Upgrading a Yamaha M-70 power amp?

Brisso57 · 6th August 2007, 06:41 AM

Has anyone upgraded or modernised their Yamaha (class A) M-70 power amp?

If so, what did you do that produced audible or measurable benefits?

cheers

Doug

Blkorpheus · 18th October 2007, 06:35 PM

I've done several upgrades and mod to this unit.

I've bypass the old level control and solder pure silver wire from the rca inputs to the input board.

Replaced stock fuses with silver -plated types.

Replaced standard power cord with an silver plated IEC power inlet.

Added Bybees to the input board.

None of these alter the timbre of unit but between the level control bypass and the bybees, more microdynamics came out and more headroom which still rivals my Adcom 555 IIs at the moment. It's an easy to mod unit but it gets hard to handle when you start modding the power and gets easily stuck in protection mode.

gni · 19th October 2007, 03:09 PM

Service Manuals:
http://www.hifiengine.com/manuals_ty...amaha&mod=M-70

Links to similar discussions:
Yamaha M-45 Blown Output Transistors
Yamaha M-45 Power Meter Mods

Recently toasted my M-45 (cousin to the M-70) while adjusting
the bias (top mounted jumpers carry voltage rails). I am in the
final stages of installing a new amp module in the shell of the old
M-45.

The darn protection circuit. . .very picky. The M-70 is technically more
advanced than the M-45 though.

dgm · 29th September 2008, 05:08 AM

There are lots of comments about M-70 protection problems. My amp has this problem - will not switch on. It was a gradual thing as it took longer and longer to start up.
Does anyone know how to fix this - whats the usual problem?
Derick

6th August 2007, 06:41 AM	#1
Brisso57 diyAudio Member Join Date: Sep 2005 Location: the leafy west of Brisbane	Upgrading a Yamaha M-70 power amp? Has anyone upgraded or modernised their Yamaha (class A) M-70 power amp? If so, what did you do that produced audible or measurable benefits? cheers Doug __________________ A speaker-builder's parable: "That burned down, fell over, then sank into the swamp. But the fourth one stayed up. And that's what you're going to get, Lad, the strongest castle of all."

18th October 2007, 06:35 PM	#2
Blkorpheus diyAudio Member Join Date: Oct 2007	M-70 I've done several upgrades and mod to this unit. I've bypass the old level control and solder pure silver wire from the rca inputs to the input board. Replaced stock fuses with silver -plated types. Replaced standard power cord with an silver plated IEC power inlet. Added Bybees to the input board. None of these alter the timbre of unit but between the level control bypass and the bybees, more microdynamics came out and more headroom which still rivals my Adcom 555 IIs at the moment. It's an easy to mod unit but it gets hard to handle when you start modding the power and gets easily stuck in protection mode.

29th September 2008, 05:08 AM	#4
dgm diyAudio Member Join Date: May 2006	M-70 protection problem There are lots of comments about M-70 protection problems. My amp has this problem - will not switch on. It was a gradual thing as it took longer and longer to start up. Does anyone know how to fix this - whats the usual problem? Derick

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19th October 2007, 03:09 PM	#3
gni diyAudio Member Join Date: Sep 2006	Service Manuals: http://www.hifiengine.com/manuals_ty...amaha&mod=M-70 Links to similar discussions: Yamaha M-45 Blown Output Transistors Yamaha M-45 Power Meter Mods Recently toasted my M-45 (cousin to the M-70) while adjusting the bias (top mounted jumpers carry voltage rails). I am in the final stages of installing a new amp module in the shell of the old M-45. The darn protection circuit. . .very picky. The M-70 is technically more advanced than the M-45 though.

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