"The Wire" Ultra-High Performance Headphone Amplifier - PCB's

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#2,721
Seems my assumption was right:

opc said:
Hi Tame,

For the BAL-BAL the gain is set as follows:

Assuming Rf = R21 = R24 = R25 = R28 and Ri = R22 = R23 = R26 = R27

Then the gain (Av) is simply Rf / Ri.

The standard BAL-BAL schematic shows Rf = 1k and Ri = 1k, so the gain is 1k/1k = 1, or in dB, that's 0dB or unity gain.

If you want more gain, you simply increase Rf or reduce Ri. If you increased Rf to 2k, then the gain becomes 2k/1k = 2 or 6dB.

It's also worth noting that Ri sets the input impedance, so using a very low value of resistor here could load the previous stage, especially if it's fed by a potentiometer. This needs to be balanced out with the use of excessively high resistance values for Rf, which will increase noise.

If you're using a 10k pot in front of the BAL-BAL in a BAL-SE configuration, then I would suggest using 10k for Ri and 20k for Rf. If you put your 10k pot in front of this, then you'll lose 6dB thanks to the resistor divider formed by the 10k pot value and the 10k input impedance, but you'll have 6dB gain in the amplifier itself which means a net gain of 0dB for the whole system.

If you're using an active preamp, with a buffer at the output, then just leave the BAL-BAL as configured with 1k resistors for Rf and Ri.

Regards,
Owen
Click to expand...


So, gain 1 works fine with my Oppo, enough loudness as Owen has pointed out so many times, but it has 4V out. To make it work with both a conventional 2V output, as well as a cell phone and DAP, I opted for gain 3.


The boards were not assembled by me. The amp board I took over from MLA here in Sweden, and the PSU I bought from patchoncas in Portugal. Many thanks to both of you!


Small amp needs a small box so that was my goal.

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Gain 3 fixed:

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#2,722
Fantastic job mdc30!

The amp looks great, and I'm glad to see people still building and enjoying these 🙂

At some point when I get some free time I will post some of these as open-source projects so people can make their own boards.

Congrats on a great build, and enjoy the listening!

Regards,
Owen
 
#2,724
sek said:
Congratulations on the successful build! 🙂

How do you like the multi-gang pot in this application (and which one is it)?
Does it track well enough?

Cheers,
Sebastian.
Click to expand...

The quad pot works fine, it's a TKD 4CP-601 which I use in most of my balanced builds.

On a similar note, with gain 1 you use the end part of the pot where every little increment makes a huge difference (and risk of painfully loud surprises).

That's why I prefer gain 2 or 3 where normal listening occurs on a more useful part of the pot in my setup.

Stefan
 
#2,726
mdr30 said:
The quad pot works fine, it's a TKD 4CP-601 which I use in most of my balanced builds.
Click to expand...

Okay, thanks.

On a similar note, with gain 1 you use the end part of the pot where every little increment makes a huge difference (and risk of painfully loud surprises).
Click to expand...

Unfortunately, playing with the pot's curve is rather complicated in a balanced stereo setup... 😉

Cheers,
Sebastian.
 
#2,728
opc said:
Fantastic job mdc30!

The amp looks great, and I'm glad to see people still building and enjoying these 🙂

At some point when I get some free time I will post some of these as open-source projects so people can make their own boards.

Congrats on a great build, and enjoy the listening!

Regards,
Owen
Click to expand...

Thanks, diy is rewarding and fun. With a good basic circuit you can just build the amp that suits your needs. This little dollhouse of an amp is more capable and powerful than its appearance suggests. Lots of detail when I run SACDs or high res files balanced from my Oppo. CDs too. I'm old fashioned.

I'm sure many would appreciate if you make the gerber files available.
 
#2,733
Schlumpfpeter said:
Is there any way to by the PCBs for this beauty here? I am looking for a very clean and neutral headphone amp project to drive my ATH-R70X and this one here seems to tick all the boxes.
Click to expand...
I was investigating this buffer too and ended up getting 2 PCBs from Nisbeth. (single ended not balanced!)
See here: LME49600 based HPA. You can download the gerber files.
I could send you one of the PCBs as I only need one but don´t know about shipping to UK these days
and if its worth it.

That said, your headphones seem to be 470Ohms and take up to 1W unless its some special version.

With the LME49600 being powered by exactly +-18V (max. rating!) you get ~250mW out of that amplifier/IC into 470Ohms.
(assuming ~32Vpp max. output swing)
Probably plenty loud already but just mentioning it as it won´t put out 1W.
 
#2,738
ziga90 said:
Hey there. I'm also planning to build an headphone amp for my Sennheiser HD598 and this could be it. As checked these pcb's are no longer available.



Does anyone have the shematic and BOM for this AMP and PSU? I just got some info where can I order custom made pcb's here in Slovenia - EU.



Perhaps if the author OPC is still here and is willing to help me out a bit...? 😀


Thank you.




Kind regards, Ziga
Click to expand...
here's something
 

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