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Old 10th April 2003, 11:04 PM   #21
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Default RE:INPUT TRANS.

Hi,

Quote:
Certainly DC currents in the primary or secondary can degrade performance. But it's rather trivially easy to keep these down to levels that they're not terribly significant.
Normally DC shouldn't be any concern here but for the ultimate paranoid amongst us you can always resort to parafeed to keep it out.

Quote:
And output transformers can have bandwidths into the tens of megahertz.
At what wattage?
Or at what price may be a better question.

Just curious to see what you meant here.

Cheers,
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Old 10th April 2003, 11:37 PM   #22
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Default The experts speak.........

And we are supposed to listen?

Quote:
there are no transformers in the new poweramps.......
Along with......

Quote:
I believe in their new gear instead of input transformers, Rowland is using InGenius line receivers from THAT Corporation.
Sorry......but I think you guys need to rethink your statments.

Jocko
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Old 10th April 2003, 11:50 PM   #23
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Default Who boast the bride...his father!!!

Quote:
So is any conductive loop.
Ok ...but with a magnetic core...the transformer is much more sensitive to magnetic loops...
Quote:
Which is why the best transformers use the best core materials with the smallest hysteresis loops. This doesn't become significant except at the lowest frequencies and the highest input levels. Linearity increases with frequency and by the time you get to a couple hundred hertz, is virtually non-existent.
But hysteresis is a issue....in a transformer....the magnitud of his
influence is debatable...
Quote:
Certainly DC currents in the primary or secondary can degrade performance. But it's rather trivially easy to keep these down to levels that they're not terribly significant.
Yes...but is also another issue that must be take in equation in the avaliation of transformers against active stages...
Quote:
. And output transformers can have bandwidths into the tens of megahertz.
Maybe here you are talking about pulse transformers...not audio output transformers...

Resuming- my previous post to Myloid had only the intention to put some perspective, in the mind of the beginers, that have blind faith in what they read in the forum...And Myloid post seams "Transformers in the wonder land"..so transformers and active stages have good and bad points in relation of each other...

But after seing your home page...Mr. SE ...now i can understand...
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Old 10th April 2003, 11:59 PM   #24
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Default Re: RE:INPUT TRANS.

Quote:
Originally posted by fdegrove
Normally DC shouldn't be any concern here but for the ultimate paranoid amongst us you can always resort to parafeed to keep it out.
The context here is line level transformers, not power output transformers. Which are not air gapped as they are for power ouput transformers for such things as single-ended tube amplifiers. And because they're not, it doesn't take a whole lot of DC current (either from output offset voltage or input bias current) to significantly degrade their performance.

Quote:
At what wattage?
Or at what price may be a better question.

Just curious to see what you meant here.
Again, the context is line level transformers. Not output power transformers.

The Jensen JT-11-DMCF output transformer for example has a bandwidth of 15 MHz and is rated at +22 dBu (about 10 volts) at 20 Hz (for 1% THD) into 600 ohms.

Price is about $80 in 1-3 quantity.

se
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Old 11th April 2003, 12:20 AM   #25
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Default REDHANDED.

Hi,

Quote:
And output transformers can have bandwidths into the tens of megahertz.
Your post, not mine.

Quote:
The context here is line level transformers, not power output transformers. Which are not air gapped as they are for power ouput transformers for such things as single-ended tube amplifiers.
Oh, I see...and FWIW SE line level input or output xformers are out there just the same.
You can have them gapped or not, if not gapped no DC...simple as that, Steve.

And as I said, in the context of line input xformers DC is not likely to be present...
Naturally if you want to account for all the fools in the world then the parafeed method takes care of that.

Guess that part wasn't in the Jensen training course either?

Cheers,
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Old 11th April 2003, 02:00 AM   #26
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Default Re: Who boast the bride...his father!!!

Quote:
Originally posted by Tube_Dude
Ok ...but with a magnetic core...the transformer is much more sensitive to magnetic loops...
Yes. I never said otherwise.

What I said was that this is more a problem with input transformers because their higher impedance (more precisely, they're much higher inductance) so with input transformers, they're mounted in MuMetal cans for magnetic shielding. Output transformers aren't nearly as sensitive and typically don't require separate magnetic shielding.

Quote:
But hysteresis is a issue....in a transformer....the magnitud of his influence is debatable...
How much of an issue it is depends on how much of an issue it is to you. For line level applications, using the transformers that I use, it hasn't been an issue for me.

Quote:
Yes...but is also another issue that must be take in equation in the avaliation of transformers against active stages...
Sure. I never said or implied that there are no issues at all to be considered. Only that most issues are not insurmountable.

Simple common sense should tell one that ANY device should be considered in the specific context in which it will be used.

Quote:
Maybe here you are talking about pulse transformers...not audio output transformers...
Nope. Talking about audio output transformers. Specifically, line level output transformers. Those huge chunks of iron hanging off the outputs of tube amps are another matter entirely.

Quote:
Resuming- my previous post to Myloid had only the intention to put some perspective, in the mind of the beginers, that have blind faith in what they read in the forum...And Myloid post seams "Transformers in the wonder land"..so transformers and active stages have good and bad points in relation of each other...
Certainly.

Quote:
But after seing your home page...Mr. SE ...now i can understand...
Not sure what it is you understand after seeing my web page. I've been using line level transformers for many years, long before I had any commercial offerings using transformers.

se
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Old 11th April 2003, 02:14 AM   #27
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Default The man and his convictions...

Hi SE

I don't agree in everything you say in your post..
...but you are a man of strong convictions and i like that...

So cheers
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Old 11th April 2003, 02:38 AM   #28
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if you search the national site there is an app note:
bpa 200
on putting these LM3886 etc in parallel
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Old 11th April 2003, 02:51 AM   #29
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Default Re: REDHANDED.

Quote:
Originally posted by fdegrove
Your post, not mine.
Yes, that is my post. Where I said that output transformers CAN HAVE bandwidths in the tens of megahertz. And they can.

You came back asking what sort of wattage rating and price indicating that you seem to think that output transformers are only made for hanging off the outputs of power amplifiers.

Quote:
Oh, I see...and FWIW SE line level input or output xformers are out there just the same.
You can have them gapped or not, if not gapped no DC...simple as that, Steve.
I'm sure someone has made line level transformers with an air gap. But I'm not aware of any standard offerings of such transformers from any of the manufacturers I'm familiar with. Could you point out one or two examples?

Quote:
And as I said, in the context of line input xformers DC is not likely to be present...
Naturally if you want to account for all the fools in the world then the parafeed method takes care of that.
DC will not be present only if your sources are capacitively coupled. However many components are direct coupled in order to avoid using capacitors in the signal path (parafeed fans seem to prefer non-linearities due to capacitors than non-linearities due to air gaps in the transformers). In which case you can have significant amounts of DC at the transformer's input depending in the component(s) in question.

A source component with an above average amount of DC output offset feeing a direct coupled preamp with an above average amount of DC output offset can add up (the preamp will amplify the DC offset of the source in addition to its own offset) to enough DC at an amplifier's input that it can seriously degrade the performance of even the best input transformers.

And with input transformers, you can capacitively couple the source with a relatively small value capacitor and get by with a good quality film cap of about 2-10 uF. But with output transformers, due to their much lower primary inductance, you need a much greater amount of capacitance to avoid low frequency resonance peaking and you need to use several hundred uF of capacitance which pretty much forces you to use electrolytics.

se
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Old 11th April 2003, 02:53 AM   #30
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Default Re: The man and his convictions...

Quote:
Originally posted by Tube_Dude
I don't agree in everything you say in your post..
...but you are a man of strong convictions and i like that...

So cheers
Thanks, I could use a drink about now.

se
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