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Old 12th February 2003, 02:28 PM   #21
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Default LOADS.

Hi Bas,


Quote:
What is a typical load that a preamplifier "sees" is that 47k?
For a MM phono stage that would be the standard input impedance in conjunction with say,100 to 150 pF capacitance to load the cartridge.

Quote:
In my case..the power transformer input rca has a grid leak resistor of 47k..
Errr,do you mean a step up xformer for a MC cart.?

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Old 12th February 2003, 02:31 PM   #22
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Hi Frank,

Its a parafeed preamp...so I want an output transformer..parafeed coupled..

So I thought the load it sees would be the poweramp?

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Bas
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Old 12th February 2003, 02:36 PM   #23
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Default I SEE...

Hi,

Quote:
So I thought the load it sees would be the poweramp?
On the secondary side it will look at the input impedance of the amp + the cable's properties.

So,in order to drive all this properly the secondry side of your step down xformer should be an order of magnitude lower than the input impedance of the amp.
Often a value of 600 Ohm is chosen for this as this is the pro standard for balanced operation.

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Old 12th February 2003, 02:46 PM   #24
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Hi again and thanks again Frank. ;-)

Ok so as this is gonna be a preamp...

This is what I should tell my tranny builder.. :

1.) SE transformer
2.) The core may be fairly small...no DC and fairly small voltages. (Maybe around 1 watt max?)
3.)Output impedance 600ohm or lower?
4.) Primary or reflected impedance as high as possible without affecting hf response. (say should only drop of after 25kHz)

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Old 12th February 2003, 02:56 PM   #25
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Default PARAFEED OPT.

Hi,

1.) SE transformer
2.) The core may be fairly small...no DC and fairly small voltages. (Maybe around 1 watt max?)
3.)Output impedance 600ohm or lower?
4.) Primary or reflected impedance as high as possible without affecting hf response. (say should only drop of after 25kHz)

I'm pretty sure that the xformer builder we have in mind has done this before.

2)If it must be a parafed job than,yes.

3)Going lower than 600 Ohm will only add to the step down ratio,and degrade performance IMO.

4)Yes,something like 15K should be fine.Bandwidth as large as possible,I'd say.

Ciao,
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Old 12th February 2003, 03:07 PM   #26
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Oki Doki.


So Long, and Thanks For All The Fish

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Bas
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