I don't think 7812 will handle the current. you need LM338T or equivalent.
Mine is adjustable and I have it set at 13.2v. I'm currently using a 18v 4.9A Compaq laptop supply to feed the reg but you could put anything from about 14v and up before it.
http://pix.minirig.org.au/main.php?g2_itemId=1054
col.
Mine is adjustable and I have it set at 13.2v. I'm currently using a 18v 4.9A Compaq laptop supply to feed the reg but you could put anything from about 14v and up before it.
http://pix.minirig.org.au/main.php?g2_itemId=1054
col.
Nice, that is a little more elegant than just soldering a 7812 in there!col said:
I was annoyed that mine was cutting out today, and a 7812 was all I had to hand. It was a LM340/LM7812 which has current limiting also, according to the datasheet, which isn't very good when the volume is turned up, but at least the amp isn't cutting out now, plus I've got the LM340 IC heatsinked.
I may try a LM338T, as I'd like to run this amp at 13v if I can, but I think the dropout voltage maybe a little high to achieve this when running 14.4v into the LM338T.
Another crude option I was thinking of is to simply have 2 x MBR745 diodes in seried with the power from the car. Each one is good for 7.5A and drops around 0.5v, so 2 in series should give me 13.4V in theory.
I was going to try bolting them to the case of the Lepai, as I thought it would make a nice heatsink... Electronically isolated tho. Any downsides to doing this?
The quality of these amps has been well debated, but i was wondering if anyone has tested how loud they go, and if they do the rated power of (apparently) 2x20watts?
I am looking into using one of these to power and a level project where i am going to build a couple of speaker enclosures into a TV stand type piece of furniture.
Cheers,
Mike
I am looking into using one of these to power and a level project where i am going to build a couple of speaker enclosures into a TV stand type piece of furniture.
Cheers,
Mike
Hi, I'm new on this forum, I've readed (with interest) all the topic, so i decided to buy a Lepai...
It's arrived! Good, it work well!
First of all I drawn the schematic:
http://img23.imageshack.us/img23/1586/scan10006k.jpg
(sorry if it's hand written, but I've no time to put in on CAD)
I hope that it's correct, the component value are of those installed.
On the input section I drawn only one channel, the second is the same.
Some annotation:
One thing that is very annoying to me is the pop noise on power-on, so i made a simple pop suppressor:
http://img188.imageshack.us/img188/2143/lepaipopsuppressor.jpg
The circuit keep the amplifier sleeping for about 2 seconds after power on.
I made the circuit on a small piece of veroboard. To connect it you have to isolate the SLEEP pin (is connected to ground) milling around the pin with something like a dreamel
Some photos:
http://img196.imageshack.us/img196/3552/dsc00586fcu.jpg
http://img189.imageshack.us/img189/373/dsc00587k.jpg
Now I have to wait the components to make other mods
See you to the next mod episode
Simone
It's arrived! Good, it work well!
First of all I drawn the schematic:
http://img23.imageshack.us/img23/1586/scan10006k.jpg
(sorry if it's hand written, but I've no time to put in on CAD)
I hope that it's correct, the component value are of those installed.
On the input section I drawn only one channel, the second is the same.
Some annotation:
The transistor circuit on the mute signal serves to mute the amplifier when the voltage exceed about 15V, is a protection? on the mute? dunno...
Some capacitor are missing on the right side of TA2020 (compared with datasheet), they are important enough (supply decoupling for H-bridge), so i planned to replace the 100u with a good 470u Panasonic and to put other 100n on the solder side.
The tone control is a Baxandall circuit, I'm curious so I simulated the frequency response:
http://img4.imageshack.us/img4/1995/lepaibaxandall.jpg
when I have a little bit of time to make some math I will find the right component value to make it more symmetric.
One thing that is very annoying to me is the pop noise on power-on, so i made a simple pop suppressor:
http://img188.imageshack.us/img188/2143/lepaipopsuppressor.jpg
The circuit keep the amplifier sleeping for about 2 seconds after power on.
I made the circuit on a small piece of veroboard. To connect it you have to isolate the SLEEP pin (is connected to ground) milling around the pin with something like a dreamel
Some photos:
http://img196.imageshack.us/img196/3552/dsc00586fcu.jpg
http://img189.imageshack.us/img189/373/dsc00587k.jpg
Now I have to wait the components to make other mods
See you to the next mod episode
Simone
djnemesi, nice work!
your simulated frequency response, was it made with the component values of the actual components used or the component values that are silk screened on the PCB? I have changed my tone control component values to the ones mentioned on the board and it made a big difference. If these values are wrong I would like to change them to the correct values. So yes, please report back once you have done the math.
Do you mean the capacitors across the pins 19-22 and 25-28 of the TA2020 data sheet? I noticed that the Lepai designer has made a short cut here and has connected the two pairs of pins together and supply's the pins via one 100uF cap. I have changed this to a 470uF. What pins do the other 100n decoupling caps go on?
I will study this mod and see if I can implement it on my Lepai. Also, will have a good look at your schematic. Do you know what the "not implemented" part is for, is it worth implementing?
Once again excellent work!
cheers,
col.
your simulated frequency response, was it made with the component values of the actual components used or the component values that are silk screened on the PCB? I have changed my tone control component values to the ones mentioned on the board and it made a big difference. If these values are wrong I would like to change them to the correct values. So yes, please report back once you have done the math.
Do you mean the capacitors across the pins 19-22 and 25-28 of the TA2020 data sheet? I noticed that the Lepai designer has made a short cut here and has connected the two pairs of pins together and supply's the pins via one 100uF cap. I have changed this to a 470uF. What pins do the other 100n decoupling caps go on?
I will study this mod and see if I can implement it on my Lepai. Also, will have a good look at your schematic. Do you know what the "not implemented" part is for, is it worth implementing?
Once again excellent work!
cheers,
col.
djnemesi, looking at your circuit diagram and comparing it with others on the net the Baxandall appears to be a "James" variation. There is some software available to simulate the values:
http://www.duncanamps.com/tsc/
col.
http://www.duncanamps.com/tsc/
col.
col said:
thanks!
the simulated frequency response is made with values of actual component, I have also tried with the silk screened value but the result are similar. Probably you changed the poor quality ceramic capacitor on the filter with better ones
Yes, exactly. I'm waiting for a 470u to arrive too. 100n capacitor are to be placed near pin 27,25,22
It seems a sort of DC offset adjust common to all output, I don't know if it works...
Yes, it can be a variation of variation, because we have an additional resistor (on the treble sliding contact). I've also tried that software, but the results are a bit different, I prefer to use Spice (LTspice) that is more reliable.
hello
Hi Djnemesi
Just wanna ask what is the outcome when you put the noise suppressor.Pls.can you specify what parts that you replaced and pls include the volts/watt too.sorry if I ask you all this things, coz I'm a begginer when it comes to electronic.
Still waiting for your new pixs!!!
Cheers,
msj
Hi Djnemesi
Just wanna ask what is the outcome when you put the noise suppressor.Pls.can you specify what parts that you replaced and pls include the volts/watt too.sorry if I ask you all this things, coz I'm a begginer when it comes to electronic.
Still waiting for your new pixs!!!
Cheers,
msj
damn! already burned!
TA2020 R.I.P.
I was using it with two 4 ohm speakers, trying to push the volume to the limit and....tuuuuk, from one channel come out a DC voltage and all are gone mute. I've done some test end I've found that the power supply (that should be 12V) was over 14V.
Measuring I found that an output of ta2020 is shorted to gnd.
Now I replace the ta2020 putting the overshoot diode
Hi! with the suppressor you hear nothing when you turn on the amplifier, after a couple of second you hear a very little tick and the sound come out. I used 1/4W resistor, but you can use what you prefer. The capacitor must be rated for a voltage greater than 5V (I found a 47u, 10V in my drawer)
TA2020 R.I.P.
I was using it with two 4 ohm speakers, trying to push the volume to the limit and....tuuuuk, from one channel come out a DC voltage and all are gone mute. I've done some test end I've found that the power supply (that should be 12V) was over 14V.
Measuring I found that an output of ta2020 is shorted to gnd.
Now I replace the ta2020 putting the overshoot diode
msj965 said:Hi Djnemesi
Just wanna ask what is the outcome when you put the noise suppressor.Pls.can you specify what parts that you replaced and pls include the volts/watt too.sorry if I ask you all this things, coz I'm a begginer when it comes to electronic.
Still waiting for your new pixs!!!
Cheers,
msj
Hi! with the suppressor you hear nothing when you turn on the amplifier, after a couple of second you hear a very little tick and the sound come out. I used 1/4W resistor, but you can use what you prefer. The capacitor must be rated for a voltage greater than 5V (I found a 47u, 10V in my drawer)
Is there any reason why the 1uF electrolytic connected to pins 27 and 29 has a 100V rating?
Can anyone suggest a suitable replacement as the stock one looks to be of very poor quality.... There are panasonic FC 1uf caps in 25 or 35V ratings I believe, but the 100V rating of the stock cap has me confused.
Can anyone suggest a suitable replacement as the stock one looks to be of very poor quality.... There are panasonic FC 1uf caps in 25 or 35V ratings I believe, but the 100V rating of the stock cap has me confused.
Hi there
(New to the forum...)
- thanks to everyone who has contributed to this thread. This is really a whole new world to me...
I got my lepai amp a few days ago and I've really grown to like the sound. It's really different to my NAD 3020 and haven't been able to stop listening to it actually.
I got this wee amp as an experiment - and if i liked the tripath sound I was planning to then buy a pre-made amp like the trend or the virtue.one but due to this forum I will probably try to make the most of this amp.
The problem is that I have zero skills in this area. The mod that I really want is the noise suppresion one - but is this really something that a total beginner can learn to do?
If I don't do it I'm worried that my speakers are going to pop out one day when turning the thing on...
Also - I am rnning the preamp out from my NAD into the input of the lepai. Is this ok?
Thanks in advance for any advice...
(New to the forum...)
- thanks to everyone who has contributed to this thread. This is really a whole new world to me...
I got my lepai amp a few days ago and I've really grown to like the sound. It's really different to my NAD 3020 and haven't been able to stop listening to it actually.
I got this wee amp as an experiment - and if i liked the tripath sound I was planning to then buy a pre-made amp like the trend or the virtue.one but due to this forum I will probably try to make the most of this amp.
The problem is that I have zero skills in this area. The mod that I really want is the noise suppresion one - but is this really something that a total beginner can learn to do?
If I don't do it I'm worried that my speakers are going to pop out one day when turning the thing on...
Also - I am rnning the preamp out from my NAD into the input of the lepai. Is this ok?
Thanks in advance for any advice...
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.