After being founded in 2019, LEA Professional is making waves across the pro audio industry. Stephen Dawson got his hands on one of the company’s recent amplifiers to check it out.

The 1504D is a professional amplifier from LEA Professional’s Connect Series and it’s the present top-of-the-line model. The first thing that stands out is that it doesn’t have its own app and that’s a great thing.

The LEA Connect Series comes in a variety of configurations and power outputs, featuring two, four or eight channels. Indeed, Amber Technology, the Australian distributor, says that the 168 (eight 160W, $6,550) and 168D (as per the 168, but with Dante, $8,350) models are particular “call-out” products for it.

But the 1504D is truly a beast, boasting four channels rated at 1,500W “RMS” into 2, 4 or 8Ω. In addition, it supports 70V and 100V modes, again with a total of 1,500W available for each output.

And if that isn’t enough, it features something called Smart Power Bridge, which lets users double the power output of one channel without combining it with another. So, you can have up to 3,000W available from one of the four channels, while retaining use of the other three. I have no idea how it manages that and I was a touch too frightened for my gear to experiment with that mode. It’s good to know that it’s available for those with very particular requirements.

The amplifiers are Class D, which means rather high efficiency. Still, to get full use of this amplifier, you will need a very high-rated power output. LEA does its part with a massive power cable connection. The speaker outputs are via oversized two-pin Euroblock-style connections (supplied).

Four channels, which means four output channels, but in this case, it also means four analogue input channels. These are via Euroblock-style three-pin connections (also supplied) which support balanced signals. Next to each is a tiny knob to allow you to trim the input levels.

But this amplifier also supports up to eight Dante digital channels via two RJ45 connections. That’s the “D” on the end of the model number. You can save the better part of two grand if you only need analogue, not digital. The Dante connections can be configured as AES67 instead. I don’t have Dante-compatible gear, so I stuck with the analogue inputs.

Since it is Class D, the analogue input signals are necessarily converted to digital, so the LEA Professional 1504D takes the opportunity to provide DSP controls for eight-band parametric EQ and crossover (high and low pass) filters with fully controllable parameters. The DSP runs at 96kHz and 32 bits of resolution. There are two sensitivity levels on those inputs. The default 36dB mode requires 1.4V RMS for full output with regular low-impedance speaker loads, along with 70V. The 24dB mode requires 2.0V RMS for full output with 100V outputs. When you select 70V or 100V output modes on a channel, a high pass filter at 80Hz automatically kicks in to stop “transformer saturation”. You can adjust that frequency.

The DSP, incidentally, doesn’t impose a significant delay on the signal. LEA says that the latency is 1ms “under any condition”. But you can dial in up to 100ms of delay for each individual channel if it would suit your installation. That’s the delay time for a sound travelling roughly 35m.

It’s probably enough adjustment on its own to take advantage of the precedence effect in medium-sized venues, although not extremely large ones. It should be enough to ensure that audio can be matched for video displays (the slowest of these tend to top out at not much more than 100ms).

All that DSP is part of the ‘Smart’ part of the amplifier while the rest concerns channel routing and control but more on that later in the article.

The LEA Professional 1504D comes with rack-mount ears and is 2U in height. It has internal cooling fans that draw air in from the front and push it out the back.

All the connections – along with the power button – are at the back. There isn’t a hard-wired power button. It operates to switch between on and standby. In the latter state, the LEA ‘Shark Fin’ logo on the front remains illuminated in green, rather than the blue it adopts when the amp is running.

To the right of that is a small LCD panel showing useful information, and to the further right of that is a grid of LEDs, five tall by four wide. Each stack of five represents a channel. The bottom row shows, for each channel, whether it’s ready. The next row indicates the presence of a signal. The row above indicates that the channel is clipping (now that would be an impressive feat with this amp!) while a lit LED on the second-top row would indicate excessive heat, leading to the limiting of that channel. And the top row shows some other fault. I only experienced the bottom two rows.

An additional I/O port can report faults and allows for remote on/off switching, something that cannot be done via the regular interface (which we’re about to get to).

There are extensive protections built in: DC, VHF, AC Mains Protection, Overtemp and Current Limiter, fan fault detection.

Setting Up

For me, setting up was in part incredibly easy with only a minor issue. My own gear is entirely consumer gear – very good consumer gear, to be sure, but consumer gear nonetheless. So all my analogue sources provide either unbalanced RCA outputs or balanced XLR ones. With only three-pin Euro-style inputs, though, I had to make up adaptors.

I used unbalanced sources connected to the ‘+’ and earth pins. That was the full extent of the pain. (LEA offers adaptors as accessories: two-pack RCA to three pin, $130; since female XLR to three pin, $75).

The incredible ease takes us back to the app used to control this amplifier. There isn’t one. Instead, there’s a web interface and you can connect a computer directly to the amp via its own internal WiFi access point or you can connect it to your network via Ethernet. Once connected via Ethernet you can simply type its IP address into the browser of any device connected to the same network.

In the past I’ve had to resort to things like network IP scanners or drilling down through the menus of my router to find the IP address for devices controlled in this manner. But not this one. It displays the address clearly on the front panel.

Once you’ve connected via Ethernet, you can switch on WiFi mode. Connecting requires the less-than-consumer-friendly method of typing in an SSID and password. There doesn’t appear to be a scanning feature for available SSIDs but since this isn’t a consumer device, that shouldn’t be a problem.

The unit also allows cloud control if you sign up for a free LEA account, and this allows for remote management. Which of course is useful for installers providing after-sales support.

I used this web UI on my computer, an iPad and an Android phone. The layout was configured conveniently in each case. Most conveniently on a large computer screen, because then I could show all four channels side-by-side, rather than having to switch between them on the other platforms.

The only wobble in operation was with the iPad. When I switched to another app for longer than a few seconds, the web connection became wobbly, dropping out. Forcing Safari to close and then restarting it always fixed that.

In Use

Since I was not attempting to fill a concert hall with sound, nor drive an enormous network of speakers throughout a large venue, my testing was necessarily limited. But what I can say is that the unit sounded fine with both a pair of decent-quality compact 100V suitable speakers, daisy-chained and with the input on the LEA 1504D set to ‘Analog 1+2’ (the left and right input channels mixed down to mono) and my almost $10k Dynaudio stereo loudspeakers (‘Analog 1+2’ sent separately to output channels three and four).

I also allocated two separate pairs of inputs to two separate output channels and played a cacophony of Rufus Du Sol and the Emperor Piano Concerto at the same time.

Switching modes was easy and instantaneous via the web interface and the EQs and such worked as advertised.

I found all the control features extremely straightforward, almost intuitive. To the point where I had to be extremely disciplined not to accidentally set the output to my Dynaudio speakers to 70V. As with all professional gear, you do need to think or you can do some damage.

There are a lot of devices with control systems that I find far from intuitive, so it could be that the arrangement on the LEA Connect Series amps just happens to suit the way I think and is perhaps less intuitive to others. I kind of doubt that, though.

I wouldn’t consider this amp suitable for even the well-heeled hi-fi person. The cooling fan, while it isn’t particularly irritating, neither is it all that quiet. LEA specifies it at 50dB at one metre even while the amp is idling, and 63dB at full cooling. But in an equipment rack in a professional or commercial rig, neither of those would be a problem.

Conclusion

The LEA Connect Series 1504D Smart Amplifier is extremely versatile, very easy to use, very easy to control and exceptionally powerful four-channel amplifier for all manner of professional and commercial applications.