Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Chip Amps Amplifiers based on integrated circuits

Resistor tolerance on Chipamp.com LM3886 boards
Resistor tolerance on Chipamp.com LM3886 boards
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 16th October 2017, 02:58 AM   #1
Hogwild is offline Hogwild  Canada
diyAudio Member
 
Join Date: Oct 2010
Default Resistor tolerance on Chipamp.com LM3886 boards

Hi everyone:

Complete newbie here. No knowledge of electronics, really. I want to substitute Rf, R2 and R3 on the Chipamp.com LM3886 dual mono boards. I believe the R2 resistors I received with the kit were 1%, but then again, they were 22.1K and the schematic shows 22K.

I'm ready to buy new resistors, but what tolerance should I use for Rf, R2 and R3. The reason I ask is that retailers near me, and the usual online retailers (DigiKey, Mouser and a local one) do not have anything better than 5% components. Oh, and while I'm at it, will 1W resistors fare well, or should I hold out for 2W resistors.

Thanks

Last edited by Hogwild; 16th October 2017 at 03:10 AM.
  Reply With Quote
Old 16th October 2017, 03:14 AM   #2
abraxalito is offline abraxalito  United Kingdom
diyAudio Member
 
abraxalito's Avatar
 
Join Date: Sep 2007
Location: Hangzhou - Marco Polo's 'most beautiful city'. 700yrs is a long time though...
Send a message via Yahoo to abraxalito
5% is perfectly OK but I just did a Mouser search and I found they have over 33,000 metal film axial resistor SKUs better than 5%.

http://www.mouser.com/Passive-Compon...z0wpn9Z1z0z819
__________________
'The total potential here must be nothing less than astronomical.'
'Nothing less. The number 10 raised almost literally to the power of infinity.'
  Reply With Quote
Old 16th October 2017, 03:19 AM   #3
Damon Hill is offline Damon Hill  United States
diyAudio Member
 
Join Date: Mar 2001
Location: Auburn, WA (somewhere between Seattle and Tacoma)
Send a message via ICQ to Damon Hill
I'd prefer to use 1% metal film; 5% are almost certainly carbon film, so of (slightly) lower quality. The suppliers you mention all have 1% metal film resistors in abundance. In the feedback circuit, I like to use .1% or better bulk foil resistors though they are very expensive.

A 2 watt resistor will probably run (a little bit) cooler than a 1 watt. But if the application calls for a quarter watt resistor at that point, a 2 watt resistor probably won't physically fit. There's little point in going for the larger size.
  Reply With Quote
Old 16th October 2017, 05:39 AM   #4
PRR is offline PRR  United States
diyAudio Member
 
PRR's Avatar
 
Join Date: Jun 2003
Location: Maine USA
Quote:
Originally Posted by Hogwild View Post
{snip}...I believe the R2 resistors I received with the kit were 1%, but then again, they were 22.1K and the schematic shows 22K. ...what tolerance should I use for Rf, R2 and R3.... should I hold out for 2W resistors.
You could use 20% resistors, if they were still around, if they were not junk; and 0.03Watts is ample.

BTW, all the resistors INside the chip are +/-30% tolerance, and it works fine.

"22K" is in the 10% series. There is an old trick, when you want a higher precision, of never saying "22K" but "22.1K". This is so your factory workers won't stuff 22K 10%, but have to look for the 22.1K parts.

This may be why you had trouble on-line. Don't look for "22K". Look for "2%" (or 1%), then find a close value in the list.

The absolute value of these parts is not very important. Some arbitrary choice of offset suggested two <25K resistors, and a third to get gain of about 32. 22K and 680 are very suitable 5% values. 20K and 618 would work but are not standard 5% values. 22K and 750 or 620 would work with hardly-different gain.

When you make a million stereos, you NEVER buy more precision than you need. Extravagant pennies here and there speeds your path to bankruptcy. DIY economics is VERY different.

If you use 10% parts to set gain in a stereo system you risk a 1dB unbalance between channels. This may be moot because speaker pairs are rarely matched L-R to 1dB. However resistors are easier to make precise than speakers, and cheaper too, so we do what we can. Many-many stereos were built with 5% gain-set resistors and balanced fine.

The key thing is *ratios*, and for stereo, pairs of ratios. The two 22K in each side may be 20% different (there's chip errors and these resistors were picked to make them small). In one side, the 22K could be 10K or 30K no real difference. But *between* sides the "22K:680" ratio should be very close.

Like building a house. It hardly matters if the first floor walls are 7'8" or 7'9". But if you get 7'8" in the west wall and 7'9" in the east wall, the upstairs floor will slant enough to notice. You want a 1:1 ratio; and (interestingly) a house's walls are "matched" to about 1%.

In the last 30 years the cost of 2% and 1% parts has been falling. Old resistors were mixed of soot and clay, then sorted. Today the deposition can be very precise right out of the pot. I was once scolded for using 5% resistors as twist-ties, but today 2% parts are cheaper than twist-ties.

So go 2% or 1%... the "added cost" is less than the postage, and far less than the value of your personal satisfaction. And just to make 2%/1% resistors, the process has to be very well controlled, so they WILL be "good" resistors.

In another thread I just advocated over-sizing resistors. But here Rf can not see more than 0.056 Watts. 1/8W would be ample on the face of it. There's some concern about thermal effects and other moonshine. It used to be that 1/2W resistors were cheaper than any other. No longer true, but if 1/2W fits the board that is what I would use.

Yes, the local store may not stock 2% parts. There are 2.5X more values in the 2% series than the 5% series so for small sales the inventory headache is too big. 1% is 2X as many values again, so only large stores (such as DigiKey and Mouser!) will handle them.

Last edited by PRR; 16th October 2017 at 05:41 AM.
  Reply With Quote
Old 16th October 2017, 07:10 AM   #5
Mark Whitney is offline Mark Whitney  Netherlands
diyAudio Member
 
Mark Whitney's Avatar
 
Join Date: Feb 2013
Location: Netherlands
The board has 5mm lead spacing for the resistors. You could use something like this.


Or, if you want to spend more, look for Caddock MK132 resistors as used by Audiosector in their kits.
__________________
Regards Mark.
  Reply With Quote
Old 16th October 2017, 08:36 AM   #6
AndrewT is offline AndrewT  Scotland
R.I.P.
 
Join Date: Jul 2004
Location: Scottish Borders
Quote:
Originally Posted by PRR View Post
............
If you use 10% parts to set gain in a stereo system you risk a 1dB unbalance between channels..............
No.
using +-10% resistors in the gain section could result in a gain imbalance of 3.486dB
0.9/1.1 = 0.81818
1.1/0.9 = 1.22222
The ratio of 1.2222:0.81818 is 1.493827, i.e. the Voltage Ratio could be out by >49% That is 3.486dB

Changing to 1% resistors reduces that maximum imbalance to <0.347dB and more likely in an actual build to <<0.2dB, i.e. virtually inaudible.

The "standard" range stocked by retailers is the E24 range for resistors and in 1% tolerance, from 10r to 1M0.
__________________
regards Andrew T.

Last edited by AndrewT; 16th October 2017 at 08:40 AM.
  Reply With Quote
Old 16th October 2017, 10:03 AM   #7
KatieandDad is offline KatieandDad  United Kingdom
diyAudio Member
 
KatieandDad's Avatar
 
Join Date: Nov 2011
Location: UK
But 10x of the value that you want and match them.
  Reply With Quote
Old 16th October 2017, 05:29 PM   #8
Hogwild is offline Hogwild  Canada
diyAudio Member
 
Join Date: Oct 2010
Uh..that was a lot of info, thanks, but I'm still confused. I don't know what tolerance Chipamp.com people used. Does anyone know? I figure I'll just use whatever they used.

Some of you are saying there are plenty of 19.6k or 20k resistors in lower than 5% tolerance 1W or more. Can you please link, cause I'm just not seeing that at Digikey or Mouser Canada, and I checked about 5 times for each. There are listings for them, but they display as ou tof stock with a lead time of 16 weeks. That doesn't help me.
  Reply With Quote
Old 16th October 2017, 05:44 PM   #9
AndrewT is offline AndrewT  Scotland
R.I.P.
 
Join Date: Jul 2004
Location: Scottish Borders
which resistors are shown as 1W in the chipamp circuit?
link to your schematic so that we can see what you are looking at.
__________________
regards Andrew T.
  Reply With Quote
Old 16th October 2017, 05:52 PM   #10
Hogwild is offline Hogwild  Canada
diyAudio Member
 
Join Date: Oct 2010
None. Chipamp.com didn't specify how many watts any of the resistors were. And since I know nearly zero about electronics, I'm at the mercy of you kind folks.
  Reply With Quote

Reply


Resistor tolerance on Chipamp.com LM3886 boardsHide 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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
WTB: Chipamp LM3886 Boards ecclesand Swap Meet 2 1st December 2016 01:31 PM
Overlays for Chipamp.com LM3886 boards? Hogwild Chipamp 20 9th May 2016 02:22 AM
ChipAmp LM3886 Boards Sheldon Swap Meet 2 25th November 2013 11:46 PM
LM3886 Chipamp bare boards Zero Cool Swap Meet 4 6th August 2012 10:40 PM
Three-resistor LM3886 chipamp Mick_F Chip Amps 20 14th August 2006 02:59 PM


New To Site? Need Help?

All times are GMT. The time now is 05:57 PM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.79%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio
Wiki