[litster]

Hi all. I am new here.    I recently built a cMoyBB V 2.03 and plan to use it to drive a pair of HD650. For R3_L and R3_R, I have it at Gain=7.25 with 1.6kΩ resistors.  Is this gain setting OK for HD650 or should I go to gain 9?  HD650's impedance is 300 ohms.  Also, would I need to mod it to using 18V instead of 9V?  I also have a 12V power supply that I connect to my cMoy.
 
Thanks.

 

[nikongod]

The difference between voltage gain of 7.5 and 9 is almost nothing.
 
Unless you are dangerously close to the top of your pot I would try LESS gain. 2.5-3.25 is a good range IME&O. There are so many advantages to lower gain, and really very few for higher.  

 

[litster]

Thanks nikongod.  I thought higher impedance headphones require higher gain, that's why I thought it would be better to go higher gain for the 300-ohm HD650.  I don't have the HD 650 yet.  I will need to check how close to the top the pot will be.
 
Thanks.

 

[AmarokCZ]

HD650 has high impedance but it also have high sensitivity - 115dB/V.
Chose gain according to expected signal souce (its level) so that output voltage at full volume would be ~3V (~120dB is enough if you'd ask me).

 

[litster]

Checked with jdslabs. John has been super helpful with my questions.

For HD 650, He suggests to set gain to 7 or 8, and use two 9v batteries or a 18v or 24v power supply.

I could listen with my HD 650 at almost maximum level with this setup, but I turn it down to middle so I don't blow my ear drums.

 

[harney]

Hi ...I am new here so no shouting at me :=)
 
 
Right i have a pair of hd650 and i understand they can accept up to 300ohm ....
 
so can i plug them into my line outs rather than my headphone out on my rme unit and would they be any difference in sound ect ect ...due to the increase in ohms....220 instead of 30...Reason for asking is i am a little worried about voltage........
 
Thx in advance... and a big bag of jelly babies to whom helps me out
 
Specs....
 
DA out
·  Resolution DA: 24 Bit
·  Signal to Noise ratio: 108 dB RMS unweighted, 111 dBA (unmuted)
·  Frequency response DA @ 44.1 kHz, -0.5 dB: 5 Hz – 20.9 kHz
·  Frequency response DA @ 96 kHz, -0.5 dB: 5 Hz - 35 kHz
·  THD: < - 98 dB, < 0.0013 %
·  THD+N: < -91 dB, < 0.002 %
·  Channel separation: > 100 dB
·  Maximum output level RCA unbalanced: +8 dBu, 2 V RMS
·  Maximum output level TRS balanced: +14 dBu, 4 V RMS
·  Output impedance: 220 Ohm
 
--------------------------------------------------------------------
 
Phones
·  Resolution DA: 24 Bit
·  Frequency response DA, -0.1 dB: 20 Hz - 20.8 kHz (sf 44,1 kHz)
·  Frequency response DA, -0.5 dB: 10 Hz - 44 kHz (sf 96 kHz)
·  Signal to Noise Ratio (SNR): 108 dB (RMS unweighted, unmuted), 111 dBA
·  THD: < - 98 dB, < 0.0013 %
·  THD+N: < -91 dB, < 0.002 %
·  Channel separation: > 100 dB
·  Maximum output level: +8 dBu
·  Ouput impedance: 30 Ohm

 

[AcousticDreams]

Thx in advance... and a big bag of jelly babies to whom helps me out.

Jelly Babies? The community prefers HARIBO Gold Bears! :wink_face: