Full balanced current (transconductance) chip-amp

swak · 6th February 2007, 05:50 PM

I have got a new soudcard with a set of full balanced outputs. As I have wanted to try a transconductance amp for some time I was wondering if I go for it in balanced mode.

As I am thinking will be building a 4 ch amp, input transformers would be too expensive. Can anyone advice me on a good wyz to do it ors point me to some schematics?

Thanks in advance.

BWRX · 6th February 2007, 06:39 PM

I've got some LM3875 boards being made that can accept a balanced input. You can find the schematic here . I'll have about 20 extra boards, so if you're interested just let me know.

swak · 6th February 2007, 11:14 PM

BWRX, tahnks for the link and for the offer, I want to do this project P2P.

How about this design http://www.jensen-transformers.com/an/ingenaes.pdf ?

The idea also comes from an instrumentation amp.. if someone is willing to help me set the resistor values and the A1, A2, A4 Opamps (AD811?) I would give it a try and report how it goes.

m8o · 8th February 2007, 08:37 PM

swak, wondering if you use a Spice program, like LTSpice? I have some schematics.

I'm presently working on the designs and aquiring parts to tri-amp my front 3 Klipsch/JBL horn mish-mosh speakers using LM4780 chips as transconductance amps. I'm not sure if I'll turn my home computer on tonight, but if I do I'll take some screen caps of the schematics of the transconductance circuits I've been working on. If you use LTSpice, I can e-mail you the circuits.

edit: but the circuits are not balanced ins .... however, I guess I should do so as I purchased a BSS prosys ps-8810
( http://www.bss.co.uk/includes/produc...?product_id=32 )
to perform the 3 channel 3-way crossover functions I need (with some minor eq'ing), which is balanced in and out.

To prototype, I bought 4 assembled boards from National Semiconductor. I plan to modify the circuits (cut the copper and add resistors as needed) to make it operate as a transconductance amp.

6th February 2007, 05:50 PM	#1
swak diyAudio Member Join Date: Jul 2003 Location: .	Full balanced current (transconductance) chip-amp I have got a new soudcard with a set of full balanced outputs. As I have wanted to try a transconductance amp for some time I was wondering if I go for it in balanced mode. As I am thinking will be building a 4 ch amp, input transformers would be too expensive. Can anyone advice me on a good wyz to do it ors point me to some schematics? Thanks in advance.

6th February 2007, 06:39 PM	#2
BWRX diyAudio Moderator Emeritus Join Date: Jan 2005 Location: Pennsylvania	I've got some LM3875 boards being made that can accept a balanced input. You can find the schematic here . I'll have about 20 extra boards, so if you're interested just let me know. __________________ Brian

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6th February 2007, 11:14 PM	#3
swak diyAudio Member Join Date: Jul 2003 Location: .	BWRX, tahnks for the link and for the offer, I want to do this project P2P. How about this design http://www.jensen-transformers.com/an/ingenaes.pdf ? The idea also comes from an instrumentation amp.. if someone is willing to help me set the resistor values and the A1, A2, A4 Opamps (AD811?) I would give it a try and report how it goes.

8th February 2007, 08:37 PM	#4
m8o diyAudio Member Join Date: Nov 2006	swak, wondering if you use a Spice program, like LTSpice? I have some schematics. I'm presently working on the designs and aquiring parts to tri-amp my front 3 Klipsch/JBL horn mish-mosh speakers using LM4780 chips as transconductance amps. I'm not sure if I'll turn my home computer on tonight, but if I do I'll take some screen caps of the schematics of the transconductance circuits I've been working on. If you use LTSpice, I can e-mail you the circuits. edit: but the circuits are not balanced ins .... however, I guess I should do so as I purchased a BSS prosys ps-8810 ( http://www.bss.co.uk/includes/produc...?product_id=32 ) to perform the 3 channel 3-way crossover functions I need (with some minor eq'ing), which is balanced in and out. To prototype, I bought 4 assembled boards from National Semiconductor. I plan to modify the circuits (cut the copper and add resistors as needed) to make it operate as a transconductance amp.