Chinese Mono LM1875 Board

[Hedliden66]

Happy with my first order I ordered a second pair from the same seller on Ebay...
... unfortunately this time I received one solderable from both sides and one only from the underside. You would think that they at least could send you 2 of the same.
I also picked up 2 new crossovers for my speakers today and of course... 2 different arrived. Just not my day today...

 

[jwicaksana]

Have you received the boards ?
I couldn't fit the three 100uf on same side, so I have one on the underside.
My caps are 10mm in diameter.

I have. I measured the space for the power supply caps, they are 10mm dia.and 5mm pitch. The feedback caps is 5mm dia. Can two 10mm caps fit side by side for on board power supply?

 

[jwicaksana]

Happy with my first order I ordered a second pair from the same seller on Ebay...
... unfortunately this time I received one solderable from both sides and one only from the underside. You would think that they at least could send you 2 of the same.
I also picked up 2 new crossovers for my speakers today and of course... 2 different arrived. Just not my day today...

I got mine from auelectronics8_6 and received double sided pair.
Who do you got it from?

 

[Hedliden66]

Changed my feedback cap to 100uf so put it on the underside. 10mm power caps fits fine.
Seller on Ebay now claims pcbs are only the new version, so they can't ship what I want.
Their photo now shows what they ship so that part is fine. I bought from kuailelaoliang.
I then wanted a better confirmation on what version is the new version.
Reply: What you received in latest order.
Well... I received 2 different versions clearly stated in mail with attached photos, so I just gave up and will go elsewhere.

I am going to use doublesided prototype boards now. Resistors will be 1206 SMD, so an experiment to make a very small curcuit.

 

[phase]

Most of the time a decent input cap won't fit on the space originally allowed for on the board.
Usually due to economics driving the layout, and a cheap electrolytic used on the original board.
I gave up on small amps unless for headphones, life is too short...

 

[nenad88]

Ok, can someone list values for all capacitors they used please and mark them by c1,c2,c3, thanks.

 

[nenad88]

found original schematic and one from ebay. so chinesse changed those 2 capacitors, on original schematic those 2 caps have NP below them, is that non polarized?

 

[gkh]

The cap is most certainly non polarized.

 

[nenad88]

Here is pdf from silicon chip magazine https://ia601300.us.archive.org/12/...-12_Dec/Silicon_Chip_Magazine_2004-12_Dec.pdf on page 16. is story about this amp. And you can buy it on their site as a kit.

 

[gkh]

Thanks for the link!

 

[jwicaksana]

Are you guys running this as a stand alone unit, or with a preamp?

 

[Hedliden66]

My "preamp" is an old Lenovo laptop with Creative X-Fi HD usb external soundcard. Mainly play my ripped cds, but I can run my record player through it also.

 

[xrk971]

I just ran across this thread and realized the TDA2030 has same pinout as 1875 but lower power. Anyhow, I have a thread for the 2030 in dual mono but on single rail supply as headphone amp. It's safer to have output coupling cap for headphone dc protection. Anyhow, many of the similar issues are on both.

TDA2030 Coffee Money Headphone Amp

 

[danielwritesbac]

AndrewT's posts on this thread are right on.

 

[JonesySA]

I've just ordered two of these amps. How is everyones experience since mid last year?

 

[pizzacat666]

In case anyone is still interested in these boards, I ordered 3 of them from ebay/China and received single sided boards with fake looking amplifier chips. I followed this thread and replaced most components except the resistors which resulted in a really nice sounding and dead quiet amplifier. But after a week, the smoke came out of my R6. I replaced R6 with 10ohm 1watt dale resistors and everything is good so far. Here is the summary of mods I did:

New Ti LM1875t chips 926-LM1875T/NOPB
C1 (input filter cap) film type 4.7uF bi polar (wima) MKS2C044701M00KSSD
C3 150uF 50v (nichicon) UPW1H151MPD
C5 & C6 (supply rail decoupling) 0.1uF x7R ceramic cap SR215C104KAA
R7 zobel 4.3ohm 1w metal film vishay
C4 zobel .22uF 100v polyester film cap kemet R82EC3220Z370J
C7 & C8 220uF 35v Nichicon UPW1V221MPD
R6 10ohm 1watt dale CMF6010R000FHEK

Testing using the power supply from an F5 with 600va transformer just to see how these sound.
Does anyone have a guess why R6 would smoke?

 

[PRR]

> R6 would smoke?

Oscillation. Layout.