Mr White's "Opus", designing a simple balanced DAC - Page 153 - diyAudio
Go Back   Home > Forums > Commercial Sector > Manufacturers > Twisted Pear

Twisted Pear Superior quality electronic kits

Reply
 
Thread Tools Search this Thread
Old 15th June 2008, 03:15 AM   #1521
diyAudio Member
 
Join Date: Mar 2007
Location: Minneapolis, MN
Quote:
Originally posted by Russ White
This is the type VFD module it is.

2 x 20 146.0 x 43.0 x 19.2

It made by Newhaven Display.

Very cool! I see on the spec sheet that the rear control circuit board is in fact too large for a 1U box (1.7"; box is 1.5" max). However, all is not lost because they also make a smaller 2 X 20 version that should fit and it uses the same control interface. The characters would be noticably smaller - and I agree that the larger text in the model you selected would be generally preferable...

I *really* appreciate this nice work!

Frank in Mpls.
  Reply With Quote
Old 15th June 2008, 04:05 AM   #1522
diyAudio Member
 
luvdunhill's Avatar
 
Join Date: Jul 2006
hey guys!

I recently replaced one of your older CS boards with the newer Wolfson receiver board for a friend. There are two Opus boards in dual mono configuration with a Zapfilter on the output. Things were working fine before. After the receiver transplant, my friend is getting soft intermittent clicks that are not in any particular pattern with the music. Like I said, things were working fine before. The 7.5VDC supply is clean and the input is via a piece of shielded coax. The switches are set as follows:

AIF/MS 1
TXSRC 0
AIFCONF1 0
AIFCONF0 1

(where 1 is far "LEFT" if you're reading the silk and 0 is far "RIGHT")

Assuming the above is correct and the wiring is correct, all I can think is that the I2S lines might have gotten crossed when the unit was shipped? I think this is unlikely, but could explain the symptoms. Yet, every time this has been a problem, the noise has been much more obvious, so that makes me think it might be either configuration issue or a bad board?

What would you guys recommend?

edit: I read some posts, I guess it's probably the i2s wiring afterall.
  Reply With Quote
Old 15th June 2008, 05:02 AM   #1523
Pulse-R is offline Pulse-R  Australia
diyAudio Member
 
Join Date: Mar 2005
Location: Melbourne
I have a simple question, please forgive my ignorance.

Russ, why are you using an IVY with the OPUS? I understood that the OPUS was V-Out, and then use a BAL/SE only... Have I missed something here?

Also, how difficult would it be to "upgrade" my 8740 modules with the new I.C.?

Thanks

Simon T
__________________
Digital is only on or off
  Reply With Quote
Old 15th June 2008, 11:53 AM   #1524
diyAudio Member
 
Russ White's Avatar
 
Join Date: Jan 2005
Location: Nashville, TN, USA
Send a message via Yahoo to Russ White
Quote:
Originally posted by Pulse-R
I have a simple question, please forgive my ignorance.

Russ, why are you using an IVY with the OPUS? I understood that the OPUS was V-Out, and then use a BAL/SE only... Have I missed something here?

Also, how difficult would it be to "upgrade" my 8740 modules with the new I.C.?

Thanks

Simon T
Hi Simon,

The IVY is just as suited to voltage output DACs as Current. The reason I like to use it is because of the super symmetrical nature of the THS41xx it cancels some distortion and common mode noise which could come from the DAC. This results in very good THD and DNR.

Using the IVY with the opus is a natural choice so long as you keep the input impedance of the IVY >= 1K.

In fact here is a cool trick I am going to do today.

1) Setup two Opus in mono mode. When you do this one channel will be the same audio channel as the other but inverse phase.

2) Setup an IVY for each opus wiring each channel to an input on the IVY. You will get a mono balanced signal out of what is usually a stereo SE signal from the IVY. The balanced outputs of the IVYs are unused in this case. This should result in even better DNR. This is very similar to the way they do Dual mono in the data sheet, but should be even better!

Cheers!
Russ
__________________
Less pulp more juice Twisted Pear Audio.
  Reply With Quote
Old 15th June 2008, 07:04 PM   #1525
diyAudio Member
 
Russ White's Avatar
 
Join Date: Jan 2005
Location: Nashville, TN, USA
Send a message via Yahoo to Russ White
Default IVY in dual mono mode.

Holy Spumoni! Its very very nice.

Only listening for about an hour, but so far its great!

Cheers!
Russ
__________________
Less pulp more juice Twisted Pear Audio.
  Reply With Quote
Old 15th June 2008, 07:21 PM   #1526
diyAudio Member
 
Russ White's Avatar
 
Join Date: Jan 2005
Location: Nashville, TN, USA
Send a message via Yahoo to Russ White
I forgot to mention one of the key benefits of the IVY.

No output capacitors on the DAC. Everything is DC coupled. Bass is pure and clean and phase accurate. Gotta love it.

Because OCM of the THS4131 is at GND there is no offset to GND at the balanced outputs or the SE outputs.

Cheers!
Russ
__________________
Less pulp more juice Twisted Pear Audio.
  Reply With Quote
Old 15th June 2008, 09:28 PM   #1527
akione is offline akione  United Kingdom
diyAudio Member
 
Join Date: Aug 2007
Hi Russ,

This sounds like my kind of mod

Does it allow you to do away with the load-balancing resistors, too ?

Colin
  Reply With Quote
Old 15th June 2008, 11:51 PM   #1528
diyAudio Member
 
Russ White's Avatar
 
Join Date: Jan 2005
Location: Nashville, TN, USA
Send a message via Yahoo to Russ White
Quote:
Originally posted by akione
Does it allow you to do away with the load-balancing resistors, too ?

Colin

Yes, because each channel is handled separately.

I think this has been my favorite experiment so far.


Cheers!
Russ
__________________
Less pulp more juice Twisted Pear Audio.
  Reply With Quote
Old 16th June 2008, 04:58 AM   #1529
diyAudio Member
 
Join Date: Dec 2004
Location: Bakersfield, CA
Okay, somebody has to ask ...

It is very obvious that you like the dual mono WM8741 DAC. But do you like it better than Buffalo?
__________________
Best Regards,
Carl Huff
  Reply With Quote
Old 16th June 2008, 06:22 AM   #1530
akione is offline akione  United Kingdom
diyAudio Member
 
Join Date: Aug 2007
Ahh yes, I see what's going on. Each channel has its own line driver, effectively doing the load-balancing, with the summing done in the LME49720.

I expect that sounds very tight and dynamic.

I assume you've set everything for unity gain. 1k's on the THS's and 2k's on the LME's ?

Question is - Can I fit 2 more IVY's in the case ?

Colin
  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



New To Site? Need Help?

All times are GMT. The time now is 10:24 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