Discrete Opamp Open Design - Page 288 - diyAudio
Go Back   Home > Forums > Source & Line > Analog Line Level

Analog Line Level Preamplifiers , Passive Pre-amps, Crossovers, etc.

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 3rd April 2013, 03:37 AM   #2871
fas42 is offline fas42  Australia
diyAudio Member
 
fas42's Avatar
 
Join Date: Jun 2012
Location: NSW, Australia
Blog Entries: 10
The aim is not to use recordings which are dynamic in their music content, rather those which are produced with certain engineering styles. Just had a quick listen to Sheffield Steel on YouTube, and it would not be a good contender for the type of testing I was thinking of - the engineering is too straightforward, wouldn't stress the system sufficiently ...

Edit: You need recordings that have everything, AND the kitchen sink to do this. Which reminds me, another excellent recording for such is the soundtrack for the film, "Moulin Rouge": this has a massive sound in many of the tracks, most systems would struggle to recreate what has been encoded at decent volumes ...
__________________
Frank . . . the truth is, I just like a bit of ASMR ...

Last edited by fas42; 3rd April 2013 at 03:44 AM.
  Reply With Quote
Old 3rd April 2013, 04:21 AM   #2872
diyAudio Member
 
Join Date: May 2005
Location: toronto
I don't think You Tube qualifies as a high quality source to judge much of anything - probably the best Shefield Steel track for dynamics is Ruby Lee, the Mobile Fidelity album or CD are nice transfers for the time, but you seem to have something else in mind - ah well back to the salt mines ......

Last edited by ticknpop; 3rd April 2013 at 04:23 AM.
  Reply With Quote
Old 3rd April 2013, 05:24 AM   #2873
fas42 is offline fas42  Australia
diyAudio Member
 
fas42's Avatar
 
Join Date: Jun 2012
Location: NSW, Australia
Blog Entries: 10
No, YouTube won't give you the quality in direct replay but you can use it to assess the processes used in the studio, the level of complexity of the mix. Having said that, many music tracks on that website are available at high bit rate, and if you download them and resample to normal uncompressed digital people might get a shock as to how good they can sound ...

The "something else" I have in mind is to give my system a hard time, force it to work hard for its living, that way I know it's got the chops for all sorts of material. Put it this way: if you're going to buy a car would you test drive on the smoothest, straightest road you can find, or would you want to know how it handles itself on a rough back road?
__________________
Frank . . . the truth is, I just like a bit of ASMR ...
  Reply With Quote
Old 6th April 2013, 11:01 PM   #2874
S.A.G. is offline S.A.G.  Italy
diyAudio Member
 
Join Date: Jun 2004
Location: Milano
Back to the drawing board

This is my own interpretation of Scott's masterpiece. Design criteria are:

- all SMD
- as small as possible but with reasonably sized components and spacings, must be hand-solderable for prototyping
- use of matched components where possible, without resorting to hard to find parts, all semis are from NXP and available through standard catalogue vendors like Digikey, Farnell, etc.
- diamond buffer is made of two complementary pairs in SO8
- current mirrors are integrated parts containing two matched BJTs
- diodes are diode connected BJTs for matching
- pinout includes gmC stage output, compensation pins, offset nulling, beside the usual ins, outs, Vccs

I'd like to hear some expert opinion on the layout of my small board. Specifically, I'd like to hear comments about manufacturability, and criticism on obvious mistakes I may have overlooked.

Thank you

Giorgio
Attached Images
File Type: png Swopa Top.png (30.4 KB, 431 views)
File Type: png Swopa Bottom.png (22.4 KB, 429 views)
File Type: png Swopa 3D_1.png (75.5 KB, 431 views)
  Reply With Quote
Old 7th April 2013, 03:01 PM   #2875
rsavas is offline rsavas  Canada
diyAudio Member
 
Join Date: Aug 2012
Location: Ontario
Quote:
I'd like to hear some expert opinion on the layout of my small board. Specifically, I'd like to hear comments about manufacturability, and criticism on obvious mistakes I may have overlooked..
"manufacturability"
Hi Giorgio,
Hard to say without knowing what exact parts (BOM) are used, there orientation referenced to the schematic, sizes of the pads etc.
Post the schematics, gerber/drill data and then I/someone can actual make any sense of a pcb with some lines drawn on it
Every pcb shop has their capabilities, so you first have to find a supplier & meet their guidelines.
If you keep (line/space) > 8mil(0.2mm) you are good to go for most fab's. I usually pick 12mil as default for signals and 25mil for power(For a small pcb as this). For vias I use (32V20) 32mil pad/20mil finished hole (batchpcb req.). If you need smaller then, 30V16,(8/8) 25V13(5/5). Your minimum pad pitch usually sets your minimum line width, a simple rule to follow. I have used a few DFN's (QFN40-6X6-LS0.5MM), I come off the pads with a 9mil trace and then wick up from there.
It is also good to use the widest trace and spacing as possible.
My acid test is always to print out the component mounting layer(s) (1:1) and physically place the comp on the footprint just to be 100% that I got it right.This means getting the components ahead of time or have mechanical equivalents to verify your new/unproven footprints. The quality of the CAD library is imperative or you are wasting money on bad pcb's. I never use the ones that come with the CAD package. From my experience, I find issues with them all, it is a long list of things to check for.
Where are you planning to get a pcb fab'd? Home or outsourced?
I have a few pcb to be made, was looking at
PCB prototype manufacturer doublesided and multilayer - PCB-POOL.COM
or
https://batchpcb.com/
Rick

Last edited by rsavas; 7th April 2013 at 03:12 PM.
  Reply With Quote
Old 7th April 2013, 05:39 PM   #2876
S.A.G. is offline S.A.G.  Italy
diyAudio Member
 
Join Date: Jun 2004
Location: Milano
Rick,

Thank you for your response.

Some more details:

- board size is 42 x 33 mm
- semis are SOT23 size and equivalents
- resistors are 1206
- signal traces are 0.33 mm / 13 mil
- power traces are 0.5 mm / 20 mil
- vias are 40 mil diameter / 20 mil hole
- PTH are 60 x 60 mil pad / 35 mil hole
- clearances are set to 6 mil minimum in DRC

Your suggestion about printing out the top layer and place components for a quick check is very good and I will definitely follow it as I'm using the standard CAD package libraries. I will check them out to see if they need improvements.

Also, PCB pool seems to exactly fit my needs.

Thank you

Regards

Giorgio
  Reply With Quote
Old 7th April 2013, 06:54 PM   #2877
rsavas is offline rsavas  Canada
diyAudio Member
 
Join Date: Aug 2012
Location: Ontario
Giorgio,

Set your DRC rules for 8 mil spacings and see how many violations that you get?
SOT-23/1206 good choices, this is my preference as well for something like this, no need for 0805.
Your design is what I know as 12/12 technology, except your 6 mil DRC is too close for 12/12, so it is a mix. 8 mil DRC min spacing, is a safer way to go for a design such as this, your choice however. These days 5 mil spacing is a safe bet even for ? pcb shops.
I am always surprised how many EE's, can not or chose not, to layout there own pcb's. It is a very important part of the design process, just like software and mechanics.
Cheers
Rick
  Reply With Quote
Old 7th April 2013, 08:00 PM   #2878
S.A.G. is offline S.A.G.  Italy
diyAudio Member
 
Join Date: Jun 2004
Location: Milano
Rick,

DRC clearances set at 8 mil passes with no errors.

The default DRC setting for ground plane to board sides clearance is 25 mils and is clearly violated in my layout. I wonder whether this is really critical however. I could easily change either the clearance setting or the ground plane area but I'm not sure it is really worth it. Any suggestion?

I totally agree with you about layout being part of the design process. I'm doing this exercise because it is a great learning experience, beside for the fun of it.

Thank you

Regards

Giorgio

Last edited by S.A.G.; 7th April 2013 at 08:02 PM.
  Reply With Quote
Old 7th April 2013, 08:01 PM   #2879
S.A.G. is offline S.A.G.  Italy
diyAudio Member
 
Join Date: Jun 2004
Location: Milano
double post. Sorry.

Giorgio

Last edited by S.A.G.; 7th April 2013 at 08:03 PM. Reason: double posting
  Reply With Quote
Old 7th April 2013, 08:22 PM   #2880
rsavas is offline rsavas  Canada
diyAudio Member
 
Join Date: Aug 2012
Location: Ontario
If you bring your copper to routed edge, then you will get burrs, as this is the last operation, routing the image out of the panel.
I am doing a design now, RF using a Si4770, I want the option of putting a shield around the whole pcb ( & ground it) , so this is the only reason why I will bring the copper to the very edge of the routed edge.
Yes layout is fun for me as well. Gives you the physical perspective, which is usually a paper design, up this point in the design cycle, unless you do some prototyping before doing final layout.
In so many designs, the pcb layout is a throw it over the wall approach, which is flawed in so many ways.
Rick

Last edited by rsavas; 7th April 2013 at 08:25 PM.
  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
Discrete OPAMP audio-gd Vendor's Bazaar 27 20th September 2012 04:02 PM
discrete opamp help blackpowderaudio Parts 0 16th December 2009 03:46 PM
THAT transistor headphone amp (250ma discrete opamp) design sanity check. Russ White Headphone Systems 19 13th December 2007 12:52 PM


New To Site? Need Help?

All times are GMT. The time now is 07:16 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