transformer attenuator directly from v-out dac

serph1nia · 22nd March 2011, 03:06 AM

Hey guys,

so. I've read into transformer output from balanced v-out dacs (e.g. wolfson wm8740). I always thought 'screw that' I'll just use a cheap coulpling cap. A waste of a balanced output and impedance but I don;t need both of those aspects when i connect it to a simple pot meter.

But then. I came across some transformer volume control.

I'm thinking about the following setup:

wm8740 -> sowter 9335 (direct coupled, no caps or anything, so there will be dc on the transformers)

SOWTER ATTENUATOR TRANSFORMERS TVC VOLUME CONTROL

So...
1. Is this possible? can the sowters handle the dc from the wm8740?
2. has anyone experience with such a setup? does it makes sense?

Thank you

Bill Fuss · 22nd March 2011, 12:43 PM

It makes sense to me, although I've never used a TVC. Unless the WM8740 needs an inordinately high load resistance it should work great.

The DC offset is a non issue. If there is no path to ground there is no DC current flow unless the output pins have differing DC potentials.

Best, Bill

dirkwright · 5th January 2012, 01:07 PM

What are you putting on the secondary side of the TVC? Be aware that any impedance there will be reflected back to the DAC, and that may effect the DAC's performance and output level. Also, the impedance reflected onto the primary side will change with changes in volume, since the secondary is tapped and thus the turns ratio effectively changes as well.

pieter t · 5th January 2012, 02:45 PM

Check datasheets guys, it's all in there.
Should work well; DC offset is 2.5V with a 5V supply.
In Sowter's application no path to ground (floating).
When secondary load impedance is 10k or higher it will work well.
Dirk, when the signal is attenuated the dac will see a higher (reflected) load, so it will actually have an easier job (output level for this voltage output dac will not be effected).

dirkwright · 5th January 2012, 07:46 PM

Quote:

Originally Posted by pieter t

Check datasheets guys, it's all in there.
Should work well; DC offset is 2.5V with a 5V supply.
In Sowter's application no path to ground (floating).
When secondary load impedance is 10k or higher it will work well.
Dirk, when the signal is attenuated the dac will see a higher (reflected) load, so it will actually have an easier job (output level for this voltage output dac will not be effected).

I didn't read the data sheets, sorry, but I was just talking in general.

22nd March 2011, 03:06 AM	#1
serph1nia diyAudio Member Join Date: Feb 2008	transformer attenuator directly from v-out dac Hey guys, so. I've read into transformer output from balanced v-out dacs (e.g. wolfson wm8740). I always thought 'screw that' I'll just use a cheap coulpling cap. A waste of a balanced output and impedance but I don;t need both of those aspects when i connect it to a simple pot meter. But then. I came across some transformer volume control. I'm thinking about the following setup: wm8740 -> sowter 9335 (direct coupled, no caps or anything, so there will be dc on the transformers) SOWTER ATTENUATOR TRANSFORMERS TVC VOLUME CONTROL So... 1. Is this possible? can the sowters handle the dc from the wm8740? 2. has anyone experience with such a setup? does it makes sense? Thank you

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Connecting a MF tube buffer directly to AKM DAC	ronenash	Tubes / Valves	7	13th December 2010 10:44 AM
DAC that will drive headphones directly	jkeny	Digital Line Level	7	27th January 2010 11:00 AM
passive I/V directly into transformer ?	Bernhard	Digital Source	6	17th August 2005 08:39 PM
DAC directly drives headphones & speakers ?	Bernhard	Digital Source	21	13th January 2005 05:02 PM
16 x TDA1543 DAC directly drives headphones	Intermod	Digital Source	3	7th September 2004 10:09 PM

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read


	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

22nd March 2011, 12:43 PM	#2
Bill Fuss RIP Join Date: Oct 2005 Location: Central Florida	It makes sense to me, although I've never used a TVC. Unless the WM8740 needs an inordinately high load resistance it should work great. The DC offset is a non issue. If there is no path to ground there is no DC current flow unless the output pins have differing DC potentials. Best, Bill

5th January 2012, 01:07 PM	#3
dirkwright diyAudio Member Join Date: May 2011 Location: Virginia	What are you putting on the secondary side of the TVC? Be aware that any impedance there will be reflected back to the DAC, and that may effect the DAC's performance and output level. Also, the impedance reflected onto the primary side will change with changes in volume, since the secondary is tapped and thus the turns ratio effectively changes as well.

5th January 2012, 02:45 PM	#4
pieter t diyAudio Member Join Date: Apr 2009	Check datasheets guys, it's all in there. Should work well; DC offset is 2.5V with a 5V supply. In Sowter's application no path to ground (floating). When secondary load impedance is 10k or higher it will work well. Dirk, when the signal is attenuated the dac will see a higher (reflected) load, so it will actually have an easier job (output level for this voltage output dac will not be effected).

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)