Output transformers near mic level wiring?

GroupDIY Audio Forum

Help Support GroupDIY Audio Forum:

bmaughan

Active member
Joined
Jul 15, 2011
Messages
39
I’m trying to add some direct out transformers to an old Yamaha desk and I have a quick question about transformer placement. I did some testing in regards to orientation and I think I found an option that greatly reduces any crosstalk but now I’m wondering about a couple thing.
I attached a couple pictures to show what I’m talking about.

Three questions:

1. That wire loom in the first picture is all mic level stuff. Is there a chance that having it that close to the output transformers induce anything from the Xfrmrs to the mic inputs?

2. In the second picture you can see that I have half of the Xfrmrs horizontally place to keep crosstalk down between transformers. But know it’s making me wonder about the flux pattern and if I might inadvertently cause interference on the channel modules right above. Any cause for concern?

3. The only shielding worth doing would be ferrous correct?

Any help would be appreciated!!
 

Attachments

  • 8359C86C-E035-4D2F-99B3-D033C463488D.jpeg
    8359C86C-E035-4D2F-99B3-D033C463488D.jpeg
    1.5 MB · Views: 0
  • 35A6B695-B3AC-49A5-8B22-78684F394BD1.jpeg
    35A6B695-B3AC-49A5-8B22-78684F394BD1.jpeg
    1.6 MB · Views: 0

CJ

Well-known member
Joined
Jun 3, 2004
Messages
14,728
Location
California
try and see,

should be alright, low level,

a pwr xfmr and tube opt will radiate a lot more than a line level xfmr,

even then it will not be an issue if the transformer core is large and therefore contains the flux better,

you could add some end bells to that open frame xfmr if there is a problem,

look at this Marantz 2325, they run the AM antenna lead (much more sensitive than mic level) right over the top of the pwr xfmr, but that xfmr is so huge it don't matter.

to me this is bragging rights, they want Sony and Pioneer to open up their box and gasp at the vast and superior knowledge that the Marantz engineers have as it pertains to CMMR, grounding, AM propagation, hum rejection, ground loops , wait, i already said half of those,
 

Attachments

  • m.jpg
    m.jpg
    137.5 KB · Views: 0

bmaughan

Active member
Joined
Jul 15, 2011
Messages
39
to me this is bragging rights, they want Sony and Pioneer to open up their box and gasp at the vast and superior knowledge that the Marantz engineers have
Haha that’s awesome. 😂
even then it will not be an issue if the transformer core is large and therefore contains the flux better,

you could add some end bells to that open frame xfmr if there is a problem
These are the Capi 2623 xfmrs. Not sure if that would be considered large or not. I would assume not.

Regarding the end bells.. it has to be ferrous I would assume? I see that the api2503 xfmrs I’ve the copper tape around the core.. would that be advantageous at all?

Really appreciate your input!
 

bmaughan

Active member
Joined
Jul 15, 2011
Messages
39
Can I ask an additional question. It was recommended to me to put a bipolar dc blocking cap before the transformer primary.
What voltage rating would be appropriate?
 

Dualflip

Electronic monk
Joined
Nov 15, 2008
Messages
1,770
Location
Mexico City, MX
Can I ask an additional question. It was recommended to me to put a bipolar dc blocking cap before the transformer primary.
What voltage rating would be appropriate?
What voltage are you using in your output? Those are to block DC from running through the primary, I would say that if you are using +/-15V PSUs you should at least use 16V rated caps to make sure, you can probably go up to 25V without a problem, more is overkill, but again, it depends on your power rails
 
Last edited:

bmaughan

Active member
Joined
Jul 15, 2011
Messages
39
The opamps are running +/-24V. The caps I have on hand are 63V rated. UVP bipolar.
what do you think? any negative trade off by using a cap so overkill?

I just posted in the thread I started regarding this specifically.
What is the real world benefit in using an "audio" cap? Like the UES muse series vs. a more standard UVP cap?
 

Ilya

Well-known member
Joined
Feb 25, 2005
Messages
691
Location
Moscow
35V rated cap would be better, but 63V is also fine. No sonic advantage and larger size. But if you have those caps handy, nothing wrong with using them.
 

bmaughan

Active member
Joined
Jul 15, 2011
Messages
39
35V rated cap would be better, but 63V is also fine. No sonic advantage and larger size. But if you have those caps handy, nothing wrong with using them.
Ben...

The standard series cap driving output trafos in Sphere desks (24v rails) was 470u/16v. 16v or higher, what ever you got should be fine for your yamaha.

GARY
Thanks so much!
Hey Gary, hope you’re well! Sent you a pm
 

Latest posts

Top