passive preamp with buffer - diyAudio
Go Back   Home > Forums > Amplifiers > Solid State

Solid State Talk all about solid state amplification.

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 12th February 2006, 06:29 PM   #1
diyAudio Member
 
Join Date: Apr 2004
Location: 12km off the alaska highway in northern BC
Default passive preamp with buffer

Hi,
I'm planning to build a passive preamp with the following feature:

three phono inputs, switched to a phono pre amp (studio type, with balanced out, the board I have already and it is very quiet)
one balanced input
two single ended inputs

all inputs will have level control through some noble pots
all single ended inputs get convertet to balanced via OPA 633 and then fed to a buffer amp build with the OPA 627 (all those I have in my kit)
Output is balanced only and will feed a digital chain.

For the converter circuit I will use the one in the opa 633 manual.

Any suggestion or thoughts?

Thanks for any deedback in advance
  Reply With Quote
Old 12th February 2006, 06:34 PM   #2
diyAudio Moderator
 
pinkmouse's Avatar
 
Join Date: Apr 2002
Location: Chatham, England
Well, for a start, it's hardly a passive preamp!
__________________
Rick: Oh Cliff / Sometimes it must be difficult not to feel as if / You really are a cliff / when fascists keep trying to push you over it! / Are they the lemmings / Or are you, Cliff? / Or are you Cliff?
  Reply With Quote
Old 12th February 2006, 07:15 PM   #3
diyAudio Member
 
Join Date: Apr 2004
Location: 12km off the alaska highway in northern BC
Passive in the sense that the buffer does not supply any gain, but I think I need? it because of the level controls.
The only gain in this amp will be from the phono pre.

I have chosen the opa 633 conversion to balanced as the transformer solution is rather expensive.
  Reply With Quote
Old 12th February 2006, 07:44 PM   #4
anatech is offline anatech  Canada
diyAudio Moderator
 
anatech's Avatar
 
Join Date: Jun 2004
Location: Georgetown, On
Hi audio-kraut,
Yes, you should use buffers to drive the output. They should give much better performance than transformers if you build them right. I question the balanced thing, but okay.

TI / Burr Brown have a new single ended to balanced converter chip you can try. It's the DRV-134.

-Chris
  Reply With Quote
Old 12th February 2006, 08:04 PM   #5
diyAudio Member
 
Join Date: Apr 2004
Location: 12km off the alaska highway in northern BC
Quote:
I question the balanced thing
thanks for the hint.
I like to stay balanced as I feed into a balanced digital processing chain which right now consistst of the scr/deq/dcx 2496.

I thought it therefore cleanest to run balanced right through the preamp, especially as the phono preamp board outputs balanced signal.

Switching will be done by multilevel five pole switches.

As to the buffer circuit including the opa 627 - the only one I could find is on the burr brown data sheet. Any others out there?

This is my first time trying to design something from scratch w/o the benefit of a well funded electronic education, so I need some help sometimes, even in an apparent simple matter as this project.
  Reply With Quote
Old 12th February 2006, 08:06 PM   #6
anatech is offline anatech  Canada
diyAudio Moderator
 
anatech's Avatar
 
Join Date: Jun 2004
Location: Georgetown, On
Hi audio-kraut,
Ah, the number I gave you was a convertor. Look for a Diamond buffer circuit. You may find it in RF circuits.

-Chris
  Reply With Quote
Old 12th February 2006, 08:11 PM   #7
diyAudio Member
 
Join Date: Apr 2004
Location: 12km off the alaska highway in northern BC
Just checked again - I am using the DRV134 (free samples) as the converter, not the 633..too early on a sunday afternoon I guess.

Wanted to use the 627 as a buffer because I have some left from previous "upgrading" projects on some phono preamps.
  Reply With Quote
Old 12th February 2006, 10:56 PM   #8
anatech is offline anatech  Canada
diyAudio Moderator
 
anatech's Avatar
 
Join Date: Jun 2004
Location: Georgetown, On
Hi audio-kraut,
The DRV134 doesn't need a driver. It will do all that by itself. Better than many op amp driver type circuits. It does "want" to see a low impedance source, so a buffer before the DRV134 is a good idea.

So all you have to do now is focus on a quiet regulator circuit and wiring. Esp. the grounds.

-Chris
  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
Pass B1 Passive Buffer Preamp. A good and simple option for chipamps?. A Sanchez Chip Amps 5 2nd January 2009 05:34 PM
Help with Tube Buffer for passive pre dsavitsk Tubes / Valves 2 13th June 2005 12:55 PM


New To Site? Need Help?

All times are GMT. The time now is 05:18 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