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Re: [AUDITORY] What amplifier should I buy to drive Etymotic ER1 / ER2 insert earphones?



Our group recently had a conversation with Etymotic about just this issue, and recommended a few options: 

Apparently several groups use a TDT HB7 headphone buffer.

"Our engineers use the Stewart Audio PA-50B: https://www.markertek.com/product/pa50b/stewart-audio-pa-50b-2-channel-half-rack-amplifier-25w-x-2-at-8-ohm They like it because it has a screwdriver setting for gain, so you can set it and not worry about it being changed inadvertently. 
From one of our engineers:
Most stereo audio amplifiers will work since they are designed to drive 8 ohm loads or less.  The biggest problem most run into is that they can easily melt the ER-2 if the volume control is set too high.  We’ve seen many ER-2’s that have been hooked to Crown amplifiers where the volume control accidently was adjusted and delivered all 100 watts of output to the poor ER-2.  That’s one reason we like the screwdriver gain controls on the Stewart amplifier. 
 Users can use the small 100 ohm resistors we provide to wire in series as a fuse, or can make sure their amplifier’s gain can’t overdrive the ER-2 through other means.  Since most amplifiers aren’t set up for unity gain, we use a 20dB attenuator out of our PC D/A card to the amplifier input, and then calibrate the gain on the Stewart amplifier to 20dB, giving a net unity gain. 
 The 100 ohm series resistor we provide will provide attenuation on the output side of the amplifier, and cut back on the requirements of the amplifier.  The user will have to calibrate their system so they know their drive levels to the transducer. "

"Output impedance is 0.3W and it’ll output nearly 7V at 16 ohms.  $99 dollars each.
The question is whether or not you can feel comfortable recommending an amp from a company called “Schiit Audio.”
http://www.schiit.com/products/magni-3 Magni 3 - Schiit Audio, Headphone amps and DACs made in USA.
www.schiit.com
Magni 3 includes preamp outputs. This means you can connect it to your desktop powered monitors for a complete system—or even connect it to a speaker power amp and ...
Even though this is a really stupidly named company, the guy behind this has been doing high-end audio design for a long time, previously designing for Theta Digital and Angstrom.  I’ve seen them in person and they seem to be built decently for the money."

Nate Greene

-----Original Message-----
From: AUDITORY - Research in Auditory Perception [mailto:AUDITORY@xxxxxxxxxxxxxxx] On Behalf Of Björn Herrmann
Sent: Monday, February 19, 2018 1:29 PM
To: AUDITORY@xxxxxxxxxxxxxxx
Subject: [AUDITORY] What amplifier should I buy to drive Etymotic ER1 / ER2 insert earphones?

Dear list,

I have thus far used headphones for my auditory experiments, but a new experiment I am setting up requires that I use our Etymotic ER1 / ER2 insert earphones. However, the sounds (played through a Focusrite 2i4 sound card) are not loud enough (limiting the range of intensities available). I thus would like to buy an amplifier, but also hope for reasonable costs.
What kind of amplifier would you recommend to drive Etymotic ER1 / ER2 insert earphones?
Thank you in advance for any input you may have.

Bjorn


----------
Björn Herrmann (PhD)

Brain and Mind Institute
The University of Western Ontario
London, Ontario N6A 5B7
Canada

email: herrmann.b@xxxxxxxxx
web: www.bjornherrmann.com