Current DIY Projects with Professional Measurements Available.

[Sythrix]

Like many of you, I need something to do during the Quarantine. I'm going to have a lot of free time on my hands. I've already built Pete Millett's NuHybrid Headphone Amp, Butte Headphone Amp, Starving Student (Gen 1. A failure, but I learned a lot from it) and have also built the WHAMMY Headphone Amplifier from diyAudio. I'm always interested in headphone amps (so if you know of one I haven't done that's been measured please let me know), but would like to try my hand at a Power Amp for some stereo speakers I have (4 ohm, 150 Watt max), should there be one that measures well and would be worth the time. I am not good at fabrication and do not have a 3D printer, though I do have access to one at my parent's (but not the knowledge of how to generate files for it, etc, so they would need already have completed models I could just feed into the printer). I can drill holes, but that's about it.

I know Amir measured the ACA Class A stereo power amplifier and needless to say, it is not on my list of things to do after seeing the measurements. I also know about some Purefi stuff he measured, but those appear to be completed modules that you just stick into an enclosure, which isn't my thing. I actually want to put together the PCB, etc.

Any ideas? I don't put much stock into subjective reviews of audio equipment anymore and a lot of DIY audio equipment seems to be limited to people describing their feelings, rather than any meaningful information or measurements.

Thanks!

 

[JEntwistle]

The Neurochrome HP-2 headphone amp is on my list. This is the successor to the HP-1, which Amir has reviewed. I have not gotten around to it yet; in fact, it would be my first DIY headphone amp, so I am practicing on some easier and less expensive things for now. If you do decide to build this, I would love to hear what you think.
https://neurochrome.com/products/hp-2

 

[Sythrix]

The Neurochrome HP-2 headphone amp is on my list. This is the successor to the HP-1, which Amir has reviewed. I have not gotten around to it yet; in fact, it would be my first DIY headphone amp, so I am practicing on some easier and less expensive things for now. If you do decide to build this, I would love to hear what you think.
https://neurochrome.com/products/hp-2

This looks really interesting. I may just have to build it. Thanks for the suggestion!

EDIT: It looks like he didn't add balanced output to this model. That's interesting, I wonder why. He does have balanced input.

 

[Sythrix]

Balanced input is just for convenience. I built one. It sounds great.

Doesn't look like much information is provided on the site as far as the build goes. Does he provide anything? It says BOM in the features, so I'm guessing that's when you buy it. Does he have a build-guide or any suggestions on putting it together, or are you on your own basically?

 

[Sythrix]

he will email you a very detailed build instruction via email afterwards.

Good to know.

Thanks!

 

[levimax]

Doesn't look like much information is provided on the site as far as the build goes. Does he provide anything? It says BOM in the features, so I'm guessing that's when you buy it. Does he have a build-guide or any suggestions on putting it together, or are you on your own basically?

I built 4 Neurochrome Modulus-86 amps and the documentation, the boards, and the uploadable (to Mouser or Digi-Key) BOM are all first rate. My only issue is he does not provide schematics (to protect his IP) but there is tech support readily available from Tom. I have also built several projects from Elliott Sound Products https://sound-au.com/ everything is first rate and you get schematics and lot of technical articles... his designs are not cutting edge like Neurochrome but they work and are well done.... and the boards are also quite a bit cheaper.

 

[Sythrix]

I built 4 Neurochrome Modulus-86 amps and the documentation, the boards, and the uploadable (to Mouser or Digi-Key) BOM are all first rate. My only issue is he does not provide schematics (to protect his IP) but there is tech support readily available from Tom. I have also built several projects from Elliott Sound Products https://sound-au.com/ everything is first rate and you get schematics and lot of technical articles... his designs are not cutting edge like Neurochrome but they work and are well done.... and the boards are also quite a bit cheaper.

I'm curious if you could you give a little more detail on what you built and your implementation? What you used? I'm having trouble figuring out what all I'd need for a power amplifier build. Did you use all 4 in the same enclosure? Thanks

 

[levimax]

I'm curious if you could you give a little more detail on what you built and your implementation? What you used? I'm having trouble figuring out what all I'd need for a power amplifier build. Did you use all 4 in the same enclosure? Thanks

I have a DIY tri-amp system. I use a DIY MOSFET stereo amp for the woofers https://sound-au.com/project101.htm and I use the 4 Mod-86's with one big PS all in one enclosure for the Mid's and High's. I use an analog active crossover after my DAC and pre-amp to split signal between the 6 channels https://sound-au.com/project09.htm . The reality of any of these DIY projects is soldering together the boards is the easy part, the hard parts are all the rest: finding the right enclosure, mounting the amps on the heat sinks without breaking a drill bit or tap, drilling holes in the right spot, mounting the boards on stand offs, wiring up the power supplies safely, routing wires for low noise, testing everything to make sure it works without blowing up what you just made. I enjoy it others may not.

For your first project I would recommend something besides a power amp as they are dangerous and unforgiving of mistakes and require some serious metal work. I think a Headphone amp or pre-amp would be a much better way to start. I built the Elliott sound products headphone amp https://sound-au.com/project113.htm and while I am sure it does not measure as well as the Neurochrome as far as distortion goes because it uses op-amps to drive discrete output transistors it puts out A LOT of power.... over 2 Watts for low impedance and over 200 mW into high impedance... works well for me and it is not expensive. There is still a lot of work after you finish the board: build the PS, find a case, install and wire jacks, volume control, etc. but it is all low voltage and current and lighter duty metal work. Good luck and have fun.

 

[Sythrix]

I have a DIY tri-amp system. I use a DIY MOSFET stereo amp for the woofers https://sound-au.com/project101.htm and I use the 4 Mod-86's with one big PS all in one enclosure for the Mid's and High's. I use an analog active crossover after my DAC and pre-amp to split signal between the 6 channels https://sound-au.com/project09.htm . The reality of any of these DIY projects is soldering together the boards is the easy part, the hard parts are all the rest: finding the right enclosure, mounting the amps on the heat sinks without breaking a drill bit or tap, drilling holes in the right spot, mounting the boards on stand offs, wiring up the power supplies safely, routing wires for low noise, testing everything to make sure it works without blowing up what you just made. I enjoy it others may not.

For your first project I would recommend something besides a power amp as they are dangerous and unforgiving of mistakes and require some serious metal work. I think a Headphone amp or pre-amp would be a much better way to start. I built the Elliott sound products headphone amp https://sound-au.com/project113.htm and while I am sure it does not measure as well as the Neurochrome as far as distortion goes because it uses op-amps to drive discrete output transistors it puts out A LOT of power.... over 2 Watts for low impedance and over 200 mW into high impedance... works well for me and it is not expensive. There is still a lot of work after you finish the board: build the PS, find a case, install and wire jacks, volume control, etc. but it is all low voltage and current and lighter duty metal work. Good luck and have fun.

Thanks. I've built several headphone amps already, the most difficult being the WHAMMY, which has an integrated power supply.

While my interest for headphone amps will never wane, I would like to explore other possibilities.

The fact of the matter is, between what I've built and bought, I simply don't need another headphone amp... Although it is tempting.

Many of these amps don't seem to have any kind of volume control or otherwise... Is that where preamps come in? I haven't ever delved into power amplifiers and I have no systems in place ( It's always been either TV speakers or my headphones) so the exact methodologies elude me.

 

[levimax]

Thanks. I've built several headphone amps already, the most difficult being the WHAMMY, which has an integrated power supply.

While my interest for headphone amps will never wane, I would like to explore other possibilities.

The fact of the matter is, between what I've built and bought, I simply don't need another headphone amp... Although it is tempting.

Many of these amps don't seem to have any kind of volume control or otherwise... Is that where preamps come in? I haven't ever delved into power amplifiers and I have no systems in place ( It's always been either TV speakers or my headphones) so the exact methodologies elude me.

Sounds like you are ready to move on to building a "real" amp then . Pre-amps serve several purposes... switching between sources, impedance match among multiple sources if needed, adding gain if needed, and volume control. A traditional dedicated power amp does not have a volume control and relies on the pre-amp or now a days a digital volume control up steam of a DAC directly driving the power amp. Many on this site think a pre-amp is a waste, and it is in a way, but on the other hand it adds a huge amount of flexibility to add different components to your system, it eliminates any worries about impedance and gain mis-match.... and the one I built uses a beautiful ALPS remote control pot.... there is nothing in the digital world that has the nice feel of a "real quality mechanical volume control".

Not sure what your final system is but there is nothing stopping you from adding a volume control to the power amp you build. You could just run your DAC to the power amp at "full volume" and use the volume control on your amp to control your volume, you could even have it "remote controlled" . You could also use "digital volume control" upstream of you DAC and in that case just turn the amp up "full volume". The only issue is good analog volume controls are fairly expensive and you need to be careful wiring them to not pick up noise and they take up room inside the case but if you plan ahead none of these are big deals. I think for where you are on building your system I would build a power amp with volume control and go from there. You also might want to look at the articles on the Elliott Sound Products web site.... there is a lot of good information there both on DIY and on theory.

 

[Sythrix]

or now a days a digital volume control up steam of a DAC directly driving the power amp

Do you mean within the DAC itself? Is this typical? Or is it sporadic based on model? Also, I've heard digital volume control actually destroys sound quality, by shaving off bits. Is that true in this scenario?

 

[levimax]

Do you mean within the DAC itself? Is this typical? Or is it sporadic based on model? Also, I've heard digital volume control actually destroys sound quality, by shaving off bits. Is that true in this scenario?

Not the DAC but the software player like room or foobar or many others that drive the DAC... 32 bit digital volume controls are probably better than any analog solution.... I am more skeptical of passive attenuators as impedence mis match is possible or likely even

 

[dunkuk]

You could look at building a modular amp in a fairly big case so you can expriement a bit, maybe build a nice split rail power supply with adjustable voltages, a volume control and speakers outs, then you could try out some different amp "modules". My understanding is the power supplies are really important for a lot of amps with maybe the exception of class D so thats a good place to start. The chip amps were all the rage about 10 years ago, you could try a gainclone type amp to start with maybe as they are very simple and cheap. Then possibly some class D modules to compare? Or a low power class A design?

You could then try some different pre-amps, or try passive pre amp to see what the difference is. I made simple op-amp buffers for my pre amp I built many years ago and that was fun as it was simple op-amp buffers and I could experiment with different op amps, and capacitors etc in the circuits to see how the sound changed. You could build little fet / transistor buffers to compare too.

That could be a fun way to do it.

 

[Sythrix]

You could look at building a modular amp in a fairly big case so you can expriement a bit, maybe build a nice split rail power supply with adjustable voltages, a volume control and speakers outs, then you could try out some different amp "modules". My understanding is the power supplies are really important for a lot of amps with maybe the exception of class D so thats a good place to start. The chip amps were all the rage about 10 years ago, you could try a gainclone type amp to start with maybe as they are very simple and cheap. Then possibly some class D modules to compare? Or a low power class A design?

You could then try some different pre-amps, or try passive pre amp to see what the difference is. I made simple op-amp buffers for my pre amp I built many years ago and that was fun as it was simple op-amp buffers and I could experiment with different op amps, and capacitors etc in the circuits to see how the sound changed. You could build little fet / transistor buffers to compare too.

That could be a fun way to do it.

Thanks for the suggestions. I don't really know where I'd begin with all that though.

 

[MZKM]

Stereophile reviewed/measured the AkitikA GT-102, which measured well except bass distortion in 4ohm (but we are more tolerable to distortion in the bass).
EDIT: I believe you solder the boards and everything (for anyone not wanting the kit, they sell it assembled for $175 more). They also have an some optional add-on volume control.

 

[Ron Texas]

Stereophile reviewed/measured the AkitikA GT-102, which measured well except bass distortion in 4ohm (but we are more tolerable to distortion in the bass). And they come in a kit version. However, I do not know how pre-completed the kit is.

I believe the boards have to be populated and there is a lot of point to point wiring. It's a lot of work which is either good or bad depending on whether you like that kind of thing.

 

[TimW]

I just finished building a Neurochrome Modulus-86 amplifier and documented it here. I was lucky enough to get the enclosure pre-made though.

For a long time I was considering building the Akitika GT-102 because it makes assembly pretty easy. The aesthetics of the pre-built case is not quite to my liking though.

 

[TimW]

Akitika Website

GT-102 Measurements

 

[Sythrix]

Stereophile reviewed/measured the AkitikA GT-102, which measured well except bass distortion in 4ohm (but we are more tolerable to distortion in the bass).
EDIT: I believe you solder the boards and everything (for anyone not wanting the kit, they sell it assembled for $175 more). They also have an some optional add-on volume control.

Thanks for the suggestion! It looks really tempting. However, I note at the start of the measurements he says it does not have sufficient heatsinking at 1/3 of its rated power. That's a little concerning, isn't it? I worry about the longevity if it's not able to maintain a safe heat level.

 

[Sythrix]

I just finished building a Neurochrome Modulus-86 amplifier and documented it here. I was lucky enough to get the enclosure pre-made though.

For a long time I was considering building the Akitika GT-102 because it makes assembly pretty easy. The aesthetics of the pre-built case is not quite to my liking though.

This is pretty cool! It's really lucky you had a case all ready to go. I am considering the Modulus-86 as well, but I'm afraid sourcing the case and making it ready is keeping me from taking the plunge. I have such a hard time with fabrication and layout. If only there was something already available, but Tom doesn't have any cases for it, unfortunately. Spending as much as they're asking for a suitable enclosure... and the amount of work that would go into making it ready for the amp, is putting me off of the project altogether.