From the Tokyo Headphone Festival writeup, anyone know what this thing is?
May 29, 2012 at 11:49 AM Thread Starter Post #1 of 17

loki993

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Saw this and was intrigued, Ive never seen small tubes used in an application before. looks like it may be a fairly simple build too. Anyone ever see anything like it or know what it is? 
 
May 31, 2012 at 11:04 AM Post #2 of 17

ManAtWork

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May 31, 2012 at 2:48 PM Post #3 of 17

loki993

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Quote:
I think it is a DIY headamp using the famous JAN 5676 mini tubes, with referring the circuit design here (http://www.tubes.tw/shop/htm/circuit/5676_circuit_1.jpg)
 
No similar commercial product is found in market.

Famous? why?
 
Yeah I figured there wasnt anything else like it that,s why I asked. You can see almost the entire circuit from the pic so I supposed with a little effort it could be duplicated. 
 
Is that pic you showed the whole circuit? It looks a little cut off. 
 
May 31, 2012 at 4:41 PM Post #4 of 17

ManAtWork

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The JAN 5676 tube is infamous by its great sounding for headphone amplifier. I am also interested to this mini amp as you, this is what I can find.
 
Jun 1, 2012 at 4:14 PM Post #5 of 17

loki993

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I see. Yeah it would be interesting to try. It definitely looks like a simple enough amp. There are a couple things hidden in the pic though. I bet someone that knows more then us about amp building could probably figure out what it would take. 
 
Jun 3, 2012 at 3:27 AM Post #6 of 17

KimLaroux

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I noticed this amplifier too and find it interesting for a few things. What amazes me the most is it seems to be running on 1.2v! The MUSES 8920 needs at least +3.5v and -3.5v, for a total of 7v. And that's not talking about the standby current the whole thing needs... How is he pulling all this out of 2 AA batteries connected in parallel?
 
confused_face(1).gif

 
The schematic posted in post #2 says that the tubes heaters are powered by a 1.2v battery. But it also says that the whole amplifier needs between 18 and 36v. Where is he getting that?
 
My guess is he's using a step up DC-DC converter, or two. I can't see any in the picture, but it might be hidden under the ledge. Also the Eneloop have an average capacity of 2Ah each. So he's got 4Ah of current out of those.
 
Jun 4, 2012 at 2:34 PM Post #8 of 17

loki993

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Interesting. I did a search and saw a couple but no pics of the insides :frowning2:. It does look quite similar. I also searched for maybe a design for the Millett portable but came up with nothing. Its a start though. 
 
Jun 4, 2012 at 3:36 PM Post #9 of 17

tomb

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Quote:
Interesting. I did a search and saw a couple but no pics of the insides :frowning2:. It does look quite similar. I also searched for maybe a design for the Millett portable but came up with nothing. Its a start though. 

Pete discounted doing a DIY design in another thread similar to this one - where someone asked about building a portable tube amp.  According to Pete, it's almost impossible to find tubes that work with batteries without microphonics.  The ones he used for the Portable Millett Hybrd are all gone.  You can read more here:
http://www.head-fi.org/t/603031/diy-portable-tube-headphone-amp/15
 
Jun 5, 2012 at 8:59 AM Post #10 of 17

loki993

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I noticed this amplifier too and find it interesting for a few things. What amazes me the most is it seems to be running on 1.2v! The MUSES 8920 needs at least +3.5v and -3.5v, for a total of 7v. And that's not talking about the standby current the whole thing needs... How is he pulling all this out of 2 AA batteries connected in parallel?
 
confused_face(1).gif

 
The schematic posted in post #2 says that the tubes heaters are powered by a 1.2v battery. But it also says that the whole amplifier needs between 18 and 36v. Where is he getting that?
 
My guess is he's using a step up DC-DC converter, or two. I can't see any in the picture, but it might be hidden under the ledge. Also the Eneloop have an average capacity of 2Ah each. So he's got 4Ah of current out of those.

 
It is interesting and I'm not sure how hes doing it either, that's why I think there are some things were not seeing in the pic. All that's a bit over my head though. 
Quote:
Pete discounted doing a DIY design in another thread similar to this one - where someone asked about building a portable tube amp.  According to Pete, it's almost impossible to find tubes that work with batteries without microphonics.  The ones he used for the Portable Millett Hybrd are all gone.  You can read more here:
http://www.head-fi.org/t/603031/diy-portable-tube-headphone-amp/15

 
Yeah from what little I could read about a portable tube amp I saw that although it was possible you couldn't really get enough power for the tube and what you end up with is basically a solid state amp what a pretty tube in ti that's just for show basically. Then again we do have better batteries now, I mean I have a 3.7 volt battery in my phone. Could something like that work?
 
Also the JAN 5676, is it a hard to find tube? Is it better then any full sized one? Basically would it be worth it to scale up to a small desktop application or would it be strictly for the novelty at that point?
 
Jun 5, 2012 at 9:24 PM Post #11 of 17

flecom

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problem with those pencil tubes with the shared heater is they are only rated for like 100~ hours of operation
 
Jun 6, 2012 at 12:23 AM Post #13 of 17

KimLaroux

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Quote:
 
It is interesting and I'm not sure how hes doing it either, that's why I think there are some things were not seeing in the pic. All that's a bit over my head though. 
 
Yeah from what little I could read about a portable tube amp I saw that although it was possible you couldn't really get enough power for the tube and what you end up with is basically a solid state amp what a pretty tube in ti that's just for show basically. Then again we do have better batteries now, I mean I have a 3.7 volt battery in my phone. Could something like that work?
 
Also the JAN 5676, is it a hard to find tube? Is it better then any full sized one? Basically would it be worth it to scale up to a small desktop application or would it be strictly for the novelty at that point?

 
Having higher voltage helps, but that usually trades off some current. For tubes you need high voltages, but you also need an important amount of current just for the tube heaters. In a portable application, the tube heaters are a serious waste of power. For example, the 12AX7 uses 2W of power for the tube heaters. And that's just one tube. Let say you use a 3.7v 1Ah battery, which stores 3.7Wh in ideal conditions. You couldn't even power the tube heater for 2 hours with this battery. And that's just the tube heaters, we're not even driving the headphones yet.
 
Next time you meet this guy, ask him about the battery life of his hybrid amplifier. I'd really like to know. 
wink.gif

 
And when I think about it, why is he even using tubes when he's got an Op-Amp in his design?
 
Jun 6, 2012 at 3:58 PM Post #14 of 17

loki993

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Quote:
 
Having higher voltage helps, but that usually trades off some current. For tubes you need high voltages, but you also need an important amount of current just for the tube heaters. In a portable application, the tube heaters are a serious waste of power. For example, the 12AX7 uses 2W of power for the tube heaters. And that's just one tube. Let say you use a 3.7v 1Ah battery, which stores 3.7Wh in ideal conditions. You couldn't even power the tube heater for 2 hours with this battery. And that's just the tube heaters, we're not even driving the headphones yet.
 
Next time you meet this guy, ask him about the battery life of his hybrid amplifier. I'd really like to know. 
wink.gif

 
And when I think about it, why is he even using tubes when he's got an Op-Amp in his design?

Ahh I see
 
I didn't meet him....it was a pic from the front page story about the Tokyo Headphone Festival, sorry if It seemed like it was something I actually saw, I saw the pic in the thread and was curious:
 
http://www.head-fi.org/t/611553/tokyo-headphone-festival-presented-by-fujiya-avic-may-12-2012-pictorial
 

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