ME Amplifiers Owners & Discussion Thread

[mloutfie]

Looking for an opinion regarding a problem i recently having with my me850. I've been using an audio gd preamp c3 fv. Recently after maybe 1 month not using it since been away the amp start to shut down when using all but one input. And even on that one input only work with one gain settings. 

 

I have been using this preamp amp combo for more than 6 months no problem. First thing I checked was the dc offset (measuring + and - of my xlr cable) it's 6-8mV so that should be fine right. I wonder what can cause the amp to shut down. I can cause the amp to shut down just by changing volume with nothing playing.

 

I tried direct streamer amplifier and not a problem. 

Edited Friday at 09:43 PM by mloutfie

[Andythiing]

I’d guess it as a dc leakage issue - but @Zaphod Beeblebrox the man 

[Zaphod Beeblebrox]

The ME850 is designed to shut down, in order to protect your speakers, under any one of the following fault conditions:

* Excessive DC at the speaker terminals. (approximately 2 VDC will cause an amplifier shut down).

* Excessive low frequency information below 20Hz.

* Excessive high frequency information above 10kHz. An ultrasonic oscillation of (say) 30kHz will cause an instant shut down.

* Improper earthing of any connected product, regardless of how remote. IE: An antenna amplifier, connected to a TV, which is, in turn, connected to any ME power can cause a shut down. Antenna amplifiers are frequently responsible for inserting dodgy signals into audio systems.

* Overheating. If heat sink temperatures reach 90 degrees C, the ME850 will shut down completely.

It seems clear that you have a problem with an item which is connected to your system.

Unplug everything, then try one item at a time to see which product is causing the ME850 to shut down.

[mloutfie]

30 minutes ago, Zaphod Beeblebrox said:

Unplug everything, then try one item at a time to see which product is causing the ME850 to shut down.

Yes done that and managed to narrow it down to the preamp. Just that weird part that I can shut down the amplifier with nothing playing and changing volume level. Maybe grounding problem the preamp uses resistor switching to change volume? So weird never have this problem with my other amp and like i said this pairing has worked well for 8 months 

[Zaphod Beeblebrox]

26 minutes ago, mloutfie said:

Yes done that and managed to narrow it down to the preamp. Just that weird part that I can shut down the amplifier with nothing playing and changing volume level. Maybe grounding problem the preamp uses resistor switching to change volume? So weird never have this problem with my other amp and like i said this pairing has worked well for 8 months 

 

No other amplifier, that I am aware of, uses the comprehensive protection system used by the ME850. Ultrasonic oscillation can only be detected by an oscilloscope.

BTW: Are you saying that you have disconnected everything from the preamp, except the power amp and the fault remains?

If so, then the preamp requires repair.

FWIW: I use an Audio-gd DAC with al my ME amplifiers with no issue.

Edited Friday at 11:37 PM by Zaphod Beeblebrox

[mloutfie]

12 minutes ago, Zaphod Beeblebrox said:

BTW: Are you saying that you have disconnected everything from the preamp, except the power amp and the fault remains?

That is correct. That was tested yesterday with balanced preamp connection. Today done more trouble shooting all disconnected with single ended with rca to xlr cable to amp all seems working change volume and gain not shutting down the amp. It does point to preamp problem just not sure what.

 

Might need to bring to someone with oscilloscope

 

[mloutfie]

Yep single ended out from the preamp is all good. Tested with another xlr cable the issue still there so not cable problem. Perplexing 

[Zaphod Beeblebrox]

8 minutes ago, mloutfie said:

Yep single ended out from the preamp is all good. Tested with another xlr cable the issue still there so not cable problem. Perplexing 

Preamp fault. The ME850 is doing exactly what it was designed to do.

 

Balanced connections are a waste of time in a domestic environment.

[mloutfie]

Sure it does looks like it's a preamp problem but I would have thought any thing in this list below would impact both single ended and balanced. I have invested on better cables on my balanced chain and would like to keep using it.

 

Also me850 is true balanced amplifier? Wouldn't you loose the benefit of the full balanced amplifier.

 

BTW checking Excessive high frequency i assume that's a typo ie 20khz not 10khz

 

* Excessive DC at the speaker terminals. (approximately 2 VDC will cause an amplifier shut down).

* Excessive low frequency information below 20Hz.

* Excessive high frequency information above 10kHz. An ultrasonic oscillation of (say) 30kHz will cause an instant shut down.

* Improper earthing of any connected product, regardless of how remote. IE: An antenna amplifier, connected to a TV, which is, in turn, connected to any ME power can cause a shut down. Antenna amplifiers are frequently responsible for inserting dodgy signals into audio systems.

* Overheating. If heat sink temperatures reach 90 degrees C, the ME850 will shut down completely.
 

[Zaphod Beeblebrox]

Not a typo. The ME850 employs a progressively more aggressive sensitivity to high frequencies, beginning at approximately 10kHz. So, at around 10kHz, the amplifier can deliver approximately 15VRMS, whilst at 20kHz, it will deliver approximately 2VRMS before shutting down. The shut-down is not instant, since some music contains significant LF and/or HF information. Improper earthing will cause an instant shut-down.  The LF side begins at around 20Hz and is progressively more aggressive as the frequency descends, reaching maximum sensitivity at DC. The HF protection system protects HF drivers, whilst the LF protection system protects bass drivers. Damage to HF drivers when using an ME amplifier are extremely rare. Some, rare, ME models (ME500, ME1000, ME1200, et al) employ less aggressive protection systems and auto-reset capability in order to satisfy professional users.

Rest assured: Your ME850 is doing it's job perfectly.

[The_nautilus]

On 19/4/2025 at 7:45 PM, Zaphod Beeblebrox said:

Not a typo. The ME850 employs a progressively more aggressive sensitivity to high frequencies, beginning at approximately 10kHz. So, at around 10kHz, the amplifier can deliver approximately 15VRMS, whilst at 20kHz, it will deliver approximately 2VRMS before shutting down. The shut-down is not instant, since some music contains significant LF and/or HF information. Improper earthing will cause an instant shut-down.  The LF side begins at around 20Hz and is progressively more aggressive as the frequency descends, reaching maximum sensitivity at DC. The HF protection system protects HF drivers, whilst the LF protection system protects bass drivers. Damage to HF drivers when using an ME amplifier are extremely rare. Some, rare, ME models (ME500, ME1000, ME1200, et al) employ less aggressive protection systems and auto-reset capability in order to satisfy professional users.

Rest assured: Your ME850 is doing it's job perfectly.

Interesting timing.

just yesterday I built a SPICE model confirming what you just said

I was trying to make sense of some odd cap values that make far more sense now.

Nice to see some action in the forum again.

Edited 21 hours ago by The_nautilus