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post #8941 of 9591
Quote:
Originally Posted by b1o2r3i4s5 View Post

wait... common mode signal rejection AND convert a unbalance to balance signal with.... a SWITCH?

You must have misread something there....

 

I'd love to see something like that done with a switch,

It would most definitely shock the world of electronics if not get you a Nobel prize biggrin.gif

 

Why not just use a transformer for your unbalanced inputs?  1:1 or even 1:2 (will help level balance between balanced and unbalanced channels) is easily found.

post #8942 of 9591
Quote:
Originally Posted by samsquanch View Post

 

Why not just use a transformer for your unbalanced inputs?  1:1 or even 1:2 (will help level balance between balanced and unbalanced channels) is easily found.

QFT, slight modifier.

 

Since the b22 does not run well at low gain, a 2or4:1 transformer may be even better. 

10k:600ohms are available from a bunch of sources. 

Run all inputs (yes, even the balanced ones) through the transformers for a good time, and ground loop proofing. 

 

I agree with the aversion to op amps, even discrete power op amps. 

 

On that note, building a b22 for IEMs is like killing a fly with an AA12

 

post #8943 of 9591
Quote:
Originally Posted by samsquanch View Post

 

Why not just use a transformer for your unbalanced inputs?  1:1 or even 1:2 (will help level balance between balanced and unbalanced channels) is easily found.

Are they? I've never used transformers in my designs before, my impression of transformers is that a decent audio one will cost $$$$.

Ill dig around, see what I can find biggrin.gif

 

Quote:
Originally Posted by nikongod View Post

I agree with the aversion to op amps, even discrete power op amps. 

 

On that note, building a b22 for IEMs is like killing a fly with an AA12

 

Even though the beta22 itself IS a discrete op-amp? rolleyes.gif

 

Overkill is my middle name wink.gif

Nah, a truly good amplifier should be able to drive anything from sensitive IEMs all the way to Speakers right?

post #8944 of 9591
Quote:
Originally Posted by nikongod View Post

QFT, slight modifier.

 

Since the b22 does not run well at low gain, a 2or4:1 transformer may be even better. 

10k:600ohms are available from a bunch of sources. 

Run all inputs (yes, even the balanced ones) through the transformers for a good time, and ground loop proofing.

 

 

So this (http://www.ebay.com/itm/120964873232?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649) won't sound as good as this (http://www.edcorusa.com/p/41/s2s600-600t)?

 

Anything else in the sub $100 range that might be better?

post #8945 of 9591

I'm a fan of Jensen Transformers, but that might just be because I've worked with them more than any other company, it's funny how we form favoritism like that...

 

http://www.jensen-transformers.com/ln_in.html

 

If you scroll down that page you'll see 4:1 step down transformers, they're about $100 each, which should be no issue for someone with the middle name of "Overkill."

 

Also, transformers, unlike opamps, require no power, so you can impress all your dreadlocked hippy friends with how green it is!  

post #8946 of 9591
Quote:
Originally Posted by FraGGleR View Post

So this (http://www.ebay.com/itm/120964873232?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649) won't sound as good as this (http://www.edcorusa.com/p/41/s2s600-600t)?

 

Anything else in the sub $100 range that might be better?

 

Oh deary me....  I just looked at that ebay auction, and I don't know if you read it or not, but, well, it's "ONLY FOR PROFESSIONALS".  Looks like you'll have to use a transformer, unless you have the proper forms that state you are indeed a professional.  People really seem to have it out for DIYer's these days!

post #8947 of 9591
Quote:
Originally Posted by samsquanch View Post

I'm a fan of Jensen Transformers, but that might just be because I've worked with them more than any other company, it's funny how we form favoritism like that...

 

http://www.jensen-transformers.com/ln_in.html

 

If you scroll down that page you'll see 4:1 step down transformers, they're about $100 each, which should be no issue for someone with the middle name of "Overkill."

 

Also, transformers, unlike opamps, require no power, so you can impress all your dreadlocked hippy friends with how green it is!  

$100! eek.gif

That's more then the cost of my ENTIRE build!!

 

Quote:
Originally Posted by samsquanch View Post

 

Oh deary me....  I just looked at that ebay auction, and I don't know if you read it or not, but, well, it's "ONLY FOR PROFESSIONALS".  Looks like you'll have to use a transformer, unless you have the proper forms that state you are indeed a professional.  People really seem to have it out for DIYer's these days!


Hahaha~

post #8948 of 9591

I built a little tube / transformer amp for my brother. Read about it and see pictures here:http://adventuresinmodioland.blogspot.com/2013/02/prototype-headphone-amp-continued.html
 

post #8949 of 9591
Quote:
Originally Posted by elliottstudio View Post

I built a little tube / transformer amp for my brother. Read about it and see pictures here:http://adventuresinmodioland.blogspot.com/2013/02/prototype-headphone-amp-continued.html
 

Looks great!

How did you make that silver PCB?

post #8950 of 9591

Made some custom cases for O2 amp and ODAC.

Used my favourite material MDF.

Sorry but don't have internal pics as after I finished this one I decided I din't like it so internals are now empty.

Got some ideas for a different case that I will do instead.

 

Raw MDF, 2 x 16mm thick, routered outside and jigsaw inside circles, then 6mm piece added on top.

 

Primed, sanded and holes drilled for volume and switch

 

Completed, rear view, DAC at the bottom

 

Completed front view, the O2 amp on top has a headphone output and the volume switch clicks in and out for power switch

"Volume knob" on the dac is a 2 way switch between headphone amp and my stereo preamp.

Or the 3.5mm jack and RCA's

 

The finish used was stone finish, topped with auotmotive clear coat.

The first layer of clear coat has some pearl flakes mixed in.

post #8951 of 9591

lol did I read b22 and iem's in the same sentence? It can be done, bit too much overkill and a bit too overpowered though...methinks

post #8952 of 9591
Quote:
Originally Posted by DefQon View Post

lol did I read b22 and iem's in the same sentence? It can be done, bit too much overkill and a bit too overpowered though...methinks


What are you talking about?
I normally drive headphones with multi-hundred watt power amps wink.gif

 

Oh and did I mention I'm using a 300VA toroid power transformer for my beta22 biggrin.gif

post #8953 of 9591

Hey everyone, this is my first post here at head fi.

 

I thought I'd share my first ever fully working headphone amp, my pretty much stock cmoy on stripboard. I had a lot of trouble with the irregularly patterened stuff shown in the tangentsoft CMoy guide since i'd never used it before. I redid it using Fred_fred's instructions early in this thread. I'm shocked how good it sounds, and I'm already eager to find out what my next project is! I have a couple CMoy PCBs coming from fred too, so that's next but I am looking at some of the tube head amps with a great deal of interest, along with the Pimeta 2.

 

Time will tell I suppose, but for now, enjoy, pictures of my amp.

 

http://i.imgur.com/VJfgcgR.jpg

http://i.imgur.com/duj4GI6.jpg

 

Sorry that the photo quality isn't anything amazing, I only have my phone for photography


Big thanks to Howard (aka fred fred) for his advice and and patience with helping me, and also getting me the new boards that inspired me to have a practice run first :D

 

I hope to see you all around the forum at some point.

 

Peace

 

chris

 

edit: it would seem img tags don't work here. those are direct links now. how many posts are required to get image attaching permissions? cheers


Edited by crispchicken - 2/6/13 at 3:12am
post #8954 of 9591
Quote:
Originally Posted by b1o2r3i4s5 View Post

Oh and did I mention I'm using a 300VA toroid power transformer for my beta22 biggrin.gif

 

 

Perfect! There should be more than enough stray magnetic fields from that huge transformer to bring the noise floor of the amp way up into the audible range with IEMs.

 

Just because you can do something does not prove that it isn't a terrible idea.

post #8955 of 9591
Quote:
Originally Posted by Beefy View Post

 

Perfect! There should be more than enough stray magnetic fields from that huge transformer to bring the noise floor of the amp way up into the audible range with IEMs.

 

Just because you can do something does not prove that it isn't a terrible idea.

Learn the maths!

Bigger transformer ≠ more magnetic field.

b-field strengths are dependent only on:

  1. current flowing through the wire
  2. number of turns
  3. permeability of the core material

 

And TBH, toroidal transformers provide some degree of self-shielding in the first place, the electromagnetic radiation coming from the transformer is probably very small compared to other current-carrying wires in the system.

 

With that said, I cannot empirically prove that what I just said is correct because I don't have the necessary equipment to do so. If you just happen to have a EM radiation meter laying around then by all means, take some measurements of toroidal transformers when they're operating and see if they will cause EMI in amplifiers. wink.gif

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