Power amp r b 981 no power to the speakers. Pre amp seems to be ok. Headphones work.

https://elektrotanya.com/nad_c370_sm.pdf/download.html

https://music-electronics-forum.com/forum/amplification/other-amps/920148-nad-c-370-no-sound-from-speaker-outputs#post920172

https://audiokarma.org/forums/index.php?threads/nad-c370-repair.916194/

If it works on the other channel, then you have a faulty amp. If the sound is good on headphones then the left power amp has gone. If not then you have a left pre-amp problem.
If the speaker doesn't work at all on any channel, then either there's a bad connection inside the speaker or one or more of the internal speakers have blown.

If the sound is also dead on that channel on a pair of headphones. Then you have probably lost the main power amp for that channel. To be certain. With you headphones on, slide or turn the balance control so you can only hear the faulty channel. With some music playing turn up the volume. If you can hear "faintly" music playing then the pre-amp is OK and the power amp has gone.
The power amp will be located on a heat sink. It will consist of 4 transistors (2 for each channel) or one big device (or two) (an IC). If it is transistors you only need to replace the two for the right channel.

Sadly this could indicate that the main power amp has failed. You should try turning it up really loud with some music playing. If you can hear it very faint, then the main amp has failed. If you can hear hum, then the pre-amp might be the cause. The only other cause is that the headphone socket has broken, cutting off both speakers and headphones.

One thing to remember about most radios, the RCA pre amp circuit will still work even if the mosfet power amp inside the radio does not. The best way to know if the amp inside the radio works is to use one matching color pair coming off the radio to wire up a random speaker right to the radio. You can use just about any old random 4 ohm speaker that is laying around to check it. The best solution if the amp inside the radio is blown is to replace the radio or amp the pre amp outputs with a small 4 channel amp. Oh, by the way. What vehicle are you connecting this into? And does the vehicle say Bose, Infinity, or ect sound or Premium sound? These usually denote a factory amplifyer already onboard and requires special connections to get the signal to these amps to then be delivered to the speakers.

hi,
normally in any amplifiers or pre amplifiers the RCA sockets used only for pre input and output. for speaker out always there will be binding post or speaker sockets, u can connect the pre amps RCA output to ur power amps input. there will be seperate connector for speaker connection in ur power amplifier . You didn't specified the make and model number of ur amplifier and pre. need any further help feel free to contact.
ok

Just curious, what preceded this? Sudden spontaneous failure with no manual action associated? Is the Tape Monitor activated?

I don't know how valuable your speakers are but you're hitting them with max power and distortion when you get that bang. I'd use cheap headphones for the troubleshooting phase.

Try to plug a set of headphones into your amp.

If only one is working this means that either you're not getting both signals into the unit (check the signal input connectors, resolder any bad contacts), the signal doesn't get to the preamp or from the preamp into the power amp or the signal does not come from the power amp (check solder connections on preamp and power amp components, also check internal connectors - unplug, clean, reconnect).

If both headphones work well instead, then you're getting both signals into the unit and the preamplifier and the final amplifier are OK, since many amps derive headphone signal from the power amplifier via some power resistors - check for any power resistors around the headphone plug or in the section that has wires going to the headphones plug to see if this is the case - if it is, this means that the signal does get amplified, but it is not getting from the power amp to the speaker - in this case, check the following:

--- speaker connector solder contacts on the circuit board could have some damage - resolder if necessary


--- A / B speakers selector switch (if there is one, it could be a physical switch or a soft touch button driven relay so check for both) - there might be a bad solder contact on the switch pins or the switch / relay contacts may be dirty - resolder and/or clean the contacts (if they can be easily accessed).


--- final amplifier section: bad solder contacts on any power transistors, voltage regulators, power resistors, diodes, coils or other components, including internal connectors (anyway, if both headphones work well, these are all unlikely because the power amp is sending both signals out OK, however, you may want to give it a check, just in case...)


--- delayed speaker turn on relay or other relays - check for dirty relay contacts, clean with some fine sandpaper (you need to remove the relay cover which can be a bit tricky / difficult to access, mostly it's a snap-on cover, could also be resin filled and therefore impossible to open).


It could as well be a bad power amp (do the headphones test), the above suggestions are just a quick look at some common audio amp problems and possible solutions.

Also, if your unit has got many hours of use, it would be fair to check the input signal connectors - the solder contacts do get damaged when you plug / unplug the RCAs many times.

Hope all of this is not getting too lenghty and confusing... just post me some feedback if you have questions.

regards

3rq8 (Triarcuate)

Do this, CD audio out jacks to the PRE-AMP INPUT jacks, then PRE-AMP OUT jacks to AMPLIFIER INPUTS then from AMPLIFIER to speakers, This will work similiar with any sound source unit ie. Radio Tuner, Tape deck, etc. Just think of it this way, a PRE-AMP is BEFORE the AMPLIFIER, all the AMPLIFIER is going to do is AMPLIFY the sound to your speakers, HOPE THIS HELPS!

Phantom power on? Turn everything down before turning the phantom power on