Douk AudioL1 Mini Stereo Line Level Booster Amplifier Audio Preamp with 20dB Gain and Volume Control

This product does exactly what it says it does, it will boost your audio line signal by around 20 decibels. My own measurement put this at 17.2 DB louder from 15 feet away before you start to get distortion. It can go up to around 19 DB or so but you get distortion. Even 15 db is plenty to make a stock stereo in a car really loud, but be warned you won't be pumping mass bass as the power output isn't there to drive your Fosgate 12s for example, obviously anyone installing quality equipment like that won't be using this thing.The product is cheap and has multiple inputs and outputs available (see pro tips below). It also comes with a USB-A power cable so you'll need a USB-A port available or otherwise supply your own power.Many of the complaints about this product seem to be curable but do require extra work and or parts.Pro Tips on how to get this to work great:1. Take into account where you will be installing this. If you are installing this around unshielded cable, high voltage etc, because of its cheap nature, it will pick up a hum, this thing is not insulated at all really. It is best to keep it away from other devices and power it cleanly off a dedicated USB or power supply. See below for ideas how to fix if you get a hum.2. The 3.5MM input will be priority and no other inputs will work at the same time if you use the 3.5MM input, however, if you use RCAs and the 5-Din this thing will take in both and mix them evenly (There is no way to to mix or boost one more than the other). The output is both 5-Din and RCA, you can use either or both at the same time.3. Since this thing isn't driving that much power, I found even the cheapest cables work fine. Normally you want to use higher quality cables for the best sound with the least leakage but in this case we are going cheap, so even cheap cables will work.4. If you are installing this in a car, you're probably like me and installing it on an old or stock in-dash stereo and those are horrible for grounding and will usually pick up a hum because of ground issues so here is:How to fix the dreaded hum that people complain about:First, you can try to ground your stereo better if you can. This can help, but if you are just hoping to plug it in and not mess around try a Ground Loop Isolator like this: https://www.amazon.com/dp/B06XQYN77L?psc=1&ref=ppx_yo2ov_dt_b_product_detailsThe linked isolator uses the 3.5MM input on the amp and takes in a 3.5MM connection. An over simplified explanation is that by using an inductor that then creates a magnetic field, a ground loop isolator can essentially force any differences in current (caused by a bad or different resistance ground) to be nullified because this is what causes the hum. Please realize you'll need to get the correct kind of isolator for your inputs and outputs. Just search Ground Loop Isolator here on amazon and you'll find many. Since this isn't putting out that much power, cheap ones usually do the trick.Also keep in mind that there are two schools of thought and which one works for you depends on your situation:1. Place the isolator between the head unit (a stereo for example) and the amp. In other words place the isolator on the input side of this amp. This is the typical way of doing things and works for the vast majority of cases in car audio although not all.2. Place the isolator after the amp but right before the speakers if there are other components in the system like a game console, or another stereo component etc. This case is more specialized but you can pick up hum caused by the amplifier itself and it bleeds on the output side but this is less likely. The amp usually get's hum fed into it and you can eliminate that on the input side and the amp will output a clean signal.3. Place an isolator on the input AND the output side. This is really rare and only happens in extreme instances where there are a lot of electronics at play causing problems for one another OR there are powered devices after the amp that are picking up hum from the combination of sources. In this case you'd add one on the input side as close to the amp as possible, and then one on the output side as close the speakers as possible.Good luck! This thing is a steal at the price for what you can do with it using a little know how.

I was initially disappointed with the hum and interference from this device, but when I swapped from using the built-in USB ports on a power strip to a high-quality USB phone charger, the unwanted noice disappeared. Provides just the extra little oomph I needed in front of my tube amp for my small audio system. I'm only using it turned up about 25%

"Mini Stereo Line Level Booster Amplifier Audio Preamp 20dB Gain Volume Control" fulfills every word of its title!Construction and finish are fine.As a preamp, it easily makes it into "hifi" performance. Maximum gain was about 20 dB. Measured performance using RightMark Audio Analyzer indicates 20-20k Hz frequency response that is very flat in the high end and rolls off gradually to -2 dB on the low end. Dynamic range is excellent, -93dBA. Total harmonic distortion is miniscule at 0.002 %, while intermodulation distortion measures 0.01%. These were measured using an ASUS/Xonar sound card and some of the specs are close to the sound card's limits.The only limitation that I see that could occur in some cases is that the output impedance is 100 kohms. If it is feeding an amplifier with low-ish input impedance, the audio performance could be degraded. Make no mistake: this is not capable of driving headphones, unless a headphone amplifier follows it to provide the required drive energy.The unit comes with a USB cable that can be used to provide +5 V power from a laptop or a cheap power adapter such as that used for charging many battery-operated devices. I haven't tested it with any other power supply, though it claims to be able to use anything from 5-20 VDC.Highly recommended to fulfill the need for boosting a line-level signal.

I'm using a Lyngdorf TDAI-1120 connected via RCA to a KEF KW1 wireless adapter that feeds my 2 KEF KC62 subs. My subwoofers kept falling asleep due to the output signal feeding from my 1120 into the KW1s being too low. The subs would fall asleep if I wasn't listening to music loud enough. To solve this, I bought this Douk line level booster. I installed in between the KW1 and the output of the 1120. Run the Douk at 50% volume, set KC62 knobs at max frequency and about 1/3 to 1/2 volume. Run Roomperfect as usual and now my subs don't fall asleep at lower volumes. No effect on overall sound from what I can tell. Everything is integrated and amazing. Even if you don't have the same setup as me, if your sub is falling asleep at lower volumes, this little device in between your sub and the amp output will likely fix your problem.

Didn’t expect much and thats exactly what I got awkward design with inputs and outputs on opposite sides making it not sit flat and not easily adjusted for gain control but all that really doesn’t matter considering the buzzing and low frequency humming that developed after about 20 hours of use. naturally my return date passed by 2 weeks save your money and spend it on a higher quality product

The amp is very small and the gold knob is very easy to see. We used it to boost levels to a second zone amp that was just not quite loud enough. The amp does not come with a power supply so we had to search for an old USB phone charger to use.