My experience with Class-D Amplifiers (Part 1 & 2)

venkatcr

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Preamble No.1
This is a loooong post. It is broken into two posts. Anil (Hifivision) was kind enough to increase the post size to 40K from 20K characters. Thanks Anil.

Preamble No. 2
I have not been actively participating in this forum for quite some time. There are many reasons for it. One, I had stopped learning anything from the forum. Two, I was tired of newbies asking stupid questions again and again. Three, I was tired of the groupism and people getting personal instead of talking about audio and audio electronics that all of us love. Four, I was also tired of a bunch of people who would always say, ‘either use a 500,000 amplifier or, you are not an audiophile.’ I certainly don’t want to be a member of a club that has such high entry costs. A cup of tea from the street corner tea wallah tastes much better than the one in a 5-star hotel. You may need the ambience and exclusivity of a 5 star. I just want a cup of tea. In other words, I just want to listen to music as much as I can. 24/7, if possible.

One of the greatest assets of an audiophile is the way he thinks. The Sun rises from his left ear and sets on his right ear. His selection of music is the best in the world. His ‘golden ears’ are far better than those of the rest of the world. He hears ‘air’, ‘depth’, ‘separation’, and a host of other features of the song that even the poor musician would not have imagined, let alone insert into the song.

I wanted to be away from these useless arguments for some time and enjoy music and movies for what they are. Mediums that entertain you and give you satisfaction. I wanted to stop listening to songs trying to find errors in the source, amplification, cables, speakers, power supply and whatnot, and enjoy the melody in Rafi’s voice, in the crooning of Jim Reeves, or the superb way Ravi Shankar tweaks his sitar. And that is what I have been doing for roughly 2 years or so.

Preamble No. 3
I don’t intend this post to be a war of words between one class of amplification and another, but I certainly want to set the tone right.

People have been disparaging Class D amplification for a very long time. But they forget many things.

Class D amplification is there everywhere. TVs, phones, expensive car audio system, subwoofers, movie halls – all use class D. In reality, you spend more time with Class D amplification than with your ‘pure’ Class A or Class AB amplification when you sit in front of your precious audio system.

Today, there is more money being pumped into systems that form the core of Class D. TI, Infineon, ST, Qualcomm and a host of other companies are spending billions of dollars into circuits that form the basis for DSP, amplification, and other forms of audio processing. Class D has a bright future while other classes of amplification have become the world of a few.

So, what are the differences between Classes A, B, and D in layman terms? Hans Beekhuyzen, who regularly reviews audio systems in YouTube, has a succinct way of explaining the difference. Non-Class D amplifiers are the equivalent of trying to push a nail into the wall using a bulldozer. You end up using enormous energy where it is neither needed nor efficient. Class D, on the other hand, is the equivalent of a hammer. You use small amounts of energy in bursts that get the job done. Just remember pulse width modulation (PWM). Class D amps watch the input signal (your music) and create enough energy when needed to ‘hammer’ the speakers to sing. The number of times the ‘hammer’ is used is called switching rate that measures the speed with which the amplifier switches between on and off positions.

Steve Munz (https://www.audioholics.com/audio-amplifier/amplifier-classes) confirms this when he says, “While all the amplifier classes previously mentioned have one or more output devices active all the time, even when the amplifier is effectively idle, Class D amplifiers rapidly switch the output devices between the off and on state; as an example, Class T designs, which are an implementation of Class D designed by Tripath as opposed to a formal class, utilize switching rates on the order of 50MHz. The output devices are typically controlled by pulse width modulation: square waves of varying widths are produced by a modulator, which represents the analogue signal to be reproduced. By tightly controlling the output devices in this way, efficiency of 100% is theoretically possible (although obviously not achievable in the real world).”

Mike Cox, in a review of a Tripath Amplifier in tnt-audio.com says, ‘The class D/T amps are now really coming of age, they sound good and offer low running costs. There will always be those who prefer the behemoths, the hot and expensive class A valve and transistor amplifiers, that are increasingly expensive to own and run’. He concludes, ‘Paired with suitably sensitive speakers the Sure TA20124 is a very good amplifier and exceptional value for money. Sometimes I wonder if my valve amplifiers are really that much better when you consider the purchase price and operating costs (electricity and replacement valves)’. And, this was in 2016. Class D/T circuits have grown significantly since then.

By the way, the ‘D’ in Class D amplification is a misnomer. It does NOT refer to digital amplification. It is just the next letter in the list of classes used – A, B, C and now D. The list goes to ‘S’ & ‘T’. Class T is a version of Class D as designed by Dr. Adya S. Tripathi and used by Sony, B&O, Apple, and a host of other companies. Class T’s are generally called Tripath amplifiers.

In my mind, one of the greatest advantages of Class D amplification is that everything can be measured. And the results of modern amplifiers today far surpass those of even the best Class A or Class AB amplifiers. Non-Class D amplifiers typically specify a THD (+noise) ratio between <0.1% to <0.05% and an SNR between 80 to 110 db. Class D circuits today are capable of delivering <0.0004% THD and SNR up to 140 db. And, most of the more expensive Class D’s use external linear or switch mode power supplies, eliminating noise and ripples from the power supply.

Now that I have finished my rant, let us move on.

My Experience with Class D Music
For a long time, I have wanted to have music in multiple rooms across my home. Music I would not have to spend too much money on, or, take too much effort to play.

What we Indian’s call the ‘drawing’ room was the prime candidate for multiple reasons. We tend to spend a large portion of our daily time there, and it is this room in which we have get-togethers etc. I did, for some time, contemplate having the get-togethers in my dedicated music plus HT room. I did try it a few times. The results were disappointing. One, the room gets too small when it has more than 10 people. Two, I am constantly worried about people touching my audio and video systems. Three, once people start drinking and talking, the music gets drowned in the noise. I end up scratching my head to understand whether people even bother to understand the efforts I have taken to set up the system.

On another front, I had decided some time ago to move completely to a digital platform. Though my current amplification is Class AB, my sources are completely digital. I will eventually have a tube amp for my main system. Though a very good friend of mine tried to make me a ‘purist’, the sound of scratch noises in tapes and records put me off no end. I also find the concept of maintaining LPs and EPs too troublesome. Once I have digitized all my CDs, I will lock them all away or simply sell them off. But, that is a long way off.

I suppose I have conditioned my mind and my ears to live without the ‘pure’ analogue sound those purists so crave for. In many ways, I may not have the ears to differentiate the sound. If and when I install a tube amp as my main amp with the single driver speakers that I have, I reckon I will be somewhere between the devil and deep blue sea!!

The Hard Search
For over two years I have fooled around with the idea and concept in addition to taking time to build a new software company.

Class-T, or, Class-D? To a large extent, Class-T had become extinct when Tripathi was pushed out of the industry and his company was bought out by Cirrus Logic. In any case, Tripathi was using a Class-D circuit but had used proprietary DSP signal processing to control the signals. He constantly compared the input signal with amplified output to render real-time control of the switching frequency. Remember the hammer? Cirrus Logic seems to have dumped Tripathi’s design and worked on improving its Class-D architecture. Taking a natural derivative of the delta-sigma converter, they claim to have pushed the signal-to-noise ratio (SNR) into the 110-120dB range. Designs that deliver very similar results have been adopted by TI, ST, and a host of other manufacturers.

So now which amplifier to buy? The prices ranged from under $50 for 2 channels to $5000 per channel! The ICEpower modules from Denmark are my ultimate buy but are very expensive. Adopted by a few such as B&O and expensive sub-woofers, these were out of price range for the requirement I had in hand.

After a lot of thinking and research, I decided I needed a sub $250 amp with a rated output of around 100 watts per channel. Several brands names came up including some with names as funny as Bassoon!! Just replace the ‘ss’s with ‘ff’s!! Hee Hee!

The most attractive (and possibly best choice) was the new NAD D3020. But at INR 50K in India, this was out of the reckoning. And, the rated power was 30 watts. I do know NAD tends to underwhelm its specs, but even then this was out. I did lust after the Onkyo 9010 as WhatHiFi has been singing its praise for over three years. But I have my issues with Onkyo, and particularly Onkyo India.

After some more research, I narrowed my choices to Topping, SMSL, Lepai, Trends, Dayton, and Fosi.

Before I discuss these, let me also say I was very interested in two British amplifiers. One was the Mini-1 amp by Ampstatic, and the other was the Bantam Gold by Temple Audio.

The Mini-1 claimed they were still using Tripath 2020 chips. Their power ratings were 20 watts into 4 Ohms with a THD+N of <0.03% @ 10W 4Ω. Good figures, even though the power output was low. I wrote to them as to how they were getting their Tripath chips, and the answers were very elusive. Either they were sourcing the real chips from the black market, or were using proxy chips and fooling the world. The first could be true as their website would suddenly go dark in terms of availability of the amplifiers. The amp also had just one input and nothing else.

Temple Audio was even better about Bantam Gold. They just did not bother to answer my emails.

Topping, SMSL, Lepai, Trends, Dayton, and Fosi
Let us set off the easy ones first.

Trends Audio
Trends Audio makes four versions of the same amplifier they call Trends-Audio TA-10.2. Two are integrated amplifiers, while two are power amplifiers. At some $350, all these deliver 15 watts. Again, very minimalistic. Just one input. Out of my price range.

Topping
Topping makes a large number of products including high-end DACs, and what they call ‘power’ amps. Their most famous amp is the TP-60 that outputs 80 watts per channel. Excepting for a claim that they use very high-quality components such as Nichicon capacitance and ALPS pots, I could not get too many details from their site. Yes, it does use the same amplifier chip as my final choice, but I was keen to understand more about the product made by Topping. I could find very few reviews. Out!

SMSL
The Shenzhen ShuangMuSanLin Electronic Company Ltd (SMSL) make a large set of interesting products including a DAC called ‘Sanskrit’. Their DP3 is an interesting product. It is a Digital Player that has every connection you can think of and every output you will want. But, my interest was with their AD18.

The AD18 is a well-endowed product that generates 80 watts per channel. It uses the Texas Instrument TAS5342A for amplification and TI’s TAS5508C for PWM. If you wondering what PWM is, remember I spoke about managing the audio output based on the input signal? The PWM, or pulse width modulation, does that. According to TI, ‘The TAS5508C uses AD modulation operating at a 384-kHz switching rate for 48-, 96-, and 192-kHz data. The 8× oversampling combined with the fifth-order noise shaper provides a broad, flat noise floor and excellent dynamic range from 20Hz to 20kHz.’

My interest was more with the TAS5342A, the power amplifier used in the AD18. The specs claim 2x100W at 10% THD+N into 4Ω. At 8Ω, it claims to deliver 65W. All this, mind you, is in the Bridge Tied Load (BTL). In BTL, the speakers are connected between two audio amplifier outputs and these can double the voltage swing at the speaker end. In normal times, the speaker is tied to the ground, and the swing is from zero to the amplifier’s supply voltage. Here, the TAS5342A fell to roughly 2x50 W at 10% THD+N into 4Ω. Not very encouraging. It also claims to have SNR of 110db but using the TAS5518 modulator. The AD18 was using the TAS5508C, so I assumed the SNR will be lower. The actual value was a dynamic figure of 102dB. The AD18 has a DAC built-in with 24/96 for USB and 24/192 for optical.

One of the attractive points about the AD18 was a large number of inputs it had. It offers AUX, USB, Optical and Bluetooth. It also offers a sub-out. It also had a large number of sound optimization in terms of treble and bass using in-built DSP. The claimed SNR was 90dB. Stated THD is 0.04% which is quite decent.

At the end of the day, what negated AD18 for me was its ‘too much processing’ inside a small package. I felt it would increase noise and interference. Besides, the reviews were pretty disappointing with some not recommending the product.

Dayton Audio
Dayton Audio is a US-based company that makes a large set of audio products. I had narrowed down to two products – their APA102BT and DTA-120BT2.

The APA102BT was attractive as I had read many interesting reviews praising the product, including one that said that Class-D had ‘arrived’ with the APA102BT. The issue with APA102BT was that it had an internal power transformer that was made for 120VAC. I did call Dayton to ask if they can give me one with 220, but they said they have no intention of doing that. I even contemplated ripping the power unit and replacing it with a 220VAC unit. But, that was too much trouble.

The DTA-120BT was based on their popular DTA-120 and added improved circuitry and Bluetooth. But, other than the reviews that seemed to be ‘sponsored’ by Dayton, I could not find any good reviews on the product. The specs were perfect, though the price was roughly $20 more than comparable products.

Fosi Audio
Fosi Audi is a very interesting company. They have a large number of products that includes DAC, pre-amplifiers, integrated and power amplifiers. They also have a power amplifier with a monstrous 300 watts per channel at less than $90!! A friend of mine makes Class-D 300 Watts amplifier using ST chips. And he charges roughly $500!!

Though I will buy some Fosi products, for this present assignment, I had narrowed down to BT20A, TDA7498E, and BT20C.

The TDA7498E was an interesting product but lost out against my final choice because of the lack of Bluetooth. I also felt that Fosi were overstating the power capabilities at 2x160W which the TDA7498E was not capable of unless you want to hear just noise.

Between the BT20A and BT20C, I leaned towards the latter as it had aptX. But it was delivering only 2x50W using a TI TPA3116D2 chip. The IC’s max rated output is 2 × 30 W into an 8-Ω BTL Load at 24 V. I felt it will quickly run out of juice when I push heavy load such as a Symphony number.

Lepai - My Final Choice

Hong Kong based Lepai Audio is a company that, I believe, is focused on quality products. Their first product – the LP-2020A - using Tripath's proprietary Class-T digital power processing technology had earned legendary status with over a million pieces sold. Though audiophile critics were not ready to acknowledge it, it’s presence in the market made them look it up. Their admiration was grudging. In a 2012 review in CNET, Steve Guttenberg had this to say. ‘The LP-2020A+ is definitely worth the money, and I wouldn't rule it out for audiophiles looking for a budget amp for a bedroom or office system. As long as you're realistic about the Lepai's capabilities and limited features set, you can't go wrong with this little amp’. You will find a lot of similar reviews across the Net.

Unfortunately, when Tripathi’s company was bought out, the famed Tripath Class-T amplifier IC became unavailable. Lepai continues to offer the product renamed and using a TPA3118 chip from TI.

My interest lay with its more recent product – the LP7498E 200W Amplifier.

The LP7498E is based on the ST TDA7498E amplifier chip. This is one of the most popular Class-D amplifier ICs available in the market today. ST claims that the IC is capable of delivering 2x160W at a THD of 10% into 4Ω with an input voltage of 36V.

A large number of people have conducted tests on the IC, and the conclusion is as follows:

When you use a 33-35V external power supply, keep the input frequency flat at 1 KHz, and THD at <1%, the IC, in reality, delivered the following:
  • 2x108W into 4Ω
  • 2x68W into 8Ω
These were decent figures. In both these cases, the IC delivered perfect Sinusoidal waves until these thresholds were crossed.

I dug deeper into the Lepai amplifier.

In a Jan 28, 2014 article, Stephen Mejias wrote this in Stereophile. ’I used the little Lepai to drive KEF's LS50 loudspeakers ($1499/pair). On paper that might seem a bit silly, but in my listening room, it sounded freaking excellent—especially with CDs. Kanye West's "Blood on the Leaves" lacked some stage height but nevertheless sounded big, bold, and emotionally compelling, with a natural midrange, sweet highs, good bass weight, and well-focused images. And while the Lepai mostly sounded comfortable at higher volumes, if I pushed it over 90dB, I noted some edginess in more complex passages of music. Around three minutes into West's "New Slaves," for instance, when the song morphs into a noisy soundscape with Frank Ocean singing over a sample of Hungarian rock band Omega's 1969 song "Gyöngyhajú lány," the Lepai couldn't extract as much beauty from the music as my NAD C 316BEE.

‘Freaking Excellent’? Wow! That was a big acknowledgement from people who would not give a <$100 product even a second look. Even 1 foot of one of their cables would cost 4 times that!! Just read this article (https://www.stereophile.com/solidpoweramps/1006sonic/index.html) to understand the reluctance of these people toward accepting Class-D as a viable alternative.

Speaking about the Bluetooth connectivity, Stephen says, ‘The Lepai's Bluetooth performance was an altogether different story. It sounded bad—gritty, compressed, and murky. I will now approach any A2DP-equipped component with special caution’.

After Stephen’s review, Lepai has replaced the main IC with the LP7498E that delivers some additional 60W per channel. They have also added aptX Bluetooth, the current king for audio transmission.

The amplifier is very minimal. Two inputs (line and Bluetooth), and one speaker output pair. That is it.

Initial Hiccups
I ordered for the Lepai amplifier with Parts-Express of the US and got it delivered to a relative of mine in the US. In turn, the product reached me mid-June, 2019. I was out of station for the second half of June. Starting July, I started putting the amplifier and speakers together and seeing how it performed.

The speakers I am using are Aperion Audio Intimus 532 LR Bookshelf speakers. Yes, these speakers are 14 years old and still sound superb! I have been using the Intimus 533VAC as my centre channel for donkey’s years. The 533VAC is a vertical array centre speaker. It adds a second crossover to the design. It also anchors voices incredibly well.

I plan to replace my complete HT with Aperion Speakers. When? That is a question that is difficult to answer. All a question of Vitamin M!!

The Intimus 532 LRs are rear-firing speakers that have a frequency range of 80-20,000Hz, 8Ω impedance, and 88dB sensitivity. You will find a large set of reviews of the speakers on the Net. Let me just quote the closing remarks of Mark Fleischmann’s June 2005 review in Sound & Vision. ‘Aperion's Intimus leans toward the upstream side of the equation with a large sound field, vocal subtlety, well-integrated bass, no obvious colouration, and an appetite for power, jazz, and action movies. That seems to be a winning combination’. He also goes on to say, ‘The simple two-way design hinges on Aperion's 1-inch silk-dome tweeter and 5.25-inch mineral-filled polypropylene woofer. This set of Aperions produced a huge sound field that retained its composure at all but the most abusive volumes’.

It was also the on the recommended list of Audioholics, a magazine I have a lot of respect for.

The Intimus 532 LRs are significantly less efficient than average. They need 50-plus watts per channel to sound right. That is one of the reasons I was searching for an amplifier that could deliver 100+ watts. I was opening the speakers after nearly 10 years, and I was very nervous.

Getting Proper Power to the Amp
At the outset, I wanted to see if I could replace the amp’s supplied power cable (US Version) with one that would fit Indian plugs. I bought a few cables and was stunned by the poor quality. Between the L(ine) and E(arth), there was a leakage of over 10Volts. The original cable had no voltage leak. I decided I will just use an adaptor and stick to that. Next, I wanted to see if I could buy a distribution board (power strip) with spike protection and EMI/RFI filters. After a lot of heartburns including looking at Belkin, I purchased two Anchor 22736s that offered all I wanted at a reasonable price of around INR500.

I was very keen to lay my hands on Elcom’s power strips. The reason I like Elcom is that their sockets are solid and work for years without becoming loose. The only issue is that distributors and retailers need a minimum order for 10 pieces. I placed an order with the company directly, but they have pushed me to a dealer again.

Initial Setup
I set up the system in my HT room, placing the Intimus speakers some 4 feet to the left and right of the Lepai. Using a pair of DAC (brand) speaker cables that were lying around, I used the banana plugs that were already connected to the cables and connected the amp to the speakers. Sending a silent prayer to the Gods, I fired up the amplifier keeping the input on BT (Bluetooth). The amp gave off two short beeps and a long beep. I understood later that this was an indication by the amplifier that it is ready to accept Bluetooth signals.

Using my smartphone, I logged into Amazon Music and played a random song. The music played and I heaved a sigh of relief. I tried it with Charu’s (my wife) smartphone, and there was no sound coming. Then I realized that you have to go through a sequence of switching to get it to work with a different Bluetooth source. On the player (smartphone, tablet, PC, etc.) you first unpair the amp. On the amp, you first switch off the power, toggle the line switch, and power the amp on again. Now the amp will be available to all Bluetooth sources. Using Charu’s phone, I paired it with the amp, and I was relieved to hear music playing.

Fooling around with my smartphone, I raised the volume on my smartphone. I was immediately punished with noise coming from the amp and speaker combination. Looking at the amp, I realised the banana plugs on the amp were loose. When I pushed them in and played the song again, I was rewarded with good music.

Speaker Cables & Connection
I sat down and thought of what I was doing. The DAC brand speaker cables were too long for my requirement, and since this system was to be used by Charu, I needed a solid connection. I threw away the DAC cables and cut a pair of Van den Hul cables I had lying around to the length I needed. I decided I am going to connect the cables directly at both ends instead of using a banana plug.

The speaker end was easy and I connected the bare cable to the binding posts. At the amp end, I ran into problems. On the right channel, there was enough spacing for me to connect the raw cables. On the left channel, the socket to connect the power was right next to the binding posts. When I inserted the power cable, I saw the positive and negative of the speaker cable was running above and below the power cable. So I picked up a pair of banana plugs, carefully cut the speaker cables, soldered the ends, and used the banana plugs at the amp end.

I ditched the smartphones and used an iPad to play the music from Amazon. I could sense an immediate improvement in music. Before some serious listening, I just allowed the amp and speaker combination to play some random numbers for two days. On the third day, when I started focusing on the music, I was rewarded with really sweet sound from the Lepai/Aperion Audio combination.

Connecting to My Asus Sound Card
Since I was hearing good sound from Amazon through Bluetooth, I wanted to see how the system would sound connected to my Asus sound card. I used my usual Acoustic Research RCA cable and connected the amp to the PC with the Asus sound card. No sound at all. I made sure that the connecting sequence was correct. Zilch. Disappointed, I started eliminating possible issues. Connected to another line source such as my DVD player, the Lepai worked perfectly. The Asus sound card connected to a Marantz amplifier worked perfectly. But, the Asus sound card and Lepai refused to speak to each other. I need to understand the reasons, but I suspect that the Lepai acts more like a power amplifier, and expects the input to have high gain.

The Asus outputs 2 Vrms (5.65 Vp-p). For what I could gleam for the TDA7498E specs, it expects a minimum of 0.8V and a max of 2.0V. Could it possibly be going into protection mode and cutting off the signals from the Asus card? Or do I need to insert a pre-amp between the Asus and Lepai?

This was disappointing. I need to find other ways of supplying good analogue signals to the Lepai amplifier.

First Listening
I spent the next few days listening to the Lepai using the iPad as a primary source. What started as possibly muddy sound became clearer and clearer and the sound was pure music in every way you looked at it. The only thing missing, maybe, was chest-thumping bass. But I was never one to appreciate that. Let me quote a YouTube reviewer on this. He calls himself Thomas & Stereo. He says, ‘When I started my audio journey, I was interested in very detailed highs, clear vocals, and crazy bass. Install a sub, pressurize the room, and get the bass to thump your chest. Now I have grown. I need instrument separation, sound stage, and air in the sound stage.’

When the heard Lepai for the first time, I must confess I was disappointed with the base. But then a few days later, I heard a good version of Rasputin by Boney-M – a 50MB file having a bit rate of 959kbps in the m4a version. This number did deliver chest-thumping bass with the same speaker + amplifier combination. That means that the Lepai is reasonably good in transparency.

Percussions of all kind sounded precise and pleasant. In particular, tablas sounded superb through the system allowing you to hear every nuance of the instrument. The roll of Sivamani’s drums played extremely well and separated from all the other bells and whistles he uses. The amp does something I appreciate a lot – complete lack of reverberation or artificial echoing.

Kenny G’s saxophone came close to hurting your ears but stopped just short, sounding very pleasant. In The Joy of Life, Kenny pushes his saxophone to the highest possible octave, and the Lepai reproduces that faithfully without any colouration.

To understand whether it can handle human voice, I tried Rahat Fateh Ali Khan’s Afreen Afreen. Rahat uses speed, high pitch, and constant variations in a way few singers can. Frankly the 3rd or 4th time I heard Afreen Afreen through the Lepai, I felt Rahat was sitting just in front of me. The naturalness of the sound was unbelievable. I just had to close my eyes to visualize the sound stage so well depicted in the video of the song.

Not that I like the song too much, but Amanda Palmer’s It Runs in The Family is an assault on your ears. The song has, I quote, ‘unrelenting drumming, sweeping piano chords, epic strings, throbbing synths’ – all mixed with Amanda’s furious, breathlessly delivered lyrics. I expected the Lepai to fail and not be able to mix all that into a song but deliver it more as noise. But how wrong I was! The Lepai played all the instruments with Amanda’s voice taking centre stage without a beat. The sound stage was deep, though narrow as I had kept the speakers just 5 feet from each other. But the depth was very heartening. The song is such an assault on your ears that you really need to focus to identify subtle change, if any, brought about by the amplifier.

Now that I was satisfied that Lepai could handle percussion, instruments and vocals well, it was time to listen to a few of my favourite numbers and do some serious analysis.

How About An iPod?
Since the Lepai was not on speaking terms with my Asus sound card, I had to find another source that would come close. I searched at home and realized that I had a 5th generation iPod that Charu had abandoned. I remembered that a few years ago I had fooled around with it, till I also abandoned it as my ears don’t like headphones at all. I did some research and found out that the iPod I have uses Wolfson WM8758 DAC which is quite decent. Read about its measurements here - https://www.stereophile.com/content/apple-ipod-portable-music-player-measurements.

I dusted and cleaned the iPod, charged it, and realised it had some of my favourite numbers in ALAC format. Yeah, baby… now you are talking!

When I connected the iPod to line-in on the Lepai, I was rewarded with good sound. As I chose some of my favourite numbers and played them, my respect for the Lepai/Aperion speakers kept going up.

.........(Continued in Part 2 Of 2)
 
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venkatcr

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.... Continued from Part 1 of 2.....

Final Serious Listening
After fooling around with the system for a few days, I had roughly 20 hours of music played on the system. In my mind, that was enough breaking in. In any case, I was never one to believe in the breaking in philosophy.

I now had the option of listening to some music, both streamed to the Lepai and played from the iPod.

Breathless. Shankar Mahadevan. Saregama. Wave files.
I once mentally counted how many times I had listened to The Wall. After mentally counting 500, I gave up. I may not have listened to Breathless that many times, but I know every nuance of the song. I know exactly when a particular instrument will take centre stage, when Shankar’s voice modulation will change, or when the ‘ting’ of a triangle would sound. When I streamed Breathless to the Lepai, I was astounded with the details the system threw at me. Every instrument sounded just right and Shankar’s voice sounded tighter as if he was holding the mike closer to his throat. I immediately played the song from the iPod, and I listened to a larger and deeper sound stage. The only troubling sound was that maybe Shankar’s higher pitches were a mite exaggerated, as was his ‘ufff’ as he breathes in at the end of the song. But what delighted me was the complete background silence as he breathes out a large gulp of air. When the electronic organs gave way to the drums, the sound stage became deeper and stronger, though there was no change in Shankar’s voice.

Afreen Afreen. Rahat Fateh Ali Khan, Momina Mustehsan, Coke Studio, Season 9, Ep 2. MP3 – 320kbps.
Afreen Afreen was written in the 1990s by Javed Akthar and composed by Nusrat Fateh Ali Khan. Though Nusrat did sing the Ghazal well, the video tried to bring in overtones of sex through Lisa Ray.

In 2016, Faakhir Mehmood took the song and literally rewrote it to be sung by Rahat Fateh Ali Khan and Momina Mustehsan in the Coke Studio Season 9. This rendering took the song to a different level making it a true Ghazal that takes away the sex and makes the appreciation of beauty, well just that.

Rahat, I would say, has excelled himself in this song. You must watch the video to see the look of sublime pleasure in his face as he sings. Pushing his throat to the extreme, he delivers notes I can never dream of singing myself. There is a nary a second of wavering or vibration in his voice. The notes are sung accurately. At 4:49, when he renders ‘Mehajabeen, Mehajabeen’ with a distinct variation, one of the accompanying artist smiles and nods his head in appreciation. In reality, Rahat outperforms Momina flat out. But she is happy to smile and enjoy the song.

Unfortunately, Coke Studio has released only an MP3 of this beautiful number, though at 320kbps. I do wish they would release a lossless version.

By this time, I had moved the speakers to some 5 feet from the Lepai on both sides. I now had nearly double the sound stage. I had also placed the speakers at a slightly elevated level.

I closed my eyes and started Afreen Afreen played from the iPod. I wanted to see how much of the video scenes and sound stage I had seen so many times I could visualize. Lepai did not disappoint me. I am sure a more expensive amp will stitch a larger soundstage and more precise locations of the instruments. But to hear Lepai doing that was heartening. At 4:49, I could sense the artist in my mind smiling and nodding. That was the kind of recall the Lepai was able to bring. The Guitar twangs were clearly audible, and the sound of the ghungroo was as pleasant as could be. Again, the drums could have been better, but that, I am sure is an issue with MP3. But the most important part of the song – the majestic vocals of Rahat was perfect.

Concerto for Sitar & Orchestra. Ravi Shankar and London Symphony Orchestra conducted by Andre Previn. Wave files. 633kbps, 44.1kHz
I can wax eloquent about this album, but let me give you a bit of history. Ravi Shankar was commissioned by the London Symphony Orchestra (LSO) in 1971 to compose a number that could have Indian instruments and the Western Symphony playing together. This was done after his experiments with Philip Glass and Yehudi Menuhin gained popularity. Unfortunately, RS knew little about Western Music. Even then, produced by Christopher Bishop, the album peaked at #6 in Billboards Classical LP’s chart in 1972.

The four movements are powered by Ravi Shankar introducing the ragas Khamaj, Sindhi Bahairavi, Adana, and Man Khamaj with the LSO both accompanying him, and at times, taking over in a crescendo of bongos, brass and strings. This is roughly 40 minutes of sheer bliss. The four movements take on a different shape as Previn brings energy and rhythm to the numbers. Sometimes Andre’s and LSO’s presence become so strong that RS quietly moves to the background. At places where the woodwinds and strings first repeat the sitar’s movements and later take over, it is as of you are waiting for them to do so.

Some 10 odd years later in 1981, Ravi Shankar collaborated with Jose Luis Greco and Zubin Mehta to bring a different version of the concert. Called ‘Raga Mala’, the concert had Mehta’s typical large presence. Instead of starting with the alap as is common with Hindustani music, Mehta jumps in with orchestral thunder and goes on to pile 21 different Ragas with dazzling notes from trumpet, clarinet, cello, and harp. Ravi comes in nearly 2:22 minutes after the start of the number but joins in with energy and vitality that makes you nod with happiness.

The teasing interplay between the sitar and trumpet is even more pronounced with Mehta leading the London Philharmonic Orchestra. The interaction between these two instruments is so perfect you would think they are made for each other.

To properly hear these numbers, I switched on the AC, waited for 30 odd minutes, switched off the AC and then played the numbers.

I increased the Lepai’s volume to roughly 12 ‘o'clock position to get the soundstage I desired. This is not an issue with the amp as I know the recordings have very low gain. I did not want to push the iPod to full volume but kept it at 75%. I reckon I must have been pumping some 45-50 watts per channel to the speakers. At that position, the Lepai rendered both numbers with a precision that gladdened my heart. The trumpets moved forward and backwards on the stage and the position of Shankar’s sitar was dead centre. The tiny cymbals were audible coming from the back of the stage on the left. Usually, the roll of drums gets muffled as one large sound, but here I could visualize the sticks hitting the drums. The strings were soothing instead of being harsh. What I liked most was the clarity with which the amp rendered the low octaves of Shankar’s Sitar. I was able to hear the vibration of the Sitar’s string even at very low octaves, something that Shankar renders beautifully in these albums.

In the beginning, there is absolute silence when a cello starts the album with gentle pulls on the strings. Then the violins take over in crescendos that are joined by trumpets and drums. The Lepai placed the cello far to the left and below the speakers. Yes, below the speakers. That was the kind of soundstage rendering that the Lepai is capable of.

The Very Best of Jim Reeves. Jim Reeves. Sony Music. Wave Files 16/44.
Though Jim Reeves is more popular with Christmas songs, he has sung many romantic songs between 1960 and 1972. Gaining popularity with ‘He Will Have to Go’, Jim sang several songs you can listen to many times including, ‘Distant Drums’, ‘Roses Are Red’, ‘I love You Because’, ‘Bimbo’.

The Lepai played Jim’s songs with a dark background that made you enjoy Jim’s unique voice. When Jim hums or croons, there is just no vibration in his throat. This is something I realized when I was listening to Distant Drums through the Lepai. And the drums were actually far away. Again Lepai rendered depth that I never expected it to.

Hotel California 24/192. Eagles. Asylum/Warner Music Group. Wave Files 24/192.
What can I say about this album? If you are a music lover and haven't heard this song several times, you have wasted your life.

With the Lepai, the first 50 seconds of introduction was sheer bliss. The guitars seemed to tease you and tell you, ‘just wait till the main song starts’. The introduction of the drums in the last few seconds seemed to herald the arrival of Don Henley’s voice.

Around 3:53 when Don sings, ‘they still can’t kill the beast’, the immediate roll of drums was simply superb.

The last two odd minutes was a sublime mixture of guitar, drums, cymbals and other instruments. With the Lepai, the high pitches of the guitar as well as the cymbals stopped short of hurting your ears and added to the magic of the song.

Take Five. The Dave Brubeck Quartet – Time Out. Columbia Records. Wave Files. 96/1504
A long time ago when I visited the US, a client of mine gifted me this album as a CD. Till today it has been one of my most cherished albums along with an expensive Jazz At The Pawnshop that I paid through my nose to get. I have multiple digital copies of this album, and this particular version has been extracted at 96kHz and 1504 kbps.

Though nearly 5:26 long, I am always left with a sad feeling as to why the song could not have been longer.

As the trumpet plays in the beginning, with the Lepai, you can actually hear the ‘air’ that audiophiles so crave for.

Around 2:20, the drums take over with a gentle background note repeated on the piano. I increased the volume to 12 ‘o'clock position to understand if the Lepai could handle the drums properly. Oh, boy, did it? It threw the sound of drums into my face with aplomb clearly separating the various notes and playing the roll of the drum sticks.

Other Notes and Conclusion
The Lepai is certainly worth the trouble I took to get it. It seems to marry extremely well with the Aperion speakers. My wife and I have been using it regularly for nearly a year now, listening to all kinds of music. We have subscribed to both Amazon Prime as well as Gaana. I have a large collection of FLAC and other files that I have ripped.

Lepai’s Bluetooth works quite well. It, of course, prefers to be paired with an aptX capable Bluetooth signal but handles 4.0 and other versions quite well. Just remember not to transmit more than one BT signal at a time. When you are using one device, you must remember to disconnect all other devices.

After prolonged playing, the Lepai unit does feel warm to the touch. But that is nothing to worry about. I have played it for up to 5 hours at a stretch, using it to play music in the background as I work.

Paired with the right speakers, the Lepai LP1601 amplifier is a worthwhile addition to any music lover’s music room. Just remember to use a 32-36 volts external power supply and you will be rewarded with wonderful music for hours together without any ear fatigue. The Lepai is not worried about the genre of the music you throw at it. Hindi or Tamil film music, slokas, jazz, serious rock, even classical numbers – it handles all of them with ease creating the soundstage required. It is, in my opinion, quite transparent and does not add any of its own twists to the music. And that, for a sub 100$ amp, is a great achievement.

Addendum
The Lepai 1601 and Aperion Audio speakers have been steadily improving the sound they deliver. Whatever I play, the sound is pleasant, and just right. The sound stage is good and the voices and instruments placed correctly. Most important, I can use the system for hours together without worrying about electricity and other costs.

I have, in the recent past, assembled a player consisting of a Raspberry Pi 3B, an Allo Boss DAC, and an Allo Isolator. Connected to the LP1601, the sound is just perfect. The sound stage is larger, the voices and drums tighter, and the background absolutely black. The Allo Isolator is critical in killing all noises between the RPi and Allo Boss DAC. I will write a review of this later.

All told, I spent 100$ on the LP1601, and roughly another 100$ on the player. For roughly 200$ I have an audio system that can seriously challenge any system costing 5 times or more.

Equipment Used
  • Amplifier: Lepai 1601 from Parts Express. Roughly US$100. (https://www.parts-express.com/lepai...fier-with-bluetooth-and-power-supply--310-303). External 32V, 3.0A.
  • Speakers: Aperion Audio Intimus 532 LR Bookshelf speakers. Only newer models are available now. (https://www.aperionaudio.com)
  • Speaker Cables: Val den Hul’s Tvvin.
  • Players (1): iPod 5th Generation, iPad Air
  • Players (2): Raspberry Pi 3B with 1 GB RAM, Allo Boss DAC v1.2, Allo Isolator v1.2, 5V 2A external power adaptors. (https://www.fabtolab.com).
  • Connector Cables: (1) Acoustic Research Performance Series audio cable. (2) Custom made audio cable using Belden cable and Neutrik connectors.
  • Sources: Ripped files of various types including FLAC, Wave, M4A, ALAC, and MP3.
The System.jpg

LP1601S_Front.jpg

LP1601S_Back.jpg
 
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Analogous

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Hi Venkatcr, I Loved reading this description of the system you have put together and the impressions from your listening sessions.
Though it sounds counterintuitive I love the fact that you achieved high quality audio (for near field listening?) on a budget.

Congratulations! Looking forward to your review of the setup with the Raspi and Allo DAC+isolator soon.
 

ssf

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Their most famous amp is the TP-60 that outputs 80 watts per channel.

I have a Topping TP-60. Nothing to complain about it except that it is nowhere near 80 W per channel. Probably at around 30 W to 35 W. It's given rating is at 10% THD and probably at 4 Ohms. I had it's amp specs somewhere. Cant find it now. But I don't have any complaints on the way it sounds. Drives my Quad S2 to my listening levels of around 75 to 80 DB without any effort.
 
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venkatcr

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In the recent past, Topping have earned a name for themselves with their DACs - in particular, the D30s, and D50s. I plan to get the D50s ASAP.
 

Nitin K

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Thanks Venkat, very well written, informative and practical. Class D amps have picked up the momentum with big companies implementing them. Also works favourably for our weather.
 

superczar

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To second Venkat's observations with a Lepai
While I have never really done so extensive a test, I can also attest that at moderate to low listening volumes, I find the output from a 500gm SMSL SA98 virtually indistinguishable from a 17 kg Marantz Integrated
The former has a bit of white noise if you hold your ears close to the tweeter but that's about it
 

MaSh

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Wow, what a description. Its like listening to the song itself while reading.

MaSh
 

captrajesh

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HFV originally had a limit of 20K character per thread. When I requested, Anil increased that to 40K. My article has nearly 45K characters!!
I think you were meaning one post. I'm thinking of merging the two threads so that it becomes one contiguous narrative.
 
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venkatcr

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Thanks Arj and captrajesh.

To second Venkat's observations with a Lepai
While I have never really done so extensive a test, I can also attest that at moderate to low listening volumes, I find the output from a 500gm SMSL SA98 virtually indistinguishable from a 17 kg Marantz Integrated
The former has a bit of white noise if you hold your ears close to the tweeter but that's about it
You got me worried as both the SMSL and Lepai use the same TDA7498 IC. I rushed down, switched on the Lepai, disconnected all inputs and moved the volume pot to 1 'o' clock position. Fortunately I did not hear any noise whatsoever.

One thing you can do is to give as much space between the amp, it's power unit, and other electronics. These units may not have high isolation and could pick up EMI from elsewhere. I have kept the Lepai at full length of the power cord cable.
 

sound and music

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Nice review, Venkat.

I am currently using two Class D amps based on Texas Instruments chips (3255 and 3251). I am highly impressed by their sound quality and overall price-performance ratio.

Before buying these amps, I was a bit hesitant to venture into Class D amps as my previous experience with Tripath chips was not good. But these TI chip-based Class D amps are a class apart - in sound quality as well as power. From now on, my first preference would be Class D amps and particularly those based on TI chips.
 

superczar

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You got me worried as both the SMSL and Lepai use the same TDA7498 IC. I rushed down, switched on the Lepai, disconnected all inputs and moved the volume pot to 1 'o' clock position. Fortunately I did not hear any noise whatsoever.

One thing you can do is to give as much space between the amp, it's power unit, and other electronics. These units may not have high isolation and could pick up EMI from elsewhere. I have kept the Lepai at full length of the power cord cable.
Don't think it's EMI. I mucked around for a few hours with multiple PSUs , sources and even (incorrectly) started checking for possible ground loops.
It's not a hum or noise really - more of a faint hiss that can only be heard if you have the ears right next to the tweeters which is absolutely non audible even in a completely quiet room once you are sitting even a feet or so away.

In either case, the interesting fact (ok, let me call it my subjective observation lest someone take offense ) is that device A cost less than 5% of the device B...
Yet delivers 90% or more in performance!
That alone says lots about the capabilities of the TDA7498 and other low cost class D boards (have a similar experience with a TAS5630 board from parts-express)

Fun fact: The auto switching plug that I had to buy for the Marantz AB amp alone cost more than the SMSL !
 

PCA

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Thank you very much Venkatcr for a fabulous post!

I would like to clear up one confusion that i have.

The section titled 'Lepai - My Final Choice' suggests that the amp finally chosen was LP7498E. I was able to find images of that amp at below two links:



However, 'Other Notes and Conclusion' and subsequent sections and the photographs posted suggest that the amp bought and used is LP1601S

Are LP7498E and LP1601S identical, except for the cosmetics and nomenclature?

Thanks
 

venkatcr

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The product is manufactured by HK based company - Lepai. That company used to call it LP7498E. The same product is sold worldwide by Parts Express and they have named is LP1601S. They are both one and the same.

Today you can only get it from Parts Express. Nowhere else.
 

PCA

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The product is manufactured by HK based company - Lepai. That company used to call it LP7498E. The same product is sold worldwide by Parts Express and they have named is LP1601S. They are both one and the same.

Today you can only get it from Parts Express. Nowhere else.

Thank you for clarifying that. Seems a good option to consider for driving recently acquired Pioneer SP-FS52 floorstanders (6 ohm speaker; max input power 130 watts).
 
The Marantz PM7000N offers big, spacious and insightful sound, class-leading clarity and a solid streaming platform in a award winning package.
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