Go Back   Home > Forums > Source & Line > Analogue Source

Analogue Source Turntables, Tonearms, Cartridges, Phono Stages, Tuners, Tape Recorders, etc.

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 15th February 2004, 11:47 AM   #1
diyAudio Member
 
scott wurcer's Avatar
 
Join Date: Jan 2004
Location: cambridge ma
Default Hybrid analog/digital preamp?

With the speed and availability of digital processing power, I was thinking that a simple one stage preamp with maybe one of the RIAA time constants feeding a DSP programmed to do the rest would be an interesting project. I'm sort of thinking out loud over my morning coffee.
  Reply With Quote
Old 15th February 2004, 03:26 PM   #2
netgeek is offline netgeek  United States
diyAudio Member
 
Join Date: Nov 2003
Location: East Coast USA
Perhaps such a thing could be one part of a whole family of dedicated widgets??? (e.g. the AD1954 or some of the alesis products). It would be great to see more dedicated "black box" type devices that could be easily integrated by "non-dsp designers"......

Hey, if you had some "in" at a place like Analog Devices I'll bet you could make it happen..........

Meanwhile, I'm still waiting for my AD1954 samples to play with.

Regards,
Bill
  Reply With Quote
Old 17th April 2004, 05:08 PM   #3
diyAudio Member
 
Join Date: Feb 2002
Came across this old post randomly, but this hybrid approach is something I've been thinking about as well since recording my vinyl to cd/dvd is a project on my todo list.
I've actually been thinking about a fully-digital approach where you just run the 'table through ~60dB of gain and apply the full RIAA digitally, but I just can't bring myself to believe that this is optimal - I'm not sure you end up with enough S/N performance in the treble after applying the filters. OTOH the midrange and treble will be at a (relatively) higher level before digitizing so you (in theory) get more 'bits' of resolution on the initial capture than when using an already-corrected signal.
The idea of applying the 50Hz section in the preamp to get 'into the ballpark' and then correcting digitally seems to be a promising idea - the phono 'pre' can be much simpler (ie cheaper) than a full RIAA approach, and you only need moderate digital correction to complete the eq.

One of the big practical factors might be the ability to handle pops/ticks - recording a pre-equalized signal will result in much lower energy from pops/clicks than if you record the un-equalized signal, which might help to avoid clipping during recording.

Anyone actually end up trying this or something similar?
  Reply With Quote
Old 21st April 2004, 01:08 PM   #4
EC8010 is offline EC8010  United Kingdom
diyAudio Moderator Emeritus
 
EC8010's Avatar
 
Join Date: Jan 2003
Location: Near London. UK
Quote:
Originally posted by dwk123
The idea of applying the 50Hz section in the preamp to get 'into the ballpark' and then correcting digitally seems to be a promising idea - the phono 'pre' can be much simpler (ie cheaper) than a full RIAA approach, and you only need moderate digital correction to complete the eq.
Exactly. A low-pass 3180us filter (shelving at 3.18us) would equalise the velocity response of the transducer, and the fiddly 318us, 75us could be done very precisely with digits.
__________________
The loudspeaker: The only commercial Hi-Fi item where a disproportionate part of the budget isn't spent on the box. And the one where it would make a difference...
  Reply With Quote
Old 21st April 2004, 01:18 PM   #5
diyAudio Member
 
jan.didden's Avatar
 
Join Date: May 2002
Location: Great City of Turnhout, Belgium
Blog Entries: 7
Scott,

I would be worried about loosing quality by going ADC - DSP - DAC.

Anyway, purist LP/vinyl lovers would probably come after you with a hatchet for this blasphemy.

Jan Didden
  Reply With Quote
Old 21st April 2004, 01:22 PM   #6
diyAudio Member
 
jan.didden's Avatar
 
Join Date: May 2002
Location: Great City of Turnhout, Belgium
Blog Entries: 7
Reply to myself: I can probably try that out easily with my Behringer Ultradrive Pro 2496, which surely has the required filter options. All that is needed is a flat pre ahead of it. And a turntable, of course. So, how about taking a RIAA preamp, removing the correction stuff (maybe leave in the 3.18uS low pass), leaving a flat gain block, and sticking its output in a Behringer?

Jan Didden
  Reply With Quote
Old 22nd April 2004, 02:42 PM   #7
diyAudio Member
 
Join Date: Feb 2002
Quote:
Originally posted by janneman
Scott,

I would be worried about loosing quality by going ADC - DSP - DAC.

Anyway, purist LP/vinyl lovers would probably come after you with a hatchet for this blasphemy.

Jan Didden

Well, the idea really only makes sense in the context of digitizing vinyl in the first place. I've ended up going with a completely digital system (using the Panasonic Digital receivers and homebrew digital xovers), and so recording the vinyl at 24/96 and burning to DVD-V is probably my best practical compromise.

I'd agree that deliberately introducing a spurious AD/DA cycle is pretty pointless.
  Reply With Quote
Old 22nd April 2004, 06:02 PM   #8
diyAudio Member
 
Onvinyl's Avatar
 
Join Date: Aug 2002
Location: Germany
Quote:
Anyway, purist LP/vinyl lovers would probably come after you with a hatchet for this blasphemy.
Vinyl Lovers are well-balanced, kind and peaceful people, I think they won't

Quote:
I'd agree that deliberately introducing a spurious AD/DA cycle is pretty pointless.
We-ell, but think about recordings with different/historic filtering, well performing analog solutions with switchable filter curves are quiet expensive, so a programmable system with memory banks can be quíet advantageous!

Rüdiger
  Reply With Quote
Old 22nd April 2004, 07:15 PM   #9
diyAudio Member
 
scott wurcer's Avatar
 
Join Date: Jan 2004
Location: cambridge ma
I'm trying to borrow one of our new AD1940 DSP development
systems to give it a crack real time, maybe with some fancy tick and pop interpolation too.
  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
Analog or digital? rfarn Solid State 0 13th February 2008 04:24 AM
Digital or analog? xplod1236 Digital Source 1 19th May 2005 02:15 AM
Analog vs. Digital XO Seth Smith Multi-Way 11 1st June 2004 09:33 PM
digital or analog? electro samurai Digital Source 0 17th February 2004 04:07 PM
Analog to Digital? Ioannis Digital Source 5 11th December 2001 06:52 PM


New To Site? Need Help?

All times are GMT. The time now is 04:31 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