MC 7270 question

kevzep · Jul 23, 2014

jameswei said:
CD_K is saying the opposite, who should I follow?

Turn the 7270 on LAST, and turn the 7270 off FIRST. Simple, have you tried this?
The right way is whatever way you do not get the "noise" when powering the system up or powering it down, this is the way I have explained here.

damacman said:
Look at it like this ... the MC7270 is an amplifier. It will amplify anything that comes into its RCA jacks - including any noises any upstream components may make on power up or power down. Therefore, it is undesirable to have the amp powered up when turning ON or turning OFF any upstream component.

Correct......:thmbsp:

c_dk · Jul 24, 2014

My error, hopefully I' ll do this better over morning coffee......

Pre on, then amp on. Amp off then pre off.

TR6man98 · Jul 24, 2014

c_dk said:
Pre on, then amp on. Amp off then pre off.

I understand the concept above but…
I have MC2205 that gets the AC power from C28 and turning on the preamp, I turn on the whole system at the same time. Very convenient… :music:

If your 7270 is like my MC2205, the speaker relay comes alive after couple of seconds and lets no noise whatsoever.
I do this for 10-15 years now and I would expect you should do the same. I am not sure what the issue with yours would be, though.

I recently got Adcom ACE515 “AC enhancer/power conditioner”, though. Unit, if properly connected, it will turn ON Power amp(s) 10 seconds AFTER the preamp (an other sources) is on and turn off the amp(s) 30 (0r so) seconds before the preamp shuts down.
It is very convenient feature and it would recommend it to you. It sounds it would solve the issue you have.

Regards,

jameswei · Jul 24, 2014

So I tried the C-28 with a Sony TA-3200F and its doing the pop noise when powering on and off, anyone knows what is wrong with the C-28? It was just recapped recently.

kevzep · Jul 24, 2014

jameswei said:
So I tried the C-28 with a Sony TA-3200F and its doing the pop noise when powering on and off, anyone knows what is wrong with the C-28? It was just recapped recently.

Why are you not trying what we are suggesting??

It is completely normal for the C28 to make a noise like this when powering up and down, this is why we are telling you the order to power up and down.......the amp will have a relay which will click on after the voltages have stabilized when powering up, this is why the amp is quiet powering up.
The C28 obviously doesn't so this is why you turn it on before you turn the 7270 on.....
The only thing wrong is the order in which you are turning the system on and off.....we keep going over it, and you seem to try everything except the correct order of powering on and off.....
Its really simple, I will say it again.....
Turn the 7270 on LAST, and turn the 7270 off FIRST.

jameswei · Jul 25, 2014

I try the order given and it didn't have any noise, so I guess everything is working correctly, just me messing up.

koogar519 · Jul 25, 2014

This is interesting. I have a c-37 pre-amp which will introduce a similair "pop". I just acquire a CA-3000 which doesn't. Doesn't matter if I run either with the BA-500 or MC 2500. If the C-37 is in the loop and is shut off before the amp I get the pop. Haven't checked swithc position. Will tonight.

CruzBay · Jul 25, 2014

I can't add much to the conversation other than the C-28 needs to be gone through by someone familiar with that device; a standard recapping doesn't address the other issues that preamp would develop over time.

I'm not saying it wasn't done right, but that preamp had other things that needed attention for continued reliable use.

kevzep · Jul 25, 2014

CruzBay said:
I can't add much to the conversation other than the C-28 needs to be gone through by someone familiar with that device; a standard recapping doesn't address the other issues that preamp would develop over time.

I'm not saying it wasn't done right, but that preamp had other things that needed attention for continued reliable use.

As stated before in this thread, it is perfectly normal for a C28 to emit a burst of noise whilst power up and powering down....
There is no soft start or muting circuit involved, so as voltages stabilize over a few milliseconds then there is noise, or a pop or a zip......

ALWAYS, Power-amp on last......and Power-amp off first.........

Little Nellie · Mar 23, 2020

If your 7270 is like my MC2205 said:
FYI, the MC7270 doesn't have a speaker relay.

clinic-audio · Mar 24, 2020

jameswei said:
So I tried the C-28 with a Sony TA-3200F and its doing the pop noise when powering on and off, anyone knows what is wrong with the C-28? It was just recapped recently.

Hello

just make a simple try :
1) MC7270 disconnect the plug
2) switch the power ON on your MC7270 main plug not connected
3) plug the power cord and listen if you have your noise in speakers
4) if no , your power switch (preamplifier) or power switch (amplifier) is bad
the noise that you can hear is coming from a spark created inside your power switch , that's all . By following my procedure you will see (or hear ) the behaviour of your amplifier without using the power switch , easy , no ?

MC 7270 question

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