SS amp with impedance switch to build for IEMs and Cans

The CK2III: http://www.amb.org/audio/ck2/

what is a SSD?

 

and what is the IEM's sensitivity?

 

What do you want the impedance switcher to do?

 

It is the bane of tube amps to be sensitive to the impedance of the load. Most SS amps are quite immune to this.

 

If you want an IEC output thats just a big fat 120ohm resistor in series with the output. Very easy to wire with a switch.

At that price range you can get a nice M^3 / M3 with a Sigma11, with a gain switch. Sounds perfect for your needs, the M^3 is considered an incredible amp for the price and near the top as far as high-end value goes.

iem really don't want (V) amplification - a step down transformer would give better noise performance than any amp - at most add a input unity gain buffer stage to the xfmr input

you can't make a "universal" amp without compromising performance - some iem can reach >120 SPL with 200 mVrms, Senn HD6xx require 6.5 Vrms for the same loudness - that's 30 dB difference - without considering K1000 or Orthos

 

box and PS are often the biggest expenses - just build 2 amps in the same box - optimize each for the load with "iem" and "regular" output connectors

 

 

Edited by jcx - 4/24/11 at 8:37am

If you want to build something specifically to drive IEMs, I would recommend building a DAC with a I/V stage
intended to drive your IEMs in addition to the typical line out.
A suitably configured TP Buffalo DAC can drive IEMs using software volume control and you can leave out the
pot and separate amp from your chain, probably the ultimate desktop IEM set-up.

The Gamma2 is similarly capable as far as power output, but theoretically suffers from bit loss when using
software volume attenuation. It still is a cleaner IEM drive than any DAP though. I use a Gamma2 as my desktop
IEM driver all the time and slightly prefer the Gamma2 to my Buffalo for single ended DAC duties, including
using it direct to IEMs.

I'd go for a transformer on the output of the DAC. The output stages don't always deal well with 12-24ohm loads (even 120-300 may bog them down) and the transformer will reduce apparent random noise. To run IEMs directly you will need to run the output stage at a really low gain: you may find yourself with a maximum output that is so low that hum pickup becomes an issue again. 

 

A bunch of people make 5K:8ohm transformers that should work well for this. I'm quite fond of my radio-shack 1k:8ohm transformers, they are worth at least $2.50 each*. Xicon sells similar (maybe they are the OEM for radio-shack? they look the same) units through mouser, at similarly sweet prices. For what the alternatives cost (like $20 each and up) Im not sure Id upgrade.

 

*I use my transformers on the volume-controlled line out of the Iriver IHP120. The idea should transfer to a home system with good gain structure nicely.

Edited by nikongod - 4/25/11 at 11:54am