Lepai T-Amp with TA2020

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panda360

panda360

Member
Joined 2009
MikeHunt79 said:

code: 233-5134 ?.44 ELC coil inductor,10uH 2.3A

Col found it, so credit goes to him.

The same manufacturer does produce a 3A (I think) inductor also, which should also be stocked by RS. I can't look it up tho as the RS site appears to be down! :(

The 3A inductors do have a larger diameter, so I'm not sure if they'd fit the Lepai, but it may be worth a go. :)
Click to expand...

Mike,

Today, I try to find toroids. I can find 10uH, 2A and 20uH, 3A only .

Accordingly official specification should use 10uH, 3A., which toroid is more suitable for this amp.
 
MikeHunt79

MikeHunt79

Member
Joined 2003
I've just added some 2.2uF film caps, I'll post pics in a bit.
panda360 said:


Mike,

Today, I try to find toroids. I can find 10uH, 2A and 20uH, 3A only .

Accordingly official specification should use 10uH, 3A., which toroid is more suitable for this amp.
Click to expand...
I'm using a 10uH 2A inductor, not a toroid, but it sounds good to me and is better than the original.

I'd go for the 10uF 2A toroid. :)
 
MikeHunt79

MikeHunt79

Member
Joined 2003
magixz said:
i worked out the opamp and power circuit for the Lepai amps...
I have a few... all running the same opamp and similar tone control (Only resistors different for different chip's input impedance)
Any software which can sketch it out?

Realised the opamps are there just to create a low impedance output to the tone controls so it will not affect tone control. (correct me if i am wrong)

There are 3 sets of signal coupling caps.
They are are
(1) 2x 10uf after volume pot before op amp,
(2) 2x 10uf after op amp to tone control,
(3) 2x 10uf or 1uf after tone control to chip.

Set 1 removed DC before Opamp, but another circuit adds in DC again.
Set 2 remove DC before tone control.
Set 3 remove DC before the Amp

They are all labeled as 2.2uf on the board.
Shouldn't we change the (3rd) set just before the chip instead of the one before the op amp?
Click to expand...
This is pretty much I have just done today:
An externally hosted image should be here but it was not working when we last tested it.


The 2 blue caps on the left are 2.2uF film caps, and they are wired to the holes in the PCB where the "(3) 2x 10uf or 1uf after tone control to chip. " caps go.

The extra wires and switch allow me to bypass the tone control altogether which is useful for me at least.

I would be interested to see some sort of sketch of how the tone controls work, have you tried eagle at all?

http://www.cadsoftusa.com/
http://en.wikipedia.org/wiki/Eagle_(program)

The free version is all you need, with few restrictions for small circuits like the Lepai. ;)

I was thinking the tone controls could be modified into some sort of crossover, making 2 of these amps ideal for a pair of bi-amped 2-way speakers.
 
M

msj965

Member
Joined 2009
Hello:)

Hi There!
Just wanna ask a big big favor to all of you guys (as a newbie) .Pls. can you check this part number for me?not sure what toroid to use.On the web site of DIGIKEY.com search on this part number m9981- nd and 732 - 1416 - nd, let me know so i can buy it here.
Thanks much,
Ann
 
Calamaro

Calamaro

Member
Joined 2008
Inductors for output filters

Tripath definitely suggests toroidal inductors with iron-powder cores as shielded bobbin construction is not as effective for EMI containment.
Powdered iron is regarded to have an higher Q and in our case this is a premium.

www.osoelectronics.com/downloads/Winding and Using Toroids.pdf

For the smallest toroid suggested by Tripath, Micrometals code is T60-2. This is the toroid provided by 41Hz.com with their kits and require 39 turns of 0.5mm magnet wire.

(A bigger one -with better specs- could be "T68-2 wound with 44 turns of 22AWG wire" according to Tripath technical informations).

As in our case space also is a premium and bobbin inductors are easier to find, we're looking for a good compromise.

Anyway, we need
  • 10mH
  • 3A
  • frequency higher than 1 MHZ
  • coil with high Q and
  • low saturation at high frequency

Unfortunately I haven't a proper meter but it seems to me that the following one could works well.
Any suggestions?

http://cgi.ebay.it/10UH-Medium-curr...4275e99b&_trksid=p3286.c0.m14&_trkparms=65:12|66%3A2|39%3A1|72%3A1229|240%3A1318|301%3A0|293%3A1|294%3A50
 
col

col

Member
Joined 2008
minirig.org.au
Calamaro,
Unfortunately I haven't a proper meter but it seems to me that the following one could works well. Any suggestions?
Click to expand...

That looks like it would do the trick. At 24mm it would be very close to the top of the case though. You would have to be careful with insulation. otherwise the inductor might arc against the case body. I still think that the 41hz amp6 toroids are the best value. Only problem is winding them, which isn't that hard but is time consuming.

col.
 
F

fabioadriano

Member
Joined 2007
Calamaro said:
Plenty on Ebay.
This one includes power supply (mine were 2.5A). I bought three from him.
http://cgi.ebay.it/Lepai-TA2020-Cla...ab4face&_trksid=p4634.c0.m14.l1262&_trkparms=|301%3A1|293%3A1|294%3A30
Click to expand...


Hi Calamaro, great combination ... i also ordered one of these from Techex in ebay ... (and this will arrive in Italy .. (:):) ).
But i have simple questions :

1st : thank you & diyaudio for your info about modify this amp !

2nd : i normally ordered components from dealextreme (do you know ? great !), but this solder communicate you ALL : e.g :

1) hy boy, we received your payment and now we are preparing all
2) after some days: hy boy we sent your order to Hong Kong
3) the last passage : hy boy , today your pack is envoyed by air mail and it will arrive to your home .....

that's all ! i think this way to buy directly from China in great !

BUT i dont know in what way Techex respect all these think ... so i ask you (and also to other people that know !) some info !

Thank you for your assistance, a risentirci !

FS
 
MikeHunt79

MikeHunt79

Member
Joined 2003
I really wanted to implement overshoot diodes on mine, as I'm planning to use it in the car with 14.4v input and running 4 ohm speakers, basically worst case scenario for this amp. :hot:

After killing a TA2020 IC a while back I figured this would be a worthwhile mod (along with overcurrent protection by removing zener).

I made a start today, and I should be able to finished it tomorrow, but I was wondering will this work ok? I'm implementing it in the same was as schematic on the TA2020 datasheet...

I've only done one channel so far:
An externally hosted image should be here but it was not working when we last tested it.


The diodes do not touch the bottom of the case, I may add a little hot glue once finished tho to be on the safe side.

:smash:

I was thinking about using the spare holes holes on the bottom left to do this until I realised the tracks are after the 10uH diodes...
 
M

magixz

Member
Joined 2009
Got my Lepai LP-2020 in a brilliant Anodised RED...
I love it... :)
Got to study the circuit before modding...

Tried with my "Arjen modded" Topping TP20 with quality components,
there was some distortion with the Lepai and the clarity is not there...

I'll change the op-amp first...
I have the NE5532, TL072C and JRC4456AD to try out with...

So far, I like the TL720P for low noise and High input impedence...
Can refer to this page for more op amp info...
http://www.dself.dsl.pipex.com/ampins/webbop/opamp.htm
 
col

col

Member
Joined 2008
minirig.org.au
Haha, that's the thing, I won't really know if it works or not... I guess if I get no sound after the mod then I know something weird is going on...
Click to expand...

Mike, looking at your photo I think your soldering them to the wrong place? THe undershoot diodes go to gnd. The overshoot diodes go back to the pins on the chip (pin 25 and pin 22).

Tried with my "Arjen modded" Topping TP20 with quality components, there was some distortion with the Lepai and the clarity is not there...
Click to expand...

magixz, I think changing the opamp is the least effective mod you can do. if you want to reduce noise start with changing the resistors, change them all for 1% metal film. Then the pots and caps.

col.
 
MikeHunt79

MikeHunt79

Member
Joined 2003
col said:


Mike, looking at your photo I think your soldering them to the wrong place? THe undershoot diodes go to gnd. The overshoot diodes go back to the pins on the chip (pin 25 and pin 22).
Click to expand...
Well, I was hoping I hadn't soldered them in the wrong place, so I'm glad I posted a pic now. :)

On the pics I posted above, VDD is on the left, and the points I have soldered to on the right go back to the pins 21 and 23. I didn't want to solder directly to the pins as it's very tight around that area.

Now I've only got to do the other two pins:
An externally hosted image should be here but it was not working when we last tested it.
 
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