Monolith by Monoprice Liquid Spark Headphone Amplifier by Alex Cavalli Expired

This is a good price for those looking for a headphone amp on a very tight budget. Its performance was acceptable, though not high end, back when it released almost six years ago. In terms of measurements it is far inferior to most modern headphone amps, but for $32 it provides an excellent value. Realistically speaking, in most real world circumstances the actual difference in audio quality for the end user will be relatively minimal compared to amps costing more than twice as much. It also provides more than sufficient power at standard listening volumes for the majority of headphones available on the market. I've heard some people have had problems with channel imbalance on this amp, so be aware.

Here's the audiosciencereview for this amp from 2018: https://www.audiosciencereview.co...-amp.5224/
Hopefully at some point slickdeals fixed their link shortening breaking links to audiosciencereview, if slickdeals broke the link either manually replace the garbage characters with slashes, or just google "monoprice liquid spark audiosciencereview".

This is an unbalanced headphone amplifier with rca inputs (and rca premp outputs) on the back, you will need a dac with unbalanced outputs to connect to this amp. Most high quality dacs will cost more than twice the cost of this headphone amp, the best value option I'm aware of (but I'm sort of out of date on the current market, so do your own research) is the SMSL SU-1 for ~$80 or less on sale. This is obviously a bit of a mismatch with a $32 headphone amp, so if you don't already have a dac I'd recommend the alternative I'll get into below.

Alternatively, for those on a very tight budget, I've heard good things about using the ~$8 apple usb-c to 3.5mm adapter dongle with a 3.5mm to rca cable (~$5) as a dac. The audio chain would look like this: computer's usb port -> apple usb to 3.5mm dongle -> 3.5mm to rca cable -> rca inputs of the liquid spark amp -> headphones. The apple dongle will only be able to output up to 1vrms, and there's always the potential for issues when using a janky setup like that. Ground loops are also always a possibility with unbalanced audio setups. Make sure to get the US version of the apple dongle, the EU version is limited to only .5vrms output. You could technically do the same thing with your motherboards audio output, though that'll typically be of extremely poor quality and I don't recommend it.

The ebay listing indicates that for: "Other Monoprice Branded products: 1 year replacement warranty only", so purcharing this amp from ebay has a worse warranty than the 3 year replacement warranty directly from monoprice's website. Cancellations are not permitted on the ebay orders, but there are 30 day returns.

Overall, at $32.49 this is a excellent value budget headphone amp for those who already have a dac or are willing to use a 3.5mm output to rca. When you add the cost of the liquid spark amp and a decent desktop dac together it's already over $110, and at that point you can get a much higher quality dac/amp combo unit for ~$50 more. Therefore, if you would be purchasing a proper desktop dac to go along with this headphone amp, I'd recommend instead to look into purchasing a high quality dac/amp combo unit in the $150-$200 range.

This was my first super budget setup. Just to dip my toes into the headphone hifi world. I had my old lg g7 phone with built in dac, liquid spark to a set of refurb hifiman he400se headphones. Minus the phone, as it was just laying around collecting dust, I was at $160 total in to my setup. It was an excellent sounding upgrade from consumer grade headphone equipment. But, beware as this will lead you down the rabbit hole of "if this sounds this good, imagine what (insert hifi item here) sounds like. Then hundreds to thousands of dollars later you think "if I would have just stuck with my first purchase I would have been completely happy".