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DizRotus

chip amps: Almost everything you ever wanted to know

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For $20.49 from Amazon I couldn't resist trying this 20 Watt/channel Chinese T-Class chip amp. Lepai claims 20W x 2 RMS, 20Hz - 20KHz, THD less than 0.4%.

How does it sound? Worth every penny.

I hooked it up to the new single driver speakers and sourced it from a Toshiba DVD/CD player and Pandora via Android phone using Bluetooth and a Logitech Bluetooth adapter.

The sound is not bad . . . not great . . . but not bad. The vintage h/k 730 (in need of refurbishing) sounds better. To my ears, the toy amp is bright or shrill. Using the defeatable tone controls helped.

With a 12V power supply, it could be powered in a car. With the Logitech adapter and some small speakers it turns any smart phone, iPod, etc. into a stereo. Dorm room stereo? It's hard to fault 20 watts for 20 bucks.

I'll be taking it to the high school when I repair the Speakon plug on the school's La Scalas. I 'm curious to see how it sounds through those speakers.

EDIT 6/26/13 @ 9:15 EDT

Same unit available from Parts Express. Glowing reviews at PE site.

Edited by DizRotus

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Here is the owner's manual. It came inside a cookie.

The best part of the amp might be the blue light around the volume knob.

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The $1/watt amp plays a pair of the single driver speakers I just built to a very loud level. The bass is surprisingly good. The treble seemed a bit harsh. Perhaps they'll improve after some time.

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Very cool little amp! It sounds like at a $1/watt...a great deal: thank for sharing the experience.

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The frequency response of a T-amp will track the impedance of the loudspeaker. So, if the impedance of that driver climbs with frequency, and it undoubtedly does - the sound will be tipped up. Also, they normally rate those at four ohms, so with an 8 ohm speaker you have 10 watts, and I think that might even be overstating things a bit - they seem to go into clipping pretty quick. I powered my Jubilees with a $100 version of one of these (Super-T) and as long as I watched the volume I thought it sounded better than a lot of high dollar stuff I'd heard.

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Dean-

I've got 2 pair of the 8 ohm single drivers. If I hook up 2/channel in parallel, it might sound better.

The tendency to sound harsh gets worse at higher volume. Your comment about early clipping seems on point.

How do you think it will do with the djk BR modded La Scalas at the high school?

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As shown in the photo, I powered all four single driver BR speakers with two 8 ohm speakers in parallel on each channel for a nominal 4 ohm load. The tendency to stridency in the high frequencies seemed to disappear. The results are consistent with Dean's comments.

The reviews for this amp on the Parts Express site are extremely favorable. On the basis of value, it's hard to fault this little amp.

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Interesting review of that little amp. I've been impressed with the T-amps that I've owned. I have not tried one that inexpensive yet. Might be good for a little desktop setup for my kids. Get them away from the tiny speakers in their iPods!

I think I'll grab one this week and open her up. See what their using in there.

Thanks for the review.

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Interesting review of that little amp. I've been impressed with the T-amps that I've owned. I have not tried one that inexpensive yet. Might be good for a little desktop setup for my kids. Get them away from the tiny speakers in their iPods!

I think I'll grab one this week and open her up. See what their using in there.

Thanks for the review.

Dale-

You did notice the reference to the h/k 730 in need of refurbishing. As soon as the SCA-35 is back the h/k 730 is headed your way.

I'm eager to get your reaction to the Lepai's sound and contents. It's a better bargain from Amazon, especially if you're eligible for free shipping.

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Yup, I saw that. I have all the parts in now for your SCA-35. Hope to start this weekend, but have been under the weather a bit. Cold, fever etc...

I ordered the amp, $20.67 with free two day shipping. I'll post my impressions here. I'll set it up in my shop so I can listen to it while I work on gear.

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Not to be overly negative, but I'm not impressed. Maybe I have a bad unit. I hooked this up to my Wharfdale W-35's and played a few CD's. First thing I noticed is how short the power cord is, second a turn on and turn off thump. Well more of a whoosh.

The sound is much brighter than my Sansui 3500 that I typically listen to on the bench. Bright to the point of being a bit harsh. I noticed a loss in bass but a few peaks that I would place at 80 Hz and 400Hz. So the begining of the midrange is farther forward that I prefer.

I could tame the harshness with the tone controls and get the bass a bit tighter by backing that off too. However, something just sounds odd. Sounds to my ears like when a driver is out of phase.

My test will be to set this up at my desk with a set of Minimus 7s. I listen to the 7s everyday, so should be easy to compare amps. I will need to open this unit up before I put it on one of my "better" rigs due to the turn on, turn off noise.

Please keep in mind this is just my opinion. Nothing more or less. I've owned at least a half dozen t-amps and am used to their signature. This is a decent amp at a great price! You can spend much more and get much less.

I'll try to get some shots of the inside tonight.

Dale

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Thanks Colin. Have done quite a bit of listening with the Trends and thought the sound was very good.

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The Lepai amp is now powering my nearly finished Bluetooth "iPod" dock on steroids (see thread of same subject).

On that unit, the amp still has a tendency to stridency also noted by Dale. Perhaps some tinkering can improve that. Nonetheless, it works well in the portable system to allow music from a phone in outdoor settings.

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I took the "iPod" dock on steroids and used the Lepai to play the school's bass modded La Scalas. It was amazing how well that tiny chip amp played those speakers.

It's almost done. The painting will have to wait until I return from a memorial service for a fallen college friend at Craig Lake in MIchigan's Upper Peninsula. A group, including 3 of his 4 sons, is gathering to spread his ashes (probably illegal, but the ring leader works for the Governor).

With a 12 volt battery, we'll be able to add some appropriate music to the event. Music was important to Jack. I don't think he'll mind the unfinished MDF.

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I wish I would have seen this sooner...

I did a pretty involved project with these amps a couple of years ago..

Basically here is the skinny:

1) You need at least a 1amp capable power supply

2) The power supply cap is a joke... I replaced it with a 10,000uf cap (had to wire outside the case). This dramatically improved the available power for bass... prior to this there was hardly any.

3) Change the input coupling caps - I went with vintage PIO military caps.

4) Change the output inductors to quality toroidal models...

5) Bypass the internal trebel and bass controls - which also bypass the input stage op-amps, which also stops the power-on thump..

6) Pull all associated, no-longer needed, componentry.

I did a couple of youtube vids on mine... I'll see if I can find the posts that discuss all the required values for the caps and inductors.

Here are my youtube vids... Sorry they are old and dark, I'll see about taking some pics...

I was powering a pair of La Scala's with them and could blow you out of the room with little effort.

This second video goes through the majority of the mods:

http://www.youtube.com/watch?v=QTZJeVKlh3w

And this was the first video when I had only modified the input caps and power supply cap I believe:

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Sounds outstanding, Escher!

A series of captioned pix here would be wonderful. Sounds like a great little project with a lot of potential for minimum bucks.

Dave

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I too would be interested in following along on this.

I three would be interested . . .

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Ok... Here are the mods with some pics..

First, The power mods:

One thing I dont have a pic of is bypassing the power switch... simply run a heavy gauge wire from the in to the out where the current power switch attaches...

Posted Image

Lepai mods by Christopher Purdy, on Flickr

Replace C1 with a much higher value cap - I used a 63V 10,000uF

Replace L1 with a toriodal high amp inductor - See my vids for which I used - I cant remember...

Next - The Input Cap / Tone / Volume circuit / Power-on Thump Fix

Posted Image

Lepai mods by Christopher Purdy, on Flickr

Bypass C20 and C21 as shown using 2.2uF (double check this on the existing caps) audio quality caps

Re-Connect to Surface mount locations below:

Posted Image

Lepai mods by Christopher Purdy, on Flickr

Attach to rear most side of C30 and C31 (Side nearest the back of the amp).

Your lead from C20 should go to one side of a 2.2uF cap. The other end of the cap connects to C31. They are both on the left.

Correspondingly, the lead from C21 then goes to the other 2.2uF cap, which then goes to C30. They both are on the right

I used jumper wire to give myself more room.

Next, Remove the tone controls, the bypass, and the volume control:

Posted Image

Lepai mods by Christopher Purdy, on Flickr

Now remove Op-Amps U1 and U2 as they have been bypassed and are needlessly drawing operating current.

Posted Image

Lepai mods by Christopher Purdy, on Flickr

Now for your Output Inductors:

Posted Image

Lepai mods by Christopher Purdy, on Flickr

Replace L2, L3, L4 and L5 with the same value toroidal inductor as used in the PSU mod. Once again - I cant remember the value so check my other videos.

And thats it - All this info came from a forum post on DIYAudio.com here:

http://www.diyaudio.com/forums/class-d/90500-lepai-t-amp-ta2020-91.html

That should put you at page 91 or so, its a huge thread that goes into every aspect of the Tripath chips and their design... Its where I got all my info... I dont claim to have the knowledge - those folks are awesome..

Ohh and one final thing - I didnt use a 1A power brick, I used a 5A brick.. 1A wasnt enough juice... So - make sure you get a 5A brick... sorry for the confusion.

And - I have to say it - If you dont have the soldering skills, dont try this... you can easily kill your amp. Perform the mods at your own risk, no warranties, blah blah.... you get the picture... Go slow and do a little at a time and its a great project - I've done two now..

- Chris

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