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Old 26th November 2013, 02:23 PM   #1
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Default PreAmp Voltage/Impedance

New here so hey all.
My Pre has:
Preamp Output Level/Output Impedance 1.0 V / 250 ohms

and am jacking into a line/HiZ combo preamps that have.
Max. Level: +6.5dBV (+8.7dBu) Input Impedance: 1.5 kOhms
Combo preamplifier with Hi-Z/line balanced input - Input Impedance: 1Mohm

Do these numbers jive for my purpose of recording?

Thanks
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Old 26th November 2013, 05:54 PM   #2
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Quote:
Originally Posted by Amped Up View Post
New here so hey all.
My Pre has:
Preamp Output Level/Output Impedance 1.0 V / 250 ohms

and am jacking into a line/HiZ combo preamps that have.
Max. Level: +6.5dBV (+8.7dBu) Input Impedance: 1.5 kOhms
Combo preamplifier with Hi-Z/line balanced input - Input Impedance: 1Mohm

Do these numbers jive for my purpose of recording?

Thanks
Zout of 250 ohms into 1500 ohms of the amp will give you an attenuation of 1500/(250+1500) = 0.86. Simpel algebra. So no problem here.

The other thing is that the 1V output (which will be attenuated to 860mV as we have seen) might be too small to fully drive the combo. But whether that is a problem depends on what you want to do with the result. Do you really need full output from the combo? Into a power amp? It may come down to turning up the volume conbtrol a bit further than otherwise.
Proof the pudding.

Jan
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Old 26th November 2013, 06:02 PM   #3
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You should be fine. You are recording, so you'll want some system headroom.
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Old 26th November 2013, 11:55 PM   #4
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Thanks guys, Once you know the math

If I may bother you further.

This Recording devise appears to use amps of different impedance. The first one mentioned 1.5k ohm at .857 (.86) And the other at 1Mohm would be .999 (1.0)

You appear to be saying the original signal would be attenuated .86db so that if I use these as a L/R configuration, one channel will be .139db louder.
Is this right?

Thanks again,

Amped Up
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Old 27th November 2013, 04:57 AM   #5
Blues is offline Blues  United States
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It will have a 1.337dB L/R channel imbalance which will be discernible.
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Old 27th November 2013, 10:49 AM   #6
DF96 is offline DF96  England
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Quote:
You appear to be saying the original signal would be attenuated .86db
No. Voltage ratio of 0.86, which is -1.31dB.
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Old 27th November 2013, 02:04 PM   #7
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Default More Distortion Too

Studios have utilized a 600 ohm transformer based line-level interconnection standard, which was adopted from the old analog telephone network, as I recall. Most line-level loads in a home system, however, range from 20k to 100k. The very lowest such load I can recall seeing specified in a commercial product was 8.8k ohms, for the bipolar transistor input stage of an power amp.

An 1.5k ohm load is unusually low by home audio line-level interconnection standards. Unless the line driver of your source was specifically designed to drive such low impedance loads with low distortion, I suspect it would well exceed it's THD spec. there.
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Old 29th November 2013, 08:31 PM   #8
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Well some good news, The manual listed 1.5k ohm and then listed the amps separately.
Apparently when used as line level L/R they sync at 1.5k. I recorded a record and tested against the cd and L/R levels were under .25db difference. And the CD was a remastered version so who knows.

As far as distortion, I think your right the Home Audio Equip into the Pro Audio Gear isn't suited.

Math question... when changing the Turntable Cartridge impedance from 100ohm to 200 ohm am i attenuating or amplifying? I want to say attenuating but not sure heh.

Thanks for your help and knowledge
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Old 1st December 2013, 09:44 AM   #9
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by Amped Up View Post
n... when changing the Turntable Cartridge impedance from 100ohm to 200 ohm am i attenuating or amplifying? I want to say attenuating but not sure........
you can't change the cartridge impedance.

You can change the load impedance.
Is this what you meant?
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Old 2nd December 2013, 07:20 PM   #10
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Quote:
Originally Posted by AndrewT View Post
you can't change the cartridge impedance.

You can change the load impedance.
Is this what you meant?

Hey Andrew,

Yeah that is what I mean to ask. What effect would altering the Load Impedance have on the sound.

Thanks again
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