Modifying a Lepai LP-2020A+ (Blue PCB Type)

[chrism]

Just wondered if anyone is interested in posting modifications to the newer style Lepai amp? Lots of postings over on DIY Audio for the older red board ones but not so much on the newer style PCB ones.

I have done the volume control / tone control bypass mod and it basically turns it into a power amp. Sounds very good and certainly to my ears betters the stock unit. I use a Beresford DAC as a preamp into it. I can post what I did (pinched from DIY Audio) if anyone wishes to try it.

Regards

Chris

[Saber]

Sounds interesting, wonder if t would work as a Power amp with the 6lj valve pre a few of us have on order. Was it tricky to do?

[chrism]

Fairly easy to do.

All I did was remove the surface mounted resistors at C30 and C31.
Remove the bipolar capacitors at C20 and C21 - carefully as I reused them below.

Add flying bypass cables as follows:
DSCF6506.jpgDSCF6507.jpgDSCF6508.jpg
Connect C30 positive side to C20 positive side and add a bipolar capacitor into the lead.
Connect C31 positive side to C21 positive side and add a bipolar capacitor into the lead.

Make sure nothing touches the cap legs (tape up the soldered leads etc)- you will see what I did from the photos - its a temp lash up but I like it and will tidy it up before I close the case.

The volume pot, tone controls and tone switch are all disabled so it runs as a power amp only.

[chrism]

Ok not much interest but here goes.

Next mod done last night and tested.

Taken out pot, tone switch and tone controls - quite tricky and need to go slowly. Make sure that the tiny casing earth wire to the front panel is not damaged. Sound is a little "cleaner" than before so I may take both op amps out next to cut the power to the redundant parts of the board. I have added a few poor quality photos of the sad looking Lepai and its Maplins bench supply. I am proposing to make a new face plate next as the holes don't look too good! and also tidy the wires.

I had added a 10,000uf smoothing cap in leau of the standard 3300uf but don't think it made much difference (possibly due to the linear supply having smoothing caps in it).

[Puffin]

I have made and modded several Class D amps. The original modding frenzy on Diyaudio was centred around the TA2024 chip amps. Sometime later the Lepai amps entered the fray and some threads emerged. I suspect that as with most of these cheaply built amps the Lepai was (allegedly) felt to be the poorest quality of those around at the time (2006 - 7 from memory) and suffered reliability issues. If the manufacturers followed the Tripath data sheet then the things should work as expected. However the modders found that by substituting better quality parts in key areas there was an advantage to be gained. Those with more technical knowledge also made changed to the circuit which others could copy.

The thing to always remember about these BTL amps is not to bridge the outputs, if you do...it is goodbye amp. I wasted a couple of TA2024 amps this way.

These days I think there are better quality boards around from the likes of Sure Electronics. I have one of their TK2050 boards which is pretty good. Of course you have to provide all the ancillary parts to make the amp and a case, if you want it to look pretty.

If you are getting into DIY stuff I would suggest you try a Gainclone or a Mosfet amp to compare with the Lepai.

[Saber]

Thanks for posting that chris, I think id need to practice my soldering.

[chrism]

Thanks for posting that chris, I think id need to practice my soldering.

Considering that the amp was around £20.00 and usually collecting dust on a shelf well worth ago. If you only want a power amp the first mod - op-amp bypass mod gives the biggest improvement and very easy to do. It is also easy to reverse as well and costs nothing except a bit of thin solid core hook up wire (bit easier to solder into the board.

Go for it as its fun but I would sort it for you if you are anywhere near Sheffield.

Regards

Chris

[chrism]

Can anyone help with a quick query please.

I have a 10uF cap on the output of my Beresford Caiman that I use as a pre-amp and just wondered if I need another cap on the input of the Lepai power amp that I am modding. I have a 2.2uf film cap on it and am tempted to remove it and just have a wired bypass.

Any thoughts?

Regards

Chris

[RothwellAudio]

All I did was remove the surface mounted resistors at C30 and C31.
Remove the bipolar capacitors at C20 and C21 - carefully as I reused them below.

It would be very unusual for resistors to be given the designator C anything. Seems to me you might have removed some capacitors. You really need to see a circuit diagram to know what you're doing - just pulling out components because someone on a forum says so doesn't sound like a great idea to me.

[RothwellAudio]

Can anyone help with a quick query please.

I have a 10uF cap on the output of my Beresford Caiman that I use as a pre-amp and just wondered if I need another cap on the input of the Lepai power amp that I am modding. I have a 2.2uf film cap on it and am tempted to remove it and just have a wired bypass.

Any thoughts?

In theory you wouldn't need two DC blocking caps. Again, seeing a circuit diagram would make me feel safer about making any specific recommendations though.