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-   -   Pass X2 Preamp (http://www.diyaudio.com/forums/pass-labs/54353-pass-x2-preamp.html)

jleaman 28th March 2005 05:27 AM

Pass X2 Preamp
 
2 Attachment(s)
In this schematic it shows 95V positive and 32V negitive is this correct ?

J

wuffwaff 28th March 2005 06:03 AM

HI,

yes this is correct. Because of the current source it is not needed to have a large negative voltage. Most use a lot less than 32Volts.

William

jleaman 28th March 2005 04:29 PM

This means i have to build to psu's..

wuffwaff 28th March 2005 05:18 PM

Hi,

no you donīt have to build two PSUīs. You can ofcourse use + and - 90V. Only change the resistor that sets the current and use enough heatsinking.
One advantage of the current source is that you can use lower supply voltage (especially the negative one) for higher efficiency without any performance disadvantages.

William

jleaman 28th March 2005 05:36 PM

Quote:

Originally posted by wuffwaff
Hi,

no you donīt have to build two PSUīs. You can ofcourse use + and - 90V. Only change the resistor that sets the current and use enough heatsinking.
One advantage of the current source is that you can use lower supply voltage (especially the negative one) for higher efficiency without any performance disadvantages.

William


Want to help me then : O )

wuffwaff 28th March 2005 05:52 PM

Hi,

yes I can help but first I would like to know why you want to build an "old" design. There are a few X-BOSOZ on the forum (with or without current source) wich do perform better than a BOSOZ with current source.

I would go for one of these.

Building an assymetrical power supply isnīt such a problem either. You only need two (smaller) transformers instead of one and connect the ground togheter or maybe ou can get a transformer with 60V and 20V windings.

William

jleaman 28th March 2005 08:27 PM

Quote:

Originally posted by wuffwaff
Hi,

yes I can help but first I would like to know why you want to build an "old" design. There are a few X-BOSOZ on the forum (with or without current source) wich do perform better than a BOSOZ with current source.

I would go for one of these.

Building an assymetrical power supply isnīt such a problem either. You only need two (smaller) transformers instead of one and connect the ground togheter or maybe ou can get a transformer with 60V and 20V windings.

William


I was just reading and toying with the idea so i can build a nice hi end one for my aleph mini's I might just redo a better layout for teh aleph P1.7 that i have already.. : O )

J

thomasfw 29th March 2005 04:41 AM

Dear William,
Which design you think is better than "X2"(old design ?). please suggest !


Thanks !

wuffwaff 29th March 2005 06:05 AM

Well,

a CCS X-BOSOZ for example?

William

jh6you 29th March 2005 07:57 AM

Dear all

I have long wondered.

Why do we need any negative feedback loop for such a simple single stage gain BOSOZ?
If we see A P1.7, it looks like having a feedback resistor from the drain of the gain FET to its gate. But, I think that the main role of the resistor is to place the drain potential of the gain FET at certain point between the +rail and the ground because it has +rail only. The resistor is not really for the negative feedback (X-feedback), IMHO!!!

I like X2 having NO negative feedback loop.

I am still wondering why we need the X-feedback loop to the simple single stage gain preamp.
Is it really improving the sound in positive way????????

Regards


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