Subwoofer pre-amp

nbergsma · 25th October 2008, 11:33 AM

Hi,

I am trying to design subwoofer pre-amp. I don't have a lot of experience (read: no experience

) with analog / audio designs and I would like your opinion on the design I made.

The requirements for this project are:
- stereo balanced line ins
- unbalanced line out
- high quality (quality over cost)
- variable cut-off frequency (~150 ... ~350Hz)
- VU-meters for both input signals and the output signal

Things I'd like know:
- are there any (big) mistakes in the design ?
- are there resistors / caps / etc. missing ?
- is the combination of opamps possible ?
- does anyone have tips on the designing the pcb ? for example should I use SMT ?

Thank you in advance.

MJL21193 · 25th October 2008, 12:16 PM

I think there is something wrong with your zip file, I can see anything when I unpack and open it.

454Casull · 26th October 2008, 07:57 AM

I am able to open the PDF file inside.

nbergsma · 26th October 2008, 08:05 PM

mmm strange... here it is again!

AndrewT · 26th October 2008, 08:20 PM

go to doug Self's site and to ESP's site and read up on balanced signals and balanced inputs.
Then read the expert, Walt Jung.

Your schematic has unbalanced impedances, 10k & 20k on the hot and cold inputs.

nbergsma · 2nd November 2008, 02:27 PM

@AndrewT, thanks you for your response. The 'hints' you gave were very useful.

I updated the schematic so that the impedances on hot and cold pins are the same.

Do you, or anyone else, have additional comments on this circuit ?

Regards,
Niels Bergsma

AndrewT · 2nd November 2008, 03:08 PM

Quote:

Originally posted by nbergsma
I updated the schematic so that the impedances on hot and cold pins are the same.

where?

nbergsma · 2nd November 2008, 10:20 PM

I added two op-amps (one for Audio IN L, one for Audio IN R). They are located on the left side of the schematic, horizontal mirrored (next time I'll resolve the component numbering)

I used the circuit from Doug self's site, figure 12 (
'Superbal'-configuration)

26th October 2008, 08:20 PM	#5
AndrewT R.I.P. Join Date: Jul 2004 Location: Scottish Borders	go to doug Self's site and to ESP's site and read up on balanced signals and balanced inputs. Then read the expert, Walt Jung. Your schematic has unbalanced impedances, 10k & 20k on the hot and cold inputs. __________________ regards Andrew T.

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
subwoofer under bed	Potato42	Subwoofers	7	13th January 2009 02:21 PM
subwoofer project, which subwoofer?	Davlaf	Subwoofers	12	9th November 2006 03:59 AM
Subwoofer crossover / subwoofer module design	derMichi	Subwoofers	4	20th April 2006 10:31 AM
how to connect a non powered subwoofer to a stereo system without a subwoofer output	JSD777	Multi-Way	4	20th September 2005 03:19 PM
I need help with subwoofer deisign: HUGE inexpensive subwoofer	hottyson	Subwoofers	16	4th May 2004 03:51 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

25th October 2008, 12:16 PM	#2
MJL21193 Account disabled at member's request Join Date: Mar 2007	I think there is something wrong with your zip file, I can see anything when I unpack and open it.

26th October 2008, 07:57 AM	#3
454Casull diyAudio Member Join Date: Jan 2004 Location: Toronto, ON, Canada	I am able to open the PDF file inside.

2nd November 2008, 10:20 PM	#8
nbergsma diyAudio Member Join Date: Aug 2008	I added two op-amps (one for Audio IN L, one for Audio IN R). They are located on the left side of the schematic, horizontal mirrored (next time I'll resolve the component numbering) I used the circuit from Doug self's site, figure 12 ( 'Superbal'-configuration)