Setting GAIN on GAINclones - 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 19th December 2006, 03:45 PM   #1
Lucas_G is offline Lucas_G  Netherlands
diyAudio Member
 
Join Date: Nov 2002
Location: Netherlands
Default Setting GAIN on GAINclones

Hi Folks,

I have build two 3886 monoblocks with the boards designed by BrianGT from www.chipamp.com

I used all the values as described on their site.

Now my gain is much too high.

I tried various preamps, but I can hardly move the volumecontrol or everything is becoming much too loud.

What is the best way to lower down the input sensitivity while still maintaining the good soundquality?

I considered adding a 10 kOhm resistor at the cinch-connectors...

In the manual it is stated that one schould increase R3 to lower gain. Is that a better method? How much higher should I go?
(National Semiconductor has a value of 1 kOhm in their circuit).

Please state the resistor numbers as shown on the picture included.

Why does the BrianGT version choose such an extremely high gain? It is much higher than all my other amps!


Thanks.

Lucas
Attached Images
File Type: jpg lm3886briangt.jpg (47.9 KB, 415 views)
  Reply With Quote
Old 19th December 2006, 04:03 PM   #2
diyAudio Member
 
Steve Eddy's Avatar
 
Join Date: Sep 2002
Location: Sacramento, CA
Default Re: Setting GAIN on GAINclones

Quote:
Originally posted by Lucas_G
In the manual it is stated that one schould increase R3 to lower gain. Is that a better method? How much higher should I go?
That's the better way to go than trying to attenuate the signal upstream.

Don't go any higher than 2k. The chip needs to maintain a minimum gain of 10 for stability reasons.

se
  Reply With Quote
Old 19th December 2006, 05:06 PM   #3
diyAudio Member
 
Join Date: Apr 2005
Location: In the Wild, Wild West
You can either lower the Rf resistor (22K) or increase the R3 resistor (680) or both. The gain is Av = 1+ Rf/R3. Right now it is at 33.3V/V or a tad over 30dB. Quite a bit of gain. If you are using the Ci cap then it would be better to increase the R3 resistor. National typically shows the circuit with a gain of 21 V/V (20K/1K). Or you can put a 1K pot in series with the R3 resistor and vary the gain from the current 33 down to 12. Figure out what you like best and then change the value once and for all.

-SL
  Reply With Quote
Old 19th December 2006, 05:12 PM   #4
Lucas_G is offline Lucas_G  Netherlands
diyAudio Member
 
Join Date: Nov 2002
Location: Netherlands
Hi Steve,

Thanks for your answer.

BrianGT states that the gain can be calculated: Gain = 1 + Rf / R3 and that with R3=660 Ohm one gets 33 dB of gain.
I do not know what Rf means here...

If I would up R3 to 1 kOhm, how much gain would that be?

Regards,

Lucas
  Reply With Quote
Old 19th December 2006, 05:16 PM   #5
Lucas_G is offline Lucas_G  Netherlands
diyAudio Member
 
Join Date: Nov 2002
Location: Netherlands
Quote:
Originally posted by SpittinLLama
You can either lower the Rf resistor (22K) or increase the R3 resistor (680) or both. The gain is Av = 1+ Rf/R3. Right now it is at 33.3V/V or a tad over 30dB. Quite a bit of gain. If you are using the Ci cap then it would be better to increase the R3 resistor. National typically shows the circuit with a gain of 21 V/V (20K/1K). Or you can put a 1K pot in series with the R3 resistor and vary the gain from the current 33 down to 12. Figure out what you like best and then change the value once and for all.

-SL

Hi Spittinlama,

That answers my last question. Thanks!

Lucas
  Reply With Quote
Old 19th December 2006, 08:04 PM   #6
diyAudio Member
 
Join Date: May 2005
Location: Seattle, WA, USa
I never adjusted my gain - it turned out fine - but I did ask a very similar question:

Matching a commercial preamp - adcom
  Reply With Quote
Old 19th December 2006, 08:31 PM   #7
Lucas_G is offline Lucas_G  Netherlands
diyAudio Member
 
Join Date: Nov 2002
Location: Netherlands
Quote:
Originally posted by schmalex
I never adjusted my gain - it turned out fine - but I did ask a very similar question:

Matching a commercial preamp - adcom

Hi Schmalex,

Thanks for that thread. It too gives some answers.

I have just tried the whole thing. I added a 1 kOhm resistor in series with the 680 Ohm resistor R3. This gives a R3 of 1.68 kOhm, and therefore a gain of 14.

I can now easily adjust the volume, but apparantly it kills the sound! The amp lacks openness and air...

Has anyone tried different R3's?
I will also try 1kOhm (as prescribed by NS), but if it is still less good sounding, I will try adding the input sensitivity by adding resistors at the input. I understand that it is not very elegant to attenuate before amplifying, but if the whole concept of the gainclone suffers from a lower gain, then there is no other option, is there?

Anyone same experiences?

Lucas
  Reply With Quote
Old 20th December 2006, 12:17 AM   #8
CarlosT is offline CarlosT  United States
diyAudio Member
 
Join Date: Oct 2006
Heck...I'm going for a gain fo 60
  Reply With Quote
Old 20th December 2006, 07:49 AM   #9
Lucas_G is offline Lucas_G  Netherlands
diyAudio Member
 
Join Date: Nov 2002
Location: Netherlands
Quote:
Originally posted by CarlosT
Heck...I'm going for a gain fo 60
Hi Carlos,

A gain of 60?????????

Then you will probably use a 500 kOhm pot and speakers with 80 dB (non-) efficiency....?

Speaking of gain. It seems that Peter Daniel, BrianGt and all the others use the Gainclone with a gain of 33 and then they choose a relatively strong pot of 25 kOhm to turn things down. Did they do comparisons versus the use of a gain of 20 and a 10 kOhm pot? COMMENTS FOLKS!

Lucas
  Reply With Quote
Old 20th December 2006, 08:02 AM   #10
diyAudio Member
 
ianpengelly's Avatar
 
Join Date: Oct 2006
I use the chipamp.com boards and driven by an either an Audiolab pre-amp or my Cambridge Audio amp (with a unity gain buffer pre-out) there seems to be a reasonable amount of control over the the volume. However, the pot in the Cambridge audio is something like a 150k device.
  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
Help with GainClone gain setting johan851 Chip Amps 35 15th February 2008 05:33 PM
Gain Setting HU/Amp vadi Car Audio 2 19th July 2006 11:57 AM
Opamp gain setting resistors values deduikertjes Solid State 7 20th June 2006 06:59 AM
Heretical Unity Gain line stage PLUS a little gain ? yagas Tubes / Valves 7 24th January 2006 01:30 PM
Question on gain setting when bridged jtfoo Chip Amps 2 16th July 2004 02:21 PM


New To Site? Need Help?

All times are GMT. The time now is 12:40 AM.


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