Pass X2 Preamp

jleaman · 28th March 2005, 05:27 AM

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 don´t have to build two PSU´s. 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 don´t have to build two PSU´s. 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 isn´t 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 isn´t 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

28th March 2005, 06:03 AM	#2
wuffwaff diyAudio Member Join Date: Aug 2001 Location: Ingolstadt Germany	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 __________________ een ooievaar is geen konijn want zijn oren zijn te klein!

28th March 2005, 05:18 PM	#4
wuffwaff diyAudio Member Join Date: Aug 2001 Location: Ingolstadt Germany	Hi, no you don´t have to build two PSU´s. 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 __________________ een ooievaar is geen konijn want zijn oren zijn te klein!

28th March 2005, 05:52 PM	#6
wuffwaff diyAudio Member Join Date: Aug 2001 Location: Ingolstadt Germany	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 isn´t 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 __________________ een ooievaar is geen konijn want zijn oren zijn te klein!

29th March 2005, 06:05 AM	#9
wuffwaff diyAudio Member Join Date: Aug 2001 Location: Ingolstadt Germany	Well, a CCS X-BOSOZ for example? William __________________ een ooievaar is geen konijn want zijn oren zijn te klein!

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search


	Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving

28th March 2005, 04:29 PM	#3
jleaman Banned Join Date: Apr 2002	This means i have to build to psu's..

29th March 2005, 04:41 AM	#8
thomasfw diyAudio Member Join Date: Jan 2005 Location: Hong Kong	Dear William, Which design you think is better than "X2"(old design ?). please suggest ! Thanks !

29th March 2005, 07:57 AM	#10
jh6you Account Disabled Join Date: Aug 2002 Location: Near to the Pacific Ocean	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

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
FS:PASS X2 preamp	rubydac	Swap Meet	3	12th May 2008 06:18 AM
FS: Pass Labs X2 preamp	Studley	Swap Meet	0	18th January 2007 10:53 PM
Preamp for Pass Aleph 0s?	Vermeer	Pass Labs	5	20th October 2004 11:46 PM
Pass DIY preamp PCB?	illenema	Pass Labs	2	28th January 2004 08:59 PM
Which pass preamp?	gregjpeters	Pass Labs	7	20th November 2002 05:48 PM

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read