Metal can audio opamps? - Page 2 - diyAudio
Go Back   Home > Forums > Design & Build > Parts

Parts Where to get, and how to make the best bits. PCB's, caps, transformers, 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 17th January 2013, 06:44 PM   #11
qusp is offline qusp  Australia
diyAudio Member
 
qusp's Avatar
 
Join Date: Oct 2009
Location: Brisbane, Australia
opa228/2228, opa2111, opa111, the newish (current feedback) lme49713HA
  Reply With Quote
Old 17th January 2013, 06:50 PM   #12
GoatGuy is offline GoatGuy  United States
diyAudio Member
 
Join Date: Dec 2012
Location: SF Bay Area
You kind of have to ask the question ... why metal cans?

Its not really like they do anything in a normal conservative design. In the "old days" they put (everything) in metal cans for 4 reasons:

[1] Because they hadn't worked out "engineering plastic" that could safely be squeezed onto chips during manufacture. [Resolved by the early 1960s]

[2] Because metal cans were hermetic, preventing moisture in particular, but for industry, other noxious gases from touching the semiconductor surfaces (which can gradually degrade and destroy them)

[3] To dissipate greater power through air convection (especially when transistors, even "low power" ones were near their limits in power dissipation

[4] Shielding and "input super-resistance" (i.e. ensuring that things like MOSFETs and JFETs had their gates attached directly to a pin that is insulated with glass, one of the best insulators when clean. When making "sample and hold" circuits, this is a large requirement.)

And I suppose

[5] Military requirements, spec-sheet conformance, to allay the fears (or ultimate-demands) of nervous designers and equipment builders.

Seriously though ... in the last 35 years, the dissipation thing has been answered (best!) by simply making more efficient op-amps and higher conduction plastics. The "insulation" thing has been resolved for decades. The plastics are great insulators (and moreover have been engineered to prevent tribo-electric effects AKA "static electricity from rubbing"). In terms of interference and shielding, the present-day op-amps are placed on circuit boards that are carefully laid out, and it isn't a problem. Op-amp chips ... unbeknownst to most people ... have been almost entirely re-engineered in the last 20 years, even if they carry "standard" designations. Much lower power, better onboard transistors, much higher accuracy of thin-film resistors. Higher Hfe and gm.

So... unless you have either

[6] Esthetics ... 'cuz cans look cool -- or --
[7] Opportunity... A bag of them sitting around

in mind, I recommend staying away from them, for circuit-to-circuit, you're far more likely to get an older "NOS - new old stock" item that has significantly more variable noise performance, dissipation and quiescent drift characteristics than a brand new, state of the art, recent-product-addition.

So sez me.

GoatGuy
  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
-: Best audio OpAmps :- audioPT Parts 62 9th April 2013 11:44 AM
FS: NOS metal cap Burr-Brown OPA602CM opamps + adapters leeperry Swap Meet 5 24th October 2011 01:28 AM
FS: Metal Can Opamps and buffer mravlca Swap Meet 3 8th March 2011 08:46 PM
FS: LME49720 Audio OpAmps zener_diode Swap Meet 2 17th February 2008 04:13 PM
Military opamps in audio Uchi Deshi Chip Amps 1 3rd August 2006 05:43 PM


New To Site? Need Help?

All times are GMT. The time now is 08:55 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