Any interest in GC input buffer and power supply regulator pcb's?

[cjd]

For the LM3886, I think this slight tweak will allow parallel circuits with as many as you choose. I believe you'll want to leave R2 off the boards and use just one at input (?) - same with the cap at input for parallel circuits. Output can come straight off the pin or through a resistor hence the dual O+ options. I have seen some suggestions that this R be used on a single board anyhow. I'm not sure whether trying to put two chips on a single board for a parallel circuit outweighs the potential to just stack as many single chip boards as you want/need.

I moved Rfb back outside the pins of the chip in case pin7 should go to the power ground directly not signal ground. If not it leaves some room to open up the schematic and insert the mute circuitry...

As for time, trust that you aren't causing me to miss anything at all. My mother in law is in town (out shopping with my wife) and it's pouring rain down.



I think I need to work on a better bypassing scheme... any suggestions would be helpful.

C

[Pedja]

C,

Yes, it seems it widened somehow… No need to move PSU caps to make a space for the speaker ground, just take that from the caps central point and make a track of few cm so you can make another pad. Bypass caps can be mounted beneath the board, though with 100u or smaller caps necessity for them becomes lesser.

I think the layout is generally very good and I think it is now most important to determine the definitive size of the parts.

Yes, the discrete (non-f/b) reg is IMO better. I have, however, two reasons not to deal with it at the moment. The first is that we may get better if doing one thing at the time, and the second is that after some late cases here I am reluctant to do some things publicly.

Pedja

[Rick NL]

Hoe about this connection between Power ground and Signal ground?
Rick

[Ed LaFontaine]

I apologize to all those who have contributed to development of the GC buffer for my mention of lm3886 taking us "off track". Pedja is right. We are better when we do just one thing at a time. I also wish I could do something for Pedja's concern #2. Thank You Pedja, however I'm afraid my gratitude won't alleviate issues brought on by others.
Sincerely,

[troystg]

Hello Moderators-

May I ask you to move the following posts to a new thread in the Chip Amp forum in a title similar to "Parallel LM3886 amp"? They seem to hijacked this thread, and for this I apologize.

1. http://www.diyaudio.com/forums/showt...419#post429419

2. http://www.diyaudio.com/forums/showt...434#post429434

3. http://www.diyaudio.com/forums/showt...900#post429900

4. http://www.diyaudio.com/forums/showt...932#post429932

5. http://www.diyaudio.com/forums/showt...975#post429975

6. http://www.diyaudio.com/forums/showt...424#post431424


edit: Include this post to please!

Thank you in advance,

Troy

[Rick NL]

Hi, I was too quick in my reply to the HiJacked post of CJD as he already mentioned the track possibility in his text.
Now i studied the PCB and text better I see taht the space can be used for the additional PosPower pin No.5. Although fron the NS data sheet you could read that it is not abolutly required, it is always the best to use all available Power pins.
More serious might be that the mute resistor is not on the PCB, This is in fact an unmute resistor and without it there will be no music from the chip.
Use 39k and it will supply the min 0.5 mA from a power supply of 22 V DC upwards. The capacitor is for delay but also decoupling. Probably 10 uF or more is OK when no delay is required, else 100uF or more might be OK.

Rick

[Pedja]

I personally do not have a problem with LM3886 here, it is in fact about a few needed changes… Its mute pin, as Nick just noted, can be used for power up delay, this spells LM3886 gives the possibility to deal with the buffer’s power up thump by one capacitor.

Though paralleled chips would probably lead us a bit further from where we are now.

Pedja

[Pedja]

Originally posted by Pedja
(...) as Nick just noted (...)

Too late to edit... Sorry, I've meant Rick.

[cjd]

I've stepped back a bit and am researching parts (to get exact sizes!) In doing this, my lack of experience in this field is becoming rather obvious - I don't know which versions of what to use! So some help here would really be appreciated, and I can keep chugging along on doing these PCB's. Things have been through a couple revisions already (on the chip boards anyhow) since I've posted previously, but I'm waiting to post again till I have part sizes down better.

I've also dug up a couple programs for designing these.

One question I have is this: Should I stick single sided? There are some advantages both ways, but I suspect double-sided wouldn't be something you could go etch yourself? But if it turns into some kind of group-buy, I think things start to get vaguely reasonable at 50 boards for manufactured, double sided with solder masks and silk-screen.

And, I actually don't feel the chip boards are out of place here, since going regulated in particular means much smaller caps at the chip. So it's a package thing in my mind. I'm looking at ways of putting this all on a single PCB so that it can be left as one piece or broken up. I'm also trying to make the amp boards in such a way that you could turn them "sideways" and run solid core wire through a stack of them to parallel them. I haven't looked at inverted topology yet to see about bridging possibilities.

C

[moving_electron]

Originally posted by cjd


One question I have is this: Should I stick single sided?

I guess I would vote for single sided if the layout experts end up happy with the layout from a performance point of view.

My thinking is that folks could try the design sooner as they could more etch it themselves rather than have to wait for a possibly one time group buy. In addition having a version that folks could easily etch allows a lot more flexibility for integrating for example the power supply into an existing gainclone.

If the true target was a group buy though, there is no doubt that professionally manufactured double sided boards are a beautiful thing.