Question About Pre-Amp Schematic

SSDIY · 9th April 2010, 09:54 AM

Hi Gents

I am studing a pre-amp schematic which is the ASR Collector I got from this forum earlier. I have a question about the connection of the emitter of the bipolars BC549/559.

According to the schematic, the emitters of the two BC559 are connected to the + rail while the collectors of the two BC549 connected to the - rail.

As far as to the other pre-amp schematic I have reviewed before, if the emitter of a bipolar is connected to the + rail, then the emitter of the other bipolar should also be connected to the - rail.

I would like to know if the connection of the bipolars of this schematic is correct but it is working on antoher way or it is a drawing error.

Please advice, thanks.

wahab · 9th April 2010, 12:43 PM

The said stage is a cascode, and i think that the bottom
side is erroneous as you point it..

knutn · 9th April 2010, 12:44 PM

Quote:

Originally Posted by SSDIY

Hi Gents

According to the schematic, the emitters of the two BC559 are connected to the + rail while the collectors of the two BC549 connected to the - rail.

As far as to the other pre-amp schematic I have reviewed before, if the emitter of a bipolar is connected to the + rail, then the emitter of the other bipolar should also be connected to the - rail.

I would like to know if the connection of the bipolars of this schematic is correct but it is working on antoher way or it is a drawing error.

It is a drawing error. The three lower BC549 have their collector and emitter exchanged.

SSDIY · 10th April 2010, 12:37 AM

Hi wahab & knutn

Thank you for advice. I will correct the schematic accordingly.

SSDIY · 15th April 2010, 08:58 AM

One more question about this schematic.
What is the function of the two trim pots connected to the +/- rails? To adjust output bias current or offset? Would anyone please advice?

knutn · 15th April 2010, 06:53 PM

Quote:

Originally Posted by SSDIY

One more question about this schematic.
What is the function of the two trim pots connected to the +/- rails? To adjust output bias current or offset? Would anyone please advice?

It is for adjustment of the output bias current.

SSDIY · 16th April 2010, 01:57 AM

Quote:

Originally Posted by knutn

It is for adjustment of the output bias current.

Thank you knutn, really appreciated.

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

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
12AU7 Pre-amp Schematic Question	Jimthemeek	Tubes / Valves	4	3rd May 2009 06:20 PM
looking for a pre-amp schematic	steamPunk	Tubes / Valves	3	3rd August 2008 01:49 PM
Pre amp? What schematic do i need?	silentblackhat	Solid State	21	16th March 2006 06:47 AM
pre-amp schematic	RichardJones	Solid State	4	22nd May 2003 10:58 PM
Pre amp schematic	HKC	Solid State	2	10th January 2003 06:07 AM

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


	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

9th April 2010, 12:43 PM	#2
wahab diyAudio Member Join Date: Nov 2009 Location: algeria/france	The said stage is a cascode, and i think that the bottom side is erroneous as you point it..

10th April 2010, 12:37 AM	#4
SSDIY diyAudio Member Join Date: Oct 2009 Location: Hong Kong	Hi wahab & knutn Thank you for advice. I will correct the schematic accordingly.

15th April 2010, 08:58 AM	#5
SSDIY diyAudio Member Join Date: Oct 2009 Location: Hong Kong	One more question about this schematic. What is the function of the two trim pots connected to the +/- rails? To adjust output bias current or offset? Would anyone please advice?

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