Chipamp as preamp? - 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 11th May 2004, 12:56 AM   #1
diyAudio Moderator Emeritus
 
lumanauw's Avatar
 
Join Date: Oct 2002
Location: Bandung
Send a message via Yahoo to lumanauw
Default Chipamp as preamp?

I wanted my system to be simple. I have only one supply, +/-35V.
I need gain preamp. I can built it by opamp, but it will need another supply, +/-15.
So, I think about building gain preamp using chipamp, like TDA7294 so I dont have to provide another supply.
Has anyone built chipamp as gainpreamp? Or it is not suitable at all for small signal gain preamp?
  Reply With Quote
Old 11th May 2004, 01:21 AM   #2
HDTVman is offline HDTVman  United States
diyAudio Member
 
Join Date: Aug 2001
Location: Chicago area
Why not use 7815/7915 regulators from main PS to give you the voltage you want for preamp power supply? I know some of the others may try to give you reasons not to do this but the big boys have been doing it for years so why can't you? After all we are only talking 4 to 6 parts. 2 regulators, 2 output caps and maybe 2 bypass caps. Seams simple enough to me.

Later BZ
__________________
What ever makes the tunes flow
  Reply With Quote
Old 11th May 2004, 05:28 AM   #3
GregGC is offline GregGC  Canada
diyAudio Member
 
Join Date: Oct 2003
Location: Toronto
Or, why don't you just set the gain you need and no preamp needed at all. If you don't know, the gain is set by the two resistors in the NFB.

How much gain do you need?

/Greg
  Reply With Quote
Old 11th May 2004, 07:12 AM   #4
djQUAN is offline djQUAN  Philippines
diyAudio Member
 
Join Date: May 2004
Location: manila
Send a message via MSN to djQUAN Send a message via Yahoo to djQUAN
.............or you can add the additional +/-15V supplies using only dropping resistors and zeners and caps, much like rod's P27 preamp.
  Reply With Quote
Old 11th May 2004, 07:49 AM   #5
diyAudio Moderator Emeritus
 
lumanauw's Avatar
 
Join Date: Oct 2002
Location: Bandung
Send a message via Yahoo to lumanauw
No, no, I do not intended to use opamp at all. Infact I wanted to use chipamp for opamp use. Why? In another thread (MOX thread) , someone built active Xover using diyopamp, the supply is more than +/-30V (opamp uses +/-15V). I think why dont we use chipamp as opamp?
  Reply With Quote
Old 11th May 2004, 07:55 AM   #6
djQUAN is offline djQUAN  Philippines
diyAudio Member
 
Join Date: May 2004
Location: manila
Send a message via MSN to djQUAN Send a message via Yahoo to djQUAN
because power opamps are more expemsive, has less SQ compared th most opamps, preamps handle only small signals and are usually stable at unity gain.
  Reply With Quote
Old 11th May 2004, 08:02 AM   #7
boholm is offline boholm  Denmark
diyAudio Member
 
boholm's Avatar
 
Join Date: Apr 2004
Location: Copenhagen
. . . but still there isn't a technical reason not to do it.

One can always discuss the normal hifi/audio quality issues, but simply and technically there shouldn't be anything against it. You must however look in the technical specs of the opamp to see, if it can handle, whatever you wish it to do. Diagrams, please . . .
__________________
Best regards
Bo
  Reply With Quote
Old 11th May 2004, 08:23 AM   #8
diyAudio Moderator Emeritus
 
lumanauw's Avatar
 
Join Date: Oct 2002
Location: Bandung
Send a message via Yahoo to lumanauw
My candidate for this is LM1875, because it is small chipamp, only TO-220 size. Just download the datasheet, I found some thing that maybe a problem if I use it as opamp.
In Xover, the opamp is only used as buffer, the -input is connected to output.

1. The LM1875 datasheet said that it is stable for gain 10 or more. Is this mean this LM chip cannot be used as buffer (-input tied to output)?

2. The datasheet also said about possibly ringing with capacitive load. In Xover, it is always capacitive load

3. The bias current is 70mA. Hmmm.... If the supply is +/-25V, then it will dissipate 3.5W? At first I think I can use chipamp without heatsink, if only used as opamp. But this dissipation certainly needs heatsink.

I just look at the LM1875 datasheet for a glance and has found this 3 obstacle if I wanted to use it as opamp.

It is not possible to use chipamp as opamp?
  Reply With Quote
Old 11th May 2004, 08:57 AM   #9
moamps is offline moamps  Croatia
diyAudio Member
 
Join Date: Oct 2002
Location: Croatia
Quote:
Originally posted by lumanauw
It is not possible to use chipamp as opamp?
Hi,
Using chipamp as opamp hasn't any sense. IMHO.

Regards
  Reply With Quote
Old 11th May 2004, 09:11 AM   #10
diyAudio Member
 
Join Date: Mar 2001
Location: Brazil
Quote:
Originally posted by lumanauw

I just look at the LM1875 datasheet for a glance and has found this 3 obstacle if I wanted to use it as opamp.

It is not possible to use chipamp as opamp?
It is possible, but no advisable.

A preamp's chip should have several capabilities that no power amp chip has: it should work in class A (if possible), it should have a large bandwidth gain and it should have low distortion.

If you look again, the MOX articles are based on a discrete op-amp, which should even be better than a monolithic chip.

You can use the +/-35v you have and filter/lower it to a voltage you can feed into +/-18v or +/-24v regulators, to power your preamp ICs.

Or you can go discrete and power it higher.


Carlos
  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
preamp for chipamp getafix Chip Amps 1 17th October 2007 10:49 AM
what preamp do you use with your chipamp? jarthel Chip Amps 5 26th June 2007 11:35 PM
chipamp passive preamp / crossover DoomPixie Chip Amps 4 23rd October 2006 09:13 PM
Preamp specs for a chipamp zenon Chip Amps 13 21st May 2006 12:15 AM
chip preamp for my chipamp? Russ White Chip Amps 3 9th March 2005 03:51 PM


New To Site? Need Help?

All times are GMT. The time now is 06:00 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