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

Digital Source Digital Players and Recorders: CD , SACD , Tape, Memory Card, 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 20th February 2007, 04:06 AM   #1
diyAudio Member
 
georgehifi's Avatar
 
Join Date: Sep 2003
Location: Manly Australia (Jewel of the Pacific)
Send a message via MSN to georgehifi
Default Need advice from all I/V Aficionados using the THS4031's

I have a dac (circuit below) that I feel the need to tinker with again. I have replace the 2 x NE5532's with 4 x AD825 and done some direct coupling mods with dc offset adjusters in yellow highlight.
I've just recieved 4 samples of TI's THS4031's.

With the ad825's having very low dc offset and fet input, the trimmers only have to be adjusted very slightly off the replaced resistor value of 2.2k to give me zero offset at the dc coupled output. The sound is very good this way.

What do you guys think the difference would be with the THS4031's replacing the AD825's, they are bipolar input does anyone know if the THS4031's have low dc offset say below 20mv and more important would they sound better than the AD825's in this position, I've noticed that a lot of people here love them and a couple have prefered them over the AD825's in the ouput stage of their players/dacs.

Cheers George
Attached Images
File Type: jpg brother scan1 1000x 94k.jpg (94.4 KB, 1761 views)
__________________
Avatar : Production Lightspeed Attenuator
www.lightspeedattenuator.com
  Reply With Quote
Old 20th February 2007, 08:31 AM   #2
diyAudio Member
 
jan.didden's Avatar
 
Join Date: May 2002
Location: Great City of Turnhout, Belgium
Blog Entries: 7
Default Re: Need advice from all I/V Aficionados using the THS4031's

Quote:
Originally posted by georgehifi
I have a dac (circuit below) that I feel the need to tinker with again. I have replace the 2 x NE5532's with 4 x AD825 and done some direct coupling mods with dc offset adjusters in yellow highlight.
I've just recieved 4 samples of TI's THS4031's.

With the ad825's having very low dc offset and fet input, the trimmers only have to be adjusted very slightly off the replaced resistor value of 2.2k to give me zero offset at the dc coupled output. The sound is very good this way.

What do you guys think the difference would be with the THS4031's replacing the AD825's, they are bipolar input does anyone know if the THS4031's have low dc offset say below 20mv and more important would they sound better than the AD825's in this position, I've noticed that a lot of people here love them and a couple have prefered them over the AD825's in the ouput stage of their players/dacs.

Cheers George

The offset value would be in the data sheet but I would think that the opamp offset would be MUCH lower than the bipolar diff amp following it, so that should not be a concern for the opamps.

Jan Didden
__________________
Never explain - your friends don't need it and your enemies won't believe you anyway - E. Hubbart
Check out Linear Audio Vol 7
!
  Reply With Quote
Old 22nd March 2007, 08:11 AM   #3
diyAudio Member
 
georgehifi's Avatar
 
Join Date: Sep 2003
Location: Manly Australia (Jewel of the Pacific)
Send a message via MSN to georgehifi
Got the 4x THS4031 's in yesterday put them in the I/V stage and only had to adjust the 5k 25 turn trimmer a half a turn to get zero offset on the output, not bad, this opamp has good low dc offset for a bipolar input opamp, put it back in the system and wow!!! the mids and highs are so so much more transpaent than the AD825 's and it made mince meat out of the NE5532 's, but the bass it was a little anaemic, no balls compared to the AD825 's, but this was their forte.

So instead of getting on the merry go round I left the THS4031 's in overnight and left it turned on. What greated me the next day was a revelation, gone was the anaemic bass, it was even better than the AD825 's now, and the mids and highs were just as good as before even a bit better maybe. These bloody things like to get used to their suroundings, before they give their best.

I can now say that the THS4031 is the best for I/V conversion that I have tried to date, give them a go you will be surprised, but don't listen to them till their 24hrs old.

Cheers George
__________________
Avatar : Production Lightspeed Attenuator
www.lightspeedattenuator.com
  Reply With Quote
Old 22nd March 2007, 08:43 AM   #4
tubee is offline tubee  Netherlands
diyAudio Member
 
tubee's Avatar
 
Join Date: Jul 2004
Location: Netherlands
I swapped opamps in CD304mk2 for THS4032's. Wow indeed.

First used NE5532 then OPA2132, sounds reasonable, THS is best til now. Tried a lot AD, OPA, and LT opamps.

Will try LM4562 in future
__________________
Daisy Bell
  Reply With Quote
Old 22nd March 2007, 09:59 AM   #5
diyAudio Member
 
Join Date: Oct 2004
Hi George,

Why do you follow your opamp with a pushpull amplifier?
Is it something to do with the 5532? Or the DAC output levels (I'm not very familiar with the Burr Brown DACs)? Or are you simply outputting a bigger signal?

If its just buffering? What does it sound like without it?

My DAC's output is straight from the LM4562 output into the preamp.

Cheers,
Phil
  Reply With Quote
Old 22nd March 2007, 10:22 AM   #6
diyAudio Member
 
georgehifi's Avatar
 
Join Date: Sep 2003
Location: Manly Australia (Jewel of the Pacific)
Send a message via MSN to georgehifi
Phil most dacs have an output opamp after the I/V opamp stage, my is just a discrete amp after the I/V opamp.
As good as opamps are for output stages, I would still rather have a discrete amp, this one is biased up strong into class A and it can output up to 6 watts, not that it ever does, and sounds better than anything I've heard. It's a Musical Fidelity A3.24, exactly the same as the MF Nuvister Dac with discrete solid state output instead of nuvister tubes.
And I've direct coupled it with some mods, you can find all my circuits here for the dac.

musical-fidelity-a3.24 mods

Cheers George
__________________
Avatar : Production Lightspeed Attenuator
www.lightspeedattenuator.com
  Reply With Quote
Old 22nd March 2007, 10:26 AM   #7
diyAudio Member
 
jan.didden's Avatar
 
Join Date: May 2002
Location: Great City of Turnhout, Belgium
Blog Entries: 7
Quote:
Originally posted by georgehifi
Phil most dacs have an output opamp after the I/V opamp stage, my is just a discrete amp after the I/V opamp.
[snip]

I think a question in a lot of people's mind is how it is possible to have such big differences in opamps if they are followed by a discrete amp that arguably is much less performing than that opamp.

Jan Didden
__________________
Never explain - your friends don't need it and your enemies won't believe you anyway - E. Hubbart
Check out Linear Audio Vol 7
!
  Reply With Quote
Old 22nd March 2007, 10:41 AM   #8
diyAudio Member
 
georgehifi's Avatar
 
Join Date: Sep 2003
Location: Manly Australia (Jewel of the Pacific)
Send a message via MSN to georgehifi
Quote:
Originally posted by janneman



I think a question in a lot of people's mind is how it is possible to have such big differences in opamps if they are followed by a discrete amp that arguably is much less performing than that opamp.

Jan Didden
Ask your countryman Gudio Tent, he sent me an email saying he listened to one that he was doing some work on, and he was impressed with it, also. I think it's still better to have common disrete amp than a chipamp (opamp).

"arguably" is the correct word, as I've stated, I've had many different dac's come through my place, and nothing has touched this one yet.
Straight out of the box it had something very special, very powerful detailed sound without a hint of hardness, all the I/V mods and direct coupling have done is given it more transparency and a bottomless pit of detailed tight bass. Not that it means anything but it got Class A rating in Stereophile
http://stereophile.com/digitalprocessors/561/
But I do read their measurments, and they do a good job of them, and this dac had the lowest measured jitter of just about any dac they have measured.

Cheers George
__________________
Avatar : Production Lightspeed Attenuator
www.lightspeedattenuator.com
  Reply With Quote
Old 22nd March 2007, 10:54 AM   #9
diyAudio Member
 
Join Date: Oct 2004
Hi George,
Thanks for the reply.
I guess I've just been used to my 4562 that can drive quite happilly.

Actually thinking about other designs, I have seen two stages (I/V conversion followed by buffer) many times. I'm just not awake!

Thanks for the patience.

Phil
  Reply With Quote
Old 22nd March 2007, 10:38 PM   #10
diyAudio Member
 
georgehifi's Avatar
 
Join Date: Sep 2003
Location: Manly Australia (Jewel of the Pacific)
Send a message via MSN to georgehifi
Here is a link to the Burr-Brown PCM1738e dac chip( E I was told stands for selected), current output (2.5mA), that is in my MF converter, for those who want to read about it.
It does not get mentioned much in these forums, but it does a very good job. It made a fully optimized Marantz CD94mkII with double TDA1541 S1 double crowns sound dirty and flat.
And last month blew away the new Belcanto Dac 3 that I had here for evaluation, made it sound thin in the mids and up top, and gutless down low.

http://focus.ti.com/lit/ds/symlink/pcm1738.pdf

Cheers George
__________________
Avatar : Production Lightspeed Attenuator
www.lightspeedattenuator.com
  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
Ths4031 5th element Analogue Source 4 30th April 2009 12:28 AM
Ths4031 5th element Digital Source 2 25th April 2009 04:11 PM
Calling All Mullard 5-20 Aficionados TheMooN Tubes / Valves 0 7th February 2008 09:18 AM
Any Flac aficionados around? Netlist Everything Else 7 16th December 2007 08:00 PM
Calling SpeakerWorkshop aficionados. Netlist Everything Else 9 4th November 2006 05:51 PM


New To Site? Need Help?

All times are GMT. The time now is 09:05 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