OT: Bowtie and Panomaniac

**Nipper** · October 28th, 2011, 04:19 PM

Got the Lepai LP-2020A+ today. It was DOA.

Opened it up and found one of the wires had not been soldered to the switch lead.

Got it up and running and I am honestly impressed!

Thanks!

Now what about these horror stories about them lasting 2 days... It seems most of the folks having trouble with them were on the older model (did not have a tone defeat switch or relay). Is this newer model any better?

**bowtie427ss** · October 28th, 2011, 07:54 PM

Mine's bouncing along in the Graceland with Paul Simon as i type this.

So far, mine's been problem free, i've even "beat" on it a bit. T-amp plus clipping is not a good sounding combination, just an FYI.

Sorry to hear yours was DOA, but glad to hear you could effect a repair Nipper!

It was my understanding when i took the plunge on mine that this is the improved version with all of the shortcomings supposedly worked out. I think Parts Express had a lot of returns on previous versions and may do some sort of quick test for function on these before they ship them out. It seems a lot of Audiokarma members have purchased these from PE in the recent past and i haven't read any posts about defective units in quite a while. At the purchase price they can't see much in the way of QC, so a lemon here and there isn't a surprise.

You have to admit, well you don't have to, but it's an impressive sounding 30 bucks huh?

EDIT: another note, keep your cell phone far away from it.

**Nipper** · October 28th, 2011, 09:01 PM

Originally Posted by bowtie427ss

You have to admit, well you don't have to, but it's an impressive sounding 30 bucks huh?

EDIT: another note, keep your cell phone far away from it.

I do have to admit it. This little thing is ANGRY.

Considering the simplicity, I find it to be damn impressive.
If I were building amps I would be very concerned with this. I let three friends hear it. Sold three. You have to hear it to believe it.

Since you took the time to edit..... Whats the story on the cell phone?

**bowtie427ss** · October 28th, 2011, 10:13 PM

Whats the story on the cell phone?

Some RFI, seems that local proximity is directly related in my case. If my phone is here on the same desk, maybe 3 feet away, the occasional interference can be as loud or even a bit above the source i'm playing. No interference with the phone in the next room. It's not a big issue, but thought it worth mentioning.

FWIW, i've read somewhere that if you use two of these amps driving only one channel of each, you can get more sonic goodness when driving them toward their limits. I'm gonna give it a try.

**mah** · October 28th, 2011, 10:18 PM

I read somewhere that these amps have a significant switch on thump through the speakers and may not be suitable for compression drivers. Has anyone experienced this?

**bowtie427ss** · October 28th, 2011, 11:05 PM

Yes, even with the relay/delayed turn on there is a low to moderate turn on transient, and a somewhat more significant transient/bump at turn off.

I should add that i'm using mine with duplex speakers using small format compression drivers(passive network). While the transients are certainly noticeable and objectionable, they're a nuisance that is quickly forgotten in my current setup. If i were bi-amping and using one of these to drive compression drivers directly, i think i'd opt for a series cap of a value that puts the knee point an octave below your intended cutoff to ensure the drivers don't see the LF content of any transients regardless of source.................... it is in reality a 30 dollar tin box of an amplifier, it just happens to sound amazingly good.

I've never been an advocate of leaving electronics powered on 24/7. But, i wonder if in this case, since it's a highly efficient design, and internally powered from 12 vdc, if leaving it powered on continuously might be the simplest solution for those running these on grid power/AC.

**mah** · October 28th, 2011, 11:49 PM

Bowtie, thanks for your response.
When I think about wallwarts and switch mode power supplies(built at lowest possible price) which infest modern consumer electronic equipment being left on 24/7, I shudder. Many years ago, I lost my brother due to a fault in a portable radio that had an inbuilt mains voltage power supply which failed and emitted toxic fumes while he slept. Recently I obtained a device which senses whether a computer is on or off and then switches peripheral devices accordingly. This makes me feel more secure but there are still more of these things dotted around the house.

**bowtie427ss** · October 29th, 2011, 08:24 AM

Originally Posted by mah

Bowtie, thanks for your response.
When I think about wallwarts and switch mode power supplies(built at lowest possible price) which infest modern consumer electronic equipment being left on 24/7, I shudder. Many years ago, I lost my brother due to a fault in a portable radio that had an inbuilt mains voltage power supply which failed and emitted toxic fumes while he slept. Recently I obtained a device which senses whether a computer is on or off and then switches peripheral devices accordingly. This makes me feel more secure but there are still more of these things dotted around the house.

Duly noted and understood.

There's certainly no hard and fast rules about what one uses for a power supply. I'm thinking that there are any of a number of vintage and modern regulated power supplies out there that would be both a cost effective alternative and much much safer alternatives to a wall wart, particularly for those of us considering running multiples of these amps.

Back in the day Radio Shack made a couple of ideal examples under their Micronta brand line. Somewhere around here i have a 12 volt DC 2.5 amp regulated supply. It's housed in an all metal chassis, uses an open frame transformer, no thermoplastics anywhere, fused, as safe as any audio component i own IMO. Sold dozens and dozens of these back in the day to people wanting to run mobile CB radios in their house. These can still be found regularly on ebay.

Bottom of page 105 here: http://www.radioshackcatalogs.com/catalogs/1977_small/

**Panomaniac** · October 29th, 2011, 11:09 AM

Glad you got it fixed! Not surprised at the bad wring job, tho. I have only the old versions and they are some of the worst build quality I've seen in years. All credit for good sound goes to the TA2020 chip. Maybe the new builds are are better, so the forums say. I used to sell an amp based on the TA2020, it was killer.

The turn on thump is due to the charging of the input caps. The bigger the caps, the bigger the thump. There are many ways to get around this, I used a soft start circuit.
Be advised that there is DC on the all the speaker terminals, it is approximately 1/2 of the supply voltage. Speaker negative is NOT ground.

Enjoy the amp. It's hard to get better value for money, that's for sure!

**bowtie427ss** · October 29th, 2011, 11:24 AM

Be advised that there is DC on the all the speaker terminals, it is approximately 1/2 of the supply voltage. Speaker negative is NOT ground.

I've seen numerous posts warning not to connect or otherwise "touch" any speaker terminals to anything other than a speaker, i suspect this is why?

I haven't opened mine yet but i'm 99.9% positive there's a relay in there. It surely does not eliminate turn on thump(maybe it reduces it considerably?), so what is it's purpose?