MXR Headphone Amp build

[Bonzai_Musik]

Hello,
I'm trying to build an MXR Headphone Amp, finished to solder everything but... no sound not even some tiny noise. Though I checked all my connections and compared to the layout.
I kinda lost perspective right now so if someone would take a fresh look a this and maybe spot a mistake I'd apreciate it !
My output jack is wired on only one side, I did that to check it wasn't the issue.
Thanks

 

[elskardio]

Did you check if your IC is getting proper voltages?
Assuming you're using a 9V DC adapter, you should have 9V at pin 7 and 4.5V at pin 3.
TBH I always found those veroboard layouts confusing

 

[Khron]

TBH I always found those veroboard layouts confusing

... Especially with no schematic shown

 

[Bonzai_Musik]

Sorry here's the schematic

 

[Khron]

Is your input jack a mono one? Kinda looks like it, assuming it's the one next to the DC input jack.

If it's a mono one (as opposed to the "stereo" one in the schematic), there's nothing connecting the negative (or ground) of the power (be it battery, or DC input) to the circuit ground.

No power, no audio...

 

[ccaudle]

Is your input jack a mono one?

That is a trick used for active guitar electronics, where the ring connector on the jack gets connected to the shield terminal on the jack because guitar cords are mono plugs, with a long shield terminal that contacts both the shield and ring contacts of the jack.
That obviously won't work if you insert a stereo plug (at least it is obvious to me, perhaps not to OP).

 

[JohnRoberts]

Basic troubleshooting 101.... Probe DC voltages on various circuit nodes to confirm power is getting to the various parts of the circuit.

You can check op amp for valid output states relative to input pin voltages.

If you mark voltages on your schematic I suspect several people here can point you in a good direction to find the fault.

JR

 

[Bonzai_Musik]

IC:
Pin1: 128mV
Pin2: 4,6V
Pin3: 2,6V
Pin4: -10mV
Pin5: 0
Pin6: 4,6 V
Pin7: 9,2 V
Pin8: 0

Q1: C: 9,2V B:5,2V. E: 4,6 V
Q2: C:-10mV. B: 4,05. E: 4,6 V

As for the input jack, it is bridged to the ground side of the dc jack, which is connected to the circuit's ground.
If more measurements of voltages are needed please tell me

 

[JohnRoberts]

IC:
Pin1: 128mV
Pin2: 4,6V

pin 2 is - input

Pin3: 2,6V

pin 3 is + input

Pin4: -10mV

should be 0V but perhaps measurement artifact

Pin5: 0
Pin6: 4,6 V

if - input pin 2 is higher than pin 3 + input then pin 6 output should be forced low... Not up to 4.6V

Pin7: 9,2 V

valid + rail

Pin8: 0

Q1: C: 9,2V B:5,2V. E: 4,6 V
Q2: C:-10mV. B: 4,05. E: 4,6 V

As for the input jack, it is bridged to the ground side of the dc jack, which is connected to the circuit's ground.
If more measurements of voltages are needed please tell me

transistor junctions appear valid.

===

Op amp is not showing a valid output state for those inputs, since it is in a socket I'd be tempted to try a second op amp.

JR

 

[k brown]

Also, a photo of the wiring on the underside of the board would be a great help.

 

[Bonzai_Musik]

Here is the underside. For the op amp I only have this TL071 that I just bought so I can't swap it out for another.

 

[k brown]

FWIW, I've found that unless your phones are very inefficient, a simple single 5532 amp with 47 to 220 ohm output resistors drive phones very nicely.

Or, at most a doubled amp circuit like used in Mackie (and other) mixers (second schem is from Folio Notepad, using 5532):

 

[melmsmidth]

Here is the underside.

I't seems that you have quite a few shorts of solder between tracks there. I've spotted in the picture some of them, but didn't search thoroughly.
I build lot of stomp box pedals on stripboards, you must be carefull with that and always clean the bits of solder and flux between tracks even if it looks good at first sight, sometimes the flux can have some residue and create shorts so the board won't work.

 

[k brown]

Yes - at the very least, give the underside a good dose of flux remover; there's a lot on there. With it gone, it will be easier to see spots that may be shorting.

 

[hcd]

Does anyone know the current draw on this circuit? thank you!

 

[JohnRoberts]

Does anyone one the current draw on this circuit? thank you!

that will depend on load (headphones impedance) and signal level... Plus the op amps quiescent current.

JR

 

[hcd]

Thank you John. I am implementing this along with a Condor Cabinet simulator into a bass preamp circuit that I built. The voltage of the preamp is 24 VDC. I am already using higher voltage rating capacitors for both the cab sim and headphones amp to be able to run it all at 24V.

I am trying to figure out a power supply for all this together. I currently have a 24 V DC 500 mA, but I fear it might be tight. I know my preamp doesn't go further than 350mA and the Condor is very little about 2-5mA, but haven't found any information regarding the headphones amp.

I tried to do my own measurements, but I must be doing something wrong because I can't seem to read anything.

My headphones are Beyerdynamic 500Ohm impedance and I am keeping the volume of the headphone amp right in the middle.

 

[hcd]

Turns out the fuse on my DMM was blown. I replaced it and I am getting 7.2mA, which seems pretty low. I need to do further tests tho to make sure.