[InSides]

Quote:

Originally Posted by dsavitsk /img/forum/go_quote.gif Also look at the Sowter 3575

These are cheaper than the Jensen, and more importantly, much easier to source given the fact I am visiting London next month.

Would you be able [much appreciated] to provide a connection diagram for my application? Meaning, balanced to single ended conversion?

The datasheet states that the transformer could be used for either unbalanced to balanced, or balanced to unbalanced conversion. I would be interested in the latter, of course, but it presents an interesting option should I need to reuse the transformers for a different application.

Thanks!

 

[luvdunhill]

Quote:

Originally Posted by InSides /img/forum/go_quote.gif Would you be able [much appreciated] to provide a connection diagram for my application? Meaning, balanced to single ended conversion?

what's the input impedance of your preamp?

 

[Steve Eddy]

Quote:

Originally Posted by luvdunhill /img/forum/go_quote.gif what's the input impedance of your source?

You want the input impedance of the load, not the source, which would be his preamp. His preamp's input impedance is 24k ohms.

se

 

[luvdunhill]

Quote:

Originally Posted by Koyaan I. Sqatsi /img/forum/go_quote.gif You want the input impedance of the load, not the source, which would be his preamp. His preamp's input impedance is 24k ohms. se

heh, yup exactly what I meant to say

looks like all the right questions have been asked.

 

[Steve Eddy]

Quote:

Originally Posted by luvdunhill /img/forum/go_quote.gif heh, yup exactly what I meant to say looks like all the right questions have been asked.

Yup.

Though knowing the output impedance of his source might be useful. As long as it's solid state it's likely to be just fine. But can't hurt to ask just in case.

se

 

[diditmyself]

Do you know how much Cinemags cost? Are they suitable for converting balanced to unbalanced instead of an opamp in a DAC?

 

[Steve Eddy]

Quote:

Originally Posted by diditmyself /img/forum/go_quote.gif Do you know how much Cinemags cost? Are they suitable for converting balanced to unbalanced instead of an opamp in a DAC?

The 15/15B is around $45 each if memory serves.

And whether they would be suitable for your application would depend on how they're implemented.

They're an input transformer, so if they're going to be the last thing in the chain in your DAC, they wouldn't be suitable. For that you'd want to use an output transformer like the CMOQ or CMOB series.

se

 

[dsavitsk]

Quote:

Originally Posted by InSides /img/forum/go_quote.gif Would you be able [much appreciated] to provide a connection diagram for my application? Meaning, balanced to single ended conversion?

See attachment. For more details, see Sound System Interconnection

Quote:

Originally Posted by diditmyself /img/forum/go_quote.gif Are they suitable for converting balanced to unbalanced instead of an opamp in a DAC?

For use right after a DAC chip, you probably want something more like a mic input transformer. Cinemag has these, as do Lundahl, Edcor, Electra-Print, Jensen, etc. MC stepups might work OK, too.

How to use transformers? Read this http://www.jensen-transformers.com/a...%20Chapter.pdf

 

[InSides]

Thank you all.

I have contacted both Cinemag and Sowther. Since with shipping both options come out to be the same, I am a bit hesitant as to which one to pick.

I know this might boil down to personal preference, but I can't really afford to try both and then decide.

 

[luvdunhill]

Steve:

Somewhere (I cannot find it) you mentioned turning the Cinemag transformers around for a certain use and I believe there was a rationale behind this. I'm not sure how the shields are configured, and perhaps you've accounted for this?

Also, have you played around with a proper RC loading for the CMLI-15/15B? I've been playing with it of late.

 

[Steve Eddy]

Quote:

Originally Posted by luvdunhill /img/forum/go_quote.gif Steve: Somewhere (I cannot find it) you mentioned turning the Cinemag transformers around for a certain use and I believe there was a rationale behind this. I'm not sure how the shields are configured, and perhaps you've accounted for this?

That was for unbalanced/balanced conversion. Basically, just flip it around and the drive the secondary from the unbalanced source with the bottom of the secondary connected to source ground. Then place a pair of 7.5k resistors across the primary cum secondary and the node between the resistors becomes your ground, which is where you'll connect the can and shield leads.

Quote:

Also, have you played around with a proper RC loading for the CMLI-15/15B? I've been playing with it of late.

Yeah. And I pretty much concluded that it's really only useful if you want to get a nice looking square wave. For all practical purposes though, I haven't really found any particular benefit to it.

I mean, a transformer doesn't resonate on its own. The resonance first has to be stimulated with a signal.

Calculate what the resonant frequency is for the 15/15B and you'll see what I'm getting at.

Though I must say you've done a pretty good job of it. What values were you using in that third shot?

se

 

[luvdunhill]

Quote:

Originally Posted by Koyaan I. Sqatsi /img/forum/go_quote.gif That was for unbalanced/balanced conversion. Basically, just flip it around and the drive the secondary from the unbalanced source with the bottom of the secondary connected to source ground. Then place a pair of 7.5k resistors across the primary cum secondary and the node between the resistors becomes your ground, which is where you'll connect the can and shield leads

Ok! So, assuming you also want to do balanced->balanced through the input transformer, what happens to pin 1 on the XLR?


Quote:

Originally Posted by Koyaan I. Sqatsi /img/forum/go_quote.gif I mean, a transformer doesn't resonate on its own. The resonance first has to be stimulated with a signal. Calculate what the resonant frequency is for the 15/15B and you'll see what I'm getting at. Though I must say you've done a pretty good job of it. What values were you using in that third shot?

From top to bottom, those values are 18K, 15K, 10K with no capacitance and 50R input impedance. The trick is, the damping varies with the input impedance, which I was surprised to see. So, I'm not sure what a good "worse case" input impedance is. With 600R input impedance, I find I need 300pF + 10K. So, I think I'll stick with this value.

 

[Steve Eddy]

Quote:

Originally Posted by luvdunhill /img/forum/go_quote.gif Ok! So, assuming you also want to do balanced->balanced through the input transformer, what happens to pin 1 on the XLR?

When I do balanced/balanced, I use a pair of transformers per channel, wired mirror imaged in series (this will also handle unbalanced inputs).

I suppose you can drive the single flipped trannie from a balanced source, but since the secondary isn't balanced, you won't get the CMRR that you would if it were.

In either case, pin 1 gets tied to the chassis.

Quote:

From top to bottom, those values are 18K, 15K, 10K with no capacitance and 50R input impedance. The trick is, the damping varies with the input impedance, which I was surprised to see. So, I'm not sure what a good "worse case" input impedance is. With 600R input impedance, I find I need 300pF + 10K. So, I think I'll stick with this value.

You mean 300pF in series with 10k? And this is also serving as the main load for the secondary?

se

 

[luvdunhill]

Quote:

Originally Posted by Koyaan I. Sqatsi /img/forum/go_quote.gif When I do balanced/balanced, I use a pair of transformers per channel, wired mirror imaged in series (this will also handle unbalanced inputs).

I'm not sure I follow, do you have a diagram?

Quote:

You mean 300pF in series with 10k? And this is also serving as the main load for the secondary?

yes indeed. After this RC, I am using a 100K pot

 

[Steve Eddy]

Quote:

Originally Posted by luvdunhill /img/forum/go_quote.gif I'm not sure I follow, do you have a diagram?

Sure.

Quote:

yes indeed. After this RC, I am using a 100K pot

Ah, ok.

se