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

Solid State Talk all about solid state amplification.

Different pre amp idea
Different pre amp idea
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
Thread Tools Search this Thread
Old 24th March 2008, 01:13 PM   #1
bartek is offline bartek  Australia
diyAudio Member
Join Date: Mar 2008
Default Different pre amp idea

Hey Guys I've just been floating around the forum the last few weeks and have already learned a lot but couldn't find the answer to my question. Its my first post and I've still got to learn a lot so be easy on me

Basically I want to make an integrated amplifier and the was thinking of making a decent quality headphone/preamp circuit and (using a select switch) choosing to send the output from the headphone/preamp straight to the headphone jack or choosing to send the headphone/preamp output to the speaker amplifier input.

I was thinking of using a Jung multiloop circuit for the headphone/preamp like the Pimeta described on Tangent's site (except only amplifying two channels and using cheaper opamps) and a basic LM3886 chip amp for the speaker amp.

...Is this a good idea or should I just put the select switch after the volume pot and send the signal to the head amp OR the chipamp?....
  Reply With Quote
Old 25th March 2008, 01:15 PM   #2
bear is offline bear
diyAudio Member
bear's Avatar
Join Date: Apr 2002
Location: New York State USA
If you have a volume pot after a switch that selects between two outputs, then you need two volume pots?

As far as using "cheaper opamps" - why?
They're dirt cheap now!!

Use good opamps.

The circuit is overkill now, with the loop feedback after the buffer.
It would probably work and sound just fine without the extra loop... but no matter...

Not sure why one needs the current source pull down at the output of the opamp - presumably to pull it into "class A" - given the vanishingly low distortion figures of the latest crop of opamps... dunno, maybe there is some justification still... guess it won't hurt.

Although it is heresy to some, my feeling is that you can likely still hear differences depending on the choices of opamps, fets, and especially buffers... maybe even the resistors.

More heresy, you might actually like listening to it more if you use carbon comp resistors not metal film...

Thing is... you do not really need a preamp to amplify things that are already at line level on their outputs, assuming the gain of the amplifier (chipamp?) that you are using drives to full power (or loud enough) with the line output of your source! You'd only want a volume pot, and perhaps it can be argued a buffer before the pot, not a gain stage.

If you use a gain stage, you'll just be knocking down the gain with the pot... it's ok, but something to think about.

http://www.bearlabs.com -- Btw, I don't actually know anything, FYI -- every once in a while I say something that makes sense... ]
  Reply With Quote
Old 25th March 2008, 03:30 PM   #3
bartek is offline bartek  Australia
diyAudio Member
Join Date: Mar 2008
Thanks for your reply bear.

I forgot to mention that I was planning to omit the class A bias, and you're right about using good opamps but pricing in Aus can be unreasonable... it will be cheaper to order everything from the US than from the shop down the road...

The idea was that if I already had a decent headphone amp circuit I could use it as a preamp for the speaker amplifier when needed; as you pointed out though the gain might be too high so perhaps i will try reducing the gain of the headamp/preamp somewhat and also tweaking the speaker amp.
  Reply With Quote
Old 25th March 2008, 03:42 PM   #4
Pan is offline Pan  Sweden
diyAudio Member
Join Date: Sep 2002
Or slap a pot on the LM3886 with an extra resistor as a pad. Then add a 50-100ohm resistor in paralell with the speaker output for feeding the cans.

  Reply With Quote


Different pre amp ideaHide 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
I really have no idea what I'm doing here... d to the g Multi-Way 10 7th March 2008 06:04 PM
P.S idea noyan Power Supplies 15 19th December 2007 08:50 PM
An idea! Fully balanced TDA1541A DAC idea. Please comment! cartman Digital Source 8 17th July 2007 08:18 AM
Just an idea bob123 Subwoofers 4 9th April 2006 02:28 PM

New To Site? Need Help?

All times are GMT. The time now is 04:45 AM.

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