Millet Hybrid - stacked buffers

woodturner-fran · 20th November 2007, 12:17 AM

Its a bit hard to know whether this belongs in here or in solid state, but here goes:

I'm nearing the end of a millet hybrid build. Case work is done, board is stuffed and tested, I'm waiting on a tread PSU and muting circuit to come yet.

So I'm using some OPA551 for the buffers and was going to stack them as per posts I have seen by people who have done this with the BUF634 - an attempt to wring a bit more out of it.

Stupid Question Alert: I take it that stacking is literally just mounting one on top of the other?

The diamond buffers would be nice, but jeez, that parts list!!!!

Any suggestions?

Fran

motherone · 20th November 2007, 03:16 AM

Stacking is literally soldering one buffer on top of the other. However, the BUF634 has an integrated resistor on the output, so the two buffers won't fight each other. The OPA551s do not, and I think it's not recommended to stack them.

Also, note that the OPA551 is plenty sufficient for most cans. The big benefit on stacking the BUF634 is lowering the output impedance (remember those output resistors). I personally find a single OPA551 works fine with all of my headphones, and that there was no real difference between them and the stacked BUF634s.

Hope you enjoy the Millett -- it's my favorite headphone amp for everyday listening.

woodturner-fran · 20th November 2007, 09:07 AM

Many thanks Motherone - very helpful.

Moderators, feel free to move this thread to SS if you deem fit..

Fran

20th November 2007, 12:17 AM	#1
woodturner-fran diyAudio Member Join Date: Jan 2006 Location: Ireland	Millet Hybrid - stacked buffers Its a bit hard to know whether this belongs in here or in solid state, but here goes: I'm nearing the end of a millet hybrid build. Case work is done, board is stuffed and tested, I'm waiting on a tread PSU and muting circuit to come yet. So I'm using some OPA551 for the buffers and was going to stack them as per posts I have seen by people who have done this with the BUF634 - an attempt to wring a bit more out of it. Stupid Question Alert: I take it that stacking is literally just mounting one on top of the other? The diamond buffers would be nice, but jeez, that parts list!!!! Any suggestions? Fran

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20th November 2007, 03:16 AM	#2
motherone diyAudio Member Join Date: Apr 2003 Location: Seattle	Stacking is literally soldering one buffer on top of the other. However, the BUF634 has an integrated resistor on the output, so the two buffers won't fight each other. The OPA551s do not, and I think it's not recommended to stack them. Also, note that the OPA551 is plenty sufficient for most cans. The big benefit on stacking the BUF634 is lowering the output impedance (remember those output resistors). I personally find a single OPA551 works fine with all of my headphones, and that there was no real difference between them and the stacked BUF634s. Hope you enjoy the Millett -- it's my favorite headphone amp for everyday listening.

20th November 2007, 09:07 AM	#3
woodturner-fran diyAudio Member Join Date: Jan 2006 Location: Ireland	Many thanks Motherone - very helpful. Moderators, feel free to move this thread to SS if you deem fit.. Fran

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