Headphone Amp (Head Grinder)

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Gustav

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Jun 4, 2004
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DK
I made this headphone amp based on an original schematic from Jakob/Gyraf.

HP-GRINDER-500x500.gif


And heres a documen you can use for self etch purposes (unless I did something wrong with the output).

https://pcbgrinder.com/download/HG_docu.pdf

Thats all...  :p

Gustav
 

elskardio

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Sep 29, 2010
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473
Location
Montreal - Canada
Hi Gustav,
since the input is not balanced, how does it performs over long cable runs? I have 50' of snake between the control room and my booth.
Thanks
 

rob_gould

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Jul 8, 2007
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Netherlands
I'm trying to build this on perfboard and I just want to run a couple of things by you all since I'm not sure...

I have built the entire circuit except for the potentiometers R17 A and B and the caps C7 and C9 because these'll be off the board.  I'm going to put it into a 51X rack so I'll be using the + / - 16V rails for power.

I just checked my voltages with the NE5534 removed from the circuit, and at pin 4 of the NE5534 socket I get -16V so that is perfect.  But at pin 7 where I was expecting to see +16V or thereabouts, I get -14.9V. 

How can this +16V invert in the circuit to give -14.9V?  I've tried to work through this circuit as well as my limited knowledge allows, and I just can't see why the +16V is getting inverted.

I've checked the voltages going into the circuit and they are correct, so it's definitely a problem in the circuit and not from the PSU...

Any ideas anyone?  My only thought is that the BD139 and BC140 I have do not have the same pin out, so the BD139 is the wrong way round.  Could that cause this issue?
 

Harpo

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Oct 29, 2005
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Rahden, Germany
rob_gould said:
...My only thought is that the BD139 and BC140 I have do not have the same pin out, so the BD139 is the wrong way round...
There is no BC140 (NPN transistor) in this circuit. You want a BD140 (PNP transistor) and beside this, the case and pinout differs as well.
 

rob_gould

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Harpo said:
rob_gould said:
...My only thought is that the BD139 and BC140 I have do not have the same pin out, so the BD139 is the wrong way round...
There is no BC140 (NPN transistor) in this circuit. You want a BD140 (PNP transistor) and beside this, the case and pinout differs as well.

Sorry, that's a mis-type rather than an error in the parts I've used. I definitely have BD139 and BD140
 

rob_gould

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Found the error...  +16V rail was not making good contact with the PSU connector.  As soon as I sorted that, it came good.
 

sharpeleven

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Feb 8, 2013
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84
Location
Zürich, Switzerland
rob_gould said:
Found the error...  +16V rail was not making good contact with the PSU connector.  As soon as I sorted that, it came good.

How did that end up working out for you in the 51X format? I was thinking of doing the same... any insights? Thanks!
 

rob_gould

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Jul 8, 2007
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Location
Netherlands
It took some work because I made 3 x headphone amps with a debalancing circuit and distribution amplifier based on (read shamelessly copied from) this thread

http://groupdiy.com/index.php?topic=53523.0

I needed to add build out resistors and I skipped the first amp section of the TL074 but after some experimenting it works very nicely.

So yes, I recommend this circuit. It was a good learning experience for me and it sounds good.
 
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