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Old 28th March 2009, 09:31 PM   #1
Buhl is offline Buhl  Denmark
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Default Q about the Aleph 1.7

I am finishig up an Aleph P1.7 preamp, but since I will only be using it for unbalanced sources, I was thinking of eliminating the input caps for the negative input and the output caps for the negative outputs- as both of these will be shorted to ground anyway - just using a short wire as I have seen done in the X2 preamp. Ánybody got any objections to that - please let me hear them

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Hans
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Old 28th March 2009, 09:56 PM   #2
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you can leave out (short) both input caps ( Papa put them probably for Foolproof convenience ) , but you MUST leave in output caps ;

both outputs are on substantial DC potential , before caps .

use your fave poison there , but be sure that you bypass them with at least 1uF of some different poison
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Old 29th March 2009, 12:55 PM   #3
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ZM, could you explain, in your own unique way, why it would be beneficial to AC short the unused output to ground. I can't get my head around the idea.

Bill
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Old 29th March 2009, 01:05 PM   #4
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Buhl, there is DC at the gate through the divider Rs on the input, but dont know if it would harm your source or not.

Bill
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Old 29th March 2009, 02:18 PM   #5
Zen Mod is offline Zen Mod  Serbia
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Quote:
Originally posted by Bill Fuss
ZM, could you explain, in your own unique way, why it would be beneficial to AC short the unused output to ground. I can't get my head around the idea.

Bill

say that you're that way not wasting any percent of output amplitude .. meaning that - what's on input - it will be on output
( amplified) ;

if you leave one output (differential ) leg just flapping around , who knows what is happening with all these left-one electrons .... anarchy in the UK ?



shortly - you'll have less output voltage ( and how much less strictly depends of load connected to output ) with that ( neg ) leg flapping around ...

go to Jensen site , there is ton of nice handy pdfs .... and they're certainly better in Engrish than I am




Quote:
Originally posted by Bill Fuss
Buhl, there is DC at the gate through the divider Rs on the input, but dont know if it would harm your source or not.

Bill

you're right !!!!

mea culpa , maxima !

seems that I was even more confused than usual .....

buhl - do not short these caps , unless you move both feedback resistors (R48 and R63 , in Papa's original pdf ) from adjacent drains to adjacent preamp outputs ( after output caps ) ........
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Old 29th March 2009, 03:11 PM   #6
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But surely he can use lower quality caps for the unused phase with no ill consequencies.
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Old 29th March 2009, 03:19 PM   #7
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Thanks for the reply ZM, as clear as bock beer.
The point I guess I'm trying to address is that the output is already inherently loaded in the output circuitry. What point would there be to pulling down the signal to zero. I'll check out the Jensen website, thanks.

Bill
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Old 29th March 2009, 04:08 PM   #8
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Quote:
Originally posted by analog_sa
But surely he can use lower quality caps for the unused phase with no ill consequencies.

if we are splitting ( as usual ) hair - no ;
if we are practical - certainly !

wise !

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Old 29th March 2009, 04:11 PM   #9
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Quote:
Originally posted by Bill Fuss

... why it would be beneficial to AC short the unused output to ground.


This will also help.


><
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File Type: jpg short the unused output - 01.jpg (48.3 KB, 335 views)
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Old 29th March 2009, 07:35 PM   #10
CfM is offline CfM  Germany
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Quote:
Originally posted by Babowana
This will also help.
Aleph P has SuSy topology?
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