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-   -   Need input buffer design or ideas for icepower 125asx2 in BTL mode. (http://www.diyaudio.com/forums/class-d/133792-need-input-buffer-design-ideas-icepower-125asx2-btl-mode.html)

makingmoney 25th November 2008 04:13 PM

Need input buffer design or ideas for icepower 125asx2 in BTL mode.
 
Looking for a simple durable design that'll work well in this app.


Page 23 BTL Sync.... -1 buffer (at least I think it's a buffer) to Vin channel 1

http://www.icepower.bang-olufsen.com...asheet_1_1.pdf


I've done a lot of DIY transistor kits and designed and built a lot of vacuum tube amps.

Thanks

Pano 25th November 2008 05:54 PM

The circuit in the app sheet is to split the signal into 2 halves of opposite phase. That's what you need for the BTL arrangement.

You can do it with opamps, but you'll have to find the power somewhere. DON'T count on the aux supply on the PCB, it isn't reliable.

A transformer would do the trick nicely.....

Remember that the input impedance of this amp is low - about 10K, IIRC.

theAnonymous1 25th November 2008 09:52 PM

The simplest way would be with a DRV134, but they like low source impedance (<600R). Here is how to do it wth op-amps.....

http://sound.westhost.com/project14.htm

My favorite is to use OPA1632/THS4131 driven with a good op-amp as a buffer.

makingmoney 26th November 2008 09:41 PM

I like the idea about using a transformer. I'll dig one out of my stuff in a few days and see if it'll work in this app. Thanks.

The aux power supply is unregulated so if I went that way I'd have to use a v reg. Starting to get a bit complex for me.

ChevyDK 28th April 2009 08:37 PM

Hey.

I'm looking in too the exact same matter.
Did you do some try outs?
What did you finally go for?

I would realy like to hear your experience here.

chipmate 18th November 2010 10:20 AM

Quote:

Originally Posted by panomaniac (Post 1667863)
The circuit in the app sheet is to split the signal into 2 halves of opposite phase. That's what you need for the BTL arrangement.

This thread is rather old but I'm having same requirement.
Anyone can advice if I can fed the ASX2 with balanced input signal and have it operated in BTL mode?
Tks

katarakt 28th July 2011 10:47 AM

Chipmate, have you figured it out? I think for BTL mode only a balanced input signal is required and it doesn't matter where it came from?

miniDSP balanced out to 125asx2 should work with BTL mode? anyone can confirm please?

StigErik 28th July 2011 07:17 PM

I've run them in BTL mode from a balanced source - no problem at all. If you have a balanced source of any kind you dont need a input buffer, but if you dont - you must build a buffer of course. I see no reason miniDSP with balanced out should not work directly connected to the ASX2 in BTL mode.

katarakt 28th July 2011 10:40 PM

Ok thanks a lot! I must go for sure before i start my project.

stokessd 29th July 2011 04:31 AM

Be careful with what you pick, those boards input impedance falls drastically at high frequencies. I measured it and have plots here:

http://www.diyaudio.com/forums/class...ents-mods.html

So whatever you build, it better have a low output impedance. I built an op-amp buffer stage and used the auxiliary power on the amp board to power it (I regulated and filtered the aux power)


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