Output Cap v. Output Transformer - diyAudio
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 16th July 2005, 04:59 PM   #1
diyAudio Member
 
dsavitsk's Avatar
 
Join Date: Jan 2005
Location: Hartford
Default Output Cap v. Output Transformer

Not sure which forum to put this is, but this seems as good as any.

Would there be any advantage to using an output transformer instead of an output cap for a NOS DAC? As I understand it, both block DC and allow AC through, but a transformer with a 1:1 winding should be able to do this while avoiding phase problems and a frequency rolloff. So, what is it I don't understand that would suggest that a cap is a better choice?

-d
  Reply With Quote
Old 16th July 2005, 06:19 PM   #2
Cobra2 is offline Cobra2  Norway
DIY !
diyAudio Member
 
Cobra2's Avatar
 
Join Date: Apr 2002
Location: Stavanger, Norway
Send a message via Skype™ to Cobra2
Default Trafos...

..don't like DC....so you still need that cap...

Arne K
__________________
Don't believe everything you think...
  Reply With Quote
Old 16th July 2005, 08:44 PM   #3
kevinkr is offline kevinkr  United States
diyAudio Moderator
 
kevinkr's Avatar
 
Join Date: Sep 2004
Location: Boston, Massachusetts
Blog Entries: 6
Use a transformer, it can provide isolation for ground loops. You should however not allow dc to flow in the primary, so depending on the spdif driver topology you may need a cap. If you are using a reclocked FF to drive it I don't think the cap is necessary.

Kevin

edit typo
  Reply With Quote
Old 17th July 2005, 11:27 AM   #4
diyAudio Member
 
Join Date: Dec 2003
Location: Sydney
Depending on your analog stage there may be no need for coupling capacitor before primary windings. However, if there's more than 10mV DC offset (with a temerature drift), it could affect high frequency transfer to secondary - so you'll have to use the capacitor. If you have to use capacitor, there's no point in using transformer. Very good, for the money, is Black Gate type C 4.7uF / 50V.

Regards,
Extreme_Boky
  Reply With Quote
Old 17th July 2005, 04:00 PM   #5
kevinkr is offline kevinkr  United States
diyAudio Moderator
 
kevinkr's Avatar
 
Join Date: Sep 2004
Location: Boston, Massachusetts
Blog Entries: 6
Hi Boky,
He was talking about spdif output, not analog output, and here I think the transformer is superior in terms of providing isolation between the transport/player electronics and the outside world - ground loops, etc.

Kevin
  Reply With Quote
Old 17th July 2005, 04:32 PM   #6
diyAudio Member
 
dsavitsk's Avatar
 
Join Date: Jan 2005
Location: Hartford
Quote:
Originally posted by Extreme_Boky
Very good, for the money, is Black Gate type C 4.7uF / 50V.
It currently has BG type N 4.7uf/50V caps and I am trying to find soemthing to replace them. It is essentially between oil caps, Auricaps or RelCaps.


Quote:
Originally posted by kevinkr
Hi Boky,
He was talking about spdif output, not analog output
I meant on the analog end, sorry I wasn't clearer.

-d
  Reply With Quote
Old 17th July 2005, 04:40 PM   #7
gmarsh is offline gmarsh  Canada
diyAudio Member
 
gmarsh's Avatar
 
Join Date: Apr 2004
Location: Halifax, NS, Canada
ideally, a transformer should work great.

Practically, you're dealing with leakage inductance (hello, phase!), saturation at low frequency, core loss at high frequency, etc... And if you're driving the transformer with a voltage source (eg, an op-amp), you'll want to put a series C in there anyway.
  Reply With Quote
Old 17th July 2005, 05:43 PM   #8
kevinkr is offline kevinkr  United States
diyAudio Moderator
 
kevinkr's Avatar
 
Join Date: Sep 2004
Location: Boston, Massachusetts
Blog Entries: 6
Sorry, I misinterpreted your question, seemed natural to me that this would relate to the spdif end and not the analog output end. Transformers are occasionally used and can sound very good, however a good one is going to cost more than a very good capacitor, a bad one may be worse than any capacitor you could find.. LOL
IMHO they make a lot of sense in I/V applications, but not much sense in a voltage source driven application unless you need galvanic isolation (LOL), need impedance transformation and/or want to drive a balanced line without any additional active circuitry. BTW the BG N type capacitor is pretty good, I would be surprised if the was a lot to be gained by replacing it with another type - I could be wrong.

Kevin
  Reply With Quote
Old 18th July 2005, 01:01 AM   #9
diyAudio Member
 
Join Date: Dec 2003
Location: Sydney
Quote:
It currently has BG type N 4.7uf/50V caps and I am trying to find something to replace them. It is essentially between oil caps, Auricaps or RelCaps.
I have tried N type and wasn't impressed. Give C type a try... It is very close to 4.7uF / 200V AURICap I use in certain applications. I personally prefer Black Gate 4.7uF / 50 V C Type.

Regarding SPDIF output, I agree that using transformers for isolation and impedance matching is the best way to go. SCHOTT's are good and I tried couple - the lower leakage inductance - the better!

Regards,
Extreme_Boky
  Reply With Quote
Old 18th July 2005, 02:43 AM   #10
diyAudio Member
 
dsavitsk's Avatar
 
Join Date: Jan 2005
Location: Hartford
Quote:
Originally posted by Extreme_Boky
Give C type a try...

Where does one get "C Type"? I have looked at http://www.kyoto-electro.com/ and Percy and neither list these?
  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
Difference between SE output transformer and push-pull output transformers hilbert_mostert Tubes / Valves 12 8th March 2009 05:10 PM
3C24 in a SE output stage - output transformer impedance recommendation !!! aldovan Tubes / Valves 15 6th September 2008 10:18 AM
Adding secondary of output transformer into cathodes of output stage ? Eico ST-70 freddymac406 Tubes / Valves 3 21st April 2007 06:15 PM
Can An Output Transformer Change A Voltage Amp's Output Impedance From 0.1 To 47 Ohms kelticwizard Everything Else 11 25th March 2007 05:17 AM
Output Tube biasing for Toroidal Output Transformer gingertube Tubes / Valves 7 17th April 2005 04:40 PM


New To Site? Need Help?

All times are GMT. The time now is 02:03 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