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Old 27th April 2013, 09:29 PM   #2101
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that is a very high bias/low rail voltage v3. are you running low impedance speakers?
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Old 27th April 2013, 09:53 PM   #2102
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Quote:
Originally Posted by AudioSan View Post
that is a very high bias/low rail voltage v3. are you running low impedance speakers?
given for 8 Ohms, but having some heavy dips, I have an impendance curve somewhere...

I read the multiple power calculation in this thread...as everybody I'd like to stay class A as long as possible... but I need to re-read that calculations again
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Old 28th April 2013, 12:46 PM   #2103
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Default Impedence plot

Any opinions ?
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File Type: jpg Zspkdroit.JPG (55.6 KB, 539 views)
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Old 29th April 2013, 10:26 AM   #2104
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Quote:
Originally Posted by Variac View Post
I assure you the PCB's won't be close to the most expensive parts. By the time you build the power supply and get enough heatsinking!

We've decided to release the rest of the boards right away, which means about a week for them to be in stock...
That should be this week then...
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Old 30th April 2013, 11:58 AM   #2105
AndrewT is offline AndrewT  Scotland
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post2103:
is that 70degrees of phase angle at 4ohms @ ~40Hz
& ~45degrees @ 3ohms @ ~60Hz?

Those will be very demanding of the output stage and drivers with short term loads.
At 40 to 70Hz the tones could be quite sustained. Could high levels of these bass tones these blow up the output stage?
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Old 1st May 2013, 09:38 AM   #2106
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Quote:
Originally Posted by AndrewT View Post
post2103:
is that 70degrees of phase angle at 4ohms @ ~40Hz
& ~45degrees @ 3ohms @ ~60Hz?

Those will be very demanding of the output stage and drivers with short term loads.
At 40 to 70Hz the tones could be quite sustained. Could high levels of these bass tones these blow up the output stage?
Yes Andrew, that's the way to read the graph!

Hence ,my question: As much Power into 4 ohms as possible (higher rails) or as much "class A" as I can get from lower rails ?

Last edited by coolnose; 1st May 2013 at 09:41 AM.
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Old 1st May 2013, 10:21 AM   #2107
AndrewT is offline AndrewT  Scotland
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Examine the reactive load temperature de-rated SOAR for the loadings your impedance plot is showing.
Clue:
use Bensen's, or other, SOAR calculations.
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Old 1st May 2013, 11:17 AM   #2108
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Andrew,

I am totally willing to have a closer look, your indications don't help me though.

Could you tell me what you mean by SOAR - I am pretty sure not a jordan village or cognitive architecture.

If it's "Safe Operating Area" then I would just need a hint on where to find information on Bensen.

Thanks,

Max
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Old 1st May 2013, 11:56 AM   #2109
AndrewT is offline AndrewT  Scotland
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He's in the Threads
I have posted many times offering a modified version of Bensen's spreadsheet that can be applied to FETs and BJTs and other changes.
Bensen's work is based on David Eather's paper. That is referenced in the spreadsheet.
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Old 1st May 2013, 02:36 PM   #2110
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Andrew,

if the spreadsheet you are referring to is something like project1.xls and all I have to do is enter my device data, my rail voltage and my capacitance for the power supply, then I think I'am safe for 8 and 4 ohms...

See attached pdf.
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