Tantalum cap to set gain in LM386 - Page 2 - diyAudio
Go Back   Home > Forums > Amplifiers > Chip Amps

Chip Amps Amplifiers based on integrated circuits

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 26th June 2011, 09:59 PM   #11
diyAudio Member
 
Join Date: Jun 2011
Quote:
Originally Posted by woody View Post
Going to a tantalium cap is probably a bad idea they sound bad. And by the way tantalium caps are electrolitic.
Yeah I know that. I meant, would there be any difference between using something like a Panasonic FM vs using a Kemet solid tantalum.
  Reply With Quote
Old 26th June 2011, 10:53 PM   #12
diyAudio Member
 
Join Date: Jun 2011
I have a nasty reputation for making things more complicated than I originally intended to make them. I think I'm just going to screw trying to make it into half guitar amp/ half iPod amp...The option will be there to use the 1/4 inch jack, but I'm not going to guarantee it sounds great. (Good friend, eh?).

I think I'll lower the gain to around 50, which will hopefully be a decent median. I could potentially add a gain knob...but I'm not sure if anyone really wants to toy with adjusting the gain when you want to play a song with your iPod. >.>
  Reply With Quote
Old 27th June 2011, 12:14 AM   #13
diyAudio Member
 
Join Date: Jan 2002
Location: Tyrone Ga. U.S.A.
Nope they are electrolic... Near the end of the articles 2 types of electrolitic caps are listed aluminum and tantalium.



Electrolytic capacitor - Wikipedia, the free encyclopedia
  Reply With Quote
Old 27th June 2011, 01:16 AM   #14
diyAudio Member
 
Join Date: Jun 2011
Using an electrolyte is just a style of making capacitors. The electrolyte makes a gap between the conductors, and thus makes capacity.
  Reply With Quote
Old 27th June 2011, 01:27 AM   #15
! is offline !  United States
diyAudio Member
 
Join Date: Jun 2005
Location: Midwest
^ wet (electrolytic) tantalum capacitors do exist but they are very rarely used today outside of military, aerospace, etc, places where there are extreme conditions and I'm not sure if they are even used in these fields anymore.

When anyone mentions "tantalum" without "wet" or "electrolytic", almost nobody assumes they mean other than solid non-electrolytic type anymore, and I'm not aware of anyone using wet tants in modern chipamps.

The typical little yellow epoxy blob tantalums about half the size of a cotton swab tip are solid non-electrolytic, as are the chip tantalums used in surface mount electronics built over the last couple decades or longer.

Last edited by !; 27th June 2011 at 01:37 AM.
  Reply With Quote
Old 27th June 2011, 01:33 AM   #16
diyAudio Member
 
Join Date: Jun 2011
Also,

I know this is a niche category, but with ~1W of power and mid-fi sound quality, what kind of driver would be ideal? I want to spend $10 or less. Remember this is just a small birthday present.

Here's some drivers I've been looking at. What's the deal on impedances? For an LM386, should I be running lower or higher impedances. I'm using LM386N-3.

2" Tymphany/Peerless: Tymphany 2" Full-Range Neodymium Driver

3" Peerless: Peerless India W3-LK76-PBK 3" Paper Cone Shielded Woofer 4 O

3" Tang Band: Tang Band W3-1053SC 3" Full Range Driver

3" Hivi: HiVi B3S 3" Shielded Aluminum Driver Square Frame

I'm kind of liking the 2" peerless because of it's price right now, but if the others can be justified, that's cool too.

Is the Hivi any good? Looks interesting.

Thanks.
  Reply With Quote
Old 27th June 2011, 03:07 AM   #17
! is offline !  United States
diyAudio Member
 
Join Date: Jun 2005
Location: Midwest
-3 is only 700mW output, ideally you would pick one with the highest SPL level you can find. All those you linked are in the 81-85db range which could be worse, but with your chip having only 700mW, and that at THD levels you probably won't want except "Maybe" with the guitar, it doesn't seem as though a long throw driver is needed and would just add cost. Does it need to be tiny? Here's one with 89.6dB SPL for $1.50:

3" x 5" Ribbed Paper Cone Shielded Woofer Speaker

As for impedances, with a 4 ohm load they're graphing 10% THD at only ~ 350mW output on the LM386 datasheet. On 8 ohm load (with only 12V power input since it's the -3 version) it jumps to about 830mW and at 16 Ohms @ 12V input it is about 1W, but also, device dissipation at 16 ohms is only half that of driving 8 ohms (0.4W vs 0.83W). I'd consider epoxying a heatsink plate of some sort on the top and using thick traces but maybe I'm way off on the volume level you want this project to be capable of.

0.83W starts to become a lot for a little chip w/o any heatsink tab, ideally I'd go with a 16 ohm speaker IF you can keep SPL high enough and stay in the budget and size you want.

The speakers you linked, they sort of seem like a mismatch, too nice for LM386. On the other hand if the speaker will be visible, all the ones you linked look *nicer* to the naked eye so if I were to pick one I'd do it based on SPL, frequency range, and impedance, making 3" Tang Band the winner,

Tang Band W3-1053SC 3" Full Range Driver

... except, we don't know what frequency range you need or how loud you want it to go, and I can't predict how loud LM386 will sound with those before it gets unpleasant to listen.

Last edited by !; 27th June 2011 at 03:13 AM.
  Reply With Quote
Old 27th June 2011, 03:22 AM   #18
diyAudio Member
 
Join Date: Jun 2011
The only reason I said I'd use the -3 is because I have a few of them. I'm going to order a few things off of Digikey anyway...so should I switch over to a different version? -1? -4?

Yeah I kind of thought it was a bit of a mismatch myself.

Perhaps something like this? Seems to fit the bill. 16ohm, 4", foam surround (vs paper), $2

JAMO 40250 4" Paper Cone Shielded Midrange 16 Ohm

Kind of tempting....There's no reviews for it, but how bad could it be?

Thanks for the detailed explanation.

Last edited by FenderBender11; 27th June 2011 at 03:46 AM.
  Reply With Quote
Old 27th June 2011, 11:55 AM   #19
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
82dB/W @ 1m is far too low for battery powered anything.
__________________
regards Andrew T.
  Reply With Quote
Old 27th June 2011, 12:28 PM   #20
Banned
 
Join Date: Nov 2006
Location: Torpoint
Quote:
Originally Posted by ! View Post
^ wet (electrolytic) tantalum capacitors do exist but they are very rarely used today outside of military, aerospace, etc, places where there are extreme conditions and I'm not sure if they are even used in these fields anymore.

When anyone mentions "tantalum" without "wet" or "electrolytic", almost nobody assumes they mean other than solid non-electrolytic type anymore, and I'm not aware of anyone using wet tants in modern chipamps.

The typical little yellow epoxy blob tantalums about half the size of a cotton swab tip are solid non-electrolytic, as are the chip tantalums used in surface mount electronics built over the last couple decades or longer.
Speaking from the MoD point of view - Yes I'm a Chief Engineer in the Royal Navy. Wet Tants have become obsolete because they tended to explode.

In Civvy Street Tants are more expensive than Electrolytics, especially in higher values.

The only real benefit of tants is that they tend to perform better when the DC voltage across them is very low. Standard electrolytics rely upon the DC voltage to make them capacitors in the first place.
  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
tantalum cap Nikon1975 Tubes / Valves 4 23rd January 2010 08:13 AM
Using a Voltage Meter to set your amp gain? Flyin11 Car Audio 29 2nd February 2008 09:03 PM
tantalum cap leakage? AndrewT Parts 5 12th December 2005 10:35 PM
How to set AC current gain in Aleph-X ? yoke Pass Labs 11 26th August 2004 08:12 AM
Tantalum cap identificaton. Please help. sv Parts 1 1st April 2004 01:31 AM


New To Site? Need Help?

All times are GMT. The time now is 01:30 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