Project files: SDS/AMB headphone amp

The other half of my recent board shipment (see the previous post) was this design, which I’ve always liked but never tried. I can’t really remember what led me to start doing a PCB for it, but probably a combination of boredom and a flash of inspiration – at least that is what usually works 😀 Anyway, here is the design for anyone else who wants to have a go at it 🙂

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Project files: Pascal I/O adapter

After a longer-than-expected delay in shipping, I received some boards. Among them was the revised version of my Pascal adapter board, so after a quick check that it still works, time to release it into the wild… 🙂

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Project files: LME49600-based headphone amp

When I built the LT1210-based preamp I thought I set a record for longest wait between making a PCB and actually trying it out. I am happy to say that the record has been broken with this – a headphone amp based on the LME49600 buffer IC, which I apparently did back in 2013 but haven’t managed to assemble and test until now (!).

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Moving with the times?

I regularly complain about the declining availability of DIY-friendly parts – as do quite a few others if you look around. An obvious case in point is opamps, where (more or less) you can say that on one hand high-quality parts have never been better or cheaper, but on the other hand these parts have never been available in less DIY-friendly packages. Even the classic SO-8 SMD footprint is starting to look big and many newer devices are only available in smaller packages, some even “leadless” and/or “powerpad” packages that are very hard for the average diy’er to solder.

However, the many available opamps are actually obvious candidates for some experiments, especially with basic preamp/CMoy-style circuits where the sound quality and sound signature of the opamp really shines though. Some years ago I made a PCB design specifically for that and a few months ago I decided to revisit this layout and update it specifically for use with SMD (SO-8) opamps.

Of course you could use the old design with DIP-adapters, but fast opamps and DIP adapters are usually very bad for stability, so it was way better to create a new version of the layout intended for SMD packages instead. This naturally means you lose the ability to “roll” opamps (i.e. experiment with replacing them), but to most people I think that is an acceptable trade-off.

I haven’t really kept up with the development on the opamp scene the last few years, but what I would look at myself are the various OPA16xx duals. Here you can get both bipolar and FET inputs, “standard” high-quality opamps as well as “audio-specific” devices and more – and the prices are a small fraction of what you paid for top-of-the-range models such as the OPA627 and OPA2107 ten or fifteen years ago. AD also does a few interesting variants by to be honest here I am even less aware of what is available than for TI – I am sure diyaudio.com has answers if I ever need them.

The prototype here is made with an OPA1656 dual opamp and the initial impression is that I was on to something with this idea, because it does sound very good. I also have both the OPA1642 (FET-input) and the OPA1612 (bipolar input) in stock and I think these would be interesting candidates as well. Another interesting thing is that the power consumption is lower – in fact so low that without the LED my lab supply is showing a consumption on 0.00A for both rails (it’s not very sensitive). That also means that battery-powered versions would definitely be viable.

The download file for the new version is added to the original project file post because that’s way easier, so go and grab it from there if you want it 🙂

Project files: The NE class A headphone amp…

I’ve now finished my testing on the NE class A headamp I described earlier, so here are the design files if anyone else thinks it looks like an interesting design and wants to give it a go 🙂

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Project files: An unloved amp?

Well this is really “unloved” in two ways, but I thought I’d share it anyway 🙂

A while ago I ws cleaning up a little and I found the boards for this amplifier based on the LT1210 IC. Despite being from 2016 I never put the design together originally (don’t remember why) so I decided “better late than never” and tried it now. And you know what – it works!

Apart from being “unloved” because it took me nearly four years to put it together and test it, this amp is also “unloved” because the LT1210 doesn’t seem to be used that much for audio applications. It is a a current feedback power opamp with a massive current capability and so it should – albeit with a few caveats – be possible to use for audio as well with good results. Also, like e.g. the AD815 the original applications for the LT1210 (ADSL line drivers and suchlike) have all but disappeared, so – again with a few caveats – it should be possible to pick these ICs up at very good prices.

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Project files: The ACP+ clone…

Well, both my ACP+ clone boards are now fully populated with relays and working as expected so I guess it is appropriate to share the design files 🙂

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Project files: The Borbely non-hybrid headamp

To supplement the original Borbely tube hybrid headphone amplifier are here the files for the solid-state version as described previously here. Have fun!

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Project files: Hypex UcD400OEM adapters

Well, since I shared these on diyaudio already I supposed they should be here as well 🙂

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Project files: The BBA3FE

Haven’t really had time to fully complete my BBA3FE project yet, but as I am otherwise happy with the design I might as well release it in case anyone wants to have a play with it 🙂

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