[samsquanch]

Quote:

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

 
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.

 

[nikongod]

Quote:

 
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
 

 

[akiroz]

Quote:

 
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

 
Quote:

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?

 
Overkill is my middle name

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

 

[FraGGleR]

Quote:

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?

 

[samsquanch]

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!  

 

[samsquanch]

Quote:

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 "[size=medium]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![/size]

 

[akiroz]

Quote:

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!

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

 
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 "[size=medium]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![/size]

Hahaha~

 

[elliottstudio]

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
 

 

[akiroz]

Quote:

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?

 

[dfferent]

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.

 

[DefQon]

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

 

[akiroz]

Quote:

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

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

 

[crispchicken]

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
http://i.imgur.com/h5kwV4m.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
 
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

 

[Beefy]

Quote:

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

 

 
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.

 

[akiroz]

Quote:

 
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:

• current flowing through the wire
• number of turns
• 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.