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

8 sources preamp
8 sources preamp
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 8th July 2006, 12:14 AM   #1
otherside is offline otherside  Greece
diyAudio Member
 
Join Date: Jul 2006
Location: Patra, Greece
Default 8 sources preamp

Hey guys,

Trying to find the best way for a preamp with multiple inputs (8).

My expertize lies with microcontrollers, digital stuff etc.

So far i had 4 ideas, but i'm not sure if these will work and what's the best.

out = (LM4780 input)

1. Input->Buffer->Relay (controlled by micro)->Tie all output from relays together->PGA2311->out

2. Input->Buffer->Clickless Audio switch (MAX4910)->Tie all outputs from switches->PGA2311->out

3. Input->OP-AMP Controlled gain from digital pot->Tie all outputs from opamps ->PGA2311->out

4. Input->Buffer->PGA2311->Tie all outputs from PGAs together ->PGA2311 (master control)-> out
(this can act as a mixer as well when needed :-)

Which solution is best ? or if all of these are not good a suggestion ?

I'm in particular interested in the solution 4. I don't really mind the cost since i'm looking for two of these pre-amps and i have already the ICs.


Note: Tie all together -> i mean seperatelly the L-R channel of course.

Also using the PGAs, by controlling the two (L-R) seperatelly i beleive you can implement balance control ? is that right or i'm missing something ?
  Reply With Quote
Old 8th July 2006, 01:15 AM   #2
jaycee is offline jaycee  United Kingdom
diyAudio Member
 
Join Date: Apr 2004
Location: Norwich, UK
Purists will tell you to use the relays. Theres a cool IC from TI (TPIC6C595 if memory serves) which is a power octal shift register designed for driving relays. That saves you having 8 switching transistors etc...

Another way would simply be to use a multiplex IC like the DG507, or an improved version from Analog Devices - ADG407. Dallas Maxim also make an improved version - MAX337. All of these would be suitable.

Digital pot's are usually crap as they only run on 5v. Maxim do have dual supply ones with log tapers, but they are in ultra-small packages that you can forget soldering. Go with the PGA2311. One placed after the multiplexer will do. You may want to have a buffer before the PGA2311 though.

For more ideas see Mark Hennessy's pre-amp here -> http://www.mhennessy.f9.co.uk/preamp
  Reply With Quote
Old 8th July 2006, 02:50 PM   #3
otherside is offline otherside  Greece
diyAudio Member
 
Join Date: Jul 2006
Location: Patra, Greece
Quote:
Purists will tell you to use the relays.
It's an option but i prefer non mechanical parts.

Quote:
Another way would simply be to use a multiplex IC like the DG507, or an improved version from Analog Devices - ADG407. Dallas Maxim also make an improved version - MAX337. All of these would be suitable.
Has enyone used them for Audio? These are pretty bulky, i've used them a lot before for other projects, even the CD4067 from TI which is cheaper than these is better. The on resistance is quite large and frankly it varies a lot depeding on the signal so my guess is that this will just add noise.
Not sure guys, you're the experts, but based on my knowledge i'd never use a analog mux for good quality audio.

Quote:
Digital pot's are usually **** as they only run on 5v. Maxim do have dual supply ones with log tapers, but they are in ultra-small packages that you can forget soldering.
I could use different supplies... Anyway you'll ve surprized with what i can solder, i just soldered a TQFP 100 with .5 pitch ;-).

Quote:
For more ideas see Mark Hennessy's pre-amp here
Excellent projects!!!.

Still will solutions 2 or 4 work well?
  Reply With Quote
Old 8th July 2006, 05:28 PM   #4
jaycee is offline jaycee  United Kingdom
diyAudio Member
 
Join Date: Apr 2004
Location: Norwich, UK
Quote:
Originally posted by otherside

Has enyone used them for Audio? These are pretty bulky, i've used them a lot before for other projects, even the CD4067 from TI which is cheaper than these is better. The on resistance is quite large and frankly it varies a lot depeding on the signal so my guess is that this will just add noise.
Not sure guys, you're the experts, but based on my knowledge i'd never use a analog mux for good quality audio.
The ADG407 is used in quite a lot of audio amps, it is an improved device from Analog which has a significantly lower on resistance of 50 ohms versus the normal 400 ohms of the standard DG407 device. It is designed for high quality audio use. They're available in PLCC format if board size is a concern.

Quote:
Originally posted by otherside
I could use different supplies... Anyway you'll ve surprized with what i can solder, i just soldered a TQFP 100 with .5 pitch ;-).
Well if you can solder that small you might well find the Dallas Maxim dual rail volume pot's usable

Method 2 sounds usable if you can solder TQFP. Method 4, i doubt the PGA2311 would provide good enough isolation in MUTE mode, plus it's rather overkill.

I would say if quality is the paramount issue, go with the relays, and if you don't like relays, use either the ADG407 or the MAX4910.
  Reply With Quote
Old 8th July 2006, 05:56 PM   #5
otherside is offline otherside  Greece
diyAudio Member
 
Join Date: Jul 2006
Location: Patra, Greece
Thanks for the comments,

One issue is availability, i'll try to see what i can get and test.
  Reply With Quote
Old 9th July 2006, 12:41 AM   #6
jaycee is offline jaycee  United Kingdom
diyAudio Member
 
Join Date: Apr 2004
Location: Norwich, UK
Analog, Maxim and TI have great sample programmes
  Reply With Quote
Old 9th July 2006, 01:15 AM   #7
otherside is offline otherside  Greece
diyAudio Member
 
Join Date: Jul 2006
Location: Patra, Greece
Programming them is the only thing (for me) which is not a issue :-). If you ever need any help with programming these things let me know.
  Reply With Quote

Reply


8 sources preampHide 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
2 sources into 1 Stereo HyperActive Analog Line Level 6 2nd October 2008 02:17 PM
is series sources? nbcd Solid State 0 20th November 2004 07:06 AM
Sources of hum. JoeBob Solid State 30 19th July 2002 04:23 PM


New To Site? Need Help?

All times are GMT. The time now is 02:30 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
Wiki