The most value is going to be in budget DAC and amp products. People who are buying more expensive products that don't have a feature advantage are not going to care how good or bad the measurements are. If a Schiit Mjolnir turns out to measure poorly it's not going to matter beyond credibility to that brand.
My suggestions for products to measure for headphones would be these:
Fiio products. Good value and high portability make them a versatile product for people who just bought their first pair of decent headphones. As Fiio products have line out functionality it makes them a good stepping point to a high power amplifier for any less sensitive headphones they may purchase in the future.
- Fiio Q1 - Portable. DAC and Amp. Own battery. 1.5Vrms line out. A lot of people want to use a portable DAC/Amp combo with their android smartphone which makes this a better choice than the Fiio E10K.
- Fiio Q1 MK2 - Not really an upgrade to the Q1. More of a sidegrade with a balanced IEM focus and weaker unbalanced power output that makes it less attractive to people outside of balanced IEM owners. Line out is unbalanced.
- Fiio Q5 - A lot of different inputs in a portable package. Modular amplifier section that can be swapped.
Other DAC products I'd recommend measuring are:
- Sabaj DA2 - I think it's the same as the SMSL iDEA but I don't know. It's small, has 2Vrms output, asynchronous, <1Ω output impedance.
- Sabaj DA3 - It has balanced and unbalanced output. It's small and has an on screen display that shows the sample rate. Only a little more expensive than a Sabaj DA2 but amazingly cheap for a balanced DAC.
For amplifiers I would recommend measuring:
- Fiio A5 - High power, portable amplifier that isn't that expensive. There needs to be something good in this niche for people who travel away from home a lot or using low sensitivity closed headphones such as T50RP mods.
- Fiio A3 - Quite cheap. Moderate power output for a portable amplifier.
- Fiio A1 - Unique in that the inline microphone of the IEM connected will still pass back through to the smartphone.
- Schiit Magni 3 - Very high power desktop amplifier. Very popular. Wonder if it is actually good.
- Fiio K5 - The Fiio high power desktop amplifier. Not as high power as Magni 3 but Fiio has better international distribution.
Fiio BTR1 - Small bluetooth DAC and amp. There are many of these kinds of products on the market but all untested. Good to know if it is good for IEM owners who want to detach their IEMS from their smartphone.
After that it becomes about finding better products than listed above at lower price points or have some advantages. Knowing the power draw from the smartphone for portable DACS is also important and
these cheap things do that well.
I was trying to say, I don't have a specific product in my mind. Just some value stuff that will help people's funds to go to headphones or other stuff. I should quote Candlesticks since he has mentioned some products. I agree with his thoughts here, in bold.
