Brian's LM3875 REV C boards

[BrianGT]

Here is the the revised board so far:


changes:
- added zobel resistor to silkscreen (can be mounted on top or bottom of pcb)
- widened the pin spacing on the zobel resistor to allow for larger resistors and more continuity on the groun plane
- changed the connection for the signal ground (SG) and power ground (PG) connection [credit to PA's suggestion for this minor change]
- added chipamp.com to the silkscreen

Let me know if you have any more suggestions. The difference in this rev.3 from the last rev.2 design is quite minimal, mostly cosmetic.

Let me know if you have any more features that you would like to have added to this pcb, as I am looking to order some relatively soon.

I still have rev.1 and rev.2 boards left, and will put up a clearance page soon to get rid of my stock.

LM3886 board here:
http://www.diyaudio.com/forums/showt...825#post554825

Also, let me know if you have any suggestions for the LM4780 board.

--
Brian

[wigginjs]

Did you decide against the snubber then?

[BrianGT]

Originally posted by m0tion
Did you decide against the snubber then?

I haven't finalized anything yet. What would need to be added to allow for the snubber setup? I haven't made any changes to the rectifier pcb yet.

Also, would anyone be interested in premium kits again with the Riken/Caddock resistors?

--
Brian

[wigginjs]

At the bottom is a link to Carlos' schematic. Looks like you could make all of the changes on the rectifier PCB, but it may require a slightly larger board. You'd need to add a place for the 2.2k resistor, then the 100nF cap, and the 2.2k->100nF cap. You would then replace the 1500uF Panasonic cap you're currently using with a ~10000uF capacitor, which may or may not require changing the footprint for the capacitors on the amp PCB. Heh, a pain I know, but this is now pretty widely accepted as an improvement that yields [B]significant[/B increases in sound quality.

Quote from Peter Daniel regarding sound quality improvements:

"...last week I tried Carlos' suggestion with regards to snubbers in GC supply (and big caps) and right away I liked the results. It is better even comparing to battery supply I was using up untill now. There is more bass slamm but at the same time the mids and highs are not veiled by anything (like it was in a case of regulators). There is more midrange presence and dynamics, but also what suprises me, more micro detail, something I wouldn't really expect."

I suppose it should also be noted that this would probably increase the price of a kit buy a few dollars ($5?). Possibly this Panasonic capacitor could be used in place of the 1500uF?

I personally think this would have a much larger improvement on over-all sound quality than the premium parts and is also a good deal cheaper. Just something to think about...

[BrianGT]

Originally posted by m0tion
[B]At the bottom is a link to Carlos' schematic. Looks like you could make all of the changes on the rectifier PCB, but it may require a slightly larger board. You'd need to add a place for the 2.2k resistor, then the 100nF cap, and the 2.2k->100nF cap. You would then replace the 1500uF Panasonic cap you're currently using with a ~10000uF capacitor, which may or may not require changing the footprint for the capacitors on the amp PCB. Heh, a pain I know, but this is now pretty widely accepted as an improvement that yields significant[/B increases in sound quality.

Quote from Peter Daniel regarding sound quality improvements:

"...last week I tried Carlos' suggestion with regards to snubbers in GC supply (and big caps) and right away I liked the results. It is better even comparing to battery supply I was using up untill now. There is more bass slamm but at the same time the mids and highs are not veiled by anything (like it was in a case of regulators). There is more midrange presence and dynamics, but also what suprises me, more micro detail, something I wouldn't really expect."

I suppose it should also be noted that this would probably increase the price of a kit buy a few dollars ($5?). Possibly this Panasonic capacitor?

I personally think this would have a much larger improvement on over-all sound quality than the premium parts and is also a good deal cheaper. Just something to think about...

Sounds like an interesting idea. I will definately look into it.

--
Brian

[SheldonD]

IF you are changing the PS and the chipamp PCB, why not combine them into one board. this way there is more flexibility
about the real estate and would still have a compact layout.

It would require then about the same space as current both PCBs

This would also reduce the number of solder holes

vote for mute function to have room for cap for delay, as well as snubber circuit, instead of expensive premium components, as was suggested..

[BrianGT]

Originally posted by SheldonD
IF you are changing the PS and the chipamp PCB, why not combine them into one board. this way there is more flexibility
about the real estate and would still have a compact layout.

It would require then about the same space as current both PCBs

This would also reduce the number of solder holes

vote for mute function to have room for cap for delay, as well as snubber circuit, instead of expensive premium components, as was suggested..

The reason that the rectifier board and amp board are seperate pcbs is so that they can be seperated from each other for better shielding, and also allow for a stereo configuration to be used with 2 amp boards per rectifier board.

I will work up a new rectifier board for the snubber setup.

--
Brian

[homer09]

I think keeping the rectifier boards separate from the amp board is the more flexible layout for people that want to either shield PSU from amp circuit or build PSU into a separate case. Joining them together would limit the possibilities this kit offers.

[SheldonD]

Homer09 and Brian:

You are so right about keepijng PS and amp PCB apart. Far more advantages than the other way.

It was not a good idea, at all.

[BrianGT]

Originally posted by SheldonD
Homer09 and Brian:

You are so right about keepijng PS and amp PCB apart. Far more advantages than the other way.

It was not a good idea, at all.

The option will still be there to keep them together as done by this person:
http://www.briangt.com/gallery/nigc-maarten/board

--
Brian