Budget T-Amp Shootout - Lepai vs. Indeed TA2020

[ernperkins]

With the limited power of these amps, I'm not sure the tone controls on the Lepai are a benefit, especially with the remarks made about the tone controls on the Lepai. Do we have an MSRP with S&H of the Indeed as a comparision to the Lepai w/PS cap mods? I have an old ATX 'puter supply (like 9 amp @12 volts) to push either one that's collecting dust. A modest (+1.8 volt?) over the rated "12 volt" input would be helpful to those who might plan to use them in a car/truck/boat (nominal 13.8 volts of a charged lead-acid battery).

I tried my Lepai with a 13.8 VDC, 3 Amp Radio Shack power supply and it didn't work. IIRC the Lepai has an overly protective overvoltage protection circuit that ties to the chip's fault line. With 13.8 VDC the unit will light up, but not work. I ended up getting a 12 VDC, 5 Amp PS. YMMV.

Regards,
Ed

[bkeane1259]

Thanks for the info. I am just barely aware of RMAA. I've never used it before, but I'd be willing to give it a whirl. Once I get the modded Lepai from XR, I will have 3 amps to test. Maybe we'll get some interesting data.

Correct me if I'm wrong, but I will need a dividing network between the amp's speaker outputs and the line-in on my sound card, right? I'm not going to be able to do measurements of the amplifier at a decent (high) volume level without something to limit the voltage going into my sound card.

I also don't want to destroy my Asus Xonar STX.

Can you briefly explain the setup for measuring an amplifier with RMAA? I have all sorts of values of resistors on hand and I have a good 8-ohm dummy load that can handle a crapload of power. In the meantime, I will try to do some research myself.....just don't want to blow anything up. The wife doesn't think it's cute when my projects involve fire, smoke, etc.

[lhwidget]

Hey Bryan,
I used the same divider network I use with SoundEasy for impedemce curve captures; A pair of 1/2W resistors, 22kΩ from + speaker lead to ground, and 47 kΩ in series in the + speaker lead, then on to the sound card input channel.

RMAA is really easy. Run a loop-back test on your sound card first. Just plug the sound card's line outs into its line inputs, set the test levels, then run the test. RMAA will do the test automatically, and generate all the test graphs.

For the amp test, plug the sound card's line outs into the amp, and the voltage divider outputs into the sound card's line inputs.

Since RMAA uses a stereo loop-back test, there is no provision for a reference signal (other than the original internally generated test signals) to seperate the sound card's characteristics from the amp's, its response and distortion will be included on top of the amp's determined specs since they're in series.

Any 10W 4Ω or 8Ω resistor should be fine for a load. Also, I'd test them with speakers for loads. I think it was Pete Schumacher who noticed some very strange freq response characteristics from some sort of class D amp when it was presented with reactive loads.

[smokarz]

i ordered the lepai, but cancelled so i am going to buy the indeed.

what power supply would work with the indeed?

i have something that says 15v 1000ma. would that work?

thanks

[bkeane1259]

i ordered the lepai, but cancelled so i am going to buy the indeed.

what power supply would work with the indeed?

i have something that says 15v 1000ma. would that work?

thanks

NO !!!

DO NOT use a 15V PS on the Indeed or the Lepai. You could do irreversible damage.

This is ideally what you want -- A 12V 5A PS

Stick with 12V and up to 5A and you will be good.

[XtremeRevolution]

I should be able to get you an amp out tomorrow morning or early next week. I'll let you know when its out.

[smokarz]

NO !!!

DO NOT use a 15V PS on the Indeed or the Lepai. You could do irreversible damage.

This is ideally what you want -- A 12V 5A PS

Stick with 12V and up to 5A and you will be good.

sorry. typo.

12V 1000mA. i think it was a bose () PSU.

i am a cheapo, thinking of saving a few bucks if i don't have to buy a new PSU.

[Deward Hastings]

12V 1000mA.

Twelve Volt, One Amp, Twelve Watt. Total. Subtract from that idle power and you might have enough left to drive very high efficiency horn speakers, or headphones . . .

[smokarz]

Twelve Volt, One Amp, Twelve Watt. Total. Subtract from that idle power and you might have enough left to drive very high efficiency horn speakers, or headphones . . .

lol. thanks for the info. looks like a gotta pony up for a psu.

[vlad335]

lol. thanks for the info. looks like a gotta pony up for a psu.

Buy the listed ebay PSU. I just received another Lepai from PE today after bricking the first one. I just reconfirmed that the Ebay PSU is a significant upgrade from the Vonage 12v/2a PS included with the PE Lepai.

As an aside, while I was waiting for the Lepai to be back in stock. I bought a Topping TP21 to try out with my Overnight Sensations. Guess what, I think the Lepai sounds better. Especially with hard rock such as Chevelle and Tool.

[smokarz]

Buy the listed ebay PSU. I just received another Lepai from PE today after bricking the first one. I just reconfirmed that the Ebay PSU is a significant upgrade from the Vonage 12v/2a PS included with the PE Lepai.

As an aside, while I was waiting for the Lepai to be back in stock. I bought a Topping TP21 to try out with my Overnight Sensations. Guess what, I think the Lepai sounds better. Especially with hard rock such as Chevelle and Tool.

so the Lepai with the 5A PSU is a significant upgrade?

[bkeane1259]

so the Lepai with the 5A PSU is a significant upgrade?

You will notice a marked difference in power output with the 5A as opposed to the 2A that ships with the Lepai. That's not to say that the TOTAL output won't distort and send the amp into clipping at very high volumes.

One thing I noticed in my comparison between the Lepai and the Indeed, was that at high volume, even MAX volume, the Indeed sounded very clean. I used 5A power supplies when testing both units.

[bkeane1259]

I should be able to get you an amp out tomorrow morning or early next week. I'll let you know when its out.

No rush bud. Wait till after New Year's...nothing is shipping till Tuesday anyway.

[bkeane1259]

For the amp test, plug the sound card's line outs into the amp, and the voltage divider outputs into the sound card's line inputs.

Ok so if I'm understanding correctly, I will have speakers connected (to introduce a proper variable load), then I will jumper from the speaker terminals back to the sound card input, but I will insert the dividing network at that point (so I don't fry my sound card).

I understand the whole part about calibrating the sound card, etc., and testing line-out devices with RMAA. I read up on it, and it seems very easy.

I couldn't find anything on their site about testing amplifiers though. I appreciate your help. i will give it a try later next week, but most likely next weekend.

I will probably post a couple pics of the setup before I do the actual testing just to be sure I have the proper wiring in place. Thanks.

[jonpike]

I'd measure the output with a voltmeter first, to see if there's DC there. Some of these switching amps have the speaker outputs floating half way between the DC supply rail and ground. The Sonic T-amp was like this, as I recall.

You'd want to avoid putting 6VDC into your sound card input, even thru a large resistor.

And, while measuring with your meter, check the power supply you use, the '2020 chip really doesn't like voltages above spec. (think it's rated at 13.8 max?) I set my wife's office system up with a brick that unloaded went to 14.2-14.4V... the T-amp only lasted a week before dying. You will get a few watts more if you go above 12.0, but be sure you don't go much higher. I was able to mod one of the PE variable supplies right where I wanted it. A little low on the current though..

[lhwidget]

Ok so if I'm understanding correctly, I will have speakers connected (to introduce a proper variable load), then I will jumper from the speaker terminals back to the sound card input, but I will insert the dividing network at that point (so I don't fry my sound card).

I understand the whole part about calibrating the sound card, etc., and testing line-out devices with RMAA. I read up on it, and it seems very easy.

I couldn't find anything on their site about testing amplifiers though. I appreciate your help. i will give it a try later next week, but most likely next weekend.

I will probably post a couple pics of the setup before I do the actual testing just to be sure I have the proper wiring in place. Thanks.

I just realized something, if the outputs of the amp consist of bridged chip outputs, there won't be a "ground" connection for the speaker (the - speaker lead isn't connected to ground, it "floats" with the opposite output of the second power amp chip).

If this is the case, I don't think you can connect the bridged amp to the sound card inputs. The problem is that the negative speaker connections will be connected to each other at the sound cards input grounds. I'm pretty sure this will damage the bridged amp.

If the amps aren't bridged, it's no problem. The easiest way to check if the amps are using bridged modules would be to check the resistance between the speaker ground connections for the left and right speaker connections. If the resistance is 0 Ω, they aren't bridged. If there is anything over 0.1 Ω, I'd assume they are bridged.

Yep, you've got it right. As long as the 47 kΩ resistor are in series between the + speaker lead and the + sig input of the sound card, it won't hurt anything. It may not work very well, but it won't hurt anything.

jonpike, I hadn't thought about DC on the amp's outputs, but it's worth checking out. Typical offset values are about 0 to 10 mV. Some bad boys may show as much as 30 mV.

I wouldn't expect any problems here, the sound card's inputs probably aren't DC coupled either, but it is definitely worth checking out.


By the way Bryan, do you have a copy of SoundEasy?

[vlad335]

so the Lepai with the 5A PSU is a significant upgrade?

Compared to the 2A? Hell Yeah.

[bkeane1259]

By the way Bryan, do you have a copy of SoundEasy?

Nope.....I do not.

[lhwidget]

Just curious, it was what I used to check out my test amp after I built it.

[Bart Oetken]

I saw that tamp on ebay, looked like a nice little tamp. I was wondering what did it cost and did they send it free shipping with air mail out of hk?

I think the indeed is a nice amp, wish it had rca hook ups on the back, like the leipai.

One other thing can you tell a difference in between the amps in sound?

I love t-amps and I am always looking for a better amp the lei, for my outside bbq's and drinking sessions, etc.

Thanks

Bart