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A Super-Simple 6DJ8 Headphone Amp
Mar 9, 2009 at 2:29 AM Post #166 of 490
I picked up a stepped drill bit from Sears to finish my case. Although I'm not crazy spending $36 on it, I could not wait to get it from eBay. I finished the hole for the tube, and added two ventilation holes on the back panel. Still, I don't feel comfortable that the amp will run cool enough with the top on. Perhaps a few vent holes on the top? Here is a picture of the completed product. In any case, I'm finished now.

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More pics:
6dj8 Headphone Amplifier pictures by kansei13 - Photobucket
 
Mar 9, 2009 at 9:47 PM Post #167 of 490
Very nice! The only real thing I did differently as far as the case goes is put the RCA jacks in the front. Which I'm glad I did as I'm most likely going to stick a small 12v fan in the back.

I ordered an Electro-Harmonix 6922 overnight that should fix my lack of gain problem. I'll build another circuit around the 6J6(portable unit?) and maybe another for the 6N1s. I may buy another PCB to do experimenting on with those units but this one i want working already.

I wonder if there is enough room in the front with it closed for the Bantam dac I got all my parts for today.... hmmm.
 
Mar 12, 2009 at 3:03 AM Post #169 of 490
Here is what I have so far. Thumbs up to thetubestore.com for their expedient shipping. I got the 6922 today, slapped it in, verified heater voltage, and this thing is awesome!

Very clean sounding amp. I think it overdrives my poor HD202s tho. If something has deep bass I can hear the drivers muddying up the midrange in an attempt to create the bass being sent to it. The 317s no longer run hot either. Apparently 300mA as opposed to 600 makes a huge difference! I snapped a couple of pics. I'll get an album when I'm closer to finished(a few minor things like me wiring the volume pot backwards to fix).

All jacks are in the front and the power switch is actually in the back by the DC jack that I'm not using in the pic. My custom mini-RCA cable works well too.
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8-second exposure showing the tube lighting up the circuit board.
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Mar 12, 2009 at 6:54 AM Post #171 of 490
Wow, that's going to look really nice - bright silvery tube sticking out of a bright silvery box! Very clean and modern. I might just have to jump on the silver 6DJ8 amp bandwagon. I'm glad you finally got it working, too, and are able to join in the fun.
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The more I listen to this, the more impressed I am with how good such a simple design can sound. Compared to some of the amp designs out there, this thing is downright primitive, but you'd never know it from just listening to it...
 
Mar 16, 2009 at 11:09 AM Post #172 of 490
I've decided to sell my first "super simple" to finance building a Bijou. It's on eBay if anyone is interested.

I have 90% of the parts, including the PCB, to build a second one. As soon as buy more stuff from Mouser I will get the rest of the parts and put it together.
 
Mar 17, 2009 at 8:34 PM Post #173 of 490
Hi all,

After a disasterous build of the SOHA v3.0 I bought this amp. It came with all parts pre mounted. All looks very nice, but I am not satisfied with the sound. There is a hugh lack of bass and all sound a bit muddy. I placed a nice PIO at C101. Are there any other changes I could make to improve the sound?
 
Mar 17, 2009 at 9:54 PM Post #176 of 490
Quote:

Originally Posted by biarritz /img/forum/go_quote.gif
Hi all,

After a disasterous build of the SOHA v3.0 I bought this amp. It came with all parts pre mounted. All looks very nice, but I am not satisfied with the sound. There is a hugh lack of bass and all sound a bit muddy. I placed a nice PIO at C101. Are there any other changes I could make to improve the sound?


What cans are you using? A good amp will expose other weaknesses in your system.

NK
 
Mar 17, 2009 at 9:56 PM Post #177 of 490
Guys, those both look awesome!

@ Kansei: You could drill out the tube-hole a bid wider, to facilitate the use of some sort of cooler/damper, if you'd like.

OItherwise, I'd just drill some small holes maybe 6-10 in a circular fashion around the base of the tube-hole. That should provide all the ventilation you need (and look classy). It's not like you're running a GM70 in there..
biggrin.gif


NK
 
Mar 18, 2009 at 1:42 AM Post #179 of 490
Quote:

Originally Posted by biarritz /img/forum/go_quote.gif
Hi all,

After a disasterous build of the SOHA v3.0 I bought this amp. It came with all parts pre mounted. All looks very nice, but I am not satisfied with the sound. There is a hugh lack of bass and all sound a bit muddy. I placed a nice PIO at C101. Are there any other changes I could make to improve the sound?


What are you feeding it with? Did you buy the power supply 8Audio offer, or are you using something else? Are you using the stock Chinese tube? And, like Nick 214 asked, what headphones are you using it with?

There should be no shortage whatsoever of bass with this amp, from my experience; quite the contrary, in fact. (But remember, my power reservoir cap, C103, is - cough! - 12000uf, which is undoubtedly excessive, and I think everyone else who built one here used something larger than the spec'd 1000uf, so upgrading that to a larger cap - 4700uf might be a good compromise between "too little" and "outright crazy" - might be something to look at.)

My only other idea would be to pick up an inexpensive name-brand 6DJ8 or 6922, just on the offhand chance the Chinese one it came with is bad. If the tube's at fault, and it's really as bad as you describe, then pretty much anything ought to be a huge improvement.
 
Mar 18, 2009 at 2:03 AM Post #180 of 490
The pre-built kit comes with the 24v supply from 8audio.

I agree with nemo tho, there should be zero lack of bass. Quite the contrary actually, I find that it is MORE than able to drive bass to the phones. For the power res cap, I used a 2200 because it was the lowest value i could find that would directly fit.
 
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