Go Back   Home > Forums > Commercial Sector > Group Buys

Group Buys Members group buys

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 31st May 2006, 02:00 AM   #31
AJT is offline AJT  Philippines
diyAudio Moderator
 
AJT's Avatar
 
Join Date: May 2003
Location: Palatiw, Pasig City
any chance for a parts kit group buy?
  Reply With Quote
Old 31st May 2006, 02:06 AM   #32
dfdye is offline dfdye  United States
diyAudio Member
 
dfdye's Avatar
 
Join Date: Dec 2005
Location: USA
After I get all of the parts ironed out that I like I would definitely consider it! So far I really like what I have seen from the prototypes, but I want to get a more robust output stage than the darlington configuration in the app sheet.

If you have specific parts in mind, I'll be happy to consider getting things together. Any suggestions?

PS I am using the Muse BP input caps bypassed with 1uf film caps if you are interested. I want to try a regulated PSU for the LM4702 stage to see how it does with an "unregulated" PSU for the output stage.
  Reply With Quote
Old 2nd June 2006, 01:16 AM   #33
dfdye is offline dfdye  United States
diyAudio Member
 
dfdye's Avatar
 
Join Date: Dec 2005
Location: USA
USA boards are in the mail!

I goofed and overestimated shipping. It turns out these will go by first class mail, making S&H $2.00 less than orignally calculated. I was going to roll that back into DIYAudio.com, but if anybody wants a refund, just let me know and I'll be happy to send it back.

International boards would be out too, but of course I forgot to fill out the customs forms, and the line was an hour long wait. I'll get those out tomorrow.

In the mean time, even though a regular waveform would be more diagnostic, the Mighty Mighty Bosstones are more fun to look at on a scope! The (bad) picture below is just my iPod going into the LM4702 board with +/-35V unregulated rails, measuring the sink, source, and feedback wires tied together. From the tests I ran last night, the boards seem to work fine, though I did notice some very faint "hum" noise in the background when I cranked the sensitivity of the scope up. I couldn't see it until I really got to some pretty low levels, but it was there. When I grounded the mute pin, the noise did go away, so this is only there when the amp is on. I'm not sure what it was from, but none of the inputs were shielded, and the grounding was awful, so I am betting that once I get everything properly configured that will go away.
Attached Images
File Type: jpg 06-01-06_0143.jpg (22.7 KB, 467 views)
  Reply With Quote
Old 2nd June 2006, 02:36 AM   #34
dfdye is offline dfdye  United States
diyAudio Member
 
dfdye's Avatar
 
Join Date: Dec 2005
Location: USA
BTW, I have noticed a couple of things while reading through the new National LM4702 Power Amplifier app sheet, and the good news is that almost all of the recommendations in that sheet follow what is in this board.

The exception, obviously, is taking out the input caps. This can be easily done by bypassing Cin with a jumper wire and feeding it directly to the first pin of Rin if you so desire. I am still playing with the input caps, but once I do this on one of my boards I will be sure to post some pictures if anybody wants.

If you have any questions about how to potentially modify these boards to match some of the aspects of the new amp note, I will be happy to answer them! Like I said when I offered these boards up, I tried to make them flexable, and based on some of the new ideas I got from reading this sheet, I will definitely configure the boards to take advantage of some of National's suggestions.
  Reply With Quote
Old 2nd June 2006, 04:07 PM   #35
djkib is offline djkib  United States
diyAudio Member
 
Join Date: Dec 2004
Location: Coatesville, PA, USA
To all,
I'm in on the group parts buy!

David,
Great idea for the "overbill" on the shipment charges...

Thanks,
Keith
__________________
Programmer / Analyst
  Reply With Quote
Old 2nd June 2006, 05:33 PM   #36
diyAudio Member
 
dshortt9's Avatar
 
Join Date: Apr 2001
Location: Milwaukee, Wisconsin
Count me in for a parts group buy when ready.

Overbill to this great forum!
  Reply With Quote
Old 2nd June 2006, 07:21 PM   #37
AJT is offline AJT  Philippines
diyAudio Moderator
 
AJT's Avatar
 
Join Date: May 2003
Location: Palatiw, Pasig City
i second that!
  Reply With Quote
Old 3rd June 2006, 01:03 AM   #38
dfdye is offline dfdye  United States
diyAudio Member
 
dfdye's Avatar
 
Join Date: Dec 2005
Location: USA
All orders are in the mail. Supposedly I can't use a scale since the post office consistently said my packages were lighter/cheper to mail than what I thought. Anway, there is a whopping $12 left over in the shipping fund, so the next time I send money to the forum I will tack on the extra.

It's not much, but I am sure every little bit helps.

Anway, packages should take about a week (possibly two for non-US shipments), so let me know when you get the boards so that we can identify problems if the occur.



Changing gears:

So far there are 3 people in for a parts buy (plus me, but I am always in!). What would everyone be interested in?

Off the top of my head, the last digikey order I made for parts for these boards had:

1/4W or 1/2W resistors (depends on what we want to go with. . .),
30pf mica caps
100nf bypass caps
220 uf panasonic FC caps
Ci/Cin caps (this warrants some discussion, I think)
1uf film Bypass caps
LM4702 chips

Comments about what values/brands you would like or want substituted?

I can also get TO-3 darlingtons that I have been using and some transistors for building simple output stages. I'm not sure who would be interested. . .

Let me know, and if we get enough interest I'll start making a formal list.
  Reply With Quote
Old 3rd June 2006, 01:24 AM   #39
hayenc is offline hayenc  United States
diyAudio Member
 
hayenc's Avatar
 
Join Date: Apr 2005
Location: Glendale, AZ
Send a message via Yahoo to hayenc
Boards arrived today. Look nice. Did you ever pull together a BOM in one place? Looks like discussions of component values are all through the discussion, but I did not see the bill in one place.

Thanks for all your hard work.

Craig
  Reply With Quote
Old 3rd June 2006, 02:03 AM   #40
dfdye is offline dfdye  United States
diyAudio Member
 
dfdye's Avatar
 
Join Date: Dec 2005
Location: USA
hey Craig,

Glad they got there OK. As for the BOM, I haven't put one together since I figured people would pick thier own resistor/cap combinations. I'll be happy to put one together quickly based on what I am using presently, but it will probably be some time tomorrow. In the mean time, I'll post my spreadsheet for calculating component values. Feel free to ask questions if the sheet isn't self explanatory.

David
Attached Files
File Type: zip lm4702 component calculator.zip (2.7 KB, 158 views)
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Lm4702 Mike Gergen Chip Amps 109 31st August 2008 01:30 AM
Lm4702 Bpa halo0925 Chip Amps 19 13th November 2006 04:47 AM
Lm4702 BPA halo0925 Solid State 0 9th November 2006 10:26 PM


New To Site? Need Help?

All times are GMT. The time now is 03:56 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2