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-   -   A47 / Crystal CMoy (http://www.diyaudio.com/forums/headphone-systems/225831-a47-crystal-cmoy.html)

evovil 16th December 2012 05:54 PM

A47 / Crystal CMoy
 
Looking to put together a combination of the two.

Couple of questions...

  1. Think its doable in a freeform/point-to-point form?
  2. Can I run an A47 off of 9V or does it require 18V?
  3. For the power supply, I'd prefer to steer clear of a voltage divider, so TLE2426, op amp based, or Sijosae's method? (buffers are rather expensive where I am so would like to avoid them)
  4. Based off of the schematics I found (below), if I eliminate the pot does anything need to change?
  5. Are those resistor values "decent"? (not 100% sure how to work out the gain in a buffered setup)
  6. OPA2134 or OPA2227 or OPA2132?
  7. In theory, if I were to implement a bass boost via a RC circuit, in which feedback loop would it be placed? Or both? (referring to the schematics)
http://img13.photobucket.com/albums/...others/A47.gif
(all credit due to image creators/owners)

jcx 17th December 2012 10:36 PM

what headphones? - headphone impedance, sensitivity numbers determines amp I, V requirements

what happened to the O2 build?

evovil 18th December 2012 11:38 AM

Ah yes forgot to put that in...

Sennheiser 558's... so 50 ohm...

O2 build will happen eventually, but probably only next year sometime, so looking to put together something smaller in the mean time

jcx 18th December 2012 03:18 PM

knowing the 112 dB SPL re 1 Vrms senstivity number helps too

these would actually be fine for most listening direct from most DAP which are designed for even lower Z loads already

3.5 Vpk, 70 mA pk would drive them to ~120 dB SPL

single 9V would be fine but you do need to do something re supply splitting or (gasp) output C DC blocking

evovil 18th December 2012 03:35 PM

Output DC blocking?
Thought that was what the input cap was for, to block DC

jcx 18th December 2012 08:44 PM

output coupling Caps let the amp signal ground run from a simple resistive supply splitter

but require large caps to get the low frequncy corner below audio with the low Z load of the headphones

if you follow the recommendations for "best" practice for the application - seriesed non-polar electrolytic, fc ~1/10 the hedphone 3dB point - they end up bigger than the battery for your 50 Ohm headphones - a detraction for portable use

evovil 18th December 2012 09:30 PM

Hmm..

I must say, im rather lost, im not going to lie

tamasic1 6th January 2013 03:52 PM

please explain more
 
.
JCX,

Are you saying every CMOY type design is flawed because they don't have output caps?

paulb 6th January 2013 11:49 PM

With the circuit as shown, it needs to be powered by a dual (+/-) power supply. If you don't know what that is you should read the headwize tutorials.

tamasic1 8th January 2013 01:39 AM

question 3 not answered
 
Paulb,

Per the OP's original inquiry, question # 3 is asking:

For the power supply, I'd prefer to steer clear of a voltage divider, so TLE2426, op amp based, or Sijosae's method? (buffers are rather expensive where I am so would like to avoid them)

So he's pretty much read all about this. Instead of giving him a drive by condescension, why not give him you insight to the methods you have tried???


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