Downscaling Zen v.9 for use as headamp - Page 4

Scott Stansbury · 11th April 2010, 04:29 AM

What, if anything, can be done to make the circuit more compatible with 300 ohm HD-600's?

Scott...

EUVL · 11th April 2010, 06:34 AM

If it is not loud enough for you coming directly from a source (e.g. CD player), then you might want to add a gain stage like a single ended version of the Blowtorch. Just use the +ve output alone and ground the -ve input.

Patrick

Scott Stansbury · 12th April 2010, 01:46 AM

Thank you, Patrick.

So it's just a matter of ensuring that there's enough voltage for the headphones?

Scott...

EUVL · 12th April 2010, 05:05 AM

You first need to decide how much SPL you need from the phones.

Then the datasheet of the phone will tell you the sensiticity, which allows you to convert SPL to voltage. A typical CD player without volume control will output 2V rms max. If 2Vrms is not sufficient to give you the SPL you want, then you need voltage amplification.

The DAO is a follower with (slightly less than) unity gain. It gives you lots and lots of current with very little distortion, but it will only follow the voltage at the input about 1:1.

The easiest way to determine whether you need additional voltage amplification is to connect a 10k log pot and a simple opamp circuit of say +10x gain using e.g. an OPA2604 or OPA2132 (for stereo) supplied by 2x 12V batteries. If this is too loud, then lower the gain of the opamp circuit until it reaches the right level for you, including the amount of volume control you need.

The you know for sure how much (if any) voltage gain you need, and only then you choose the voltage gain block circuit. The output (current gain) stage is the DAO, already done for you.

Patrick

Scott Stansbury · 12th April 2010, 01:06 PM

Got it. Thanks again for the clear explanation.

Scott...

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11th April 2010, 04:29 AM	#31
Scott Stansbury diyAudio Member Join Date: Nov 2004 Location: Central Mass	What, if anything, can be done to make the circuit more compatible with 300 ohm HD-600's? Scott...

11th April 2010, 06:34 AM	#32
EUVL diyAudio Member Join Date: Oct 2003	If it is not loud enough for you coming directly from a source (e.g. CD player), then you might want to add a gain stage like a single ended version of the Blowtorch. Just use the +ve output alone and ground the -ve input. Patrick

12th April 2010, 01:46 AM	#33
Scott Stansbury diyAudio Member Join Date: Nov 2004 Location: Central Mass	Thank you, Patrick. So it's just a matter of ensuring that there's enough voltage for the headphones? Scott...

12th April 2010, 05:05 AM	#34
EUVL diyAudio Member Join Date: Oct 2003	You first need to decide how much SPL you need from the phones. Then the datasheet of the phone will tell you the sensiticity, which allows you to convert SPL to voltage. A typical CD player without volume control will output 2V rms max. If 2Vrms is not sufficient to give you the SPL you want, then you need voltage amplification. The DAO is a follower with (slightly less than) unity gain. It gives you lots and lots of current with very little distortion, but it will only follow the voltage at the input about 1:1. The easiest way to determine whether you need additional voltage amplification is to connect a 10k log pot and a simple opamp circuit of say +10x gain using e.g. an OPA2604 or OPA2132 (for stereo) supplied by 2x 12V batteries. If this is too loud, then lower the gain of the opamp circuit until it reaches the right level for you, including the amount of volume control you need. The you know for sure how much (if any) voltage gain you need, and only then you choose the voltage gain block circuit. The output (current gain) stage is the DAO, already done for you. Patrick

12th April 2010, 01:06 PM	#35
Scott Stansbury diyAudio Member Join Date: Nov 2004 Location: Central Mass	Got it. Thanks again for the clear explanation. Scott...

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