Amp and preamp on same outlet?

I agree with Mrvordo!, he has the krell 750MCX mono amps with 30 amp breaker!, he knows first hand this works on our monster amps!

Edit post, 03-09-15: Jea48.

So if the branch circuit feeding the amp is 30 amps, what if there is a ground fault event anywhere in the 120Vac power wiring inside the amp, including the hot side fed of a primary winding of one of the 4kva transformers, to the safety equipment grounded metal chassis of the amp? Will the ground contacts of the plug/wall receptacle combo be able to handle the ground fault current that will travel back to the source, the electrical panel? If the receptacle and plug are NEMA 30 amp rated and UL and or CSA Listed then yes the equipment ground contacts of the plug and receptacle will be able to handle the possibly extremely high current the 30 amp breaker can supply until it reacts to the ground fault load current placed on it and hopefully trips open and breaks the ground fault circuit.

If it's a NEMA 5-15P plug/5-20R receptacle connection who knows? Not the manufacture of the devices. Not UL or CSA.
And I would be willing to bet Krell doesn't know either.

Quote
"Will the ground contacts of the plug/wall receptacle combo be able to handle the ground fault current that will travel back to the source, the electrical panel?"

It should have been obvious but I should have included the plug/wall receptacle Hot contact connection as the Hot brach circuit conductor that is connected to the Hot contact of the receptacle is feeding the high current, caused by the ground fault event, back to the source, the electrical panel, through the safety equipment grounding conductor. "Houston, we have ignition!"

Also in case it was not clear my load calculations, in the post, were for possible FLA full load of the two 4 KVA power transformers. I have no idea what the actuals loads could be. If Al couldn't figure them out from the Krell specs given, I assure you I can't. I did try to find a wiring diagram for the amp on the net without any luck.

03-09-15: Ct0517 post reminded me again from a previous post of his the rear panel 50 amp breaker has a pair of wires for hard wire remote control of the breaker. Just a guess, and that's all it is, the 50 amp breaker has a shunt trip solenoid that when energized will mechanically trip the breaker open. The shunt trip circuit could be controlled through relay contacts of relays that are controlled from each channel of the amp. This could be part of overload protection for the two power amplifiers of the amp. A wiring diagram of the amp's overcurrent protection would be nice.

For those interested, a look inside the Krell 700CX

It's just a shame Krell did not put a 30 plug on the end of the power cord to began with.

The power of electricity
.

In the "old days" Preamps had switched outlets on the back where you would plug the amps into because the amps did not have a power switch. Some examples from ARC were the SP3A (still one of the best sounding Preamps I have ever heard) and the SP6 etc. So not only was the Amp and Preamp on the same circuit, but the amp was plugged into the Preamp, and I never thought that was detrimental to the sound. Of course that was back in the days before people were sold on $1,000 power cords and $5,000 speaker cables, etc.

Just an update for Jea48 and others(?) following the Krell amp rear breaker panel value saga here. :^)

To backtrack, I tried to be of service to the thread as a messenger. I posted info from an email from Patrick of Krell advising that the breaker panel value on the back of these amps is 50 amps. I was however curious so I contacted Dan D'Agostino. He advised the breaker value for 120v service amps is 20 amps for reasons noted below. Fwiw I use a custom made 20 amp power cord, with the 20 amp dedicated circuit on my Krell amp.

I can therefore only recommend that any Krell amp owner with questions, clarify directly with Krell for their specific amp if they are curious. Patrick is a great resource for me, and I would find it awkward (as you can imagine) to approach him about Dan's info. It won't change my personal situation.
The emails follow

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Patrick Bresnahan 09/03/2015
To:
PBresnahan@krellonline.com

These are 50 amp breakers.

Sent: Friday, March 06, 2015 2:36 PM
To: Patrick Bresnahan
Subject: RE: breaker value on back of amp ?

what is the breaker value on the back of my fpb600 or the other high power amps. FPB-700cx ?
the Krell stock cord looks like a 15 amp ? and my wall is 20 amp service.
is the breaker 15 amp ?

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I asked the same question to Dan D'Agostino

From: dan@dandagostino.com

Date: Tue, 10 Mar 2015 17:14:28 -0700
You have very little protection if there was a failure with a 50 amp breaker. If the unit is set for 120 volts the most a standard 120 volt receptacle can safely have is 20 amps.
There is no reason for a 50 amp breaker. It is not safe
Dan


From: dan@dandagostino.com

Date: Tue, 10 Mar 2015 16:27:03 -0700
Hello Chris that amplifier should Have a 20 amp breaker not a 50

J_stereo, I had a ARC SP3 along with a Dual 51 and Dual 75. I never even thought of using the switched or unswitched outlets on the back. I don't remember doing any experiments to discourage using them, but perhaps others advised against doing so.

But I certainly do remember little concern about power cords, vibrations, EMI or RFI much less ics and speaker wires. My first special speaker wires were from Bob Fulton and I realized that I had used identical wires on my welding rig while in undergraduate days in a material testing lab.