Balanced Inputs on Leach Amp

wigginjs · 29th June 2004, 12:41 PM

How would I add the ability to accept a balanced input (via an XLR connector) to the Leach Amp design? Anyone ever done this?

pooge · 29th June 2004, 02:11 PM

Use an input transformer, a la Jensen JT-11P-1 or the like, and change the input resistor on the Leach to 10K to properly load the transformer.

tool49 · 29th June 2004, 02:27 PM

Or you could also make a small zener supply, regulate it and use the INA134 chip.

Sébastien

wigginjs · 29th June 2004, 02:37 PM

Sorry, but those answers are a little over my head. I'd perfer to construct something that could intergrate into the existing design (so it still allows the unbalaced input to function) and would not require modifications to the leachamp PCB. Anyone have a diagram of a circuit that could accomplish this?

tool49 · 29th June 2004, 02:52 PM

I believe that my solution answers to all your requirements!

Sadly I do not have time right now to go into more details.

Sébastien

richie00boy · 29th June 2004, 03:42 PM

See ESP Project for balanced line driver/receiver. You would also need to tap off the rails to power the op-amp circuitry - Rod also has a project for this (simple pre-regulator I think it is).

pooge · 29th June 2004, 04:39 PM

Quote:

Originally posted by m0tion
Sorry, but those answers are a little over my head. I'd perfer to construct something that could intergrate into the existing design (so it still allows the unbalaced input to function) and would not require modifications to the leachamp PCB. Anyone have a diagram of a circuit that could accomplish this?

Well, you're going to have to alter SOMETHING. You have to connect the input to the board. If you don't want to change the input resistor on the board, you can add a 20k resistor across the connectors of the XLR so that it will be in parallel to the 20k input resistor on the Leach. You can find a circuit at the link. It ain't cheap, though. You could also wire the unbalanced input in parallel with the XLR, but don't connect to both inputs at the same time.

Jensen input transformer

djk · 30th June 2004, 10:03 AM

I second the use of a transformer.

Electronic balanced inputs are a waste of time and money.

A lower priced alternative to the Jensen is from EDCOR

http://www.edcorusa.com/sound/matchers/s2s10k_10k.htm

richie00boy · 30th June 2004, 01:11 PM

Whilst transformers are undoubedly the ultimate, for a tenth (maybe even less than that) of the price the electronic version cannot be dismissed, and done properly results can be very good.

Nelson Pass · 30th June 2004, 07:19 PM

Quote:

Originally posted by m0tion
How would I add the ability to accept a balanced input (via an XLR connector) to the Leach Amp design? Anyone ever done this?

As I recall, the Leach is a simple enough differential input, and
is easily adapted to balanced inputs. Check out the discussion
of differential inputs on the A75 article at www.passdiy.com
and you'll see good enough examples.

29th June 2004, 12:41 PM	#1
wigginjs diyAudio Member Join Date: Dec 2003 Location: Columbia, SC	Balanced Inputs on Leach Amp How would I add the ability to accept a balanced input (via an XLR connector) to the Leach Amp design? Anyone ever done this? __________________ The Four Chairs DIY Home Theater

29th June 2004, 02:37 PM	#4
wigginjs diyAudio Member Join Date: Dec 2003 Location: Columbia, SC	Sorry, but those answers are a little over my head. I'd perfer to construct something that could intergrate into the existing design (so it still allows the unbalaced input to function) and would not require modifications to the leachamp PCB. Anyone have a diagram of a circuit that could accomplish this? __________________ The Four Chairs DIY Home Theater

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29th June 2004, 02:11 PM	#2
pooge diyAudio Member Join Date: May 2003 Location: Northern Va.	Use an input transformer, a la Jensen JT-11P-1 or the like, and change the input resistor on the Leach to 10K to properly load the transformer.

29th June 2004, 02:27 PM	#3
tool49 diyAudio Member Join Date: Apr 2003 Location: Montreal	Or you could also make a small zener supply, regulate it and use the INA134 chip. Sébastien

29th June 2004, 02:52 PM	#5
tool49 diyAudio Member Join Date: Apr 2003 Location: Montreal	I believe that my solution answers to all your requirements! Sadly I do not have time right now to go into more details. Sébastien

29th June 2004, 03:42 PM	#6
richie00boy Did it Himself diyAudio Member Join Date: Nov 2003 Location: Gloucestershire, England, UK	See ESP Project for balanced line driver/receiver. You would also need to tap off the rails to power the op-amp circuitry - Rod also has a project for this (simple pre-regulator I think it is).

30th June 2004, 10:03 AM	#8
djk diyAudio Member Join Date: Feb 2001 Location: USA	I second the use of a transformer. Electronic balanced inputs are a waste of time and money. A lower priced alternative to the Jensen is from EDCOR http://www.edcorusa.com/sound/matchers/s2s10k_10k.htm

30th June 2004, 01:11 PM	#9
richie00boy Did it Himself diyAudio Member Join Date: Nov 2003 Location: Gloucestershire, England, UK	Whilst transformers are undoubedly the ultimate, for a tenth (maybe even less than that) of the price the electronic version cannot be dismissed, and done properly results can be very good.