PGA2310 and Source Selection, right direction? - 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 9th April 2009, 05:36 AM   #1
diyAudio Member
 
geekysuavo's Avatar
 
Join Date: Apr 2008
Location: United States
Question PGA2310 and Source Selection, right direction?

hi all,

here's my end-goal:
* 8-source stereo selection
* one pga2310 per source
* microcontroller-based

i've put together and attached a schematic to show a bit more of what i mean. there is only one source (relay and pga) in the diagram now, but essentially the idea is to daisy-chain the pga's together and control them all with an atmel avr micro.

what are your suggestions for making this design better? i'm curious if optical isolation between the analog and digital grounds would improve quality, but how is it doable?

[EDIT:] oh! and do the inputs of the pga's need to be buffered and, if so, would an opa2134 be sufficient?

thanks a bunch!
~ brad.
Attached Files
File Type: pdf source.pdf (11.0 KB, 376 views)
  Reply With Quote
Old 9th April 2009, 01:42 PM   #2
diyAudio Member
 
geekysuavo's Avatar
 
Join Date: Apr 2008
Location: United States
Wink oh... :P

aha!

well, in a flash of clarity and slight self-deprecation, i realized that there's no benefit to having a separate pga for each source. instead, just assume the design uses 8 relays into one pga, and the volume level of each source is recalled upon switching by the controlling micro.

i feel a bit silly.

still, is there anything you'd recommend to improve the design?

thanks,
~ brad.
  Reply With Quote
Old 9th April 2009, 04:15 PM   #3
nonoise is offline nonoise  South Africa
diyAudio Member
 
Join Date: Jun 2006
Your idea of using a input buffer is a good one, I would perhaps also add a output buffer using for example a BUF634 + OP634, this will let you drive headphone well too.
  Reply With Quote
Old 9th April 2009, 08:31 PM   #4
diyAudio Member
 
Join Date: Oct 2006
check the data sheet on the PGA if the inputs should be buffered (I know the SSM2160 needs to be, similar VCA idea...)

anyways are you sure you want to use relays for switching your inputs? I really hate relays in the audio path, IMHO you should look into using analog switches/muxs i have used 74HCT4053 muxs with great success, actually i am currently working on an integrated amp/preamp. I should be posting with in a couple weeks. just my $0.02

Isolating grounds great idea, have the analog and digital grounds connect at one point only. You could use opto couplers from the micro to the muxs, for your digital I/O's this would keep everything seperate

Dave
  Reply With Quote
Old 9th April 2009, 10:47 PM   #5
diyAudio Member
 
geekysuavo's Avatar
 
Join Date: Apr 2008
Location: United States
Quote:
It is important to drive the PGA2310 with a low source impedance. If a source impedance of greater than 600Ω is used, the distortion performance of the PGA2310 will begin to degrade.
i've attached the finished (well, nothing's ever finished...) schematic of my idea. the SN74HC595 controls the outputs of the ULN2064B darlington drivers, which supply 500mA to each relay when on. the PGA2310 is buffered by an OPA2134 opamp and takes its inputs from the relay which is currently on. ten digital I/O lines go back to a controller board, where an AVR will make this thing actually function.

please, any more thoughts?

thanks,
~ brad.
Attached Files
File Type: pdf source.pdf (18.2 KB, 194 views)
  Reply With Quote
Old 9th April 2009, 10:50 PM   #6
diyAudio Member
 
geekysuavo's Avatar
 
Join Date: Apr 2008
Location: United States
Quote:
Originally posted by drummer_Dave
are you sure you want to use relays for switching your inputs? I really hate relays in the audio path, IMHO you should look into using analog switches/muxs
any reason why a relay would be unsuitable as compared to an integrated circuit?

~ brad.
  Reply With Quote
Old 9th April 2009, 11:28 PM   #7
glt is offline glt  United States
diyAudio Member
 
Join Date: Oct 2004
Someone is doing the same thing here: http://www.arduino.cc/cgi-bin/yabb2/...num=1236803143
  Reply With Quote
Old 10th April 2009, 06:19 AM   #8
diyAudio Member
 
Join Date: May 2008
Quote:
Originally posted by drummer_Dave
IMHO you should look into using analog switches/muxs i have used 74HCT4053 muxs with great success
Quote:
Originally posted by geekysuavo
any reason why a relay would be unsuitable as compared to an integrated circuit?
On the contrary. Any integrated circuit, also a mux, has a high "on resistance", because the switching can only be done with semiconductors. You trade the small parasitic inductance and capacitance of a relay (or switch!) contact for the typical non-linearities of transistors and their surrounding components. E. g. the 74HCT4053 is given with 80 Ohms at 4,5 V. The lower the voltage, the higher the resistance and you rarely pass 4,5 V signals, do you?. Relays have contact resistances in the range of 0,1 Ohm and (much) below.

Switches must be very sophisticated and therefore expensive, if they are to be as good as relays in the signal path. Many relays, even cheap ones, come with gold-, silver- or rhodium-plated contacts for low contact and corrosion resistance. If you want a switch with those platings, the manufacturers call it 'high-end' or 'audiophile' and charge you an eye for it. You can get vacuum sealed relays and relays with inert gas filling to improve corrosion resistance and sparking even further. Some models come in metal housings for better electro-magnetic compatibility. On top of that relays are easier to integrate into a PCB and make it easier to maintain the signal path short.

Drawbacks? Yes, relays need a power supply. And you need a switch to control the relays, albeit any cheapo will do.
__________________
If you've always done it like that, then it's probably wrong. (Henry Ford)
  Reply With Quote
Old 11th April 2009, 03:23 AM   #9
zdavesf is offline zdavesf  Canada
diyAudio Member
 
Join Date: Apr 2006
Location: alberta canada
pacificblue i do agree with you... yes due to the larger on resistance of the mux's doing voltage switching can degrade the signal, but have you ever tried using the mux's to switch current instead? by switching the current you wont get the voltage drop across the switch... anyways it sounds better to me... but like i said just my $0.02, the audiophile business is full of controversy

Dave


P.S. I also don't like the clicking
__________________
we all have to start somewhere...
  Reply With Quote
Old 11th April 2009, 07:01 AM   #10
diyAudio Member
 
Join Date: May 2008
Quote:
Originally posted by zdavesf
by switching the current you wont get the voltage drop across the switch.
Is Ohm's law in Canada different from Ohm's law in the rest of the world?
__________________
If you've always done it like that, then it's probably wrong. (Henry Ford)
  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 source selection using relays question. sjalloq Solid State 5 31st July 2009 02:01 PM
Need source for a wide selection of trin nuts. ChrisA Parts 1 18th June 2009 04:28 PM
Source Selection IC danward79 Parts 28 25th November 2008 12:13 AM
pga2310/pga2311 source ygm Parts 6 17th May 2006 01:52 PM
Sub Amp..in need of direction sickss Solid State 2 16th February 2005 04:01 PM


New To Site? Need Help?

All times are GMT. The time now is 02:40 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