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dirkwright 10th February 2012 09:45 PM

My Head Phone Amp Project
1 Attachment(s)
Well, this is where I'm at with this project now. It's a 1U rack box from Hammond that I've modified. I'm not happy with Hammond's quality but not sure anyone else is better. Holes don't line up, stuff like that. Hate it. I added the shiny aluminum angle strips on each side since Hammond didn't see fit to provide support there. Thank God for rivet nuts.

Anyway, the boards are from Jim's Audio. His LME49600 headphone amp, with two of his Kubota power supply regulators are included. Input will be switch selectable between balanced and unbalanced, with Jensen input transformers and dual wire wound pots for volume control. The pots will be controlled by a single shaft using miniature plastic roller chain with sprockets. It's all pretty simple really. The square bar stock is for heat sinks from TO-220 power transistors on the Kubota boards. Normal heat sinks are too tall, as are normal electrolytic capacitors. I had to get special short ones to fit in the 1U rack space.

dirkwright 12th February 2012 12:57 PM

1 Attachment(s)
The amplifier board fully stuffed. The circuit has an LME49710 input and paralleled LME 49600 outputs per channel. I made some changes to the original circuit. I added a high frequency pole in the feedback loop as well as an RC low pass filter on the input.

dirkwright 12th February 2012 04:04 PM

3 Attachment(s)
The volume control. Since I couldn't find any 2 gange wire wound potentiometers, I came up with this arrangement for controlling 2 pots with one shaft. Thanks to McMaster Carr for the parts.

diy didi 12th February 2012 04:49 PM


dirkwright 12th February 2012 05:27 PM


Originally Posted by diy didi (

Thanks! I've never done this kind of project before. The chain is tight enough so that there's no slack and the two pots turn together. They have a linearity of +/-0.25% so if they are synchronized they should stay that way over the entire travel of the wiper.

dirkwright 12th February 2012 10:24 PM

2 Attachment(s)
OK, more progress today. One Kubota regulator is stuffed, and 4 heatsinks are filed and sanded. The heatsinks are 3/8" square bar stock. One screw through the TO220 device and two up from the bottom on the back side of the panel to hold it in place. Time to drill and tap some holes.

The front support for the volume control shaft is finished as well.

Stuffing of second Kubota regulator is ongoing.

Stixx 13th February 2012 07:00 AM

Good work there!

I like the use of the bar stock to connect to the bottom plate as one big heatsink... ;)

dirkwright 13th February 2012 12:15 PM


Originally Posted by Stixx (
Good work there!

I like the use of the bar stock to connect to the bottom plate as one big heatsink... ;)

Thanks. The 1U rack height box is not tall enough for regular upright heatsinks so I had to come up with this solution. I need to buy the tap and drill though. It's going to be tricky I think drilling such small holes and then tapping them. I have a drill press now which makes this kind of work a lot easier.

JustFJ 16th February 2012 04:25 PM

why don't you try "the wire headphone amp" instead? their pcb are avaiable nowon, its better performance than this bad quality pcb

gumleguf 16th February 2012 04:41 PM

Nice work. Great sense of detail for sure... :-)

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