| BrianGT |
I should receive the next batch of LM1875 boards soon, and have put them up on my website for pre-order.
Details on boards here:
http://www.diyaudio.com/forums/show...threadid=122793
and here:
http://chipamp.com/lm1875.shtml
I should begin shipping out the new kits in 2 weeks. I have put up a pre-order special for the kits, including an extra stereo pcb set along with the purchase of a kit. I will run this special until the kits start shipping out.
Drop me a mail if you have any questions. Sorry it took so long to get these kits out. I have been really busy at work, and wanted to make sure to get a few amps built with the boards and used for a while before making them available on the webpage.
Pic from initial prototype:
I will see if I can get pics posted from the assembled amp soon also.
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Brian |
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| ppcblaster |
| Thank You Brian for doing this project.. |
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| morepower4me |
Looks fantastic, thank you.
Do you think this would make a good first amp DIY project (as compared to your 3886 kit?)
It will be driving bookshelf speakers in a medium sized room.
And for the other newbs... What else besides your kit, the PE transformer, soldering equipment (and patience,) will I need? |
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| korben69 |
Hi Brian
Paypal sent for 1xLM1875 and 1xLM3886 PCB kits. :cool: |
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| tschrama |
just ordered two LM1875 PCB sets...
I messed up, so I had to send the money in to paypal transmission.. but I hope everything goes allright...:att'n:
Thanks,
Thijs |
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| Peter Menting |
Brian; Could you tell me what the board sizes are? Have a special project in mind.
Thanks,
Pete |
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| ppcblaster |
| quote: | Originally posted by morepower4me
Looks fantastic, thank you.
Do you think this would make a good first amp DIY project (as compared to your 3886 kit?)
It will be driving bookshelf speakers in a medium sized room.
And for the other newbs... What else besides your kit, the PE transformer, soldering equipment (and patience,) will I need? |
http://www.partsexpress.com/pe/show...tnumber=122-620
From www.Chipamp.com |
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| BrianGT |
The boards have arrived, and I have started putting the kits together. They will ship out on Monday, and I will remove the special at that point.
| quote: | Originally posted by morepower4me
Looks fantastic, thank you.
Do you think this would make a good first amp DIY project (as compared to your 3886 kit?)
It will be driving bookshelf speakers in a medium sized room.
And for the other newbs... What else besides your kit, the PE transformer, soldering equipment (and patience,) will I need? |
The LM1875 is just as simple as the LM3886 kit, and will be a great project for a beginner.
| quote: | Originally posted by tschrama
just ordered two LM1875 PCB sets...
I messed up, so I had to send the money in to paypal transmission.. but I hope everything goes allright...:att'n:
Thanks,
Thijs |
Everything looks good. Orders will go out Monday.
| quote: | Originally posted by Peter Menting
Brian; Could you tell me what the board sizes are? Have a special project in mind.
Thanks,
Pete |
The amp boards are roughly 1/2 the size of the LM3886/LM3875 boards. I don't have dimensions on me now, but I will look then up when I get home.
Sorry for the delay, let me know if any of you guys have more questions,
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Brian |
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| korben69 |
Hi Brian I've got one.
In my system, Tri active amp, DEQ/DCX 2496, I'm wondering wich amp will be the more accurate in driving a CP21F, 105dB tweeter, 6.1 Ohms ? 3886 or 1875 ? Freq range from 2KHz to 20KHz.
I don't need a lot of power, but definition.
Your opinion ?
Thanks |
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| BrianGT |
| quote: | Originally posted by korben69
Hi Brian I've got one.
In my system, Tri active amp, DEQ/DCX 2496, I'm wondering wich amp will be the more accurate in driving a CP21F, 105dB tweeter, 6.1 Ohms ? 3886 or 1875 ? Freq range from 2KHz to 20KHz.
I don't need a lot of power, but definition.
Your opinion ?
Thanks |
If you don't need the power, I would try the LM1875.
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Brian |
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| BrianGT |
| quote: | Originally posted by Peter Menting
Brian; Could you tell me what the board sizes are? Have a special project in mind.
Thanks,
Pete |
The board sizes are:
LM1875 amp board:
1.6" x 1.2"
PSU board:
1.6" x 2.4" |
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| KT |
Received the kit and boards today, Brian. Thanks!
KT |
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| korben69 |
Hi brain, received the PCBs today.
Thanks !
Do you have some hints to improve LM1875 response in high frequency ? ;) |
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| sonidos |
Brian,
Thank you!! Got mine today and everything arrived in great shape. Can't wait to get started on this build. |
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| vonfilm |
Brian,
When will the assembly manual be available on your website? |
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| sonidos |
I've got it pretty much figured out from the photos, but I want to be sure that I populate the locations for the resistors with the correct values.
I've already got the psu done and I'm heading to our local electronics surplus store at lunch to see if they have heatsinks and other assorted hardware so I can keep moving forward.
Brian, also, on your web page, I found the resistor designators but now I'm not certain what to do about those components that are considered optional. From the images, it looks like the boards are pretty well populated. When you have docs ready, can you address under what circumstances we will want to populate the optional components?
Thanks! |
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| BrianGT |
| quote: | Originally posted by vonfilm
Brian,
When will the assembly manual be available on your website? |
I will put more time into it this week, and try to get something up by the end of the week.
| quote: | Originally posted by sonidos
I've got it pretty much figured out from the photos, but I want to be sure that I populate the locations for the resistors with the correct values.
I've already got the psu done and I'm heading to our local electronics surplus store at lunch to see if they have heatsinks and other assorted hardware so I can keep moving forward.
Brian, also, on your web page, I found the resistor designators but now I'm not certain what to do about those components that are considered optional. From the images, it looks like the boards are pretty well populated. When you have docs ready, can you address under what circumstances we will want to populate the optional components?
Thanks! |
As for the optional components, they are provided for optimal amplifier stability for using with a variety of output loads/impedances. It depends on your setup, whether you need them or not. Here is a list of optional components:
R1 - not used (optional resistor to ground before C1)
R5 - 2.7 2w (optional - zobel network)
R6 - jumper (optional resistor between input ground and output ground)
C1 - 2.2µF (optional input capacitor)
C2 - 22µF bipolar (optional)
For R1, this is omitted from the kit, and is provided if you wish to put a resistor to ground before the input capacitor. This is not needed, but provided for versatility for various input sources. I had a request for this a long time back, and retained it in the PCB layout, as it doesn't have any side effects if not populated.
For R5/C7, these are for the optional zobel network, which can stabilize the output by creating a pole that reduces high frequency instabilities. If you don't want to use these, simply omit these components from the pcb.
For R6, this is for an optional resistor between the input signal ground, and the output ground. This is specified as a jumper, meaning a simple wire connecting these terminals. You can utilize the extra wire from the 2.2uF film capacitor lead. You should not need to use this, unless you are having ground loop issues.
For C1, this is the optional input capacitor that blocks DC offset from the input source from propagating to the input of the LM1875.
For C2, this is the optional feedback capacitor that ensure unity gain at DC.
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
I hope that clears it up for you. |
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| sonidos |
Brian,
Thanks for your patience and quick response to a noob building his first chip amp!:) |
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| vonfilm |
Brian,
Any idea when the 1875 manual will be up? |
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