What is an 'NFR' and 'NFL' lead?

[fallbalance]

Thanks for the responses.

Sorry, this is a bit new to me - what does FB stand for? I traced the leads on the main board... it looks like they run to part# C104 and C103... which in the index is labeled as a 'mylar cap'. I couldn't trace it beyond that.

So I should just run this wire to my positive speaker lead?

Thanks-

[fallbalance]

// I meant should I connect this wire to my positive binding post along with my signal wire...?

[CBRworm]

I know this is a DIY board, but why are you bypassing the relay? You may get some nasty turn on/off noises without it (maybe not), and you will probably loose whatever protection is offered by the circuit driving it, yet the circuitry will still be there - just no relay, correct?

If there is something wrong with the relay, replacing it may be a better option. If the relay is interrupting your music, the problem may not be the relay - it might be protecting your speakers from massive DC.

[fallbalance]

I know it seems crazy, but this is actually a somewhat common modification for these amps. Apparently they made a switching board to save on costs - they are known to crack commonly as well as add a small amount of noise to the signal. Also, the stock binding posts are bare-wire only and aren't of the highest quality. These parts of the M80 aren't up to specs with the rest of the amp, which is excellent.

The Yamaha M series were designed to have binding posts for 3 sets of speakers. I'm eliminating this and installing quality posts for just one set. I have an M40 that was modded by someone else and they took the entire board out as well, hard wiring the speaker leads to the binding posts. It works and sounds excellent.

It looks like, judging from the schematics, that the M80's wiring is slightly different from the M40, but the same principle applies - sooooo I'm hoping that removing the relay board will have no ill effect.

[CBRworm]

That's cool, sometimes people just want to bypass things or remove/improve parts without any idea what effect it will have or why they are there in the first place. If it is an accepted upgrade, go for it.

Yes, the NFL lead should be connected to the L+ post and the NFR lead should be connected to the R+ post. This assumes that the two channels grounds are the same and that it is not a balanced or bridged amp. I have seen other amps like this where the connections are made at the farthest possible point inside the amp but before any switches or relays. On amps with no relays I have seen them connected right to the back of the posts. Make sure the amp is not operated without those leads connected, it will quite possibly oscillate into self destruction if the connection is bad. That self destruction would likely take out your tweeters as well. I would test it with some sacrificial speakers before hooking up your beloved speakers.

[EchoWars]

Originally Posted by fallbalance

sooooo I'm hoping that removing the relay board will have no ill effect.

The difference is, that with the relay out of the circuit you have NO protection for your speakers. Blow up the amp, and wave goodbye to your woofers (keep a fire extinguisher handy too).

[fallbalance]

Thanks for the info CBRworm!

Echo - Really!? Are you sure it doesn't just act as a switching board for the three speaker sets? I have an M40 with the relay board removed, and it still kicks into protection mode on startup, whenever there is a power drop, when speaker wire is crossed, etc...

Originally, speaker sets A and B were run in parallel, and set C was run in series, so the wiring was easier for Yamaha to do with a circuit board I think.

How can I tell if there is a protection circuit on the relay board? I'm looking at it now and it all just looks like speaker switching circuits... but I am pretty new to this, so I could be missing something.

[fallbalance]

Hey again everyone,

Another question here. I just spoke with a relative who is circuit savvy. He said the experience he has seen with negative feedback loops has been in OPamps. He said that the signal being fed back to the negative feedback circuit was usually attenuated to something around a tenth (1/10) of the actual amplified signal being fed to the speakers.

This made me nervous, of course. Yet, I don't see anything in the schematics of the relay board that would attenuate the signal being fed to the feedback wires...

Could it be that the attenuation happens on the main board? Or could it be that the feedback signal is built to be equal to the actual output signal? What do you guys think?