Should I remove capacitors after power transistors?

[Iplayloud]

I have a Fender FM65dsp and right at the end of the circuit, before the speaker output, there's tiny disc capacitors between the white wire and ground, and also one between the black wire and ground. (Ground floating i guess) Are these there to reduce some noise?
* I saw the solid state forum but it's not under Guitar Amps so I thought maybe it's for PAs. I can delete this thread if it's in the wrong section. Thx

[Enzo]

Or increase stability

[Greg Robinson]

No, why would you?

[Iplayloud]

The reason I'm asking is the amp could use some extra high-end clarity treble. If these were only there to reduce noise (while also killing treble) I would gladly remove them and and take back some treble, even if it came with extra noise.

[Greg Robinson]

Removing those will not gain you any extra treble. If you want that, you should focus on the preamp.

EDIT: or, probably a better idea, consider changing speaker for something brighter.

[Mick Bailey]

I'm also thinking they're there for stability. A 560pf cap to ground each side of a floating 8 ohm speaker is going to be outside the upper frequency response for the speaker. Over the years I've found that changing the speaker is the biggest single improvement you can do to any amp - think of it as the final filter that's applying its own tone-stack to the signal (as well as the enclosure to some extent). The factory speaker is likely chosen as a compromise between cost and functionality - cost probably being the deciding factor.

[loudthud]

Those caps are probably a last minute addition to get the amp to pass FCC part 15 regulations on radiated interference from the speaker leads.

[Mick Bailey]

Good point.

[loudthud]

For those unfamiliar with the procedure, it goes something like this. It may be different in some countries, this is my experience here in USA.

Every product that has any kind of microprocessor or significant digital circuitry has to be tested by an independent lab for emissions that might interfere with radio communications. This requires an Anechoic chamber. Generally, you have to book an appointment at a lab that does such tests, perhaps an afternoon or a whole day. You send your product along with an engineer and a tech or two to set up and operate your product as a purchaser of the product would operate it. Techs and engineers at the lab conduct the tests. If your product fails any of the tests, you have the opportunity to make adjustments in an attempt to get your product to pass. A sniffer probe is used to localize where RF is leaking out of your product. One popular adjustment is to tighten up any screws that hold together any metal panels that may shield the the internal circuitry. Any wire that comes out of the metal box may act as an antenna, and radiate RF. This antenna may cause your product to fail. I suspect this is the reason you see caps and sometimes inductors around the input jacks to certain guitar amps. In this case, the speaker leads were radiating RF and caps to the chassis were employed to reduce emissions. There are also tests on power quality and RF sent down the mains leads required in some countries.

If your product passes, the lab generates a report and you can begin manufacturing your product. If you fail, it's back to the drawing board, you change your product, book another appointment and hope you pass the next time.

[pdf64]

Anechoic chamber in regard of external electromagnetic interference, rather than acoustics / mechanical vibrations.
In Cheshire, some testing companies use disused, exhausted caverns in the depths of the local salt mine

[J M Fahey]

Yes, I much suspect tīs a Faraday Cage

https://en.wikipedia.org/wiki/Faraday_cage