gainclone and jeff rowland

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diyAudio Senior Member
Joined 2002
RE:INPUT TRANS.

Hi,

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.

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.:cool:

Cheers,;)
 
Who boast the bride...his father!!!

So is any conductive loop.

Ok ...but with a magnetic core...the transformer is much more sensitive to magnetic loops...
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...
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...
. 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...
 
Re: RE:INPUT TRANS.

fdegrove said:
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.

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

Just curious to see what you meant here.:cool:

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
 
diyAudio Senior Member
Joined 2002
REDHANDED.

Hi,

And output transformers can have bandwidths into the tens of megahertz.

Your post, not mine.

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.:cool:

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?:devily:

Cheers,;)
 
Re: Who boast the bride...his father!!!

Tube_Dude said:
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.

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.

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.

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.

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.

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
 
Re: REDHANDED.

fdegrove said:
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.

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.:cool:

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?

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
 
haldor said:


I don't know about that, I just bought one of these for my wife so she can stay in touch and and entertain herself wherever the US Navy decides to send her. Could of bought a lot of nice drivers and amp parts for that much money

http://www.fujitsu-siemens.com/rl/products/notebooks/professional/lifebook/lifebooks/lifebooks.html

Phil, :up:
Sweet laptop. She's a lucky gal to have a guy like you. I was kidding in my post, although I would like a present like that but my command provides Dells for us, so my wife buys shoes instead. Everyone has to have a vice, I guess. ;)
 
I think we (I?) are missing an important point here: is it worth to convert an unbalanced signal into a balanced one inside the amplifier?
With a balanced signal we could use two opamps in the power stage in oposition of phase, and this would give a nice power output even from a 12 V split supply. So the use of batteries would be simplified. The PSU for the input opamps could be separated, so all the talk about the "fast" :confused: PSU of the gainclone would not be important because ripple rejection would be made by the balanced signal.
But I WILL NOT pay an expensive transformer :mafioso:
What do you think of the following design? Simulation results show a strong decrease in the amplification over 10KHz, which is not good. Phase is not good also over the 10 KHz.
 

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jocko

let me refrase the Q - what does rowland use as input device in there model 10, 12 and 112 its not a transformer.
some time ago i noticed that rjones mentioned that he owned one of these amps, so i asked him if he would take a look inside and tell us the secret , but never got an answer.

well how about it mr. rjones - please.....!

best regards,
troels



:wave2:
 
Re: jocko

miguel2 said:
I think we (I?) are missing an important point here: is it worth to convert an unbalanced signal into a balanced one inside the amplifier?

Depends on what you want to achieve.

With a balanced signal we could use two opamps in the power stage in oposition of phase, and this would give a nice power output even from a 12 V split supply. So the use of batteries would be simplified.

Sure, you could do that. But really you don't need the additional opamps. You can simply use the two power opamps directly in a bridged configuration.

se
 
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