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At last! The Biketronics BT4180 amp review you've all been waiting for!

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#1 · (Edited)
At last, the Biketronics BT4180 review!!! This has been months in the making; thankfully my day job has slowed down enough due to the holidays that I can finally write this without distraction. I’ve also attempted this review a few different times and scrapped each draft. It is difficult to write a review on amps given how polarizing amp SQ is. With that, I only have two guidelines for this thread:

1.) I am not here to convince you that amps sound different. No one ever wins these arguments, we might as well start talking about religion or sports team loyalty. Literally no one has ever changed anyone's mind regarding any of these topics by arguing online and I am not about to attempt this impossible task today.

2.) Please do not argue about our ability to or lack thereof to hear a difference between amps. If you believe we can hear a difference, awesome. If you do not, guess what, I have an area in this review for you as well. If you want to argue this topic, please see the Higher End Amp SQ Myth thread here: http://www.diymobileaudio.com/forum...stry-dogma/141216-higher-end-amp-sq-myth.html

Now that we’ve performed that bit of housekeeping, let me first introduce you to the company known as Biketronics:

Years ago my mom told me that she and my father had some friends who built and sold parts for Harley Davidsons in my hometown of Moscow, ID. I’m not a huge fan of motorcycles and especially Harleys so this piece of information went in one ear and out the other. Fast forward to the summer of 2012, I was back in Idaho for a friend’s wedding when another one of my closest friends from high school called me up saying he had the field trip of a lifetime for me. He said it was a small electronics manufacturer and proceeded to tell me that they were building some really cool niche market audio equipment. Audio field trip? Don’t have to tell me twice about such an offer. I was extremely excited, especially given the escape from wedding preparations.

The next day we ventured down to the end of a large metal commercial building. It looked like where you see startup body shops or small town gymnastics studios; the affordable commercial mini mall. We went inside and were greeted by their purchasing director who gave me a personal tour of the place. It was BUSTLING with activity, people working on PCBs, taking orders over the phone, packing up shipments for UPS, etc. They were obviously very busy and outgrowing their space.

The director showed me all sorts of cool stuff. Woofers, tweeters, power supplies, amplifiers, even funny stories about a speaker “torture chamber” that he built to simulate intense heat/cold/humidity. That was an interesting discussion as I learned that the most resilient speakers he had ever tested were the HAT Imagines which took extreme head/cold/humidity with ease for a 24 hour period as it played at maximum output and did not skip a beat. Meanwhile he had destroyed the likes of Focal, Rockford Fosgate, and many other speakers with this same testing as well as many micro amps from other manufacturers (Rockford’s “boosted rail” amps were a dirty word there given how quickly they go into limp mode even with easy loads). This was my first real exposure to HAT which would later lead to me installing Unity components in my wife’s Jeep Grand Cherokee. His dedication to testing and finding the best products for his end customers was fascinating.

At this point in 2012 I had avoided the car audio world since departing it in 2004 to focus my time and money on finishing school and subsequently starting my career in the Seattle area. However, I had just recently re-entered the DIY home audio hobby about 6 months prior and I was in the process of evolving my active 2 channel speaker system loosely based on the Linkwitz Orions. I was using a 6-channel Rotel RB-976 for my amplification but I had been learning a lot about a company known as Hypex based in the Netherlands, mostly from extensive reading on Class D - diyAudio and Hypex Owners Circle. I was extremely excited to recognize Hypex modules on the purchasing director’s workbench. Even some modules I did not recognize, known as the UcD100OEM which they used in an older model of their amp. He began to tell me about these amazing little amps and how they are nearly 100% efficient, highly tolerant to volatile physical/electrical conditions, incredibly good noise rejection, tiny footprint, etc. I was considering building my own Hypex amp for home use but it had never occurred to me to use them in a car, though it made perfect sense.

Suddenly it occurred to me that these were my parents’ friends! Except they didn’t build just normal parts for Harleys, they were building audiophile grade packages for these bikes. First, I had no idea that there was such a market for high end audio gear. And second, I was extremely impressed with how much they did in house. They build the 12v power supplies, input stages and cases all there in the same facility before installing the Hypex amp modules for final shipping. What a small world it is!

Over the last ten years my mother’s health has been quite a roller coaster. She’s undergone numerous surgeries, emergency room visits and even a week in ICU with 50/50 odds of living. Like many mothers, she has a very stubborn side and sometimes needs a little coaxing to seek out the right medical assistance. Additionally, I am the only family member that she typically listens to and so I decided to move back to the Idaho area to help guide her on a path of recovery for her conditions. This meant I was also going to be local to Biketronics! Not a bad side benefit and fast forward to today, my mother’s health is very good now :)

During the 10 months that we lived in the area I came to know the owners very well. They had since taken over a retired Honda dealership which was ~20x larger than their old space, though last I visited only a few months ago in August, they appeared on track to outgrow that space as well! At the time, when my schedule permitted I would also attend a Tuesday evening session they would hold at their headquarters for anyone who wanted to come talk tech and use any of the tooling there to streamline prototyping of their own projects. An especially priceless offering for the many nearby engineering students at the University of Idaho and Washington State University. In fact, this open-door facility is formally known as their “Fab-Lab”, first announced here in 2010: BIKETRONICS OWNER DREAMS OF A FAB LAB IN MOSCOW. - States News Service | HighBeam Research
And most recently for winning an award in June of this year, reported here: Palouse Knowledge Corridor | Palouse Knowledge Corridor award highlights local entrepreneurs

In June of 2013 we finally moved back home to the Seattle area after seeing my mother through to good health. We were sad to move away from Biketronics; my wife was managing their logistics department and I was visiting on a regular basis, tinkering with amps with the owner and eating as much Mexican food as possible, prepared by one of their employees, Maria, who is from Mexico. To this day, Maria’s homemade hot sauce is still the best I have ever had.

After our return to Seattle we remained in close contact with the owners. I was having issues fitting amps in my truck, there is literally no space in these Hummers for anything, it is pretty ridiculous. The factory amp location is only 10”x10” so I did not have much space to work with. It finally occurred to me that I should try a Biketronics BT4180. At only 5”x7” I could even fit two of them. Here’s my current BT4180 installed:



Mike Meehan, the owner, sent me a BT4180 to test and it only took 15 minutes to install thanks to its small size and simple spring terminals. Only a fine-tipped object is required for installation to depress each spring terminal while fitting each wire. Super simple and RCAs attach with ease as well.

Each BT4180 is built with four UcD180OEM modules, an input stage which converts the single ended inputs to differential for the UcD modules and then their own homegrown power supply which converts 12v to the high rail voltage required by the UcD modules. Here’s the inside of my BT4180 which shows how well these utilize their diminutive cases. Notice the four UcD modules on the left, custom power supply on the right, input stage board on top and then two cooling fans on the far right (which I have never heard turn on, even on 4-5 hour drives at high volume):



For those of you who believe all amps sound the same, here are the objective benefits of this amp:

1.) Zero noise, even at high volume. Literally the lowest noise floor I have ever worked with in an automotive environment.

2.) Huge power output. Even at very high volumes driving my Dynaudio Esotar 650 mids and CSS LD25X tweeters, I have never been able to send the amp into clipping. With 180wpc RMS@4ohms, this amp definitely meets or beats output of the top 20 percentile of amps on the market. I haven’t seen an amp move my Esotars as much as this does. Tons of midbass kick.

3.) Small, smaller than the smallest USPS flat rate box. You could probably fit 3 of these under most seats. You could even fit one of these in some dashboards, one could easily fit behind my P99 in my truck.

4.) Easy to set up with the spring terminals. No gains to worry about. The Hypex modules can take a huge signal without clipping yet need a very small signal to reach full power output. I have no idea how they do this but it just works…kind of nice for people who do not want to worry about calibrating gains. It is a great match for my P99 which was able to gain down its own outputs during the auto-calibration process, further lowering the noise floor.

5.) Efficient, these are made to create full power on a Harley charging system. You can run a few of these in a typical car without needing to upgrade your electrical. Great for high end installs where the stock electrical system must be utilized (expensive/exotic cars, boats, etc.).

6.) Lifetime warranty…wow!

My subjective listening impressions:

1.) Crystal clear sound at all volumes. Even at very low volume, music sounds clearer than any amp I’ve had in here before. I can make out lyrics even when I turn it down. Something that wasn’t ever quite possible with other amps I’ve had in this truck. Could be a function of the higher power output but basically it translates to better perceived clarity.

2.) Big sound. Other amps I have used sounded a bit more narrow or hollow. The BT4180 creates a sound stage that feels large and enveloping.

3.) More dynamic…again, probably thanks to the higher power capability.

4.) Neutral sound…I’ve never been a huge fan of overly warm amps because of the amount of distortion that seems to be added in the midrange at higher volumes. The BT4180 lets you just crank it louder and louder while remaining absolutely crystal clear. No biases at any frequencies and no perceived distortion. Very transparent to the music.

I’m hoping to have a response plot available to post soon after the team at BT throws one of these on their Audio Precision analyzer, though I know prior versions have tested ruler flat from 12hz-20khz+. Yes, flat down to 12hz at full power, no smoothing. Meaning one of these could be used to drive subwoofers with ease. Which I am planning next for a pair of SI BM MKIV 12’s under my back seat, driven by a BT2180 (2 channel version of the BT4180). I am planning a similar setup in a Mustang Cobra convertible this spring to keep equipment weight/size to a minimum for improved performance without sacrificing sound. In fact, I really have no reason why I would use any other amp from now on. They’re certainly not the cheapest amp around but being made in the USA and the lifetime warranty are two great features that help justify the investment.

Bottom line, even from a purely objective perspective these are the best amps I have ever used. I recommend them for anyone with the right budget available. Though Biketronics is very well known in the motorcycle market, they are relatively unknown in the car audio market. To help them get the word out, I am organizing a group buy so please PM me if you are interested in an amp (or two or three). I even have two extra BT4180 amps in case anyone can’t wait for the group buy (originally purchased for my wife’s Jeep but we are returning it to stock before selling it later this year to upgrade to a full size SUV). Both brand new sealed in box with full warranties.

There are a few more of these amps in the possession of some prominent members here who will likely chime in with their listening/ownership impressions as well. :)

Thanks for reading!

EDIT: I TOTALLY forgot to mention that these have a VERY steep filter at 45hz which drastically reduces the amount of warrantied speakers that Biketronics has to deal with. I'm working with the owner to get these removed from a BT2180 for subwoofer usage, stay tuned :)
 
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#5 · (Edited)
It is class D, nothing really new there except for how Hypex has implemented the design, especially in the Class A front end which I think helps make it a more "musical" sounding amp than grittier Class D which we tend to think about, especially when Class D first hit the consumer market. These on the other hand are about as refined as I have ever heard. They don't need to give up anything because Class D is inherently small to begin with. It is the power supply that requires the size due to capacitance and transformer footprint. If you want I can post Hypex's 100+ slide presentation on how the UcD design works :D Really the only tradeoff is power output. The bigger the footprint, the more power these make. Here's 2kwrms the size of your hand:

https://www.hypexshop.com/DetailServlet?detailID=3538

I am actually building two Hypex home amps right now, a 6 channel which will either power an active pair of speakers or the surround channels for Dolby Atmos when Anthem releases their new receivers in 2016. Just needs the right power supply, probably a switching type from ConnexElectronics. Also a 2 channel which uses a pair of UcD180ST modules and a toroidal power supply which needs to be rewired (previous owner did not have the best soldering skills). That one will probably drive my Accuton mids in my high end active speaker setup I'm building for the ultimate mancave system :D

Eventually I would love to build an ultimate home HT amp with all Hypex modules, either UcD700HXG or NCore 400 modules. But this would be astronomically expensive compared to the amp I use now, my big Vincent SAV-P200 which cost me about as much as a naked pair of NCores for six channels of very high performance amplification. So in the interest of $$$ it is not in the cards right now.

The cool thing about the BT amps is that they barely cost more than the raw parts. Add in USA assembly and quality control and you can't really build them yourself for much less than MSRP. You don't see that every day!
 
#7 ·
How is heat build up with these little guys? I am really interested in a couple of these but they would be hidden with not a ton of air flow so heat is a little concerning.
 
#18 ·
Like SQ_TSX said they run very cool. And they have two built-in fans in case things do heat up but mine has never had a heat issue, even when driven hard in 95 degree conditions.

They do a mono?
Not at this time but definitely possible by swapping modules for a larger module. We'll probably see this possibility in a few months.

Is there a bridged power rating, couldn't find it on their site?
They do not bridge out of the box but the Hypex modules can be bridged very easily. Again, this will probably be built-in functionality at some point.

That lack of gain control could be an issue for some folks. And they may not be bridgeable if there is no way to invert a channel.
Of all the people I have spoken to, no one has had gain issues with these even when used with very high voltage preamp signals. Again, no idea how BT did it with their input section but somehow it works.
 
#8 · (Edited)
These little guys are usually installed in saddle bags. Tons of vibrations from these bikes with limited ventilation and moisture.
They have done testing on the speakers in some very harsh environments. One would only think that the same environment that these speakers are exposed to are the same as these amps in real world use.
Very solid product for a demanding clientele.
 
G
#20 ·
On the input gain question.... best I can tell.... The input section is DSP controlled... continually adjusting the voltage, within reason, to match the power supply needs...

Buy I'm just guessing since I'm not an EE....
 
G
#23 ·
I'm pretty sure the input on the BT4180 is DSP controlled... I've opened the amplifier up to inspect the construction but haven't gone to the point of disassembling it....

I'm not so sure that test would prove much... Theoretically, the amplifier would produce 180 watts into the HLCD's and into the midbass'.... the horns would still be much louder than the midbass'
 
#24 ·
The director showed me all sorts of cool stuff. Woofers, tweeters, power supplies, amplifiers, even funny stories about a speaker “torture chamber” that he built to simulate intense heat/cold/humidity. That was an interesting discussion as I learned that the most resilient speakers he had ever tested were the HAT Imagines which took extreme head/cold/humidity with ease for a 24 hour period as it played at maximum output and did not skip a beat. Meanwhile he had destroyed the likes of Focal, Rockford Fosgate, and many other speakers with this same testing as well as many micro amps from other manufacturers (Rockford’s “boosted rail” amps were a dirty word there given how quickly they go into limp mode even with easy loads). This was my first real exposure to HAT which would later lead to me installing Unity components in my wife’s Jeep Grand Cherokee. His dedication to testing and finding the best products for his end customers was fascinating.
Thank you for noting this in your review. :)

Scott
 
#27 · (Edited)
Wish I was better equipped to do the necessary testing to figure out the intput level limitations, etc. of these...but they seem to work really well with even just 1v max voltage. I'm IM'ing with one of the engineers over there right now to see if they have any more data that might help us figure it out :)

These guys have a 100% satisfaction guaranteed policy so if someone were to buy one of these and find it doesn't work well with their current source, you can send it back for full refund. These guys really take great care of their customers.



You're welcome Scott! I was blown away with what they were putting Imagines through there, amazing what you've done with those. The team there speaks very highly of you, cool that it is such a small world :)
 
#33 ·
I pulled the trigger on one of these a few weeks back. Reading all of this makes me even more mad that I have been to busy to get my new install in motion. I will note also about the great customer service I have been shown so far. It has been great. The signatures on the back of the amp of everyone who worked on your amp is an awesome touch. Gives you the feeling that they stand by their work and want their name to be a part of it. All the little things so far have been above and beyond. Now the only thing left is to see if the dyn's like it.
 
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