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Old 12th August 2003, 12:22 AM   #1
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Default Going Balanced All The Way...

Hi,

Thought I'd open this new thread to serve as a container for all to use.

The purpose is to provide some ideas on the development of a phono preamp capable of taking in MC carts in the lowish region of output types and carry the balanced topology through as far as you care to take it.

As our domestic environment gets more and more polluted by RFI and EMC I feel this approach has tremendous potential.

The thread is by no means restricted to the die-hard vinyl users and is open to CD based systems as well...they may benefit more than they realise anyways...

This new thread is a spin-off of this one:

Phono Stage only....

As far as I'm concerned all types of valves get the green light as long as they don't belong to the unobtainium superexpensive department.

Transformer coupling is accepted provided they show impeccable pedigree and bandwidth beyond reproach.

Have fun,
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Old 12th August 2003, 04:15 AM   #2
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How 'bout this?
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Old 12th August 2003, 04:19 AM   #3
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As long as those are ideal transformers they'll work

Tim
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Old 12th August 2003, 05:03 AM   #4
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Quote:
Originally posted by Sch3mat1c
As long as those are ideal transformers they'll work
Not sure if they're Ideal, Mattel or Whammo.

se
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Old 12th August 2003, 11:06 AM   #5
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Default Transformers

Hello


Since I work on/with commercial audio systems everyday I feel that its onlt fair that I throw my 2 cents in. Transformer technology has come a long way since first coming into heavy play in the early 50's. It used to be that if a transformer was used one could count on reduced frequency response. Todays modern transformers are ruler or near ruler flat in response. I use transformers between pieces of equipment whether they are 2 feet apart or 1000' apart.

My opinion is that its the smart way to go especially when dealing with a delicate circuit or a circuit needing the extra isolation. Nearly any impedance and ratio are available now days at a cost that won't have you eating cereal for the next month.

Joe
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Old 12th August 2003, 05:08 PM   #6
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Default Re: Transformers

Quote:
Originally posted by burnedfingers
Since I work on/with commercial audio systems everyday I feel that its onlt fair that I throw my 2 cents in. Transformer technology has come a long way since first coming into heavy play in the early 50's. It used to be that if a transformer was used one could count on reduced frequency response. Todays modern transformers are ruler or near ruler flat in response. I use transformers between pieces of equipment whether they are 2 feet apart or 1000' apart.
Same here.

In the original thread that this was split off from, some recommended against using transformers due to Barkhausen noise. Noise due to the "stickiness" of the magnetic domains in the core material causing them to move (and hence polarize) not in a smooth continuous fashion, but in little jumps.

I've been using Jensen's transformers for about 20 years now and haven't noticed any deliterious effects that I could lay at the feet of Barkhausen noise. Even when I've used them at the inputs of headphone amplifiers.

Barkhausen noise is a very low frequency phenomenon (often you'll see it demonstrated at frequencies below 1Hz) and it drops like a rock as frequency increases. The domains simply can't move fast enough to keep up with the signal (this is also why hysteresis distortion drops like a rock with increasing frequency).

If we're going to dismiss transformers due to Barkhausen noise, I guess we should also dismiss tubes due to shot noise.

se
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Old 12th August 2003, 05:55 PM   #7
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Peter Baxandall (he of the tone control) commented on Barkhausen noise in the "Microphone Engineering Handbook". He was concerned with microphone levels (which are pretty similar to cartridge levels), and concluded that at the low flux densities in microphone transformers, Barkhausen noise was not a problem.
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Old 12th August 2003, 07:52 PM   #8
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Quote:
Originally posted by EC8010
Peter Baxandall (he of the tone control) commented on Barkhausen noise in the "Microphone Engineering Handbook". He was concerned with microphone levels (which are pretty similar to cartridge levels), and concluded that at the low flux densities in microphone transformers, Barkhausen noise was not a problem.
Thanks. All I know is that the only bark in my hausen seems only to come from critters covered with fur, not MuMetal.

Certainly not everyone cares for transformers. And I don't expect that everyone should and don't really care if they don't.

I just like to encourage people to try things for themselves and come to their own conclusions. When we express a subjective dislike for something and then try and reinforce that subjective dislike by pointing to various objective causes, I think it tends to discourage people from trying things for themselves.

I only say this because when I was first getting involved in this hobby, there were quite a few things that I'd dismissed completely out of hand without even trying simply because someone else didn't care for it only to come back to it later and discover that I quite liked them.

In fact, transformers were one of those things.

se
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Old 12th August 2003, 08:11 PM   #9
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Hi,

Quote:
I just like to encourage people to try things for themselves and come to their own conclusions.
The trouble with trying out several MC input xformers is it's rather expensive to experiment with.
Past experiences with MC stepup xformers have been all but positive.

OTOH I'm certain things have improved considerably on all fronts as far as xformers go.

Personally, and you may view it as a prejudice, I'd rather have control over what's going on by finding optimum operating points for the tubes and so.

IOW, about a year of fiddling to find the magic and than move on to the next challenge.

Cheers,
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Old 12th August 2003, 08:24 PM   #10
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Quote:
Originally posted by fdegrove
The trouble with trying out several MC input xformers is it's rather expensive to experiment with.
Yes, they can indeed be rather expensive. But some tubes can be even more expensive.

Quote:
Past experiences with MC stepup xformers have been all but positive.
Sorry to hear that. Haven't had any experience with MC stepups so nothing to offer on that front.

Quote:
OTOH I'm certain things have improved considerably on all fronts as far as xformers go.
Yes. Many of the basic techniques remain the same. I think much of the improvement has come about from materials science.

Quote:
Personally, and you may view it as a prejudice, I'd rather have control over what's going on by finding optimum operating points for the tubes and so.
Prejudice? Naaah. As you said, they can be quite expensive. So I don't see this as being prejudice as pragmatism.

Quote:
IOW, about a year of fiddling to find the magic and than move on to the next challenge.
Yup.

se
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