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A Super-Simple 6DJ8 Headphone Amp - Page 4

post #46 of 490
For the phones I'll be using the 1000uF and 10ohms works out perfectly, but all of the phones I'll run on this thing are low-resistance(32 ohms at the most).

I'd complain that I still haven't gotten my PCB but I haven't gotten anything else either. This project is REALLY testing my ability to hurry up and wait.
post #47 of 490
^That's why I suggested making C102 socketed or something to make it easy to experiment with different caps, although it isn't very difficult just to desolder/solder them.
Maybe one week you feel like a Blackgate, then next week you might want to try a Panasonic, or whatever you may have in your parts box, and don't forget bypassing.
post #48 of 490
Can those be socketed away from the board without introducing too much noise?
post #49 of 490
Thread Starter 
Ah. I did the math, but thought R108/R208 factored into the equation. Bother. I did say I was going to try the Wimas, for what it's worth.

Now off to order some appropriately-sized Muse... or Cerafine... or other capacitors.
post #50 of 490
If your referring to a 3.3uF Wima, yes they will work, you'll hear music, it just won't have any bass at all. It may make a very good bypass cap for a larger cap.
The output on this amp is very much similar to the one on mine(Aikido), and I would venture to say you will be pleasantly pleased with it's performance
post #51 of 490

Kit Case

Does the original ebay seller also sell pre-cut/drilled cases for this kit? If not, what are you guys planning on using?
post #52 of 490
Thread Starter 
They have one or two cases on their website, but they're not designed for this amp, and would have to be drilled, et cetera, to fit.

There should be an aluminum Hammond case that fits; I'll be using a plastic PacTec case, probably with custom laser-cut end panels.

For what it's worth, the PCB should fit in one of these, sideways, with beaucoup room to spare. (Actually, you could just fit two of these boards in there, sideways. And still have lots of room for things like a DAC, a power supply, a crossfeed circuit, a small speaker amp, an integrated iPod LOD, and other stuff, as well.) Hmmn...

It'll fit into one of these, without a lot of room to spare.

I used one of the latter for my SOHA, and they're quite well-made cases; they're also quite thick (I believe the top and bottom are around 3mm), so anyone planning on putting lots of holes in the case with hand tools might want to consider another option. They're not the prettiest things in the world, but they get the job done... only 1/2" or so of tube will stick out, however; the larger case up top mounts the PCB differently, so you'd get to see a lot more of the tube, if that's important to you...
post #53 of 490
Thanks for the enclosure suggestions. I ordered the PCB and the tube socket yesterday, now looking to get a tube or two from the "not-too-overpriced" category. I think I have at least a week or two until the PCB shows up.
post #54 of 490
If any of you wants a NOS 7DJ8, I have quite a few of them. I sent one pair to Donald and one to Digger, and they both liked them. I will probably have to send some stuff to the US so shipping would be very cheap, and the tubes cost me about 10$ each. I have Philips with A-frame getters from the Amperex factory, and Russian tubes probably from the Reflektor factory. The offer is good only for those building this amp, other people (except Digger who wants an extra pair) will get them only if there's any left, and will have to pay more.
post #55 of 490
Is it possible those tubes were absolutely factory brand new Ludo?
The longer I listen to them the better and better they sound. Perhaps they needed a little time to allow all the parts to settle in.
post #56 of 490
Quote:
Originally Posted by digger945 View Post
Is it possible those tubes were absolutely factory brand new Ludo?
The longer I listen to them the better and better they sound. Perhaps they needed a little time to allow all the parts to settle in.
They are factory brand new. They come from the stock of a place that used to build and repair radios in the '40s-60s, and now sells electronic components. It's what's left from their old stock used for spares or repairs, I discovered they have them by accident, as they don't advertise having them.
post #57 of 490
This is a little off-topic, but I didn't want to start a new thread. How do you determine compatible tube part numbers and/or how do you read them? I was at a surplus store around here and they have boxes upon boxes of new old stock tubes that I want to go through but don't know what to look for lol
post #58 of 490
Quote:
Originally Posted by DKJones96 View Post
This is a little off-topic, but I didn't want to start a new thread. How do you determine compatible tube part numbers and/or how do you read them? I was at a surplus store around here and they have boxes upon boxes of new old stock tubes that I want to go through but don't know what to look for lol
I'm not an expert, but 7DJ8 are often used in place of the 6DJ8 as their main difference is the heater, which requires 7V instead of 6.3 (and posibly slightly more current, can't remember now). The ECC86 is a low voltage double triode, so in theory it should be perfect for this kind of amp/voltage. But it needs some tweaks. A good explanation on how to chose values for the ECC86 is the MEHA page.

Other than that, I don't know.
post #59 of 490
Thread Starter 
Quote:
Originally Posted by DKJones96 View Post
This is a little off-topic, but I didn't want to start a new thread. How do you determine compatible tube part numbers and/or how do you read them? I was at a surplus store around here and they have boxes upon boxes of new old stock tubes that I want to go through but don't know what to look for lol
To be cynical, you're unlikely to come across anything in too much demand; I'd guess that 95% of NOS tubes at surplus stores these days are television tubes with few other ready applications, and the remainder are - if you're extremely lucky - very common radio tubes like the 12BE6, 12BA6, 50EH5, and so on.

It's usually easy enough to remember what tubes will work in an amp you own. If you want to discover new and obscure tubes that could perhaps be made to work in amps yet unbuilt, I suggest picking up a copy of the RCA tube handbook, and bringing it with you. Then you can least figure out what the tubes you're looking at were meant for, which is of course not always a good indicator of what they'll do. If nothing else, it'll prevent you buying a bunch of tubes just because they say "Amperex" on them, only to later discover they're rectifier tubes, or something similarly un-useful for amplifier use.

For example, someone gave me a NOS Westinghouse 76 tube a while ago. A type 76? Never heard of it. A quick check, though, shows that it's a 6.3v triode meant for use as an amplifier, albeit at plate voltages over 100v. Equally quickly, one will see that, though it has a fairly usable gain (for a headphone amp, anyway) of 13.8, as a triode, you'd need two to build a stereo amp with 'em...
post #60 of 490
I pretty much expected to see what my grandfather has at his house. A bunch of old tubes from the 30s and 40s that don't do what i need them to and, if they do, probably have stupidly high plate voltages. But you never know til you look and even ones with high voltage requirements can always make for an interesting project later on.
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