SMSL H300 Amplifier just arrived

Equipment / Electronics / Gear / Accessories Headphone Amps
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I just got another SMSL H300 amplifier, but not much out there in the way of reviews or discussion. I’ve had one before for the business and this is the second one. I put it on an SMSL DO300 which outputs 5.2 volts and it’s really amazing. The volume wheel is smooth and precise, but the front buttons make it too easy to accidentally move it into high gain when trying for medium if you’re not careful every time. It gets hot on the bottom if you don’t put it on a vented monitor riser or put something under the feet to get more airflow under it. Then it’s no warmer than the A30 Pro which I’ve been using for the last week. Do not just set it on top of a DAC or table without raising it up though.
I have a Topping A70Pro and it competes with sound quality. With a 4 volt DAC it sounded a little flat, but give it the beans with extra voltage and drum hits are more dynamic and it’s very similar to the SMSL SP400/M400 stack which I also have. The Hifiman HE6se is fully powered with this combo, even when equalizing. Last week I had the Drop/SMSL HO150x and they sound really similar and would recommend either depending on your power requirements.

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I’m going to put it on a wattmeter later to see how much power it draws at idle and going full tilt on the He6se. Temps are warm but not hot as long as it’s on the slotted monitor riser, so not worried about that anymore. Channel matching on this unit lines up around 30 percent, so it’s good. I’d only recommend IEMs or sensitive headphones on the single ended side which has a lower gain than the balanced side, so you can get the volume wheel up for channel alignment.
I’m running it from a USB hub with an optical USB cable going to it and the noise floor is complete silence, couldn’t ask for more. It’s right there with the A70Pro, SP400, but those have the advantage of perfect channel balance since they’re digital (and a lot more expensive). If you keep the volume over 30 percent on this one it’s matched up anyway. This one is never more than .5db apart in the beginning, in line with Topping and SMSL specifications.
I’m going to keep this stack for a daily driver for a few weeks, if anyone has questions about it.

Update: In standby (turned on but not used) it draws 13 watts, in full operation it’s 25 watts in medium gain. Also got some large rubber feet on Aliexpress and it raised it up over the stock ones so it runs cooler in a normal stack configuration.
The HE6se both the 68 ohm and 50 ohm versions I have run great with it. Medium gain stock, and bottom of high gain using a -6db preamp reduction to equalize and fed by a 5 volt DAC. It sits perfect on top of an SMSL DL200 and DL100. I prefer the DL100 since it’s got XLR inputs (to match a lot of my cables) and also doesn’t have the tick sound when changing bit rates the DL200 has. I’ve switched back to the A70Pro and A30Pro and still like the H300 better. All are transparent, but this is just more engaging to me.

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How does it handle the HE6? Does it get above 90% of the way there sound wise? I am not in the market for that type of amp, but it peaks my curiosity. :wink:

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On the He6se with 5.2v DAC I can do a -6db preamp reduction and still have 20 percent volume wheel left at the loudest I’d be comfortable with. With the Topping A70Pro there’s -17db left at on stock settings for headroom just to compare it to. It generates a lot of heat on the bottom though compared to something like the A90D discrete. It was aimed clearly at the Topping A30Pro, but it has to be on a slotted/vented platform or heat builds up. If someone is in a room that’s always too cold like a basement, you’ll love it. On top it’s not hot to the touch, just warm. Try to pick it up after leaving it idle and you’ll lightly singe your fingers, it’s that hot.

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I have a Schiit Audio Mjolnir 3 sitting in front of me, I feel your pain. Some amps just run hotter than others, just ask the folks at Schiit Audio and Burson. :wink:

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The only other that is close to it was the Gustard X26 Pro with two 9038Pro chips in current mode. I saw one on eBay where the finish on the side has bubbled from the heat since it was in a cabinet.
I like the sound of the HO150X Drop version just as much. For temps the Topping A30 Pro is warm but never hot. I have a silver one for a daily driver and it disperses heat better than the black ones. The H300 is the only headphone amp I’d put a USB fan under it.

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