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μPA... a super simple, all-tube, good sounding, very Stax-ious and very evil headphone amp for... - Page 2

post #16 of 22
5/15/11 at 10:56am
Thread Starter 

and don't forget it can also serve as an active LOD to connect to speaker amps.  

 

Quote:
Originally Posted by KuKuBuKu View Post

I don't know DIY much, but props, this is a cool and very unique looking amp! Never seen a home amp made to drive IEMs. 



 

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post #17 of 22
5/15/11 at 11:43am
To be clear, are you using a B+ of +20V?
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post #18 of 22
5/15/11 at 1:39pm
Thread Starter 

It is 20V, for right now.

 

Higher B+ seems to bring out sharper details, the difference between 12V and 20V is quite obvious, I picked 20V as being good enough. 

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post #19 of 22
5/15/11 at 3:07pm
So, beyond the winding ratio, do your have the specs on the transformers?

Not everyone can come across a set of stax transformers. wink.gif
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post #20 of 22
5/15/11 at 5:54pm
Thread Starter 

Don't have stax transformers floating around? then you wait, you search, you hunt them little steel boxes down! You do want the sound to be "stax-ious", no? wink_face.gif

 

Now if you want to use other transformers, then why use 6GM8?ph34r.gif Might as well go one 5687 per channel (parallel both sections),  use air-gapped SE output transformers (probably $200 a pair from Hammond, they will give you that "hammond-ious" soundtongue.gif),  set B+ to around 250V, set idel current at 15mA per tube... That should drive all >105dB/mW IEM's well. However that will be a large and expensive build, not suitable for DIY beginners, not super safe (as a bedside rig), and has no potential of going battery-powered/transportable. why would anybody want to do that? wink_face.gif

 

 

 


Edited by AudioCats - 5/15/11 at 5:56pm
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post #21 of 22
5/15/11 at 7:09pm

Well, that is indeed one option. Not really where I was looking to go though.

 

I happen to have a stash of 6GM8's, so, doing a low power implementation based upon that tube is appealing. Same with the stash of millet tubes I have (12AE6/FK6). 

 

I will keep my eyes open for the stax transformers, but, realistically, I want to keep my options open. I will do the design work and find a properly spec'ed transformer. They have me intrigued as of late.

 

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post #22 of 22
5/15/11 at 8:00pm
Thread Starter 

IMGP2307.jpg

 

SRD6 transformers don't sound nearly as good as the SRD7, but they are smaller and can be used in battery powered "transportable" configuration.

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