[cetoole]

A while ago, a friend challenged me to design a PCB for a high quality headphone amp that fits in a mint tin. I personally dont care for the use of mint tins as amp cases, but I thought it would be fun to see if I could do it, and as I had a board designed that was similar in size, felt that it wouldnt be too much work to achieve. The board I came up with is 57mm wide and 39.4mm tall. I dont have any mint tins to measure, so I cant be sure this will fit correctly, but I believe it should fit fine, along with two 9v batteries. AD744, with the output stage bypassed via the compensation pin would likely be a good opamp to use for this amp, and if one wanted it for ground as well, it comes in an SO8 package, so you can just use browndog style 2 single to dual opamp adapters. I just thought I would post this for fun; I dont really have intentions of building one, though maybe if I decide to get a multi project panel made for me, I will add one or two on to try it out.

 

[tomb]

Looks pretty interesting - always like good SMD. What do you think the battery drain will be like with the discrete buffers?

 

[cetoole]

Quote:

Originally Posted by tomb /img/forum/go_quote.gif Looks pretty interesting - always like good SMD. What do you think the battery drain will be like with the discrete buffers?

Well Tom, that is one of the great things about discrete; you get to choose what the current draw is. Since I was so pushed for space here, I was forced to use CRDs for all of the biasing, but these come in a decent selection of values, which you can choose to determine the level of biasing. You also get to play with emitter resistor values in the buffers, which impacts the level of biasing of the output transistors. Finally, what monolithic opamp you choose plays a role in current draw. You could go anywhere from extremely efficient opamps without external bias applied, and class B output buffers, which would get great battery life, to something like the OPA627 in all channels, biased up pretty high, and output buffers which are biased sufficiently to run headphones like the amazing Sennheiser HD580 in class A, which would get an hour or two, depending on your batteries.