eBay mono LM1875 kit

[chermann]

Hi


Fine list. i personally try to use as big cap at the input the get more subsonic bass but to be honest its maybe not needed. if the lead space is the same and the price is nearly equal then i would go for a 4,7µF.


please remember that your components are for 1 board


chris

 

[DaveFred]

I found Brian Bell's LM1875 component values but no schematic. In brackets [ ] are the components I used in this build.

Reference: Brian Bell (Chipamp.com) LM1875 (schematic unknown)

Default configuration [components used in rabbitz build 2019]
R1 - not used (optional resistor to ground before C1) [not used]
R2 - 22k (input to ground resistor) [0.5W MF]
R3 - 1k (gain resistor , gain = 1 + R4/R [0.5W MF]
R4 - 22k (nfb resistor - on bottom of pcb) [0.5W MF]
R5 - 2.7 2w (optional - zobel network) [2R7 2W MF]
R6 - jumper (optional resistor between input ground and output ground) [not used, linked]
C1 - 2.2µF (optional input capacitor) [1uF MMK]
C2 - 22µF bipolar (optional) [Nichicon ES 22uF 25V]
C3 - 0.1µF (power supply decoupling) [ceramic X7R Vishay BC]
C4 - 47µF (power supply decoupling) [Nichicon KZ 47uF 50V]
C5 - 0.1µF (power supply decoupling) [ceramic X7R Vishay BC]
C6 - 47µF (power supply decoupling) [Nichicon KZ 47uF 50V]
C7 - 0.1µF (optional - zobel network) [MKT]
Note: 1K resistor after input cap not listed above but installed [0.5W MF]

As for a bare minimum configuration, here is what you could run:
R1 not populated
R2 22k (input to ground resistor)
R3 1k (gain resistor, gain = 1 + R4/R3)
R4 22k (nfb resistor - on bottom of pcb)
R5 not populated
R6 jumper
C1 jumper, or put input source into pad by C1 label on pcb
C2 jumper
C3 0.1µF (power supply decoupling)
C4 47µF (power supply decoupling)
C5 0.1µF (power supply decoupling)
C6 47µF (power supply decoupling)
C7 not populated

Here is the original ChipAmp L1875 manual,

Original ChipAmp LM1875 Manual

 

[DaveFred]

If anyone is looking for a link to the boards with plating in the through holes and on top of the board, I think these are them,

Aliexpress LM1875T boards

 

[chermann]

yes...fine David thanks



But be aware of the low quality of the pcb and therefore do not try to solder twice at one point. it is because the solder dot will be gone
chris

 

[rabbitz]

These are harder to rework as well and I found the boards without the though hole plating easier to work with.

 

[DaveFred]

What would be the better component for C2, 330pF capacitor,

Vishay Multilayer Ceramic Capacitors MLCC - Leaded 330pF 50volts 5% C0G 5mm LS

or

Murata Multilayer Ceramic Capacitors MLCC - Leaded

 

[asuslover]

C0G is superior to X7R.

 

[chermann]

jep. at this size of capacity.

 

[OldDIY]

https://aliexpress.ru/item/40005834...sk_RU_RMKT_SMART_CPC_DMPfeed_0_Perform_lhttlG

 

[chermann]

Hi


A price of about 58 Euro for unknown parts is for me useless.
the PCB kit (forget the parts) is about 1,6 or 2 euro max.


chris

 

[OldDIY]

Handmade (under the order)

 

[DaveFred]

My tiny little Ebay LM1875 kits are coming together nicely, now to decide on a layout...

 

[jamesfeline]

This is my work in progress ... just started this project

 

[jamesfeline]

https://aliexpress.ru/item/40005834...sk_RU_RMKT_SMART_CPC_DMPfeed_0_Perform_lhttlG

love this build ... well done

 

[rabbitz]

My tiny little Ebay LM1875 kits are coming together nicely, now to decide on a layout...

I'd go with the amps at the back on each side, the pot in the middle with an extension shaft to the front.

 

[chermann]

yes ...rabbitz is right.
then you get short cables to the speaker terminals and a short way at input cable.
input coax RG178...inner cable is partly silver

%product-title% kaufen


to be honest with the smps you could have the space for 4 amps inside - so you could go for bi amping (bi wiring) if your speakers can handle that.
i dont try this up to now....



chris

 

[chermann]

This is my work in progress ... just started this project

well done...its a DIY pcb!

 

[rabbitz]

This is my work in progress ... just started this project

Nice work on the PCB. Much better than my attempts with a Dremel.

 

[rabbitz]

This is what I mean with the pot extension shaft. Even though this is for a pre amp, it still applies for a power amp and you can see close RCA and short signal wires.

For short runs I just use twisted Cat5 but for longer I use Mogami W2944 which I discovered in a CF My Ref thread.

 

[DaveFred]

Has anyone seen or taken a look at this LM187 layout?



Link to circuit board