Q about the Aleph 1.7

[Buhl]

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

Regards
Hans

 

[Zen Mod]

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

 

[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

 

[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

 

[Zen Mod]

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

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 ) ........

 

[analog_sa]

But surely he can use lower quality caps for the unused phase with no ill consequencies.

 

[Bill Fuss]

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

 

[Zen Mod]

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 !

 

[Babowana]

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

This will also help.


><

 

[CfM]

This will also help.

Aleph P has SuSy topology?

 

[Babowana]

Aleph P has SuSy topology?

No, I don't think so.


><

 

[Bill Fuss]

I was wondering about that post from NP also. I started searching threads to no avail and got sidetracked. I think that post was from an X preamp discussion. Someone please enlighten us.
Bill

 

[Zen Mod]

I was wondering about that post from NP also. I started searching threads to no avail and got sidetracked. I think that post was from an X preamp discussion. Someone please enlighten us.
Bill

almost SUSY , but not completelly - due to common source degeneration of input differential ;

if you decrease R51 and R66 to few ohms ( up to 10 ) , connect just one - lower - CCS ( with doubled current comparing to previous situation ) to middle point between them ( off course - deleting trimpot ....... ) , you'll have fully functional SUSY center of universe

then - just set adequate gain of circ with values of R48/R5 and R63/R6 - for left and right side , respectively

 

[Buhl]

Thanks for the all the replys guys! - I knew that there would be DC fed back from the feedback resistor, and I would defenetly keep the input cap
But back to my original question, I am not sure that everybody noticed that I will be running strictly unbalanced? They reason is that I saw that the balanced input circuit from the X2 (which I am not happy to post due to the IP of Nelson) only uses the positive output and leaves the drain of the negative side just hang (connected to positive supply).

I guess I will go for the all cap everywhere - better safe than sorry!

Regards
Hans