Input buffer for DRV134

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Hi, I'm building a bridged LM3875 in bridge mode using DRV134. Is an input stage necessary for DRV134? I searched DIYAUDIO and came across this schematic in the thread Gainclone super symmetry.

http://www.diyaudio.com/forums/showthread.php?s=&threadid=36398

Has anybody tried this circuit? Does it make any differences?

Thank you !
 

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Well i have some samples of the DRV134 at work and read in the datasheet (building personal DIY at work makes time fly ;) ) just 2 hours ago that a OP or buffer is recomended.

Quote DRV134 datasheet page 10, Layout Considerations:

"The DRV134 input should be driven by a low impedance source such as an op amp or buffer "

Regarding the circut, sorry cant help. Have not build it..
 
CJ900RR said:
Well i have some samples of the DRV134 at work and read in the datasheet (building personal DIY at work makes time fly ;) ) just 2 hours ago that a OP or buffer is recomended.

Quote DRV134 datasheet page 10, Layout Considerations:

"The DRV134 input should be driven by a low impedance source such as an op amp or buffer "

Regarding the circut, sorry cant help. Have not build it..

I expirienced that the DVR134 gets noisy if it isn't driven by low impedance. I drive it with a OPA134.

stephanr
 
I use the OPA2277, or the OP200, or the TL072, or the 2134. I havn't decided yet witch OP that suits my need's :whazzat:

But. Here is a schematic you can use, made my a guy called Nagref at a swedish forum, www.faktiskt.se .

Schematic

Component list

It's really a preamp made for the OPA2134, but you can use almost every other Dual OP you want.

Then you take the out-signal from one channel at the preamp and hook it in to the DRV134, pin 4, Gnd to Gnd (pin 3). V+ to pin 6, V- to pin 5.

Then pin 1 and 2 goes to one amp's input, pin 7 and 8 to the other amp. From the amp's you take the out positive signal only and hook it up to one loudspeaker. First amp positive to loudspeaker positiv, seccond amp positive to loudspeaker negative.

Ok?

Just use the basic schematic in BurrBrown/TIs datasheet, located here , page 8.
 
PMA said:
DRV134 - they do not sound good. The worst preamp I have ever made.

Would you recommend constructing a bridge driver from individual opamps? Perhaps 3 Buf634's wired as per the schematic on page 1 of the DRV134 datasheet, or even 3 OPA627's. Any other suggestions for a bridge driver, what about a discrete solution? I'm interested in using this to make a bridged-parallel chipamp.

G.
 
PMA said:
G.,

I had a very good experience with 2 buffers (2 x OPA627or similar +BUF634), 1st noniverting and 2nd inverting. It was not true balanced output, as output did not double ofter one output shorted to ground. But sounded very good.

Pavel

Thanks Pavel, sounds like a pretty simple way to do it. How closely do you need to match your resistors? I wonder if it might be better for me to put some more gain in the bridging section I could then use a pair of OPA637 and use a much lower gain in the power amp section (OPA549 or LM3886). Seems to me this should optomize the GBP of the devices.

G.
 
anatech said:
Hi Mrpong,
I have build some diamond buffers very close to your reference. They work very well. Board layout is important as always.

-Chris


Hi Chris...

How did it sound in chip amp? I'm using the same schematic shown on that website and building a PCB layout for this buffer. What do you mean "Board layout is important"? Could you please explain a bit more?

- Koapong.
 
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Hi Koapong,
They sound like they are not there. I built discrete units using 2SC1775A and 2SA872A and 2SA970 and 2SC2240 for current sources.

I also built a bigger one using the same parts but 2SC3421 and 2SA1358 as pass devices. It is designed to work from bipolar 25 V supplies. Again, no sonic footprint that I could hear. This one drives headphones with no trouble.

Circuit board layout is always important. It depends where you run the traces and where the parts are on the board.

-Chris
 
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