it can reduce music clarity and transparency.

To be honest, I did not made special calculations, just take large enough low ESR caps and 1 ohm was what lying in my part box and what I usually see in others low voltage CRC PS filters.

Schematic I posted is mostly for part numbers, related with my PCB, they are different from schematic in the page 1 in this thread. Part values is just what I  use in my build, anyone can recalculate and use something slightly different.


10 ohm resistor in output is from original schematic (page 1 in this thread), I believe it is for protecting FET from short circuiting wen plugging phone jack on working amp.

If you believe, you can always plug and unplug phones with amp off, newer with amp on, you can short this 10 ohm resistor, probably gain in sound quality.

Edited by Zigis - 6/11/12 at 4:01pm
post #408 of 490

Nice to hear, you got the board, ludoo.


If I made changes on board (in fact going to order completely different board) expenses are larger. Only if there are interest for at least 15-20 boards, price will stay reasonable (about 10 euro). The same PCB, without changes, I can reorder in smallest quantity and same price.


If there would be large enough interest, we can discuss changes and make new board design.

One handy extra, I can imagine - additional contact pad with small hole for DMM probe, for 15V point on each channel. After each tube changing small 15V correction required.


One thing, I forgot to say before. PCB maker forgot to make 2 x 3mm mounting holes for screws near tube socket, however i make them in file. For my amp I drilled holes myself.

post #409 of 490

i must have the worst luck, my amp not even working on the first try and the only place to to turn to is a thread that's no longer active... but here goes :(


 all my transistors r from dubious sources. irf510 could be fake, lm317 also. and then i got 2sk30 instead of 117 because that's the only suitable one the shop owner could offer.

the amp doesn't work. 

at first i realized i installed the 2sk30 with wrong pinouts. (they need to be turned 180 degrees) and then after fixin that, the amp still doesn't turn on. no tube glow, heatsink heat, sound, nothing :(


voltage reads 24v across every pin. resistors, tubes, caps. i did use 220uf caps in c102,103 instead of 470uf, and 230ohm instead of 220ohms where specified. i don't think they matter as much, do they?


i really hope to hear that it's probably the nfet transistor.



post #410 of 490

it works now after changing the fuse. i had 1a slow blow fuse when my psu was 1.8a. :P i put 2a fuse in, did the star grounding mod, and now the sound is simply gorgeous. for the price it's a steal, and it's actually the best headphone amp i've heard in my limited experience. 

post #411 of 490
Originally Posted by curiousmuffin View Post

it works now after changing the fuse. i had 1a slow blow fuse when my psu was 1.8a. :P i put 2a fuse in, did the star grounding mod, and now the sound is simply gorgeous. for the price it's a steal, and it's actually the best headphone amp i've heard in my limited experience. 


This logic is wrong. It's not the power rating of the PSU that dictates how much current flows trough the fuse, it's the power the amplifier actually uses. Look at it this way: the AC power socket in your room are rated for 15A, does everything you connect to them uses 15A? An electric trimmer pulling 15A would be powerful enough to cut down a tree. So no, a wall socket is rated 15A because it will melt (actually, the breaker should trigger) and catch fire if you load it with more than 15A. And that's why your fuse should never be higher than the current rating of your PSU. The point of a fuse is to protect the power supply against overload and short circuits. Using a 2A fuse on a PSU rated for 1.8A is useless, you might as well have no fuse. The PSU will die before the fuse blows. And if you're using a switching PSU, then the fuse really IS useless, since switching PSU have overload and short circuit protections built in.


The starving student amplifier uses around 350 milliamps, or 0.35 Amps. These amplifiers being very similar, I would venture in saying they use about the same amount of power. Actually, this one could be more efficient than the SSMH since you can limit the current bias using the LM317. A 0.5 Amps fuse would be a lot more appropriate.


Which makes me think, was the original fuse blown when you put it in, or did the amplifier blow it? Because if the amplifier actually blew the 1A slow blow fuse, there might be something wrong in your circuit. Aren't the heat sinks getting overly hot? No wires melted yet?

post #412 of 490
well i wouldn't call this a logic. more like a foolish assumption out of not knowing what the heck i was doing. x)

logic calls for fundamental reasoning- electrical knowledge is hardly a requirement for that.

everythings working soundly as far as i can tell. and the amp actually runs much cooler than i expected.

i do have a 24v 5a psu tho. i think i wanna try this out with the same fuse.

edit: I hooked it up to the said psu and the sound is much more powerful and sweeter. lm317 sinks are now almost too hot to touch.

here's the sorry state my amp's in atm. the 'casing', for the lack of a better description, was done in hurry with a handsaw with some scrapwood, just to elevate the amp of the ground. in the future it will be housed in a proper chassis with the tubes and caps sticking out on the top.

i tried to use boutique components throughout as this unit was also going to serve as a preamp in my main rig. panasonic thsa 10000uf smoothing cap with a pair of blackgate 220ufs. outputs are silmic ii 1000uf bypassed with mundorf supreme. the red ones are .33uf jantzen supreme, and carbon film resistors in most locations.

sound is simply gorgeous. rich, powerful and very tubey with that inevitable mosfet 'sheen' that i actually like.smily_headphones1.gif

Edited by curiousmuffin - 6/29/12 at 3:27am
post #413 of 490

All my PCBs are sold out.

If someone are still interested in boards, please let me know. I can order new bunch, if there are interests in at least 7-10 boards. They made ordered PCBs in one week, usually.


Edited by Zigis - 7/21/12 at 8:33am
post #414 of 490

Zigis, I really like your PCB. One suggestion though: if you make a next revision, could you leave more space for larger caps? In my build I use the Elna Silmic II but they are too large to fit on your board. It makes sense to leave space for good components, since you already designed the board with a good pot in mind. :)

post #415 of 490

Hi ludoo, yes I remember about caps. As I say before, I can make changes if there is enough interest in boards. Any change in layout manufacturer understand like "new design" and this is more expensive than just repeat existing board (they use old templates).

b.t.w., what diam. is your Elnas? 17mm? PanasonicFM 1000uf 35V are 13mm.


On board are missing 2 wholes, 3mm diam. for mounting board to enclosure. I drilled wholes myself.





Here is board layout wit marked with yellow missing wholes. This is manufacturers fault, I hope in next bunch this will be fixed.

post #416 of 490

The Elna Silmic II 470uF 35V are 16x31.5 mm, the 1000uF 35V 18x35.5 mm. Large caps, but they do sound good. :)

post #417 of 490

Zigis I wrote to you about the PCBs, but I caught up on the thread and see you're looking for more interest.


I can order 3x boards myself, and also request space for bigger caps please!


Lets see if some other members are also interested.

post #418 of 490

Hi jsanddin, I just read your PM.

If you are willing to present board design, I can order PCB's tomorrow and they may be ready after week or so.

If you prefer larger space for caps or any other change, new design PCB cost me about 150 euro. This mean, I can do it if there is interest for at least 15 boards for 10 euro each. Or less boards for higher price.


In the mean time we can discuss changes and draw new board.

post #419 of 490
Originally Posted by jsandin View Post

Lets see if some other members are also interested.

After already built one zigis board , I am interested in one more.

Too say that I was impressed with the sound would be an understatement.

However, I do not need more space for bigger caps, but if majority here decide on the new layout I will obeybiggrin.gif.

post #420 of 490
Sorry if this a DIY only thread, but are these amps available as already assembled? I have a lot of interest in a nice tube amp, but I already have too many hobbies & time demands to train a new skill wink.gif So, I appreciate what all of you have invested in yourselves smily_headphones1.gif
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