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Old 13th May 2013, 12:39 PM   #11
AndrewT is offline AndrewT  Scotland
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This Forum has many links to external papers.
Just do a search on Jung, Self, Rane, Whitlock and balanced.
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Old 13th May 2013, 12:40 PM   #12
FoMoCo is offline FoMoCo  United States
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You could do a quick buffer using a couple of OPA2134s. You might need a couple in parallel, with current sharing resistors. That could drive 600 ohms and can give a 10k input resistance. Barring that... An emitter follower with a 4401 would probably work also.
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Old 13th May 2013, 12:40 PM   #13
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by borg7x9 View Post
....................get my local tube prof to change the input transformer to something more "Normal" Maybe that's the best way to go.
No.
Check the actual input impedance.
It may not be 600ohm.
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Old 13th May 2013, 01:18 PM   #14
godfrey is offline godfrey  South Africa
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Quote:
Originally Posted by AndrewT View Post
No.
Check the actual input impedance.
It may not be 600ohm.
I did, It is. From the user manual:

Quote:
Input impedance: 600 ohm (RCA), 300 ohm (XLR)
Input Power Voltage: 200mV
Output Power: 50W Class A
Output impedance: 4, 8Ω
Frequency Response: 20Hz-20KHz
THD: less than 1.5%
S/N Ratio: 85dB
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Old 13th May 2013, 01:20 PM   #15
AndrewT is offline AndrewT  Scotland
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Zin is not 600ohms. It is 300ohms, if the manual is correct.
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Old 13th May 2013, 02:20 PM   #16
DF96 is offline DF96  England
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It is conceivable that there is a similar confusion for inputs as there is for outputs, so 'input impedance' might actually (wrongly) be 'optimum source impedance'.

This problem arises because when lines are long compared to wavelengths (RF and long line audio) you need impedance matching at both ends, and are happy with the corresponding -6dB loss. Unthinking people then carry over the idea of matching into short audio connections, where a match is usually the last thing you need. Or 'impedance match' gets re-used to label not matching but using appropriate impedances - which then confuses people.
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Old 13th May 2013, 04:01 PM   #17
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by AndrewT View Post
The input might be specified as 600ohms compatible.............
Quote:
Originally Posted by AndrewT View Post
Zin....is 300ohms, if the manual is correct.
Quote:
Originally Posted by DF96 View Post
It is conceivable that there is a similar confusion for inputs as there is for outputs, so 'input impedance' might actually (wrongly) be 'optimum source impedance'.............
Yes Mooly,
I still think the manual is wrong.
It is more likely to be stating the required source impedance rather than the actual input impedance.

The actual input impedance needs to be checked before any decisions are made about purchases or modifications.
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Old 13th May 2013, 04:28 PM   #18
AndrewT is offline AndrewT  Scotland
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just found this link for Whitlock + balanced.
Ballanced Unballanced what does it mean??

But self + balanced does not work.
It returns the message that self is too common and has been omitted from the search string and search only returns the >37000 results for balanced.
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Old 13th May 2013, 10:46 PM   #19
Pano is online now Pano  United States
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Quote:
Originally Posted by DF96 View Post
It is conceivable that there is a similar confusion for inputs as there is for outputs, so 'input impedance' might actually (wrongly) be 'optimum source impedance'.
That make sense to me. Why would you want an RCA in with a 600 ohm impedance.

With the right tools, the input impedance could actually be measured. With a couple of resistors and some clip leads, it could be estimated.
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Old 14th May 2013, 02:17 AM   #20
borg7x9 is offline borg7x9  New Zealand
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Pano, would you like to see the circuit diagram of the power amp ??
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